llvm-project/lldb/source/Symbol/DWARFCallFrameInfo.cpp

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//===-- DWARFCallFrameInfo.cpp ----------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "lldb/Symbol/DWARFCallFrameInfo.h"
#include "lldb/Core/Module.h"
#include "lldb/Core/Section.h"
#include "lldb/Core/dwarf.h"
#include "lldb/Host/Host.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Symbol/UnwindPlan.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/Thread.h"
#include "lldb/Utility/ArchSpec.h"
#include "lldb/Utility/Log.h"
#include "lldb/Utility/Timer.h"
#include <list>
using namespace lldb;
using namespace lldb_private;
// GetDwarfEHPtr
//
// Used for calls when the value type is specified by a DWARF EH Frame pointer
// encoding.
static uint64_t
GetGNUEHPointer(const DataExtractor &DE, offset_t *offset_ptr,
uint32_t eh_ptr_enc, addr_t pc_rel_addr, addr_t text_addr,
addr_t data_addr) //, BSDRelocs *data_relocs) const
{
if (eh_ptr_enc == DW_EH_PE_omit)
return ULLONG_MAX; // Value isn't in the buffer...
uint64_t baseAddress = 0;
uint64_t addressValue = 0;
const uint32_t addr_size = DE.GetAddressByteSize();
assert(addr_size == 4 || addr_size == 8);
bool signExtendValue = false;
// Decode the base part or adjust our offset
switch (eh_ptr_enc & 0x70) {
case DW_EH_PE_pcrel:
signExtendValue = true;
baseAddress = *offset_ptr;
if (pc_rel_addr != LLDB_INVALID_ADDRESS)
baseAddress += pc_rel_addr;
// else
// Log::GlobalWarning ("PC relative pointer encoding found with
// invalid pc relative address.");
break;
case DW_EH_PE_textrel:
signExtendValue = true;
if (text_addr != LLDB_INVALID_ADDRESS)
baseAddress = text_addr;
// else
// Log::GlobalWarning ("text relative pointer encoding being
// decoded with invalid text section address, setting base address
// to zero.");
break;
case DW_EH_PE_datarel:
signExtendValue = true;
if (data_addr != LLDB_INVALID_ADDRESS)
baseAddress = data_addr;
// else
// Log::GlobalWarning ("data relative pointer encoding being
// decoded with invalid data section address, setting base address
// to zero.");
break;
case DW_EH_PE_funcrel:
signExtendValue = true;
break;
case DW_EH_PE_aligned: {
// SetPointerSize should be called prior to extracting these so the pointer
// size is cached
assert(addr_size != 0);
if (addr_size) {
// Align to a address size boundary first
uint32_t alignOffset = *offset_ptr % addr_size;
if (alignOffset)
offset_ptr += addr_size - alignOffset;
}
} break;
default:
break;
}
// Decode the value part
switch (eh_ptr_enc & DW_EH_PE_MASK_ENCODING) {
case DW_EH_PE_absptr: {
addressValue = DE.GetAddress(offset_ptr);
// if (data_relocs)
// addressValue = data_relocs->Relocate(*offset_ptr -
// addr_size, *this, addressValue);
} break;
case DW_EH_PE_uleb128:
addressValue = DE.GetULEB128(offset_ptr);
break;
case DW_EH_PE_udata2:
addressValue = DE.GetU16(offset_ptr);
break;
case DW_EH_PE_udata4:
addressValue = DE.GetU32(offset_ptr);
break;
case DW_EH_PE_udata8:
addressValue = DE.GetU64(offset_ptr);
break;
case DW_EH_PE_sleb128:
addressValue = DE.GetSLEB128(offset_ptr);
break;
case DW_EH_PE_sdata2:
addressValue = (int16_t)DE.GetU16(offset_ptr);
break;
case DW_EH_PE_sdata4:
addressValue = (int32_t)DE.GetU32(offset_ptr);
break;
case DW_EH_PE_sdata8:
addressValue = (int64_t)DE.GetU64(offset_ptr);
break;
default:
// Unhandled encoding type
assert(eh_ptr_enc);
break;
}
// Since we promote everything to 64 bit, we may need to sign extend
if (signExtendValue && addr_size < sizeof(baseAddress)) {
uint64_t sign_bit = 1ull << ((addr_size * 8ull) - 1ull);
if (sign_bit & addressValue) {
uint64_t mask = ~sign_bit + 1;
addressValue |= mask;
}
}
return baseAddress + addressValue;
}
DWARFCallFrameInfo::DWARFCallFrameInfo(ObjectFile &objfile,
SectionSP &section_sp, Type type)
: m_objfile(objfile), m_section_sp(section_sp), m_type(type) {}
FuncUnwinders: remove "current_offset" from function arguments Summary: This argument was added back in 2010 (r118882) to support the ability to unwind from functions whose eh_frame entry does not cover the entire range of the function. However, due to the caching happening in FuncUnwinders, this solution is very fragile. FuncUnwinders will cache the plan it got from eh_frame regardless of the value of the current_offset, so our ability to unwind from a given function depended what was the value of "current_offset" the first time that this function was called. Furthermore, since the "image show-unwind" command did not know what's the right offset to pass, this created an unfortunate situation where "image show-unwind" would show no valid plans for a function, even though they were available and being used. In this patch I implement the feature slightly differently. Instead of giving just a base address to the eh_frame unwinder, I give it the entire range we are interested in. Then, I change the unwinder to return the first plan that covers (even partially) that range. This way even a partial plan will be returned, regardless of the address in the function where we are stopped at. This solution is still not 100% correct, as it will not handle a function which is covered by two independent fde entries. However, I don't expect anybody will write this kind of functions, and this wasn't handled by the previous implementation either. If this is ever needed in the future. The eh_frame unwinder can be extended to return "composite" unwind plans created by merging sevelar fde entries. I also create a test which triggers this scenario. As doing this is virtually impossible without hand-written assembly, the test only works on x86 linux. Reviewers: jasonmolenda, clayborg Subscribers: lldb-commits Differential Revision: https://reviews.llvm.org/D60829 llvm-svn: 358964
2019-04-23 17:57:14 +08:00
bool DWARFCallFrameInfo::GetUnwindPlan(const Address &addr,
UnwindPlan &unwind_plan) {
return GetUnwindPlan(AddressRange(addr, 1), unwind_plan);
}
bool DWARFCallFrameInfo::GetUnwindPlan(const AddressRange &range,
UnwindPlan &unwind_plan) {
FDEEntryMap::Entry fde_entry;
FuncUnwinders: remove "current_offset" from function arguments Summary: This argument was added back in 2010 (r118882) to support the ability to unwind from functions whose eh_frame entry does not cover the entire range of the function. However, due to the caching happening in FuncUnwinders, this solution is very fragile. FuncUnwinders will cache the plan it got from eh_frame regardless of the value of the current_offset, so our ability to unwind from a given function depended what was the value of "current_offset" the first time that this function was called. Furthermore, since the "image show-unwind" command did not know what's the right offset to pass, this created an unfortunate situation where "image show-unwind" would show no valid plans for a function, even though they were available and being used. In this patch I implement the feature slightly differently. Instead of giving just a base address to the eh_frame unwinder, I give it the entire range we are interested in. Then, I change the unwinder to return the first plan that covers (even partially) that range. This way even a partial plan will be returned, regardless of the address in the function where we are stopped at. This solution is still not 100% correct, as it will not handle a function which is covered by two independent fde entries. However, I don't expect anybody will write this kind of functions, and this wasn't handled by the previous implementation either. If this is ever needed in the future. The eh_frame unwinder can be extended to return "composite" unwind plans created by merging sevelar fde entries. I also create a test which triggers this scenario. As doing this is virtually impossible without hand-written assembly, the test only works on x86 linux. Reviewers: jasonmolenda, clayborg Subscribers: lldb-commits Differential Revision: https://reviews.llvm.org/D60829 llvm-svn: 358964
2019-04-23 17:57:14 +08:00
Address addr = range.GetBaseAddress();
// Make sure that the Address we're searching for is the same object file as
// this DWARFCallFrameInfo, we only store File offsets in m_fde_index.
ModuleSP module_sp = addr.GetModule();
if (module_sp.get() == nullptr || module_sp->GetObjectFile() == nullptr ||
module_sp->GetObjectFile() != &m_objfile)
return false;
FuncUnwinders: remove "current_offset" from function arguments Summary: This argument was added back in 2010 (r118882) to support the ability to unwind from functions whose eh_frame entry does not cover the entire range of the function. However, due to the caching happening in FuncUnwinders, this solution is very fragile. FuncUnwinders will cache the plan it got from eh_frame regardless of the value of the current_offset, so our ability to unwind from a given function depended what was the value of "current_offset" the first time that this function was called. Furthermore, since the "image show-unwind" command did not know what's the right offset to pass, this created an unfortunate situation where "image show-unwind" would show no valid plans for a function, even though they were available and being used. In this patch I implement the feature slightly differently. Instead of giving just a base address to the eh_frame unwinder, I give it the entire range we are interested in. Then, I change the unwinder to return the first plan that covers (even partially) that range. This way even a partial plan will be returned, regardless of the address in the function where we are stopped at. This solution is still not 100% correct, as it will not handle a function which is covered by two independent fde entries. However, I don't expect anybody will write this kind of functions, and this wasn't handled by the previous implementation either. If this is ever needed in the future. The eh_frame unwinder can be extended to return "composite" unwind plans created by merging sevelar fde entries. I also create a test which triggers this scenario. As doing this is virtually impossible without hand-written assembly, the test only works on x86 linux. Reviewers: jasonmolenda, clayborg Subscribers: lldb-commits Differential Revision: https://reviews.llvm.org/D60829 llvm-svn: 358964
2019-04-23 17:57:14 +08:00
if (llvm::Optional<FDEEntryMap::Entry> entry = GetFirstFDEEntryInRange(range))
return FDEToUnwindPlan(entry->data, addr, unwind_plan);
return false;
}
bool DWARFCallFrameInfo::GetAddressRange(Address addr, AddressRange &range) {
// Make sure that the Address we're searching for is the same object file as
// this DWARFCallFrameInfo, we only store File offsets in m_fde_index.
ModuleSP module_sp = addr.GetModule();
if (module_sp.get() == nullptr || module_sp->GetObjectFile() == nullptr ||
module_sp->GetObjectFile() != &m_objfile)
return false;
if (m_section_sp.get() == nullptr || m_section_sp->IsEncrypted())
return false;
GetFDEIndex();
FDEEntryMap::Entry *fde_entry =
m_fde_index.FindEntryThatContains(addr.GetFileAddress());
if (!fde_entry)
return false;
range = AddressRange(fde_entry->base, fde_entry->size,
m_objfile.GetSectionList());
return true;
}
FuncUnwinders: remove "current_offset" from function arguments Summary: This argument was added back in 2010 (r118882) to support the ability to unwind from functions whose eh_frame entry does not cover the entire range of the function. However, due to the caching happening in FuncUnwinders, this solution is very fragile. FuncUnwinders will cache the plan it got from eh_frame regardless of the value of the current_offset, so our ability to unwind from a given function depended what was the value of "current_offset" the first time that this function was called. Furthermore, since the "image show-unwind" command did not know what's the right offset to pass, this created an unfortunate situation where "image show-unwind" would show no valid plans for a function, even though they were available and being used. In this patch I implement the feature slightly differently. Instead of giving just a base address to the eh_frame unwinder, I give it the entire range we are interested in. Then, I change the unwinder to return the first plan that covers (even partially) that range. This way even a partial plan will be returned, regardless of the address in the function where we are stopped at. This solution is still not 100% correct, as it will not handle a function which is covered by two independent fde entries. However, I don't expect anybody will write this kind of functions, and this wasn't handled by the previous implementation either. If this is ever needed in the future. The eh_frame unwinder can be extended to return "composite" unwind plans created by merging sevelar fde entries. I also create a test which triggers this scenario. As doing this is virtually impossible without hand-written assembly, the test only works on x86 linux. Reviewers: jasonmolenda, clayborg Subscribers: lldb-commits Differential Revision: https://reviews.llvm.org/D60829 llvm-svn: 358964
2019-04-23 17:57:14 +08:00
llvm::Optional<DWARFCallFrameInfo::FDEEntryMap::Entry>
DWARFCallFrameInfo::GetFirstFDEEntryInRange(const AddressRange &range) {
if (!m_section_sp || m_section_sp->IsEncrypted())
return llvm::None;
GetFDEIndex();
FuncUnwinders: remove "current_offset" from function arguments Summary: This argument was added back in 2010 (r118882) to support the ability to unwind from functions whose eh_frame entry does not cover the entire range of the function. However, due to the caching happening in FuncUnwinders, this solution is very fragile. FuncUnwinders will cache the plan it got from eh_frame regardless of the value of the current_offset, so our ability to unwind from a given function depended what was the value of "current_offset" the first time that this function was called. Furthermore, since the "image show-unwind" command did not know what's the right offset to pass, this created an unfortunate situation where "image show-unwind" would show no valid plans for a function, even though they were available and being used. In this patch I implement the feature slightly differently. Instead of giving just a base address to the eh_frame unwinder, I give it the entire range we are interested in. Then, I change the unwinder to return the first plan that covers (even partially) that range. This way even a partial plan will be returned, regardless of the address in the function where we are stopped at. This solution is still not 100% correct, as it will not handle a function which is covered by two independent fde entries. However, I don't expect anybody will write this kind of functions, and this wasn't handled by the previous implementation either. If this is ever needed in the future. The eh_frame unwinder can be extended to return "composite" unwind plans created by merging sevelar fde entries. I also create a test which triggers this scenario. As doing this is virtually impossible without hand-written assembly, the test only works on x86 linux. Reviewers: jasonmolenda, clayborg Subscribers: lldb-commits Differential Revision: https://reviews.llvm.org/D60829 llvm-svn: 358964
2019-04-23 17:57:14 +08:00
addr_t start_file_addr = range.GetBaseAddress().GetFileAddress();
const FDEEntryMap::Entry *fde =
m_fde_index.FindEntryThatContainsOrFollows(start_file_addr);
if (fde && fde->DoesIntersect(
FDEEntryMap::Range(start_file_addr, range.GetByteSize())))
return *fde;
FuncUnwinders: remove "current_offset" from function arguments Summary: This argument was added back in 2010 (r118882) to support the ability to unwind from functions whose eh_frame entry does not cover the entire range of the function. However, due to the caching happening in FuncUnwinders, this solution is very fragile. FuncUnwinders will cache the plan it got from eh_frame regardless of the value of the current_offset, so our ability to unwind from a given function depended what was the value of "current_offset" the first time that this function was called. Furthermore, since the "image show-unwind" command did not know what's the right offset to pass, this created an unfortunate situation where "image show-unwind" would show no valid plans for a function, even though they were available and being used. In this patch I implement the feature slightly differently. Instead of giving just a base address to the eh_frame unwinder, I give it the entire range we are interested in. Then, I change the unwinder to return the first plan that covers (even partially) that range. This way even a partial plan will be returned, regardless of the address in the function where we are stopped at. This solution is still not 100% correct, as it will not handle a function which is covered by two independent fde entries. However, I don't expect anybody will write this kind of functions, and this wasn't handled by the previous implementation either. If this is ever needed in the future. The eh_frame unwinder can be extended to return "composite" unwind plans created by merging sevelar fde entries. I also create a test which triggers this scenario. As doing this is virtually impossible without hand-written assembly, the test only works on x86 linux. Reviewers: jasonmolenda, clayborg Subscribers: lldb-commits Differential Revision: https://reviews.llvm.org/D60829 llvm-svn: 358964
2019-04-23 17:57:14 +08:00
return llvm::None;
}
void DWARFCallFrameInfo::GetFunctionAddressAndSizeVector(
FunctionAddressAndSizeVector &function_info) {
GetFDEIndex();
const size_t count = m_fde_index.GetSize();
function_info.Clear();
if (count > 0)
function_info.Reserve(count);
for (size_t i = 0; i < count; ++i) {
const FDEEntryMap::Entry *func_offset_data_entry =
m_fde_index.GetEntryAtIndex(i);
if (func_offset_data_entry) {
FunctionAddressAndSizeVector::Entry function_offset_entry(
func_offset_data_entry->base, func_offset_data_entry->size);
function_info.Append(function_offset_entry);
}
}
}
const DWARFCallFrameInfo::CIE *
DWARFCallFrameInfo::GetCIE(dw_offset_t cie_offset) {
cie_map_t::iterator pos = m_cie_map.find(cie_offset);
if (pos != m_cie_map.end()) {
// Parse and cache the CIE
if (pos->second == nullptr)
pos->second = ParseCIE(cie_offset);
return pos->second.get();
}
return nullptr;
}
The first part of an lldb native stack unwinder. The Unwind and RegisterContext subclasses still need to be finished; none of this code is used by lldb at this point (unless you call into it by hand). The ObjectFile class now has an UnwindTable object. The UnwindTable object has a series of FuncUnwinders objects (Function Unwinders) -- one for each function in that ObjectFile we've backtraced through during this debug session. The FuncUnwinders object has a few different UnwindPlans. UnwindPlans are a generic way of describing how to find the canonical address of a given function's stack frame (the CFA idea from DWARF/eh_frame) and how to restore the caller frame's register values, if they have been saved by this function. UnwindPlans are created from different sources. One source is the eh_frame exception handling information generated by the compiler for unwinding an exception throw. Another source is an assembly language inspection class (UnwindAssemblyProfiler, uses the Plugin architecture) which looks at the instructions in the funciton prologue and describes the stack movements/register saves that are done. Two additional types of UnwindPlans that are worth noting are the "fast" stack UnwindPlan which is useful for making a first pass over a thread's stack, determining how many stack frames there are and retrieving the pc and CFA values for each frame (enough to create StackFrameIDs). Only a minimal set of registers is recovered during a fast stack walk. The final UnwindPlan is an architectural default unwind plan. These are provided by the ArchDefaultUnwindPlan class (which uses the plugin architecture). When no symbol/function address range can be found for a given pc value -- when we have no eh_frame information and when we don't have a start address so we can't examine the assembly language instrucitons -- we have to make a best guess about how to unwind. That's when we use the architectural default UnwindPlan. On x86_64, this would be to assume that rbp is used as a stack pointer and we can use that to find the caller's frame pointer and pc value. It's a last-ditch best guess about how to unwind out of a frame. There are heuristics about when to use one UnwindPlan versues the other -- this will all happen in the still-begin-written UnwindLLDB subclass of Unwind which runs the UnwindPlans. llvm-svn: 113581
2010-09-10 15:49:16 +08:00
DWARFCallFrameInfo::CIESP
DWARFCallFrameInfo::ParseCIE(const dw_offset_t cie_offset) {
CIESP cie_sp(new CIE(cie_offset));
lldb::offset_t offset = cie_offset;
if (!m_cfi_data_initialized)
GetCFIData();
uint32_t length = m_cfi_data.GetU32(&offset);
dw_offset_t cie_id, end_offset;
bool is_64bit = (length == UINT32_MAX);
if (is_64bit) {
length = m_cfi_data.GetU64(&offset);
cie_id = m_cfi_data.GetU64(&offset);
end_offset = cie_offset + length + 12;
} else {
cie_id = m_cfi_data.GetU32(&offset);
end_offset = cie_offset + length + 4;
}
if (length > 0 && ((m_type == DWARF && cie_id == UINT32_MAX) ||
(m_type == EH && cie_id == 0ul))) {
size_t i;
// cie.offset = cie_offset;
// cie.length = length;
// cie.cieID = cieID;
cie_sp->ptr_encoding = DW_EH_PE_absptr; // default
cie_sp->version = m_cfi_data.GetU8(&offset);
if (cie_sp->version > CFI_VERSION4) {
Host::SystemLog(Host::eSystemLogError,
"CIE parse error: CFI version %d is not supported\n",
cie_sp->version);
return nullptr;
}
for (i = 0; i < CFI_AUG_MAX_SIZE; ++i) {
cie_sp->augmentation[i] = m_cfi_data.GetU8(&offset);
if (cie_sp->augmentation[i] == '\0') {
// Zero out remaining bytes in augmentation string
for (size_t j = i + 1; j < CFI_AUG_MAX_SIZE; ++j)
cie_sp->augmentation[j] = '\0';
break;
}
}
if (i == CFI_AUG_MAX_SIZE &&
cie_sp->augmentation[CFI_AUG_MAX_SIZE - 1] != '\0') {
Host::SystemLog(Host::eSystemLogError,
"CIE parse error: CIE augmentation string was too large "
"for the fixed sized buffer of %d bytes.\n",
CFI_AUG_MAX_SIZE);
return nullptr;
}
// m_cfi_data uses address size from target architecture of the process may
// ignore these fields?
if (m_type == DWARF && cie_sp->version >= CFI_VERSION4) {
cie_sp->address_size = m_cfi_data.GetU8(&offset);
cie_sp->segment_size = m_cfi_data.GetU8(&offset);
}
cie_sp->code_align = (uint32_t)m_cfi_data.GetULEB128(&offset);
cie_sp->data_align = (int32_t)m_cfi_data.GetSLEB128(&offset);
cie_sp->return_addr_reg_num =
m_type == DWARF && cie_sp->version >= CFI_VERSION3
? static_cast<uint32_t>(m_cfi_data.GetULEB128(&offset))
: m_cfi_data.GetU8(&offset);
if (cie_sp->augmentation[0]) {
// Get the length of the eh_frame augmentation data which starts with a
// ULEB128 length in bytes
const size_t aug_data_len = (size_t)m_cfi_data.GetULEB128(&offset);
const size_t aug_data_end = offset + aug_data_len;
const size_t aug_str_len = strlen(cie_sp->augmentation);
// A 'z' may be present as the first character of the string.
// If present, the Augmentation Data field shall be present. The contents
// of the Augmentation Data shall be interpreted according to other
// characters in the Augmentation String.
if (cie_sp->augmentation[0] == 'z') {
// Extract the Augmentation Data
size_t aug_str_idx = 0;
for (aug_str_idx = 1; aug_str_idx < aug_str_len; aug_str_idx++) {
char aug = cie_sp->augmentation[aug_str_idx];
switch (aug) {
case 'L':
// Indicates the presence of one argument in the Augmentation Data
// of the CIE, and a corresponding argument in the Augmentation
// Data of the FDE. The argument in the Augmentation Data of the
// CIE is 1-byte and represents the pointer encoding used for the
// argument in the Augmentation Data of the FDE, which is the
// address of a language-specific data area (LSDA). The size of the
// LSDA pointer is specified by the pointer encoding used.
cie_sp->lsda_addr_encoding = m_cfi_data.GetU8(&offset);
break;
case 'P':
// Indicates the presence of two arguments in the Augmentation Data
// of the CIE. The first argument is 1-byte and represents the
// pointer encoding used for the second argument, which is the
// address of a personality routine handler. The size of the
// personality routine pointer is specified by the pointer encoding
// used.
//
// The address of the personality function will be stored at this
// location. Pre-execution, it will be all zero's so don't read it
// until we're trying to do an unwind & the reloc has been
// resolved.
{
uint8_t arg_ptr_encoding = m_cfi_data.GetU8(&offset);
const lldb::addr_t pc_rel_addr = m_section_sp->GetFileAddress();
cie_sp->personality_loc = GetGNUEHPointer(
m_cfi_data, &offset, arg_ptr_encoding, pc_rel_addr,
LLDB_INVALID_ADDRESS, LLDB_INVALID_ADDRESS);
}
break;
case 'R':
// A 'R' may be present at any position after the
// first character of the string. The Augmentation Data shall
// include a 1 byte argument that represents the pointer encoding
// for the address pointers used in the FDE. Example: 0x1B ==
// DW_EH_PE_pcrel | DW_EH_PE_sdata4
cie_sp->ptr_encoding = m_cfi_data.GetU8(&offset);
break;
}
}
} else if (strcmp(cie_sp->augmentation, "eh") == 0) {
// If the Augmentation string has the value "eh", then the EH Data
// field shall be present
}
// Set the offset to be the end of the augmentation data just in case we
// didn't understand any of the data.
offset = (uint32_t)aug_data_end;
}
The first part of an lldb native stack unwinder. The Unwind and RegisterContext subclasses still need to be finished; none of this code is used by lldb at this point (unless you call into it by hand). The ObjectFile class now has an UnwindTable object. The UnwindTable object has a series of FuncUnwinders objects (Function Unwinders) -- one for each function in that ObjectFile we've backtraced through during this debug session. The FuncUnwinders object has a few different UnwindPlans. UnwindPlans are a generic way of describing how to find the canonical address of a given function's stack frame (the CFA idea from DWARF/eh_frame) and how to restore the caller frame's register values, if they have been saved by this function. UnwindPlans are created from different sources. One source is the eh_frame exception handling information generated by the compiler for unwinding an exception throw. Another source is an assembly language inspection class (UnwindAssemblyProfiler, uses the Plugin architecture) which looks at the instructions in the funciton prologue and describes the stack movements/register saves that are done. Two additional types of UnwindPlans that are worth noting are the "fast" stack UnwindPlan which is useful for making a first pass over a thread's stack, determining how many stack frames there are and retrieving the pc and CFA values for each frame (enough to create StackFrameIDs). Only a minimal set of registers is recovered during a fast stack walk. The final UnwindPlan is an architectural default unwind plan. These are provided by the ArchDefaultUnwindPlan class (which uses the plugin architecture). When no symbol/function address range can be found for a given pc value -- when we have no eh_frame information and when we don't have a start address so we can't examine the assembly language instrucitons -- we have to make a best guess about how to unwind. That's when we use the architectural default UnwindPlan. On x86_64, this would be to assume that rbp is used as a stack pointer and we can use that to find the caller's frame pointer and pc value. It's a last-ditch best guess about how to unwind out of a frame. There are heuristics about when to use one UnwindPlan versues the other -- this will all happen in the still-begin-written UnwindLLDB subclass of Unwind which runs the UnwindPlans. llvm-svn: 113581
2010-09-10 15:49:16 +08:00
if (end_offset > offset) {
cie_sp->inst_offset = offset;
cie_sp->inst_length = end_offset - offset;
}
while (offset < end_offset) {
uint8_t inst = m_cfi_data.GetU8(&offset);
uint8_t primary_opcode = inst & 0xC0;
uint8_t extended_opcode = inst & 0x3F;
if (!HandleCommonDwarfOpcode(primary_opcode, extended_opcode,
cie_sp->data_align, offset,
cie_sp->initial_row))
break; // Stop if we hit an unrecognized opcode
}
}
return cie_sp;
}
void DWARFCallFrameInfo::GetCFIData() {
if (!m_cfi_data_initialized) {
Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
if (log)
m_objfile.GetModule()->LogMessage(log, "Reading EH frame info");
m_objfile.ReadSectionData(m_section_sp.get(), m_cfi_data);
m_cfi_data_initialized = true;
}
}
// Scan through the eh_frame or debug_frame section looking for FDEs and noting
// the start/end addresses of the functions and a pointer back to the
// function's FDE for later expansion. Internalize CIEs as we come across them.
The first part of an lldb native stack unwinder. The Unwind and RegisterContext subclasses still need to be finished; none of this code is used by lldb at this point (unless you call into it by hand). The ObjectFile class now has an UnwindTable object. The UnwindTable object has a series of FuncUnwinders objects (Function Unwinders) -- one for each function in that ObjectFile we've backtraced through during this debug session. The FuncUnwinders object has a few different UnwindPlans. UnwindPlans are a generic way of describing how to find the canonical address of a given function's stack frame (the CFA idea from DWARF/eh_frame) and how to restore the caller frame's register values, if they have been saved by this function. UnwindPlans are created from different sources. One source is the eh_frame exception handling information generated by the compiler for unwinding an exception throw. Another source is an assembly language inspection class (UnwindAssemblyProfiler, uses the Plugin architecture) which looks at the instructions in the funciton prologue and describes the stack movements/register saves that are done. Two additional types of UnwindPlans that are worth noting are the "fast" stack UnwindPlan which is useful for making a first pass over a thread's stack, determining how many stack frames there are and retrieving the pc and CFA values for each frame (enough to create StackFrameIDs). Only a minimal set of registers is recovered during a fast stack walk. The final UnwindPlan is an architectural default unwind plan. These are provided by the ArchDefaultUnwindPlan class (which uses the plugin architecture). When no symbol/function address range can be found for a given pc value -- when we have no eh_frame information and when we don't have a start address so we can't examine the assembly language instrucitons -- we have to make a best guess about how to unwind. That's when we use the architectural default UnwindPlan. On x86_64, this would be to assume that rbp is used as a stack pointer and we can use that to find the caller's frame pointer and pc value. It's a last-ditch best guess about how to unwind out of a frame. There are heuristics about when to use one UnwindPlan versues the other -- this will all happen in the still-begin-written UnwindLLDB subclass of Unwind which runs the UnwindPlans. llvm-svn: 113581
2010-09-10 15:49:16 +08:00
void DWARFCallFrameInfo::GetFDEIndex() {
if (m_section_sp.get() == nullptr || m_section_sp->IsEncrypted())
return;
if (m_fde_index_initialized)
return;
std::lock_guard<std::mutex> guard(m_fde_index_mutex);
if (m_fde_index_initialized) // if two threads hit the locker
return;
static Timer::Category func_cat(LLVM_PRETTY_FUNCTION);
Timer scoped_timer(func_cat, "%s - %s", LLVM_PRETTY_FUNCTION,
m_objfile.GetFileSpec().GetFilename().AsCString(""));
bool clear_address_zeroth_bit = false;
if (ArchSpec arch = m_objfile.GetArchitecture()) {
if (arch.GetTriple().getArch() == llvm::Triple::arm ||
arch.GetTriple().getArch() == llvm::Triple::thumb)
clear_address_zeroth_bit = true;
}
lldb::offset_t offset = 0;
if (!m_cfi_data_initialized)
GetCFIData();
while (m_cfi_data.ValidOffsetForDataOfSize(offset, 8)) {
const dw_offset_t current_entry = offset;
dw_offset_t cie_id, next_entry, cie_offset;
uint32_t len = m_cfi_data.GetU32(&offset);
bool is_64bit = (len == UINT32_MAX);
if (is_64bit) {
len = m_cfi_data.GetU64(&offset);
cie_id = m_cfi_data.GetU64(&offset);
next_entry = current_entry + len + 12;
cie_offset = current_entry + 12 - cie_id;
} else {
cie_id = m_cfi_data.GetU32(&offset);
next_entry = current_entry + len + 4;
cie_offset = current_entry + 4 - cie_id;
}
if (next_entry > m_cfi_data.GetByteSize() + 1) {
Host::SystemLog(Host::eSystemLogError, "error: Invalid fde/cie next "
"entry offset of 0x%x found in "
"cie/fde at 0x%x\n",
next_entry, current_entry);
// Don't trust anything in this eh_frame section if we find blatantly
// invalid data.
m_fde_index.Clear();
m_fde_index_initialized = true;
return;
}
// An FDE entry contains CIE_pointer in debug_frame in same place as cie_id
// in eh_frame. CIE_pointer is an offset into the .debug_frame section. So,
// variable cie_offset should be equal to cie_id for debug_frame.
// FDE entries with cie_id == 0 shouldn't be ignored for it.
if ((cie_id == 0 && m_type == EH) || cie_id == UINT32_MAX || len == 0) {
auto cie_sp = ParseCIE(current_entry);
if (!cie_sp) {
// Cannot parse, the reason is already logged
m_fde_index.Clear();
m_fde_index_initialized = true;
return;
}
m_cie_map[current_entry] = std::move(cie_sp);
offset = next_entry;
continue;
}
if (m_type == DWARF)
cie_offset = cie_id;
if (cie_offset > m_cfi_data.GetByteSize()) {
Host::SystemLog(Host::eSystemLogError,
"error: Invalid cie offset of 0x%x "
"found in cie/fde at 0x%x\n",
cie_offset, current_entry);
// Don't trust anything in this eh_frame section if we find blatantly
// invalid data.
m_fde_index.Clear();
m_fde_index_initialized = true;
return;
}
const CIE *cie = GetCIE(cie_offset);
if (cie) {
const lldb::addr_t pc_rel_addr = m_section_sp->GetFileAddress();
const lldb::addr_t text_addr = LLDB_INVALID_ADDRESS;
const lldb::addr_t data_addr = LLDB_INVALID_ADDRESS;
lldb::addr_t addr =
GetGNUEHPointer(m_cfi_data, &offset, cie->ptr_encoding, pc_rel_addr,
text_addr, data_addr);
if (clear_address_zeroth_bit)
addr &= ~1ull;
lldb::addr_t length = GetGNUEHPointer(
m_cfi_data, &offset, cie->ptr_encoding & DW_EH_PE_MASK_ENCODING,
pc_rel_addr, text_addr, data_addr);
FDEEntryMap::Entry fde(addr, length, current_entry);
m_fde_index.Append(fde);
} else {
Host::SystemLog(Host::eSystemLogError, "error: unable to find CIE at "
"0x%8.8x for cie_id = 0x%8.8x for "
"entry at 0x%8.8x.\n",
cie_offset, cie_id, current_entry);
}
offset = next_entry;
}
m_fde_index.Sort();
m_fde_index_initialized = true;
}
bool DWARFCallFrameInfo::FDEToUnwindPlan(dw_offset_t dwarf_offset,
Address startaddr,
UnwindPlan &unwind_plan) {
Log *log = GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND);
lldb::offset_t offset = dwarf_offset;
lldb::offset_t current_entry = offset;
if (m_section_sp.get() == nullptr || m_section_sp->IsEncrypted())
return false;
if (!m_cfi_data_initialized)
GetCFIData();
uint32_t length = m_cfi_data.GetU32(&offset);
dw_offset_t cie_offset;
bool is_64bit = (length == UINT32_MAX);
if (is_64bit) {
length = m_cfi_data.GetU64(&offset);
cie_offset = m_cfi_data.GetU64(&offset);
} else {
cie_offset = m_cfi_data.GetU32(&offset);
}
// FDE entries with zeroth cie_offset may occur for debug_frame.
assert(!(m_type == EH && 0 == cie_offset) && cie_offset != UINT32_MAX);
// Translate the CIE_id from the eh_frame format, which is relative to the
// FDE offset, into a __eh_frame section offset
if (m_type == EH) {
unwind_plan.SetSourceName("eh_frame CFI");
cie_offset = current_entry + (is_64bit ? 12 : 4) - cie_offset;
unwind_plan.SetUnwindPlanValidAtAllInstructions(eLazyBoolNo);
} else {
unwind_plan.SetSourceName("DWARF CFI");
// In theory the debug_frame info should be valid at all call sites
// ("asynchronous unwind info" as it is sometimes called) but in practice
// gcc et al all emit call frame info for the prologue and call sites, but
// not for the epilogue or all the other locations during the function
// reliably.
unwind_plan.SetUnwindPlanValidAtAllInstructions(eLazyBoolNo);
}
unwind_plan.SetSourcedFromCompiler(eLazyBoolYes);
const CIE *cie = GetCIE(cie_offset);
assert(cie != nullptr);
const dw_offset_t end_offset = current_entry + length + (is_64bit ? 12 : 4);
const lldb::addr_t pc_rel_addr = m_section_sp->GetFileAddress();
const lldb::addr_t text_addr = LLDB_INVALID_ADDRESS;
const lldb::addr_t data_addr = LLDB_INVALID_ADDRESS;
lldb::addr_t range_base =
GetGNUEHPointer(m_cfi_data, &offset, cie->ptr_encoding, pc_rel_addr,
text_addr, data_addr);
lldb::addr_t range_len = GetGNUEHPointer(
m_cfi_data, &offset, cie->ptr_encoding & DW_EH_PE_MASK_ENCODING,
pc_rel_addr, text_addr, data_addr);
AddressRange range(range_base, m_objfile.GetAddressByteSize(),
m_objfile.GetSectionList());
range.SetByteSize(range_len);
addr_t lsda_data_file_address = LLDB_INVALID_ADDRESS;
if (cie->augmentation[0] == 'z') {
uint32_t aug_data_len = (uint32_t)m_cfi_data.GetULEB128(&offset);
if (aug_data_len != 0 && cie->lsda_addr_encoding != DW_EH_PE_omit) {
offset_t saved_offset = offset;
lsda_data_file_address =
GetGNUEHPointer(m_cfi_data, &offset, cie->lsda_addr_encoding,
pc_rel_addr, text_addr, data_addr);
if (offset - saved_offset != aug_data_len) {
// There is more in the augmentation region than we know how to process;
// don't read anything.
lsda_data_file_address = LLDB_INVALID_ADDRESS;
}
offset = saved_offset;
}
offset += aug_data_len;
}
Address lsda_data;
Address personality_function_ptr;
if (lsda_data_file_address != LLDB_INVALID_ADDRESS &&
cie->personality_loc != LLDB_INVALID_ADDRESS) {
m_objfile.GetModule()->ResolveFileAddress(lsda_data_file_address,
lsda_data);
m_objfile.GetModule()->ResolveFileAddress(cie->personality_loc,
personality_function_ptr);
}
if (lsda_data.IsValid() && personality_function_ptr.IsValid()) {
unwind_plan.SetLSDAAddress(lsda_data);
unwind_plan.SetPersonalityFunctionPtr(personality_function_ptr);
}
uint32_t code_align = cie->code_align;
int32_t data_align = cie->data_align;
unwind_plan.SetPlanValidAddressRange(range);
UnwindPlan::Row *cie_initial_row = new UnwindPlan::Row;
*cie_initial_row = cie->initial_row;
UnwindPlan::RowSP row(cie_initial_row);
unwind_plan.SetRegisterKind(GetRegisterKind());
unwind_plan.SetReturnAddressRegister(cie->return_addr_reg_num);
std::vector<UnwindPlan::RowSP> stack;
UnwindPlan::Row::RegisterLocation reg_location;
while (m_cfi_data.ValidOffset(offset) && offset < end_offset) {
uint8_t inst = m_cfi_data.GetU8(&offset);
uint8_t primary_opcode = inst & 0xC0;
uint8_t extended_opcode = inst & 0x3F;
if (!HandleCommonDwarfOpcode(primary_opcode, extended_opcode, data_align,
offset, *row)) {
if (primary_opcode) {
switch (primary_opcode) {
case DW_CFA_advance_loc: // (Row Creation Instruction)
{ // 0x40 - high 2 bits are 0x1, lower 6 bits are delta
// takes a single argument that represents a constant delta. The
// required action is to create a new table row with a location value
// that is computed by taking the current entry's location value and
// adding (delta * code_align). All other values in the new row are
// initially identical to the current row.
unwind_plan.AppendRow(row);
UnwindPlan::Row *newrow = new UnwindPlan::Row;
*newrow = *row.get();
row.reset(newrow);
row->SlideOffset(extended_opcode * code_align);
break;
}
case DW_CFA_restore: { // 0xC0 - high 2 bits are 0x3, lower 6 bits are
// register
// takes a single argument that represents a register number. The
// required action is to change the rule for the indicated register
// to the rule assigned it by the initial_instructions in the CIE.
uint32_t reg_num = extended_opcode;
// We only keep enough register locations around to unwind what is in
// our thread, and these are organized by the register index in that
// state, so we need to convert our eh_frame register number from the
// EH frame info, to a register index
if (unwind_plan.IsValidRowIndex(0) &&
unwind_plan.GetRowAtIndex(0)->GetRegisterInfo(reg_num,
reg_location))
row->SetRegisterInfo(reg_num, reg_location);
break;
}
}
} else {
switch (extended_opcode) {
case DW_CFA_set_loc: // 0x1 (Row Creation Instruction)
{
// DW_CFA_set_loc takes a single argument that represents an address.
// The required action is to create a new table row using the
// specified address as the location. All other values in the new row
// are initially identical to the current row. The new location value
// should always be greater than the current one.
unwind_plan.AppendRow(row);
UnwindPlan::Row *newrow = new UnwindPlan::Row;
*newrow = *row.get();
row.reset(newrow);
row->SetOffset(m_cfi_data.GetPointer(&offset) -
startaddr.GetFileAddress());
break;
}
case DW_CFA_advance_loc1: // 0x2 (Row Creation Instruction)
{
// takes a single uword argument that represents a constant delta.
// This instruction is identical to DW_CFA_advance_loc except for the
// encoding and size of the delta argument.
unwind_plan.AppendRow(row);
UnwindPlan::Row *newrow = new UnwindPlan::Row;
*newrow = *row.get();
row.reset(newrow);
row->SlideOffset(m_cfi_data.GetU8(&offset) * code_align);
break;
}
case DW_CFA_advance_loc2: // 0x3 (Row Creation Instruction)
The first part of an lldb native stack unwinder. The Unwind and RegisterContext subclasses still need to be finished; none of this code is used by lldb at this point (unless you call into it by hand). The ObjectFile class now has an UnwindTable object. The UnwindTable object has a series of FuncUnwinders objects (Function Unwinders) -- one for each function in that ObjectFile we've backtraced through during this debug session. The FuncUnwinders object has a few different UnwindPlans. UnwindPlans are a generic way of describing how to find the canonical address of a given function's stack frame (the CFA idea from DWARF/eh_frame) and how to restore the caller frame's register values, if they have been saved by this function. UnwindPlans are created from different sources. One source is the eh_frame exception handling information generated by the compiler for unwinding an exception throw. Another source is an assembly language inspection class (UnwindAssemblyProfiler, uses the Plugin architecture) which looks at the instructions in the funciton prologue and describes the stack movements/register saves that are done. Two additional types of UnwindPlans that are worth noting are the "fast" stack UnwindPlan which is useful for making a first pass over a thread's stack, determining how many stack frames there are and retrieving the pc and CFA values for each frame (enough to create StackFrameIDs). Only a minimal set of registers is recovered during a fast stack walk. The final UnwindPlan is an architectural default unwind plan. These are provided by the ArchDefaultUnwindPlan class (which uses the plugin architecture). When no symbol/function address range can be found for a given pc value -- when we have no eh_frame information and when we don't have a start address so we can't examine the assembly language instrucitons -- we have to make a best guess about how to unwind. That's when we use the architectural default UnwindPlan. On x86_64, this would be to assume that rbp is used as a stack pointer and we can use that to find the caller's frame pointer and pc value. It's a last-ditch best guess about how to unwind out of a frame. There are heuristics about when to use one UnwindPlan versues the other -- this will all happen in the still-begin-written UnwindLLDB subclass of Unwind which runs the UnwindPlans. llvm-svn: 113581
2010-09-10 15:49:16 +08:00
{
// takes a single uword argument that represents a constant delta.
// This instruction is identical to DW_CFA_advance_loc except for the
// encoding and size of the delta argument.
unwind_plan.AppendRow(row);
UnwindPlan::Row *newrow = new UnwindPlan::Row;
*newrow = *row.get();
row.reset(newrow);
row->SlideOffset(m_cfi_data.GetU16(&offset) * code_align);
break;
The first part of an lldb native stack unwinder. The Unwind and RegisterContext subclasses still need to be finished; none of this code is used by lldb at this point (unless you call into it by hand). The ObjectFile class now has an UnwindTable object. The UnwindTable object has a series of FuncUnwinders objects (Function Unwinders) -- one for each function in that ObjectFile we've backtraced through during this debug session. The FuncUnwinders object has a few different UnwindPlans. UnwindPlans are a generic way of describing how to find the canonical address of a given function's stack frame (the CFA idea from DWARF/eh_frame) and how to restore the caller frame's register values, if they have been saved by this function. UnwindPlans are created from different sources. One source is the eh_frame exception handling information generated by the compiler for unwinding an exception throw. Another source is an assembly language inspection class (UnwindAssemblyProfiler, uses the Plugin architecture) which looks at the instructions in the funciton prologue and describes the stack movements/register saves that are done. Two additional types of UnwindPlans that are worth noting are the "fast" stack UnwindPlan which is useful for making a first pass over a thread's stack, determining how many stack frames there are and retrieving the pc and CFA values for each frame (enough to create StackFrameIDs). Only a minimal set of registers is recovered during a fast stack walk. The final UnwindPlan is an architectural default unwind plan. These are provided by the ArchDefaultUnwindPlan class (which uses the plugin architecture). When no symbol/function address range can be found for a given pc value -- when we have no eh_frame information and when we don't have a start address so we can't examine the assembly language instrucitons -- we have to make a best guess about how to unwind. That's when we use the architectural default UnwindPlan. On x86_64, this would be to assume that rbp is used as a stack pointer and we can use that to find the caller's frame pointer and pc value. It's a last-ditch best guess about how to unwind out of a frame. There are heuristics about when to use one UnwindPlan versues the other -- this will all happen in the still-begin-written UnwindLLDB subclass of Unwind which runs the UnwindPlans. llvm-svn: 113581
2010-09-10 15:49:16 +08:00
}
case DW_CFA_advance_loc4: // 0x4 (Row Creation Instruction)
{
// takes a single uword argument that represents a constant delta.
// This instruction is identical to DW_CFA_advance_loc except for the
// encoding and size of the delta argument.
unwind_plan.AppendRow(row);
UnwindPlan::Row *newrow = new UnwindPlan::Row;
*newrow = *row.get();
row.reset(newrow);
row->SlideOffset(m_cfi_data.GetU32(&offset) * code_align);
break;
}
case DW_CFA_restore_extended: // 0x6
{
// takes a single unsigned LEB128 argument that represents a register
// number. This instruction is identical to DW_CFA_restore except for
// the encoding and size of the register argument.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
if (unwind_plan.IsValidRowIndex(0) &&
unwind_plan.GetRowAtIndex(0)->GetRegisterInfo(reg_num,
reg_location))
row->SetRegisterInfo(reg_num, reg_location);
break;
}
case DW_CFA_remember_state: // 0xA
{
// These instructions define a stack of information. Encountering the
// DW_CFA_remember_state instruction means to save the rules for
// every register on the current row on the stack. Encountering the
// DW_CFA_restore_state instruction means to pop the set of rules off
// the stack and place them in the current row. (This operation is
// useful for compilers that move epilogue code into the body of a
// function.)
stack.push_back(row);
UnwindPlan::Row *newrow = new UnwindPlan::Row;
*newrow = *row.get();
row.reset(newrow);
break;
}
case DW_CFA_restore_state: // 0xB
{
// These instructions define a stack of information. Encountering the
// DW_CFA_remember_state instruction means to save the rules for
// every register on the current row on the stack. Encountering the
// DW_CFA_restore_state instruction means to pop the set of rules off
// the stack and place them in the current row. (This operation is
// useful for compilers that move epilogue code into the body of a
// function.)
if (stack.empty()) {
if (log)
log->Printf("DWARFCallFrameInfo::%s(dwarf_offset: %" PRIx32
", startaddr: %" PRIx64
" encountered DW_CFA_restore_state but state stack "
"is empty. Corrupt unwind info?",
__FUNCTION__, dwarf_offset,
startaddr.GetFileAddress());
break;
}
lldb::addr_t offset = row->GetOffset();
row = stack.back();
stack.pop_back();
row->SetOffset(offset);
break;
}
case DW_CFA_GNU_args_size: // 0x2e
{
// The DW_CFA_GNU_args_size instruction takes an unsigned LEB128
// operand representing an argument size. This instruction specifies
// the total of the size of the arguments which have been pushed onto
// the stack.
// TODO: Figure out how we should handle this.
m_cfi_data.GetULEB128(&offset);
break;
}
case DW_CFA_val_offset: // 0x14
case DW_CFA_val_offset_sf: // 0x15
default:
break;
}
}
}
}
unwind_plan.AppendRow(row);
return true;
}
bool DWARFCallFrameInfo::HandleCommonDwarfOpcode(uint8_t primary_opcode,
uint8_t extended_opcode,
int32_t data_align,
lldb::offset_t &offset,
UnwindPlan::Row &row) {
UnwindPlan::Row::RegisterLocation reg_location;
if (primary_opcode) {
switch (primary_opcode) {
case DW_CFA_offset: { // 0x80 - high 2 bits are 0x2, lower 6 bits are
// register
// takes two arguments: an unsigned LEB128 constant representing a
// factored offset and a register number. The required action is to
// change the rule for the register indicated by the register number to
// be an offset(N) rule with a value of (N = factored offset *
// data_align).
uint8_t reg_num = extended_opcode;
int32_t op_offset = (int32_t)m_cfi_data.GetULEB128(&offset) * data_align;
reg_location.SetAtCFAPlusOffset(op_offset);
row.SetRegisterInfo(reg_num, reg_location);
return true;
}
}
} else {
switch (extended_opcode) {
case DW_CFA_nop: // 0x0
return true;
case DW_CFA_offset_extended: // 0x5
{
// takes two unsigned LEB128 arguments representing a register number and
// a factored offset. This instruction is identical to DW_CFA_offset
// except for the encoding and size of the register argument.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
int32_t op_offset = (int32_t)m_cfi_data.GetULEB128(&offset) * data_align;
UnwindPlan::Row::RegisterLocation reg_location;
reg_location.SetAtCFAPlusOffset(op_offset);
row.SetRegisterInfo(reg_num, reg_location);
return true;
}
case DW_CFA_undefined: // 0x7
{
// takes a single unsigned LEB128 argument that represents a register
// number. The required action is to set the rule for the specified
// register to undefined.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
UnwindPlan::Row::RegisterLocation reg_location;
reg_location.SetUndefined();
row.SetRegisterInfo(reg_num, reg_location);
return true;
}
case DW_CFA_same_value: // 0x8
The first part of an lldb native stack unwinder. The Unwind and RegisterContext subclasses still need to be finished; none of this code is used by lldb at this point (unless you call into it by hand). The ObjectFile class now has an UnwindTable object. The UnwindTable object has a series of FuncUnwinders objects (Function Unwinders) -- one for each function in that ObjectFile we've backtraced through during this debug session. The FuncUnwinders object has a few different UnwindPlans. UnwindPlans are a generic way of describing how to find the canonical address of a given function's stack frame (the CFA idea from DWARF/eh_frame) and how to restore the caller frame's register values, if they have been saved by this function. UnwindPlans are created from different sources. One source is the eh_frame exception handling information generated by the compiler for unwinding an exception throw. Another source is an assembly language inspection class (UnwindAssemblyProfiler, uses the Plugin architecture) which looks at the instructions in the funciton prologue and describes the stack movements/register saves that are done. Two additional types of UnwindPlans that are worth noting are the "fast" stack UnwindPlan which is useful for making a first pass over a thread's stack, determining how many stack frames there are and retrieving the pc and CFA values for each frame (enough to create StackFrameIDs). Only a minimal set of registers is recovered during a fast stack walk. The final UnwindPlan is an architectural default unwind plan. These are provided by the ArchDefaultUnwindPlan class (which uses the plugin architecture). When no symbol/function address range can be found for a given pc value -- when we have no eh_frame information and when we don't have a start address so we can't examine the assembly language instrucitons -- we have to make a best guess about how to unwind. That's when we use the architectural default UnwindPlan. On x86_64, this would be to assume that rbp is used as a stack pointer and we can use that to find the caller's frame pointer and pc value. It's a last-ditch best guess about how to unwind out of a frame. There are heuristics about when to use one UnwindPlan versues the other -- this will all happen in the still-begin-written UnwindLLDB subclass of Unwind which runs the UnwindPlans. llvm-svn: 113581
2010-09-10 15:49:16 +08:00
{
// takes a single unsigned LEB128 argument that represents a register
// number. The required action is to set the rule for the specified
// register to same value.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
UnwindPlan::Row::RegisterLocation reg_location;
reg_location.SetSame();
row.SetRegisterInfo(reg_num, reg_location);
return true;
}
case DW_CFA_register: // 0x9
{
// takes two unsigned LEB128 arguments representing register numbers. The
// required action is to set the rule for the first register to be the
// second register.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
uint32_t other_reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
UnwindPlan::Row::RegisterLocation reg_location;
reg_location.SetInRegister(other_reg_num);
row.SetRegisterInfo(reg_num, reg_location);
return true;
}
case DW_CFA_def_cfa: // 0xC (CFA Definition Instruction)
{
// Takes two unsigned LEB128 operands representing a register number and
// a (non-factored) offset. The required action is to define the current
// CFA rule to use the provided register and offset.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
int32_t op_offset = (int32_t)m_cfi_data.GetULEB128(&offset);
row.GetCFAValue().SetIsRegisterPlusOffset(reg_num, op_offset);
return true;
}
case DW_CFA_def_cfa_register: // 0xD (CFA Definition Instruction)
{
// takes a single unsigned LEB128 argument representing a register
// number. The required action is to define the current CFA rule to use
// the provided register (but to keep the old offset).
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
row.GetCFAValue().SetIsRegisterPlusOffset(reg_num,
row.GetCFAValue().GetOffset());
return true;
}
case DW_CFA_def_cfa_offset: // 0xE (CFA Definition Instruction)
{
// Takes a single unsigned LEB128 operand representing a (non-factored)
// offset. The required action is to define the current CFA rule to use
// the provided offset (but to keep the old register).
int32_t op_offset = (int32_t)m_cfi_data.GetULEB128(&offset);
row.GetCFAValue().SetIsRegisterPlusOffset(
row.GetCFAValue().GetRegisterNumber(), op_offset);
return true;
}
case DW_CFA_def_cfa_expression: // 0xF (CFA Definition Instruction)
{
size_t block_len = (size_t)m_cfi_data.GetULEB128(&offset);
const uint8_t *block_data =
static_cast<const uint8_t *>(m_cfi_data.GetData(&offset, block_len));
row.GetCFAValue().SetIsDWARFExpression(block_data, block_len);
return true;
}
case DW_CFA_expression: // 0x10
{
// Takes two operands: an unsigned LEB128 value representing a register
// number, and a DW_FORM_block value representing a DWARF expression. The
// required action is to change the rule for the register indicated by
// the register number to be an expression(E) rule where E is the DWARF
// expression. That is, the DWARF expression computes the address. The
// value of the CFA is pushed on the DWARF evaluation stack prior to
// execution of the DWARF expression.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
uint32_t block_len = (uint32_t)m_cfi_data.GetULEB128(&offset);
const uint8_t *block_data =
static_cast<const uint8_t *>(m_cfi_data.GetData(&offset, block_len));
UnwindPlan::Row::RegisterLocation reg_location;
reg_location.SetAtDWARFExpression(block_data, block_len);
row.SetRegisterInfo(reg_num, reg_location);
return true;
}
case DW_CFA_offset_extended_sf: // 0x11
{
// takes two operands: an unsigned LEB128 value representing a register
// number and a signed LEB128 factored offset. This instruction is
// identical to DW_CFA_offset_extended except that the second operand is
// signed and factored.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
int32_t op_offset = (int32_t)m_cfi_data.GetSLEB128(&offset) * data_align;
UnwindPlan::Row::RegisterLocation reg_location;
reg_location.SetAtCFAPlusOffset(op_offset);
row.SetRegisterInfo(reg_num, reg_location);
return true;
}
case DW_CFA_def_cfa_sf: // 0x12 (CFA Definition Instruction)
{
// Takes two operands: an unsigned LEB128 value representing a register
// number and a signed LEB128 factored offset. This instruction is
// identical to DW_CFA_def_cfa except that the second operand is signed
// and factored.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
int32_t op_offset = (int32_t)m_cfi_data.GetSLEB128(&offset) * data_align;
row.GetCFAValue().SetIsRegisterPlusOffset(reg_num, op_offset);
return true;
}
case DW_CFA_def_cfa_offset_sf: // 0x13 (CFA Definition Instruction)
{
// takes a signed LEB128 operand representing a factored offset. This
// instruction is identical to DW_CFA_def_cfa_offset except that the
// operand is signed and factored.
int32_t op_offset = (int32_t)m_cfi_data.GetSLEB128(&offset) * data_align;
uint32_t cfa_regnum = row.GetCFAValue().GetRegisterNumber();
row.GetCFAValue().SetIsRegisterPlusOffset(cfa_regnum, op_offset);
return true;
}
case DW_CFA_val_expression: // 0x16
{
// takes two operands: an unsigned LEB128 value representing a register
// number, and a DW_FORM_block value representing a DWARF expression. The
// required action is to change the rule for the register indicated by
// the register number to be a val_expression(E) rule where E is the
// DWARF expression. That is, the DWARF expression computes the value of
// the given register. The value of the CFA is pushed on the DWARF
// evaluation stack prior to execution of the DWARF expression.
uint32_t reg_num = (uint32_t)m_cfi_data.GetULEB128(&offset);
uint32_t block_len = (uint32_t)m_cfi_data.GetULEB128(&offset);
const uint8_t *block_data =
(const uint8_t *)m_cfi_data.GetData(&offset, block_len);
reg_location.SetIsDWARFExpression(block_data, block_len);
row.SetRegisterInfo(reg_num, reg_location);
return true;
}
}
}
return false;
}
void DWARFCallFrameInfo::ForEachFDEEntries(
const std::function<bool(lldb::addr_t, uint32_t, dw_offset_t)> &callback) {
GetFDEIndex();
for (size_t i = 0, c = m_fde_index.GetSize(); i < c; ++i) {
const FDEEntryMap::Entry &entry = m_fde_index.GetEntryRef(i);
if (!callback(entry.base, entry.size, entry.data))
break;
}
}