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Change the kernel searching code to not go through the 

memory cache subsystem so we're reading only the 4 bytes
needed to check for the magic word at the start of a mach-o
binary instead of the default 512 block.  It can be a small
performance help to reduce the size of memory reads from 
possibly unmapped memory.

<rdar://problem/29256385> 

llvm-svn: 286926
This commit is contained in:
Jason Molenda 2016-11-15 01:41:27 +00:00
parent e3733bc53e
commit 2b0a7be96e
1 changed files with 37 additions and 17 deletions
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54
lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
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@ -239,27 +239,40 @@ DynamicLoaderDarwinKernel::SearchForKernelWithDebugHints(Process *process) {
return LLDB_INVALID_ADDRESS;
Error read_err;
addr_t addr = LLDB_INVALID_ADDRESS;
addr_t kernel_addresses_64[] = {
0xfffffff000004010ULL, // newest arm64 devices
0xffffff8000004010ULL, // 2014-2015-ish arm64 devices
0xffffff8000002010ULL, // oldest arm64 devices
LLDB_INVALID_ADDRESS};
addr_t kernel_addresses_32[] = {0xffff0110, LLDB_INVALID_ADDRESS};
uint8_t uval[8];
if (process->GetAddressByteSize() == 8) {
for (size_t i = 0; kernel_addresses_64[i] != LLDB_INVALID_ADDRESS; i++) {
addr = process->ReadUnsignedIntegerFromMemory(
kernel_addresses_64[i], 8, LLDB_INVALID_ADDRESS, read_err);
if (CheckForKernelImageAtAddress(addr, process).IsValid()) {
return addr;
}
if (process->ReadMemoryFromInferior (kernel_addresses_64[i], uval, 8, read_err) == 8)
{
DataExtractor data (&uval, 8, process->GetByteOrder(), process->GetAddressByteSize());
offset_t offset = 0;
uint64_t addr = data.GetU64 (&offset);
if (CheckForKernelImageAtAddress(addr, process).IsValid()) {
return addr;
}
}
}
}
if (process->GetAddressByteSize() == 4) {
for (size_t i = 0; kernel_addresses_32[i] != LLDB_INVALID_ADDRESS; i++) {
addr = process->ReadUnsignedIntegerFromMemory(
kernel_addresses_32[i], 4, LLDB_INVALID_ADDRESS, read_err);
if (CheckForKernelImageAtAddress(addr, process).IsValid()) {
return addr;
}
if (process->ReadMemoryFromInferior (kernel_addresses_32[i], uval, 4, read_err) == 4)
{
DataExtractor data (&uval, 4, process->GetByteOrder(), process->GetAddressByteSize());
offset_t offset = 0;
uint32_t addr = data.GetU32 (&offset);
if (CheckForKernelImageAtAddress(addr, process).IsValid()) {
return addr;
}
}
}
}
return LLDB_INVALID_ADDRESS;
@ -380,12 +393,19 @@ DynamicLoaderDarwinKernel::CheckForKernelImageAtAddress(lldb::addr_t addr,
// (the first field of the mach_header/mach_header_64 struct).
Error read_error;
uint64_t result = process->ReadUnsignedIntegerFromMemory(
addr, 4, LLDB_INVALID_ADDRESS, read_error);
if (result != llvm::MachO::MH_MAGIC_64 && result != llvm::MachO::MH_MAGIC &&
result != llvm::MachO::MH_CIGAM && result != llvm::MachO::MH_CIGAM_64) {
return UUID();
}
uint8_t magicbuf[4];
if (process->ReadMemoryFromInferior (addr, magicbuf, sizeof (magicbuf), read_error) != sizeof (magicbuf))
return UUID();
const uint32_t magicks[] = { llvm::MachO::MH_MAGIC_64, llvm::MachO::MH_MAGIC, llvm::MachO::MH_CIGAM, llvm::MachO::MH_CIGAM_64};
bool found_matching_pattern = false;
for (int i = 0; i < llvm::array_lengthof (magicks); i++)
if (::memcmp (magicbuf, &magicks[i], sizeof (magicbuf)) == 0)
found_matching_pattern = true;
if (found_matching_pattern == false)
return UUID();
// Read the mach header and see whether it looks like a kernel
llvm::MachO::mach_header header;