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linux-sg2042
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[PATCH] x86-64: Speed up dwarf2 unwinder 

This changes the dwarf2 unwinder to do a binary search for CIEs
instead of a linear work. The linker is unfortunately not
able to build a proper lookup table at link time, instead it creates
one at runtime as soon as the bootmem allocator is usable (so you'll continue
using the linear lookup for the first [hopefully] few calls).
The code should be ready to utilize a build-time created table once
a fixed linker becomes available.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
This commit is contained in:
Jan Beulich 2006-10-21 18:37:01 +02:00 committed by Andi Kleen
parent cdfce1f571
commit 690a973f48
5 changed files with 298 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Makefile
View File

@ -499,6 +499,7 @@ endif
ifdef CONFIG_UNWIND_INFO
CFLAGS += -fasynchronous-unwind-tables
LDFLAGS_vmlinux += --eh-frame-hdr
endif
ifdef CONFIG_DEBUG_INFO

16
include/asm-generic/vmlinux.lds.h
View File

@ -125,6 +125,10 @@
*(__param) \
VMLINUX_SYMBOL(__stop___param) = .; \
} \
\
/* Unwind data binary search table */ \
EH_FRAME_HDR \
\
__end_rodata = .; \
. = ALIGN(4096);
@ -157,6 +161,18 @@
*(.kprobes.text) \
VMLINUX_SYMBOL(__kprobes_text_end) = .;
#ifdef CONFIG_STACK_UNWIND
/* Unwind data binary search table */
#define EH_FRAME_HDR \
.eh_frame_hdr : AT(ADDR(.eh_frame_hdr) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start_unwind_hdr) = .; \
*(.eh_frame_hdr) \
VMLINUX_SYMBOL(__end_unwind_hdr) = .; \
}
#else
#define EH_FRAME_HDR
#endif
/* DWARF debug sections.
Symbols in the DWARF debugging sections are relative to
the beginning of the section so we begin them at 0. */

2
include/linux/unwind.h
View File

@ -26,6 +26,7 @@ struct module;
* Initialize unwind support.
*/
extern void unwind_init(void);
extern void unwind_setup(void);
#ifdef CONFIG_MODULES
@ -73,6 +74,7 @@ extern int unwind_to_user(struct unwind_frame_info *);
struct unwind_frame_info {};
static inline void unwind_init(void) {}
static inline void unwind_setup(void) {}
#ifdef CONFIG_MODULES

1
init/main.c
View File

@ -503,6 +503,7 @@ asmlinkage void __init start_kernel(void)
printk(KERN_NOTICE);
printk(linux_banner);
setup_arch(&command_line);
unwind_setup();
setup_per_cpu_areas();
smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */

316
kernel/unwind.c
View File

@ -11,13 +11,15 @@
#include <linux/unwind.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/bootmem.h>
#include <linux/sort.h>
#include <linux/stop_machine.h>
#include <asm/sections.h>
#include <asm/uaccess.h>
#include <asm/unaligned.h>
extern char __start_unwind[], __end_unwind[];
extern const u8 __start_unwind_hdr[], __end_unwind_hdr[];
#define MAX_STACK_DEPTH 8
@ -100,6 +102,8 @@ static struct unwind_table {
} core, init;
const void *address;
unsigned long size;
const unsigned char *header;
unsigned long hdrsz;
struct unwind_table *link;
const char *name;
} root_table;
@ -145,6 +149,10 @@ static struct unwind_table *find_table(unsigned long pc)
return table;
}
static unsigned long read_pointer(const u8 **pLoc,
const void *end,
signed ptrType);
static void init_unwind_table(struct unwind_table *table,
const char *name,
const void *core_start,
@ -152,14 +160,30 @@ static void init_unwind_table(struct unwind_table *table,
const void *init_start,
unsigned long init_size,
const void *table_start,
unsigned long table_size)
unsigned long table_size,
const u8 *header_start,
unsigned long header_size)
{
const u8 *ptr = header_start + 4;
const u8 *end = header_start + header_size;
table->core.pc = (unsigned long)core_start;
table->core.range = core_size;
table->init.pc = (unsigned long)init_start;
table->init.range = init_size;
table->address = table_start;
table->size = table_size;
/* See if the linker provided table looks valid. */
if (header_size <= 4
|| header_start[0] != 1
|| (void *)read_pointer(&ptr, end, header_start[1]) != table_start
|| header_start[2] == DW_EH_PE_omit
|| read_pointer(&ptr, end, header_start[2]) <= 0
|| header_start[3] == DW_EH_PE_omit)
header_start = NULL;
table->hdrsz = header_size;
smp_wmb();
table->header = header_start;
table->link = NULL;
table->name = name;
}
@ -169,7 +193,143 @@ void __init unwind_init(void)
init_unwind_table(&root_table, "kernel",
_text, _end - _text,
NULL, 0,
__start_unwind, __end_unwind - __start_unwind);
__start_unwind, __end_unwind - __start_unwind,
__start_unwind_hdr, __end_unwind_hdr - __start_unwind_hdr);
}
static const u32 bad_cie, not_fde;
static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *);
static signed fde_pointer_type(const u32 *cie);
struct eh_frame_hdr_table_entry {
unsigned long start, fde;
};
static int cmp_eh_frame_hdr_table_entries(const void *p1, const void *p2)
{
const struct eh_frame_hdr_table_entry *e1 = p1;
const struct eh_frame_hdr_table_entry *e2 = p2;
return (e1->start > e2->start) - (e1->start < e2->start);
}
static void swap_eh_frame_hdr_table_entries(void *p1, void *p2, int size)
{
struct eh_frame_hdr_table_entry *e1 = p1;
struct eh_frame_hdr_table_entry *e2 = p2;
unsigned long v;
v = e1->start;
e1->start = e2->start;
e2->start = v;
v = e1->fde;
e1->fde = e2->fde;
e2->fde = v;
}
static void __init setup_unwind_table(struct unwind_table *table,
void *(*alloc)(unsigned long))
{
const u8 *ptr;
unsigned long tableSize = table->size, hdrSize;
unsigned n;
const u32 *fde;
struct {
u8 version;
u8 eh_frame_ptr_enc;
u8 fde_count_enc;
u8 table_enc;
unsigned long eh_frame_ptr;
unsigned int fde_count;
struct eh_frame_hdr_table_entry table[];
} __attribute__((__packed__)) *header;
if (table->header)
return;
if (table->hdrsz)
printk(KERN_WARNING ".eh_frame_hdr for '%s' present but unusable\n",
table->name);
if (tableSize & (sizeof(*fde) - 1))
return;
for (fde = table->address, n = 0;
tableSize > sizeof(*fde) && tableSize - sizeof(*fde) >= *fde;
tableSize -= sizeof(*fde) + *fde, fde += 1 + *fde / sizeof(*fde)) {
const u32 *cie = cie_for_fde(fde, table);
signed ptrType;
if (cie == &not_fde)
continue;
if (cie == NULL
|| cie == &bad_cie
|| (ptrType = fde_pointer_type(cie)) < 0)
return;
ptr = (const u8 *)(fde + 2);
if (!read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType))
return;
++n;
}
if (tableSize || !n)
return;
hdrSize = 4 + sizeof(unsigned long) + sizeof(unsigned int)
+ 2 * n * sizeof(unsigned long);
header = alloc(hdrSize);
if (!header)
return;
header->version = 1;
header->eh_frame_ptr_enc = DW_EH_PE_abs|DW_EH_PE_native;
header->fde_count_enc = DW_EH_PE_abs|DW_EH_PE_data4;
header->table_enc = DW_EH_PE_abs|DW_EH_PE_native;
put_unaligned((unsigned long)table->address, &header->eh_frame_ptr);
BUILD_BUG_ON(offsetof(typeof(*header), fde_count)
% __alignof(typeof(header->fde_count)));
header->fde_count = n;
BUILD_BUG_ON(offsetof(typeof(*header), table)
% __alignof(typeof(*header->table)));
for (fde = table->address, tableSize = table->size, n = 0;
tableSize;
tableSize -= sizeof(*fde) + *fde, fde += 1 + *fde / sizeof(*fde)) {
const u32 *cie = fde + 1 - fde[1] / sizeof(*fde);
if (!fde[1])
continue; /* this is a CIE */
ptr = (const u8 *)(fde + 2);
header->table[n].start = read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
fde_pointer_type(cie));
header->table[n].fde = (unsigned long)fde;
++n;
}
WARN_ON(n != header->fde_count);
sort(header->table,
n,
sizeof(*header->table),
cmp_eh_frame_hdr_table_entries,
swap_eh_frame_hdr_table_entries);
table->hdrsz = hdrSize;
smp_wmb();
table->header = (const void *)header;
}
static void *__init balloc(unsigned long sz)
{
return __alloc_bootmem_nopanic(sz,
sizeof(unsigned int),
__pa(MAX_DMA_ADDRESS));
}
void __init unwind_setup(void)
{
setup_unwind_table(&root_table, balloc);
}
#ifdef CONFIG_MODULES
@ -193,7 +353,8 @@ void *unwind_add_table(struct module *module,
init_unwind_table(table, module->name,
module->module_core, module->core_size,
module->module_init, module->init_size,
table_start, table_size);
table_start, table_size,
NULL, 0);
if (last_table)
last_table->link = table;
@ -303,6 +464,26 @@ static sleb128_t get_sleb128(const u8 **pcur, const u8 *end)
return value;
}
static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *table)
{
const u32 *cie;
if (!*fde || (*fde & (sizeof(*fde) - 1)))
return &bad_cie;
if (!fde[1])
return &not_fde; /* this is a CIE */
if ((fde[1] & (sizeof(*fde) - 1))
|| fde[1] > (unsigned long)(fde + 1) - (unsigned long)table->address)
return NULL; /* this is not a valid FDE */
cie = fde + 1 - fde[1] / sizeof(*fde);
if (*cie <= sizeof(*cie) + 4
|| *cie >= fde[1] - sizeof(*fde)
|| (*cie & (sizeof(*cie) - 1))
|| cie[1])
return NULL; /* this is not a (valid) CIE */
return cie;
}
static unsigned long read_pointer(const u8 **pLoc,
const void *end,
signed ptrType)
@ -610,49 +791,108 @@ int unwind(struct unwind_frame_info *frame)
unsigned i;
signed ptrType = -1;
uleb128_t retAddrReg = 0;
struct unwind_table *table;
const struct unwind_table *table;
struct unwind_state state;
if (UNW_PC(frame) == 0)
return -EINVAL;
if ((table = find_table(pc)) != NULL
&& !(table->size & (sizeof(*fde) - 1))) {
unsigned long tableSize = table->size;
const u8 *hdr = table->header;
unsigned long tableSize;
for (fde = table->address;
tableSize > sizeof(*fde) && tableSize - sizeof(*fde) >= *fde;
tableSize -= sizeof(*fde) + *fde,
fde += 1 + *fde / sizeof(*fde)) {
if (!*fde || (*fde & (sizeof(*fde) - 1)))
break;
if (!fde[1])
continue; /* this is a CIE */
if ((fde[1] & (sizeof(*fde) - 1))
|| fde[1] > (unsigned long)(fde + 1)
- (unsigned long)table->address)
continue; /* this is not a valid FDE */
cie = fde + 1 - fde[1] / sizeof(*fde);
if (*cie <= sizeof(*cie) + 4
|| *cie >= fde[1] - sizeof(*fde)
|| (*cie & (sizeof(*cie) - 1))
|| cie[1]
|| (ptrType = fde_pointer_type(cie)) < 0) {
cie = NULL; /* this is not a (valid) CIE */
continue;
smp_rmb();
if (hdr && hdr[0] == 1) {
switch(hdr[3] & DW_EH_PE_FORM) {
case DW_EH_PE_native: tableSize = sizeof(unsigned long); break;
case DW_EH_PE_data2: tableSize = 2; break;
case DW_EH_PE_data4: tableSize = 4; break;
case DW_EH_PE_data8: tableSize = 8; break;
default: tableSize = 0; break;
}
ptr = hdr + 4;
end = hdr + table->hdrsz;
if (tableSize
&& read_pointer(&ptr, end, hdr[1])
== (unsigned long)table->address
&& (i = read_pointer(&ptr, end, hdr[2])) > 0
&& i == (end - ptr) / (2 * tableSize)
&& !((end - ptr) % (2 * tableSize))) {
do {
const u8 *cur = ptr + (i / 2) * (2 * tableSize);
startLoc = read_pointer(&cur,
cur + tableSize,
hdr[3]);
if (pc < startLoc)
i /= 2;
else {
ptr = cur - tableSize;
i = (i + 1) / 2;
}
} while (startLoc && i > 1);
if (i == 1
&& (startLoc = read_pointer(&ptr,
ptr + tableSize,
hdr[3])) != 0
&& pc >= startLoc)
fde = (void *)read_pointer(&ptr,
ptr + tableSize,
hdr[3]);
}
}
if (fde != NULL) {
cie = cie_for_fde(fde, table);
ptr = (const u8 *)(fde + 2);
startLoc = read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType);
endLoc = startLoc
+ read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType & DW_EH_PE_indirect
? ptrType
: ptrType & (DW_EH_PE_FORM|DW_EH_PE_signed));
if (pc >= startLoc && pc < endLoc)
break;
cie = NULL;
if(cie != NULL
&& cie != &bad_cie
&& cie != &not_fde
&& (ptrType = fde_pointer_type(cie)) >= 0
&& read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType) == startLoc) {
if (!(ptrType & DW_EH_PE_indirect))
ptrType &= DW_EH_PE_FORM|DW_EH_PE_signed;
endLoc = startLoc
+ read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType);
if(pc >= endLoc)
fde = NULL;
} else
fde = NULL;
}
if (fde == NULL) {
for (fde = table->address, tableSize = table->size;
cie = NULL, tableSize > sizeof(*fde)
&& tableSize - sizeof(*fde) >= *fde;
tableSize -= sizeof(*fde) + *fde,
fde += 1 + *fde / sizeof(*fde)) {
cie = cie_for_fde(fde, table);
if (cie == &bad_cie) {
cie = NULL;
break;
}
if (cie == NULL
|| cie == &not_fde
|| (ptrType = fde_pointer_type(cie)) < 0)
continue;
ptr = (const u8 *)(fde + 2);
startLoc = read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType);
if (!startLoc)
continue;
if (!(ptrType & DW_EH_PE_indirect))
ptrType &= DW_EH_PE_FORM|DW_EH_PE_signed;
endLoc = startLoc
+ read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType);
if (pc >= startLoc && pc < endLoc)
break;
}
}
}
if (cie != NULL) {