Hi Dave and all,
The attached patch read the .debug_frame section of vmlinux into
crash. By doing this, we could backtrace kernel stack frame using
dwarf unwind information contained in that section.
ChangeLog:
- Modified section_header_info() function to initialize the offset
and size of .debug_frame section.
- Modified init_unwind_table() function to read in .debug_frame.
- Modified the prototype of unwind(), adding a int argument to
indicate whether .eh_frame or .debug_frame is used. Also there're
a few changes due to the difference between these two sections.
Well, it's the first time I came to crash utility, and I hope that
I didn't do anything wrong.
Thanks,
Wang Chao
The following patch read the .debug_frame section of vmlinux into
crash. By doing this, we could backtrace kernel stack frame using
dwarf unwind information contained in that section.
ChangeLog:
- Modified section_header_info() function to initialize the offset
and size of .debug_frame section.
- Modified init_unwind_table() function to read in .debug_frame.
- Modified the prototype of unwind(), adding a int argument to
indicate whether .eh_frame or .debug_frame is used. Also there're
a few changes due to the difference between these two sections.
Signed-off-by: Wang Chao <wang.chao@xxxxxxxxxxxxxx>
---
defs.h | 2 ++
symbols.c | 8 ++++++++
unwind_x86_32_64.c | 43 ++++++++++++++++++++++++++++---------------
unwind_x86_64.h | 2 +-
4 files changed, 39 insertions(+), 16 deletions(-)
diff --git a/defs.h b/defs.h
index dcece4a..ec85279 100755
--- a/defs.h
+++ b/defs.h
@@ -1977,6 +1977,8 @@ struct symbol_table_data {
struct load_module *load_modules;
off_t dwarf_eh_frame_file_offset;
ulong dwarf_eh_frame_size;
+ off_t dwarf_debug_frame_file_offset;
+ ulong dwarf_debug_frame_size;
ulong first_ksymbol;
ulong __per_cpu_start;
ulong __per_cpu_end;
diff --git a/symbols.c b/symbols.c
index ec9c893..78fca5a 100755
--- a/symbols.c
+++ b/symbols.c
@@ -8271,6 +8271,10 @@ section_header_info(bfd *bfd, asection *section, void *reqptr)
st->dwarf_eh_frame_file_offset = (off_t)section->filepos;
st->dwarf_eh_frame_size = (ulong)bfd_section_size(bfd, section);
}
+ if (STREQ(bfd_get_section_name(bfd, section), ".debug_frame")) {
+ st->dwarf_debug_frame_file_offset = (off_t)section->filepos;
+ st->dwarf_debug_frame_size = (ulong)bfd_section_size(bfd, section);
+ }
break;
case (ulong)MODULE_SECTIONS:
@@ -8291,6 +8295,10 @@ section_header_info(bfd *bfd, asection *section, void *reqptr)
st->dwarf_eh_frame_file_offset = (off_t)section->filepos;
st->dwarf_eh_frame_size = (ulong)bfd_section_size(bfd, section);
}
+ if (STREQ(bfd_get_section_name(bfd, section), ".debug_frame")) {
+ st->dwarf_debug_frame_file_offset = (off_t)section->filepos;
+ st->dwarf_debug_frame_size = (ulong)bfd_section_size(bfd, section);
+ }
break;
default:
diff --git a/unwind_x86_32_64.c b/unwind_x86_32_64.c
index 13d86a9..754890e 100644
--- a/unwind_x86_32_64.c
+++ b/unwind_x86_32_64.c
@@ -496,7 +496,7 @@ static int processCFI(const u8 *start,
/* Unwind to previous to frame. Returns 0 if successful, negative
* number in case of an error. */
int
-unwind(struct unwind_frame_info *frame)
+unwind(struct unwind_frame_info *frame, int is_ehframe)
{
#define FRAME_REG(r, t) (((t *)frame)[reg_info[r].offs])
const u32 *fde = NULL, *cie = NULL;
@@ -527,17 +527,22 @@ unwind(struct unwind_frame_info *frame)
fde += 1 + *fde / sizeof(*fde)) {
if (!*fde || (*fde & (sizeof(*fde) - 1)))
break;
- if (!fde[1])
+ if (is_ehframe && !fde[1])
+ continue; /* this is a CIE */
+ else if (fde[1] == 0xffffffff)
continue; /* this is a CIE */
if ((fde[1] & (sizeof(*fde) - 1))
|| fde[1] > (unsigned long)(fde + 1)
- (unsigned long)unwind_table)
continue; /* this is not a valid FDE */
- cie = fde + 1 - fde[1] / sizeof(*fde);
+ if (is_ehframe)
+ cie = fde + 1 - fde[1] / sizeof(*fde);
+ else
+ cie = unwind_table + fde[1];
if (*cie <= sizeof(*cie) + 4
|| *cie >= fde[1] - sizeof(*fde)
|| (*cie & (sizeof(*cie) - 1))
- || cie[1]
+ || (cie[1] != 0xffffffff && cie[1])
|| (ptrType = fde_pointer_type(cie)) < 0) {
cie = NULL; /* this is not a (valid) CIE */
continue;
@@ -783,10 +788,13 @@ init_unwind_table(void)
try_eh_frame:
- if (st->dwarf_eh_frame_size) {
+ if (st->dwarf_eh_frame_size || st->dwarf_debug_frame_size) {
int fd;
+ int is_ehframe = (!st->dwarf_debug_frame_size &&
+ st->dwarf_eh_frame_size);
- unwind_table_size = st->dwarf_eh_frame_size;
+ unwind_table_size = is_ehframe ? st->dwarf_eh_frame_size :
+ st->dwarf_debug_frame_size;
if (!(unwind_table = malloc(unwind_table_size))) {
error(WARNING, "cannot malloc unwind table space\n");
@@ -794,18 +802,21 @@ try_eh_frame:
}
if ((fd = open(pc->namelist, O_RDONLY)) < 0) {
- error(WARNING, "cannot open %s for .eh_frame data\n",
- pc->namelist);
+ error(WARNING, "cannot open %s for %s data\n",
+ pc->namelist, is_ehframe ? ".eh_frame" : ".debug_frame");
free(unwind_table);
return;
}
- lseek(fd, st->dwarf_eh_frame_file_offset, SEEK_SET);
+ if (is_ehframe)
+ lseek(fd, st->dwarf_eh_frame_file_offset, SEEK_SET);
+ else
+ lseek(fd, st->dwarf_debug_frame_file_offset, SEEK_SET);
- if (read(fd, unwind_table, st->dwarf_eh_frame_size) !=
- st->dwarf_eh_frame_size) {
- error(WARNING, "cannot read .eh_frame data from %s\n",
- pc->namelist);
+ if (read(fd, unwind_table, unwind_table_size) !=
+ unwind_table_size) {
+ error(WARNING, "cannot read %s data from %s\n",
+ is_ehframe ? ".eh_frame" : ".debug_frame", pc->namelist);
free(unwind_table);
return;
}
@@ -1054,6 +1065,7 @@ dwarf_backtrace(struct bt_info *bt, int level, ulong stacktop)
struct syment *sp;
char *name;
struct unwind_frame_info *frame;
+ int is_ehframe = (!st->dwarf_debug_frame_size && st->dwarf_eh_frame_size);
frame = (struct unwind_frame_info *)GETBUF(sizeof(struct unwind_frame_info));
// frame->regs.rsp = bt->stkptr;
@@ -1102,7 +1114,7 @@ dwarf_backtrace(struct bt_info *bt, int level, ulong stacktop)
UNW_PC(frame), frame->regs.rbp);
while ((UNW_SP(frame) < stacktop)
- && !unwind(frame) && UNW_PC(frame)) {
+ && !unwind(frame, is_ehframe) && UNW_PC(frame)) {
/* To prevent rip pushed on IRQ stack being reported both
* both on the IRQ and process stacks
*/
@@ -1193,6 +1205,7 @@ dwarf_debug(struct bt_info *bt)
{
struct unwind_frame_info *frame;
ulong bp;
+ int is_ehframe = (!st->dwarf_debug_frame_size && st->dwarf_eh_frame_size);
if (!bt->hp->eip) {
dump_local_unwind_tables();
@@ -1220,7 +1233,7 @@ dwarf_debug(struct bt_info *bt)
sizeof(unsigned long), "reading bp", FAULT_ON_ERROR);
frame->regs.rbp = bp; /* fixme for x86 */
- unwind(frame);
+ unwind(frame, is_ehframe);
fprintf(fp, "frame size: %lx (%lx)\n",
(ulong)UNW_SP(frame), (ulong)UNW_SP(frame) - bt->hp->esp);
diff --git a/unwind_x86_64.h b/unwind_x86_64.h
index 52fcf7a..d3fae15 100644
--- a/unwind_x86_64.h
+++ b/unwind_x86_64.h
@@ -54,7 +54,7 @@ struct unwind_frame_info
struct pt_regs regs;
};
-extern int unwind(struct unwind_frame_info *);
+extern int unwind(struct unwind_frame_info *, int);
extern void init_unwind_table(void);
extern void free_unwind_table(void);
--
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