Hi Namhyung:
Using perf-probe from top of Linus' tree I get a segfault on both Fedora
16 and 18 (does not crash on Fedora 20). Command used is:
perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
git bisect points to:
commit 03d89412981a7681971bc77edba1669595763030
Author: Namhyung Kim <[email protected]>
Date: Mon Apr 7 16:05:48 2014 +0900
perf probe: Use dwarf_getcfi_elf() instead of dwarf_getcfi()
Backtrace at time of crash is:
(gdb) bt
#0 parse_eh_frame_hdr (hdr=0x0, hdr_size=2596, hdr_vaddr=71788,
ehdr=0x7fffffffd390, eh_frame_vaddr=
0x7fffffffd378, table_entries=0x8808d8, table_encoding=0x8808e0 "")
at dwarf_getcfi_elf.c:79
#1 0x000000385f81615a in getcfi_scn_eh_frame (hdr_vaddr=71788,
hdr_scn=0x8839b0, shdr=0x7fffffffd2f0,
scn=<optimized out>, ehdr=0x7fffffffd390, elf=0x882b30) at
dwarf_getcfi_elf.c:231
#2 getcfi_shdr (ehdr=0x7fffffffd390, elf=0x882b30) at
dwarf_getcfi_elf.c:283
#3 dwarf_getcfi_elf (elf=0x882b30) at dwarf_getcfi_elf.c:309
#4 0x00000000004d5bac in debuginfo__find_probes (pf=0x7fffffffd4f0,
dbg=Unhandled dwarf expression opcode 0xfa
) at util/probe-finder.c:993
#5 0x00000000004d634a in debuginfo__find_trace_events (dbg=0x880840,
pev=<optimized out>, tevs=0x880f88,
max_tevs=<optimized out>) at util/probe-finder.c:1200
#6 0x00000000004aed6b in try_to_find_probe_trace_events
(target=0x881b20 "/lib64/libpthread-2.14.90.so",
max_tevs=128, tevs=0x880f88, pev=0x859b30) at util/probe-event.c:482
#7 convert_to_probe_trace_events (target=0x881b20
"/lib64/libpthread-2.14.90.so", max_tevs=128, tevs=0x880f88,
pev=0x859b30) at util/probe-event.c:2356
#8 add_perf_probe_events (pevs=<optimized out>, npevs=1, max_tevs=128,
target=
0x881b20 "/lib64/libpthread-2.14.90.so", force_add=false) at
util/probe-event.c:2391
#9 0x000000000044014f in __cmd_probe (argc=<optimized out>,
argv=0x7fffffffe2f0, prefix=Unhandled dwarf expression opcode 0xfa
)
at builtin-probe.c:488
#10 0x0000000000440313 in cmd_probe (argc=5, argv=0x7fffffffe2f0,
prefix=<optimized out>) at builtin-probe.c:506
#11 0x000000000041d133 in run_builtin (p=0x805680, argc=5,
argv=0x7fffffffe2f0) at perf.c:341
#12 0x000000000041c8b2 in handle_internal_command (argv=<optimized out>,
argc=<optimized out>) at perf.c:400
#13 run_argv (argv=<optimized out>, argcp=<optimized out>) at perf.c:444
#14 main (argc=5, argv=0x7fffffffe2f0) at perf.c:559
David
On Mon, Dec 29, 2014 at 09:39:18PM -0700, David Ahern wrote:
> Hi Namhyung:
>
> Using perf-probe from top of Linus' tree I get a segfault on both Fedora 16
> and 18 (does not crash on Fedora 20). Command used is:
>
> perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
>
> git bisect points to:
>
> commit 03d89412981a7681971bc77edba1669595763030
> Author: Namhyung Kim <[email protected]>
> Date: Mon Apr 7 16:05:48 2014 +0900
>
> perf probe: Use dwarf_getcfi_elf() instead of dwarf_getcfi()
>
It seems to be related to below commit in elfutils. We might need to
check .eh_frame section has SHT_PROGBITS. Will send a patch soon.
Thanks,
Namhyung
commit 5704c8c4fa717b6e9c2d2e4304dfbc810ad42e4b
Author: Mark Wielaard <[email protected]>
Date: Tue Jul 2 11:22:35 2013 +0200
getcfi_scn_eh_frame: Don't crash and burn when .eh_frame bits aren't there.
Trying to read non-existing bits sometimes works and normally a sanity
check will fail. But it could also lead to an unexpected crash much later
when trying to use the non-existing data.
Signed-off-by: Mark Wielaard <[email protected]>
diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 700c166..22f8b0c 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,7 @@
+2013-07-02 Mark Wielaard <[email protected]>
+
+ * dwarf_getcfi_elf.c (getcfi_shdr): Check sh_type == SHT_PROGBITS.
+
2013-06-26 Mark Wielaard <[email protected]>
* libdw_visit_scopes.c (__libdw_visit_scopes): Don't reject root
diff --git a/libdw/dwarf_getcfi_elf.c b/libdw/dwarf_getcfi_elf.c
index ba00e05..a423ef3 100644
--- a/libdw/dwarf_getcfi_elf.c
+++ b/libdw/dwarf_getcfi_elf.c
@@ -280,8 +280,13 @@ getcfi_shdr (Elf *elf, const GElf_Ehdr *ehdr)
hdr_vaddr = shdr->sh_addr;
}
else if (!strcmp (name, ".eh_frame"))
- return getcfi_scn_eh_frame (elf, ehdr, scn, shdr,
- hdr_scn, hdr_vaddr);
+ {
+ if (shdr->sh_type == SHT_PROGBITS)
+ return getcfi_scn_eh_frame (elf, ehdr, scn, shdr,
+ hdr_scn, hdr_vaddr);
+ else
+ return NULL;
+ }
}
}
> Backtrace at time of crash is:
>
> (gdb) bt
> #0 parse_eh_frame_hdr (hdr=0x0, hdr_size=2596, hdr_vaddr=71788,
> ehdr=0x7fffffffd390, eh_frame_vaddr=
> 0x7fffffffd378, table_entries=0x8808d8, table_encoding=0x8808e0 "") at
> dwarf_getcfi_elf.c:79
> #1 0x000000385f81615a in getcfi_scn_eh_frame (hdr_vaddr=71788,
> hdr_scn=0x8839b0, shdr=0x7fffffffd2f0,
> scn=<optimized out>, ehdr=0x7fffffffd390, elf=0x882b30) at
> dwarf_getcfi_elf.c:231
> #2 getcfi_shdr (ehdr=0x7fffffffd390, elf=0x882b30) at
> dwarf_getcfi_elf.c:283
> #3 dwarf_getcfi_elf (elf=0x882b30) at dwarf_getcfi_elf.c:309
> #4 0x00000000004d5bac in debuginfo__find_probes (pf=0x7fffffffd4f0,
> dbg=Unhandled dwarf expression opcode 0xfa
> ) at util/probe-finder.c:993
> #5 0x00000000004d634a in debuginfo__find_trace_events (dbg=0x880840,
> pev=<optimized out>, tevs=0x880f88,
> max_tevs=<optimized out>) at util/probe-finder.c:1200
> #6 0x00000000004aed6b in try_to_find_probe_trace_events (target=0x881b20
> "/lib64/libpthread-2.14.90.so",
> max_tevs=128, tevs=0x880f88, pev=0x859b30) at util/probe-event.c:482
> #7 convert_to_probe_trace_events (target=0x881b20
> "/lib64/libpthread-2.14.90.so", max_tevs=128, tevs=0x880f88,
> pev=0x859b30) at util/probe-event.c:2356
> #8 add_perf_probe_events (pevs=<optimized out>, npevs=1, max_tevs=128,
> target=
> 0x881b20 "/lib64/libpthread-2.14.90.so", force_add=false) at
> util/probe-event.c:2391
> #9 0x000000000044014f in __cmd_probe (argc=<optimized out>,
> argv=0x7fffffffe2f0, prefix=Unhandled dwarf expression opcode 0xfa
> )
> at builtin-probe.c:488
> #10 0x0000000000440313 in cmd_probe (argc=5, argv=0x7fffffffe2f0,
> prefix=<optimized out>) at builtin-probe.c:506
> #11 0x000000000041d133 in run_builtin (p=0x805680, argc=5,
> argv=0x7fffffffe2f0) at perf.c:341
> #12 0x000000000041c8b2 in handle_internal_command (argv=<optimized out>,
> argc=<optimized out>) at perf.c:400
> #13 run_argv (argv=<optimized out>, argcp=<optimized out>) at perf.c:444
> #14 main (argc=5, argv=0x7fffffffe2f0) at perf.c:559
>
> David
> --
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> Please read the FAQ at http://www.tux.org/lkml/
On Tue, Dec 30, 2014 at 05:47:08PM +0900, Namhyung Kim wrote:
> On Mon, Dec 29, 2014 at 09:39:18PM -0700, David Ahern wrote:
> > Hi Namhyung:
> >
> > Using perf-probe from top of Linus' tree I get a segfault on both Fedora 16
> > and 18 (does not crash on Fedora 20). Command used is:
> >
> > perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
> >
> > git bisect points to:
> >
> > commit 03d89412981a7681971bc77edba1669595763030
> > Author: Namhyung Kim <[email protected]>
> > Date: Mon Apr 7 16:05:48 2014 +0900
> >
> > perf probe: Use dwarf_getcfi_elf() instead of dwarf_getcfi()
> >
>
> It seems to be related to below commit in elfutils. We might need to
> check .eh_frame section has SHT_PROGBITS. Will send a patch soon.
>From f56964e74d60a9921214d0e2e5c3d082f5a910c1 Mon Sep 17 00:00:00 2001
From: Namhyung Kim <[email protected]>
Date: Tue, 30 Dec 2014 17:47:47 +0900
Subject: [PATCH] perf probe: Fix a segfault on old libdw
David reported that perf can segfault when adding an uprobe event like
this:
$ perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
(gdb) bt
#0 parse_eh_frame_hdr (hdr=0x0, hdr_size=2596, hdr_vaddr=71788,
ehdr=0x7fffffffd390, eh_frame_vaddr=
0x7fffffffd378, table_entries=0x8808d8, table_encoding=0x8808e0 "") at
dwarf_getcfi_elf.c:79
#1 0x000000385f81615a in getcfi_scn_eh_frame (hdr_vaddr=71788,
hdr_scn=0x8839b0, shdr=0x7fffffffd2f0, scn=<optimized out>,
ehdr=0x7fffffffd390, elf=0x882b30) at dwarf_getcfi_elf.c:231
#2 getcfi_shdr (ehdr=0x7fffffffd390, elf=0x882b30) at dwarf_getcfi_elf.c:283
#3 dwarf_getcfi_elf (elf=0x882b30) at dwarf_getcfi_elf.c:309
#4 0x00000000004d5bac in debuginfo__find_probes (pf=0x7fffffffd4f0,
dbg=Unhandled dwarf expression opcode 0xfa) at util/probe-finder.c:993
#5 0x00000000004d634a in debuginfo__find_trace_events (dbg=0x880840,
pev=<optimized out>, tevs=0x880f88, max_tevs=<optimized out>) at
util/probe-finder.c:1200
#6 0x00000000004aed6b in try_to_find_probe_trace_events (target=0x881b20
"/lib64/libpthread-2.14.90.so",
max_tevs=128, tevs=0x880f88, pev=0x859b30) at util/probe-event.c:482
#7 convert_to_probe_trace_events (target=0x881b20
"/lib64/libpthread-2.14.90.so", max_tevs=128, tevs=0x880f88,
pev=0x859b30) at util/probe-event.c:2356
#8 add_perf_probe_events (pevs=<optimized out>, npevs=1, max_tevs=128,
target=0x881b20 "/lib64/libpthread-2.14.90.so", force_add=false) at
util/probe-event.c:2391
#9 0x000000000044014f in __cmd_probe (argc=<optimized out>,
argv=0x7fffffffe2f0, prefix=Unhandled dwarf expression opcode 0xfa) at
at builtin-probe.c:488
#10 0x0000000000440313 in cmd_probe (argc=5, argv=0x7fffffffe2f0,
prefix=<optimized out>) at builtin-probe.c:506
#11 0x000000000041d133 in run_builtin (p=0x805680, argc=5,
argv=0x7fffffffe2f0) at perf.c:341
#12 0x000000000041c8b2 in handle_internal_command (argv=<optimized out>,
argc=<optimized out>) at perf.c:400
#13 run_argv (argv=<optimized out>, argcp=<optimized out>) at perf.c:444
#14 main (argc=5, argv=0x7fffffffe2f0) at perf.c:559
And I found a related commit (5704c8c4fa71 "getcfi_scn_eh_frame: Don't
crash and burn when .eh_frame bits aren't there.") in elfutils that
can lead to a unexpected crash like this. To safely use the function,
it needs to check the .eh_frame section is a PROGBITS type.
Reported-by: David Ahern <[email protected]>
Cc: Mark Wielaard <[email protected]>
Signed-off-by: Namhyung Kim <[email protected]>
---
tools/perf/util/probe-finder.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index c7918f83b300..b5247d777f0e 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -989,8 +989,24 @@ static int debuginfo__find_probes(struct debuginfo *dbg,
int ret = 0;
#if _ELFUTILS_PREREQ(0, 142)
+ Elf *elf;
+ GElf_Ehdr ehdr;
+ GElf_Shdr shdr;
+
/* Get the call frame information from this dwarf */
- pf->cfi = dwarf_getcfi_elf(dwarf_getelf(dbg->dbg));
+ elf = dwarf_getelf(dbg->dbg);
+ if (elf == NULL)
+ return -EINVAL;
+
+ if (gelf_getehdr(elf, &ehdr) == NULL)
+ return -EINVAL;
+
+ if (elf_section_by_name(elf, &ehdr, &shdr, ".eh_frame", NULL) &&
+ shdr.sh_type == SHT_PROGBITS) {
+ pf->cfi = dwarf_getcfi_elf(elf);
+ } else {
+ pf->cfi = dwarf_getcfi(dbg->dbg);
+ }
#endif
off = 0;
--
2.1.3
On 12/30/14 2:05 AM, Namhyung Kim wrote:
> From f56964e74d60a9921214d0e2e5c3d082f5a910c1 Mon Sep 17 00:00:00 2001
> From: Namhyung Kim <[email protected]>
> Date: Tue, 30 Dec 2014 17:47:47 +0900
> Subject: [PATCH] perf probe: Fix a segfault on old libdw
>
> David reported that perf can segfault when adding an uprobe event like
> this:
>
> $ perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
>
> (gdb) bt
> #0 parse_eh_frame_hdr (hdr=0x0, hdr_size=2596, hdr_vaddr=71788,
> ehdr=0x7fffffffd390, eh_frame_vaddr=
> 0x7fffffffd378, table_entries=0x8808d8, table_encoding=0x8808e0 "") at
> dwarf_getcfi_elf.c:79
> #1 0x000000385f81615a in getcfi_scn_eh_frame (hdr_vaddr=71788,
> hdr_scn=0x8839b0, shdr=0x7fffffffd2f0, scn=<optimized out>,
> ehdr=0x7fffffffd390, elf=0x882b30) at dwarf_getcfi_elf.c:231
> #2 getcfi_shdr (ehdr=0x7fffffffd390, elf=0x882b30) at dwarf_getcfi_elf.c:283
> #3 dwarf_getcfi_elf (elf=0x882b30) at dwarf_getcfi_elf.c:309
> #4 0x00000000004d5bac in debuginfo__find_probes (pf=0x7fffffffd4f0,
> dbg=Unhandled dwarf expression opcode 0xfa) at util/probe-finder.c:993
> #5 0x00000000004d634a in debuginfo__find_trace_events (dbg=0x880840,
> pev=<optimized out>, tevs=0x880f88, max_tevs=<optimized out>) at
> util/probe-finder.c:1200
> #6 0x00000000004aed6b in try_to_find_probe_trace_events (target=0x881b20
> "/lib64/libpthread-2.14.90.so",
> max_tevs=128, tevs=0x880f88, pev=0x859b30) at util/probe-event.c:482
> #7 convert_to_probe_trace_events (target=0x881b20
> "/lib64/libpthread-2.14.90.so", max_tevs=128, tevs=0x880f88,
> pev=0x859b30) at util/probe-event.c:2356
> #8 add_perf_probe_events (pevs=<optimized out>, npevs=1, max_tevs=128,
> target=0x881b20 "/lib64/libpthread-2.14.90.so", force_add=false) at
> util/probe-event.c:2391
> #9 0x000000000044014f in __cmd_probe (argc=<optimized out>,
> argv=0x7fffffffe2f0, prefix=Unhandled dwarf expression opcode 0xfa) at
> at builtin-probe.c:488
> #10 0x0000000000440313 in cmd_probe (argc=5, argv=0x7fffffffe2f0,
> prefix=<optimized out>) at builtin-probe.c:506
> #11 0x000000000041d133 in run_builtin (p=0x805680, argc=5,
> argv=0x7fffffffe2f0) at perf.c:341
> #12 0x000000000041c8b2 in handle_internal_command (argv=<optimized out>,
> argc=<optimized out>) at perf.c:400
> #13 run_argv (argv=<optimized out>, argcp=<optimized out>) at perf.c:444
> #14 main (argc=5, argv=0x7fffffffe2f0) at perf.c:559
>
> And I found a related commit (5704c8c4fa71 "getcfi_scn_eh_frame: Don't
> crash and burn when .eh_frame bits aren't there.") in elfutils that
> can lead to a unexpected crash like this. To safely use the function,
> it needs to check the .eh_frame section is a PROGBITS type.
>
> Reported-by: David Ahern <[email protected]>
> Cc: Mark Wielaard <[email protected]>
> Signed-off-by: Namhyung Kim <[email protected]>
Solves the crash for me.
Tested-by: David Ahern <[email protected]>
Thanks for the quick response, Namhyung.
David
(2014/12/30 18:05), Namhyung Kim wrote:
> On Tue, Dec 30, 2014 at 05:47:08PM +0900, Namhyung Kim wrote:
>> On Mon, Dec 29, 2014 at 09:39:18PM -0700, David Ahern wrote:
>>> Hi Namhyung:
>>>
>>> Using perf-probe from top of Linus' tree I get a segfault on both Fedora 16
>>> and 18 (does not crash on Fedora 20). Command used is:
>>>
>>> perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
>>>
>>> git bisect points to:
>>>
>>> commit 03d89412981a7681971bc77edba1669595763030
>>> Author: Namhyung Kim <[email protected]>
>>> Date: Mon Apr 7 16:05:48 2014 +0900
>>>
>>> perf probe: Use dwarf_getcfi_elf() instead of dwarf_getcfi()
>>>
>>
>> It seems to be related to below commit in elfutils. We might need to
>> check .eh_frame section has SHT_PROGBITS. Will send a patch soon.
>
>
>>From f56964e74d60a9921214d0e2e5c3d082f5a910c1 Mon Sep 17 00:00:00 2001
> From: Namhyung Kim <[email protected]>
> Date: Tue, 30 Dec 2014 17:47:47 +0900
> Subject: [PATCH] perf probe: Fix a segfault on old libdw
>
> David reported that perf can segfault when adding an uprobe event like
> this:
>
> $ perf probe -x /lib64/libc-2.14.90.so -a 'malloc size=%di'
>
> (gdb) bt
> #0 parse_eh_frame_hdr (hdr=0x0, hdr_size=2596, hdr_vaddr=71788,
> ehdr=0x7fffffffd390, eh_frame_vaddr=
> 0x7fffffffd378, table_entries=0x8808d8, table_encoding=0x8808e0 "") at
> dwarf_getcfi_elf.c:79
> #1 0x000000385f81615a in getcfi_scn_eh_frame (hdr_vaddr=71788,
> hdr_scn=0x8839b0, shdr=0x7fffffffd2f0, scn=<optimized out>,
> ehdr=0x7fffffffd390, elf=0x882b30) at dwarf_getcfi_elf.c:231
> #2 getcfi_shdr (ehdr=0x7fffffffd390, elf=0x882b30) at dwarf_getcfi_elf.c:283
> #3 dwarf_getcfi_elf (elf=0x882b30) at dwarf_getcfi_elf.c:309
> #4 0x00000000004d5bac in debuginfo__find_probes (pf=0x7fffffffd4f0,
> dbg=Unhandled dwarf expression opcode 0xfa) at util/probe-finder.c:993
> #5 0x00000000004d634a in debuginfo__find_trace_events (dbg=0x880840,
> pev=<optimized out>, tevs=0x880f88, max_tevs=<optimized out>) at
> util/probe-finder.c:1200
> #6 0x00000000004aed6b in try_to_find_probe_trace_events (target=0x881b20
> "/lib64/libpthread-2.14.90.so",
> max_tevs=128, tevs=0x880f88, pev=0x859b30) at util/probe-event.c:482
> #7 convert_to_probe_trace_events (target=0x881b20
> "/lib64/libpthread-2.14.90.so", max_tevs=128, tevs=0x880f88,
> pev=0x859b30) at util/probe-event.c:2356
> #8 add_perf_probe_events (pevs=<optimized out>, npevs=1, max_tevs=128,
> target=0x881b20 "/lib64/libpthread-2.14.90.so", force_add=false) at
> util/probe-event.c:2391
> #9 0x000000000044014f in __cmd_probe (argc=<optimized out>,
> argv=0x7fffffffe2f0, prefix=Unhandled dwarf expression opcode 0xfa) at
> at builtin-probe.c:488
> #10 0x0000000000440313 in cmd_probe (argc=5, argv=0x7fffffffe2f0,
> prefix=<optimized out>) at builtin-probe.c:506
> #11 0x000000000041d133 in run_builtin (p=0x805680, argc=5,
> argv=0x7fffffffe2f0) at perf.c:341
> #12 0x000000000041c8b2 in handle_internal_command (argv=<optimized out>,
> argc=<optimized out>) at perf.c:400
> #13 run_argv (argv=<optimized out>, argcp=<optimized out>) at perf.c:444
> #14 main (argc=5, argv=0x7fffffffe2f0) at perf.c:559
>
> And I found a related commit (5704c8c4fa71 "getcfi_scn_eh_frame: Don't
> crash and burn when .eh_frame bits aren't there.") in elfutils that
> can lead to a unexpected crash like this. To safely use the function,
> it needs to check the .eh_frame section is a PROGBITS type.
>
Looks good to me :)
> Reported-by: David Ahern <[email protected]>
> Cc: Mark Wielaard <[email protected]>
> Signed-off-by: Namhyung Kim <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
Thank you!
> ---
> tools/perf/util/probe-finder.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index c7918f83b300..b5247d777f0e 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -989,8 +989,24 @@ static int debuginfo__find_probes(struct debuginfo *dbg,
> int ret = 0;
>
> #if _ELFUTILS_PREREQ(0, 142)
> + Elf *elf;
> + GElf_Ehdr ehdr;
> + GElf_Shdr shdr;
> +
> /* Get the call frame information from this dwarf */
> - pf->cfi = dwarf_getcfi_elf(dwarf_getelf(dbg->dbg));
> + elf = dwarf_getelf(dbg->dbg);
> + if (elf == NULL)
> + return -EINVAL;
> +
> + if (gelf_getehdr(elf, &ehdr) == NULL)
> + return -EINVAL;
> +
> + if (elf_section_by_name(elf, &ehdr, &shdr, ".eh_frame", NULL) &&
> + shdr.sh_type == SHT_PROGBITS) {
> + pf->cfi = dwarf_getcfi_elf(elf);
> + } else {
> + pf->cfi = dwarf_getcfi(dbg->dbg);
> + }
> #endif
>
> off = 0;
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]
On Tue, Dec 30, 2014 at 06:05:33PM +0900, Namhyung Kim wrote:
> And I found a related commit (5704c8c4fa71 "getcfi_scn_eh_frame: Don't
> crash and burn when .eh_frame bits aren't there.") in elfutils that
> can lead to a unexpected crash like this. To safely use the function,
> it needs to check the .eh_frame section is a PROGBITS type.
Sorry about that bug. It was fixed in elfutils 0.156, released July 2013.
Latest elfutils release is 0.161.
Checking .eh_frame is SHT_PROGBITS (and not SHT_NOBITS) looks like the
correct workaround if you have to deal with older elfutils releases.
Note that dwarf_getcfi_elf gets the CFI information from the .eh_frame
section associated with the ELF file underlying the Dwarf dbg and needs
to be released with a call to dwarf_cfi_end (). dwarf_getcfi () gets the
CFI information from the .debug_frame section data of the Dwarf dbg
and gets automatically releassed when dwarf_end () is called (you should
not call dwarf_cfi_end () on the result).
If the Dwarf dbg handle is associated with a separate debuginfo file,
then the .eh_frame section data will not be available (has SHT_NOBITS)
and you can get the .eh_frame section (and call dwarf_getcfi_elf ()) on
the original ELF file from which the Dwarf debuginfo file was split off.
In your patch you call dwarf_getcfi () as backup to get some CFI
information when you cannot call dwarf_getcfi_elf (). In general it
might make sense to also do this when dwarf_getcfi_elf fails. Or try
to get the CFI through both .eh_frame (from the executable ELF file)
with dwarf_getcfi_elf () and .debug_frame (from the Dwarf dbg file)
with dwarf_getcfi () and try to match an address in both tables
if one or the other fails.
Cheers,
Mark