[Bug threads/20293] New: bfd/elfxx-aarch64.c _bfd_aarch64_elf_grok_prstatus use error offset of pr_pid on arm64_ilp32

[nixiaoming at huawei dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20293

Bug ID: 20293
Summary: bfd/elfxx-aarch64.c _bfd_aarch64_elf_grok_prstatus
use error offset of pr_pid on arm64_ilp32
Product: gdb
Version: HEAD
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: threads
Assignee: unassigned at sourceware dot org
Reporter: nixiaoming at huawei dot com
Target Milestone: ---

When I use gdb to analysis a core generated by multithread ilp32 exe
Gdb can’t get accurate threads info.
after read gdb and linux code,
I think maybe gdb use a error pr_pid offset in function
_bfd_aarch64_elf_grok_prstatus for arm64 ilp32

Patch:
fix error offset of pr_pid on arm64_ilp32

diff --git a/bfd/elfxx-aarch64.c b/bfd/elfxx-aarch64.c
index f34ad9f..8e699cd 100644
--- a/bfd/elfxx-aarch64.c
+++ b/bfd/elfxx-aarch64.c
@@ -563,8 +563,12 @@ _bfd_aarch64_elf_grok_prstatus (bfd *abfd,
Elf_Internal_Note *note)
= bfd_get_16 (abfd, note->descdata + 12);

/* pr_pid */
+ /* ilp32 use compat_elf_prstatus, and pr_pid offset is 24
+ * (gdb) p &((struct compat_elf_prstatus*) 0)->pr_pid
+ * $1 = (compat_pid_t *) 0x18
+ */
elf_tdata (abfd)->core->lwpid
- = bfd_get_32 (abfd, note->descdata + 32);
+ = bfd_get_32 (abfd, note->descdata + 24);

/* pr_reg */
offset = 72;


test code:
ulimit -c unlimited
./mul_thread &
sleep 1
kill -11 $!

gdb ./mul_thread -c ./core-

[New LWP 1631]
[New LWP 1631]
[New LWP 1631]
[New LWP 1631]
[New LWP 1631]
[New LWP 1631]
[New LWP 1631]
[New LWP 1631]
[New LWP 1631]
[New LWP 1631]

warning: Could not load shared library symbols for
linux-ilp32-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?
Warning: couldn't activate thread debugging using libthread_db: Cannot
find new threads: debugger service failed

warning: Unable to find libthread_db matching inferior's thread
library, thread debugging will not be available.
Warning: couldn't activate thread debugging using libthread_db: Cannot
find new threads: debugger service failed

warning: Unable to find libthread_db matching inferior's thread
library, thread debugging will not be available.
Core was generated by `./mul_thread'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0xf709be70 in pthread_join () from /libilp32/libpthread.so.0
(gdb) info threads
Id Target Id Frame
* 31 LWP 1631 0xf709be70 in pthread_join () from
/libilp32/libpthread.so.0
(gdb)

objdump -h core
16 .reg/1631 00000110 00000000 00000000 00001474 2**2
CONTENTS
17 .reg2/1631 00000210 00000000 00000000 000015a0 2**2
CONTENTS
18 .reg-aarch-tls/1631 00000008 00000000 00000000 000017c4 2**2
CONTENTS
19 .reg-aarch-hw-break/1631 00000108 00000000 00000000 000017e0
2**2
CONTENTS
20 .reg-aarch-hw-watch/1631 00000108 00000000 00000000 000018fc
2**2
CONTENTS
21 .reg/1631 00000110 00000000 00000000 00001a78 2**2
CONTENTS
22 .reg2/1631 00000210 00000000 00000000 00001ba4 2**2
CONTENTS
23 .reg-aarch-tls/1631 00000008 00000000 00000000 00001dc8 2**2
CONTENTS
24 .reg-aarch-hw-break/1631 00000108 00000000 00000000 00001de4
2**2
CONTENTS
25 .reg-aarch-hw-watch/1631 00000108 00000000 00000000 00001f00
2**2
CONTENTS
26 .reg/1631 00000110 00000000 00000000 0000207c 2**2
CONTENTS
27 .reg2/1631 00000210 00000000 00000000 000021a8 2**2
CONTENTS
28 .reg-aarch-tls/1631 00000008 00000000 00000000 000023cc 2**2
CONTENTS
29 .reg-aarch-hw-break/1631 00000108 00000000 00000000 000023e8
2**2
CONTENTS
30 .reg-aarch-hw-watch/1631 00000108 00000000 00000000 00002504
2**2
CONTENTS
31 .reg/1631 00000110 00000000 00000000 00002680 2**2
CONTENTS
32 .reg2/1631 00000210 00000000 00000000 000027ac 2**2


code:
read gdb code, gdb ilp32 get pid form offset 32 of note->descdata

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=888a447e15f0f3349826358a16f7d2756b0bb226
+ /* pr_pid */
+ elf_tdata (abfd)->core->lwpid
+ = bfd_get_32 (abfd, note->descdata + 32);

But in arch/arm64/kernel/binfmt_ilp32.c, pr_pid offset is 24

https://github.com/norov/linux/blob/1a67337e3dfbae194f07d899f04042768490466f/arch/arm64/kernel/binfmt_ilp32.c
#define elf_prstatus compat_elf_prstatus

(gdb) p &((struct compat_elf_prstatus*) 0)->pr_pid
$1 = (compat_pid_t *) 0x18

So, maybe we should update offset here

[alahay01 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=20293

--- Comment #1 from Alan Hayward <alahay01 at gcc dot gnu.org> ---
*** Bug 20294 has been marked as a duplicate of this bug. ***