> Thanks. Any idea what might be amiss with my case where I am not seeing
> proper function parameter values while analyzing kdump generated crash
> dump with gdb. I am using following gdb and gcc versions.
>
> GNU gdb Red Hat Linux (6.1post-1.20040607.62rh)
> gcc (GCC) 3.4.3 20041212 (Red Hat 3.4.3-9.EL4)
>
Some more info. I dumped the stack contents and it seems that stack is fine
and parameters are intact on stack. So now it seems to be a matter of
how gdb is interpreting the stack contents. Any guess, what the problem is?
Why func2() and func1() are not showing right parameter values.
Unfortunately I lost the previous dump image and vmlinux. I have taken a
fresh dump and reproduced the problem again. So I am reporting all the
details again.
- Test Patch
- gdb back trace
- Raw stack dump
- Relevant vmlinux objdump output.
Thanks
Vivek
Following is the test patch I applied on 2.6.12-rc6-mm1.
---
linux-2.6.12-rc6-mm1-1M-root/kernel/ksysfs.c | 23 +++++++++++++++++++++++
1 files changed, 23 insertions(+)
diff -puN kernel/ksysfs.c~kdump-gdb-stack-debug kernel/ksysfs.c
--- linux-2.6.12-rc6-mm1-1M/kernel/ksysfs.c~kdump-gdb-stack-debug 2005-06-27 16:32:18.000000000 +0530
+++ linux-2.6.12-rc6-mm1-1M-root/kernel/ksysfs.c 2005-06-28 11:01:57.000000000 +0530
@@ -30,6 +30,19 @@ static ssize_t hotplug_seqnum_show(struc
KERNEL_ATTR_RO(hotplug_seqnum);
#endif
+int func2(int a, int *b, char c)
+{
+ printk("a=%d, b=%p, c=%c \n", a, b, c);
+ panic("Vivek: Invoked panic\n");
+ return 0;
+}
+int func1(int a, int *b, char c)
+{
+ printk("a=%d, b=%p, c=%c\n", a, b, c);
+ func2(a, b, c);
+ return 0;
+}
+
#ifdef CONFIG_KEXEC
#include <asm/kexec.h>
@@ -38,6 +51,15 @@ static ssize_t crash_notes_show(struct s
return sprintf(page, "%p\n", (void *)crash_notes);
}
KERNEL_ATTR_RO(crash_notes);
+static ssize_t stack_debug_show(struct subsystem *subsys, char *page)
+{
+ int a=20;
+ int *b=&a;
+ char c='d';
+ func1(a, b, c);
+ return sprintf(page, "%s\n", "copied");
+}
+KERNEL_ATTR_RO(stack_debug);
#endif
decl_subsys(kernel, NULL, NULL);
@@ -49,6 +71,7 @@ static struct attribute * kernel_attrs[]
#endif
#ifdef CONFIG_KEXEC
&crash_notes_attr.attr,
+ &stack_debug_attr.attr,
#endif
NULL
};
Following is the stack trace I received from gdb when it opened kdump
generated kernel dump image.
(gdb) bt
#0 0xc0113d22 in crash_get_current_regs (regs=0xec9cfe6c)
at arch/i386/kernel/crash.c:102
#1 0xc0113d9d in crash_save_self (saved_regs=0xec9cfe6c)
at arch/i386/kernel/crash.c:134
#2 0xc013d19a in crash_kexec (regs=0x3) at kernel/kexec.c:1059
#3 0xc011c999 in panic (fmt=0x3 <Address 0x3 out of bounds>)
at kernel/panic.c:86
#4 0xc014086a in func2 (a=3, b=0x3, c=100 'd') at kernel/ksysfs.c:36
#5 0xc01408a5 in func1 (a=20, b=0xc044cae8, c=100 'd') at kernel/ksysfs.c:42
#6 0xc01408f8 in stack_debug_show (subsys=0xc044cb00,
page=0x3 <Address 0x3 out of bounds>) at kernel/ksysfs.c:59
#7 0xc0198e3f in subsys_attr_show (kobj=0xc044cb18, attr=0x3,
page=0x3 <Address 0x3 out of bounds>) at fs/sysfs/file.c:30
#8 0xc0198ed8 in fill_read_buffer (dentry=0x1, buffer=0xefd9bda0)
at fs/sysfs/file.c:86
#9 0xc0198fe7 in sysfs_read_file (file=0x1,
buf=0x3 <Address 0x3 out of bounds>, count=3, ppos=0x3)
at fs/sysfs/file.c:153
#10 0xc0160599 in vfs_read (file=0xedafd560,
buf=0x804d858 <Address 0x804d858 out of bounds>, count=4096,
pos=0xec9cffa4) at fs/read_write.c:238
#11 0xc0160871 in sys_read (fd=3, buf=0x3 <Address 0x3 out of bounds>, count=3)
at fs/read_write.c:321
Following is the raw stack dump. I have tried segregating/mapping calls to
func1 and func2.
(gdb) info registers
eax 0x3 3
ecx 0xec9cfe6c -325255572
edx 0x1 1
ebx 0xec9cfe6c -325255572
esp 0xec9cfe60 0xec9cfe60
ebp 0xc044cae8 0xc044cae8
esi 0x3 3
edi 0x14 20
eip 0xc0113d22 0xc0113d22
eflags 0x46 70
cs 0x60 96
ss 0x68 104
ds 0x7b 123
es 0x7b 123
fs 0x0 0
gs 0x33 51
(gdb) x/100x 0xec9cfe60
0xec9cfe60: 0xc0113d9d 0xec9cfe6c 0x00000003 0xec9cfe6c
0xec9cfe70: 0xec9cfe6c 0x00000001 0x00000003 0x00000000
0xec9cfe80: 0xc044c000 0x00000003 0x00000000 0xc0113a75
0xec9cfe90: 0x00000004 0x013ef000 0x01455498 0x00000001
0xec9cfea0: 0x013ef000 0xefc948a0 0xec9cff1c 0x00000014
0xec9cfeb0: 0xc044cae8 0xc013d19a 0xefc948a0 0x00000064
0xec9cfec0: 0xc011c999 0x00000000 0xc054e140 0xc03f3d4e
0xec9cfed0: 0xec9cfee0 0x00000064 0xc014086a 0xc03f3d39
0xec9cfee0: 0x00000014
0xec9cff1c
0x00000064
0xc01408a5 (Call to func2)
0xec9cfef0: 0x00000014 (parameter a)
0xec9cff1c (parameter b)
0x00000064 (parameter c)
0x00000064
0xec9cff00: 0xc044cb00
0xc044cb18
0xc04537a0
0xc01408f8 (Call to func1)
0xec9cff10: 0x00000014 (parameter a)
0xec9cff1c (parameter b)
0x00000064 (parameter c)
0x00000014
0xec9cff20: 0xc0198e3f 0xc044cb00 0xeccfc000 0xefd9bda0
Following is objdump output of vmlinux. (Snippet of relevant portion)
c0140836 <func2>:
c0140836: 83 ec 10 sub $0x10,%esp
c0140839: 0f be 44 24 1c movsbl 0x1c(%esp),%eax
c014083e: c7 04 24 26 3d 3f c0 movl $0xc03f3d26,(%esp)
c0140845: 89 44 24 0c mov %eax,0xc(%esp)
c0140849: 8b 44 24 18 mov 0x18(%esp),%eax
c014084d: 89 44 24 08 mov %eax,0x8(%esp)
c0140851: 8b 44 24 14 mov 0x14(%esp),%eax
c0140855: 89 44 24 04 mov %eax,0x4(%esp)
c0140859: e8 b6 c9 fd ff call c011d214 <printk>
c014085e: c7 04 24 39 3d 3f c0 movl $0xc03f3d39,(%esp)
c0140865: e8 c5 c0 fd ff call c011c92f <panic>
c014086a <func1>:
c014086a: 57 push %edi
c014086b: 56 push %esi
c014086c: 53 push %ebx
c014086d: 83 ec 10 sub $0x10,%esp
c0140870: 8b 7c 24 20 mov 0x20(%esp),%edi
c0140874: 8b 74 24 24 mov 0x24(%esp),%esi
c0140878: 0f be 5c 24 28 movsbl 0x28(%esp),%ebx
c014087d: 89 5c 24 0c mov %ebx,0xc(%esp)
c0140881: 89 74 24 08 mov %esi,0x8(%esp)
c0140885: 89 7c 24 04 mov %edi,0x4(%esp)
c0140889: c7 04 24 4f 3d 3f c0 movl $0xc03f3d4f,(%esp)
c0140890: e8 7f c9 fd ff call c011d214 <printk>
c0140895: 89 5c 24 08 mov %ebx,0x8(%esp)
c0140899: 89 74 24 04 mov %esi,0x4(%esp)
c014089d: 89 3c 24 mov %edi,(%esp)
c01408a0: e8 91 ff ff ff call c0140836 <func2>
c01408a5: 31 c0 xor %eax,%eax
c01408a7: 83 c4 10 add $0x10,%esp
c01408aa: 5b pop %ebx
c01408ab: 5e pop %esi
c01408ac: 5f pop %edi
c01408ad: c3 ret
c01408d1 <stack_debug_show>:
c01408d1: 83 ec 10 sub $0x10,%esp
c01408d4: 8d 44 24 0c lea 0xc(%esp),%eax
c01408d8: c7 44 24 0c 14 00 00 movl $0x14,0xc(%esp)
c01408df: 00
c01408e0: c7 44 24 08 64 00 00 movl $0x64,0x8(%esp)
c01408e7: 00
c01408e8: 89 44 24 04 mov %eax,0x4(%esp)
c01408ec: c7 04 24 14 00 00 00 movl $0x14,(%esp)
c01408f3: e8 72 ff ff ff call c014086a <func1>
c01408f8: 8b 44 24 18 mov 0x18(%esp),%eax
c01408fc: c7 44 24 08 6d 3d 3f movl $0xc03f3d6d,0x8(%esp)
c0140903: c0
c0140904: c7 44 24 04 36 67 40 movl $0xc0406736,0x4(%esp)
c014090b: c0
c014090c: 89 04 24 mov %eax,(%esp)
c014090f: e8 64 94 0c 00 call c0209d78 <sprintf>
c0140914: 83 c4 10 add $0x10,%esp
c0140917: c3 ret
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