> From:
>
> Dave Anderson <anderson@xxxxxxxxxx>
>
> To:
>
> ----- "ville mattila" <ville.mattila@xxxxxxxxxxxxx> wrote:
>
> > Hello,
> >
> > I get segementation fault from our 64-bit kernel crash
> > This crash is caused by "echo c > /proc/sys-trigger".
> > The reason seems to be that the x86_64_cpu_pda_init is
> > not called at least gdb do not break there.
> >
> > Here is a little patch that fixes it. Everyting seems to
> > work correctly. I'll provide more info if needed.
> >
> >
> > --- crash-5.0.0/x86_64.c 2010-01-06 21:38:27.000000000 +0200
> > +++ crash-5.0.0-64bit/x86_64.c 2010-01-14 08:24:13.679603706 +0200
> > @@ -6325,6 +6325,12 @@ x86_64_get_active_set(void)
> >
> > ms = machdep->machspec;
> >
> > + if (!ms->current) {
> > + error(INFO, "%s: Cannot get active set, ms->current is NULL\n",
> > + __func__);
> > + return;
> > + }
> > +
>
> That patch just masks the real problem.
>
> What kernel version is it?
>
> If it's 2.6.30 or later, then x86_64_per_cpu_init() should
> be called, otherwise x86_64_cpu_pda_init() is called. And
> whichever one that gets called should allocate the array.
>
> 2.6.30 or later kernels should show:
>
> crash> struct x8664_pda
> struct: invalid data structure reference: x8664_pda
> crash>
>
> and they will use x86_64_per_cpu_init().
>
> Kernels prior to 2.6.30 should show:
>
> crash> struct x8664_pda
> struct x8664_pda {
> struct task_struct *pcurrent;
> long unsigned int data_offset;
> long unsigned int kernelstack;
> long unsigned int oldrsp;
> long unsigned int debugstack;
> int irqcount;
> int cpunumber;
> char *irqstackptr;
> int nodenumber;
> unsigned int __softirq_pending;
> unsigned int __nmi_count;
> int mmu_state;
> struct mm_struct *active_mm;
> unsigned int apic_timer_irqs;
> }
> SIZE: 128
> crash>
>
> and they will use x86_64_cpu_pda_init().
>
> If you're having trouble with gdb, can you put some fprintf(fp, ...)
> calls in the relevant function and find out why it isn't doing
> the calloc() call?
Yes I thought so. This is a customized 2.6.31.7 kernel.org
kernel. This is a UP configuration e.g. CONFIG_SMP is n.
I think the problem is that the PER_CPU_OFF is not set.
Breakpoint 1, x86_64_per_cpu_init () at x86_64.c:797
797 if (!(kt->flags & PER_CPU_OFF))
(gdb) bt
#0 x86_64_per_cpu_init () at x86_64.c:797
#1 0x00000000004cb1c9 in x86_64_init (when=3) at x86_64.c:325
#2 0x000000000045f0cc in main_loop () at main.c:546
#3 0x0000000000544869 in captured_command_loop (data="" at ./main.c:226
#4 0x0000000000542aa4 in catch_errors (func=0x544860 <captured_command_loop>,
func_args=0x0, errstring=0x7f949c "", mask=<value optimized out>)
at exceptions.c:520
#5 0x00000000005442f6 in captured_main (data="" optimized out>)
at ./main.c:924
#6 0x0000000000542aa4 in catch_errors (func=0x543900 <captured_main>,
func_args=0x7fff2be0e3c0, errstring=0x7f949c "",
mask=<value optimized out>) at exceptions.c:520
#7 0x00000000005436ef in gdb_main_entry (argc=<value optimized out>,
argv=<value optimized out>) at ./main.c:939
#8 0x000000000045fe8e in main (argc=3, argv=0x7fff2be0e518) at main.c:517
(gdb) p/x kt->flags
$2 = 0x102000
Btw, the "struct" command caused another segementation fault.
Here is gdb bt:
(gdb) bt
#0 0x00007f74b3524a92 in strcmp () from /lib/libc.so.6
#1 0x0000000000534284 in lookup_partial_symtab (name=0x120e3c0 "x8664_pda")
at symtab.c:276
#2 0x00000000005344ed in lookup_symtab (name=0x120e3c0 "x8664_pda")
at symtab.c:228
#3 0x000000000060019d in c_lex () at c-exp.y:2149
#4 0x00000000006008f5 in c_parse_internal () at c-exp.c.tmp:1468
#5 0x00000000006022dd in c_parse () at c-exp.y:2225
#6 0x000000000055f614 in parse_exp_in_context (stringptr=0x7fffbc2f2260,
block=<value optimized out>, comma=<value optimized out>,
void_context_p=0, out_subexp=0x0) at parse.c:1094
#7 0x000000000055f924 in parse_expression (string=0x7fffbc2f2950 "x8664_pda")
at parse.c:1144
#8 0x000000000053291b in gdb_command_funnel (req=0xca2c00) at symtab.c:4992
#9 0x00000000004c1740 in gdb_interface (req=0xca2c00) at gdb_interface.c:407
#10 0x00000000004e9dca in datatype_info (name=0xb618a7 "x8664_pda",
member=0x0, dm=0x7fffbc2f3620) at symbols.c:4146
#11 0x00000000004eb1ee in arg_to_datatype (s=0xb618a7 "x8664_pda",
dm=0x7fffbc2f3620, flags=524290) at symbols.c:4867
#12 0x00000000004efa1b in cmd_datatype_common (flags=2048) at symbols.c:4664
#13 0x000000000045efd9 in exec_command () at main.c:644
#14 0x000000000045f1fa in main_loop () at main.c:603
#15 0x00000000005452a9 in captured_command_loop (data="">
at ./main.c:226
#16 0x00000000005434e4 in catch_errors (func=0x5452a0 <captured_command_loop>,
func_args=0x0, errstring=0x7f9d7c "", mask=<value optimized out>)
at exceptions.c:520
#17 0x0000000000544d36 in captured_main (data="" optimized out>)
at ./main.c:924
#18 0x00000000005434e4 in catch_errors (func=0x544340 <captured_main>,
func_args=0x7fffbc2f38b0, errstring=0x7f9d7c "",
mask=<value optimized out>) at exceptions.c:520
#19 0x000000000054412f in gdb_main_entry (argc=<value optimized out>,
argv=<value optimized out>) at ./main.c:939
#20 0x000000000045fece in main (argc=3, argv=0x7fffbc2f3a08) at main.c:517
(gdb) frame 1
#1 0x0000000000534284 in lookup_partial_symtab (name=0x120e3c0 "x8664_pda")
at symtab.c:276
276 if (FILENAME_CMP (name, pst->filename) == 0)
(gdb) p name
$4 = 0x120e3c0 "x8664_pda"
(gdb) p pst
$5 = (struct partial_symtab *) 0x14d6040
(gdb) p pst->filename
$6 = 0x0
(gdb) p *pst
$7 = {next = 0x0, filename = 0x0, fullname = 0x0, dirname = 0x0,
objfile = 0x0, section_offsets = 0x0, textlow = 0, texthigh = 0,
dependencies = 0x0, number_of_dependencies = 0, globals_offset = 0,
n_global_syms = 0, statics_offset = 0, n_static_syms = 0, symtab = 0x0,
read_symtab = 0, read_symtab_private = 0x0, readin = 0 '\0'}
(gdb)
I fixed it with the patch below:
-- crash-5.0.0/gdb-7.0/gdb/symtab.c 2010-01-15 10:41:00.919973440 +0200
+++ crash-5.0.0-64bit/gdb-7.0/gdb/symtab.c 2010-01-15 10:19:21.436128740 +0200
@@ -256,7 +256,7 @@ got_symtab:
struct partial_symtab *
lookup_partial_symtab (const char *name)
{
- struct partial_symtab *pst;
+ struct partial_symtab *pst = NULL;
struct objfile *objfile;
char *full_path = NULL;
char *real_path = NULL;
@@ -273,7 +273,7 @@ lookup_partial_symtab (const char *name)
ALL_PSYMTABS (objfile, pst)
{
- if (FILENAME_CMP (name, pst->filename) == 0)
+ if (pst->filename && FILENAME_CMP (name, pst->filename) == 0)
{
return (pst);
}
@@ -311,7 +311,7 @@ lookup_partial_symtab (const char *name)
if (lbasename (name) == name)
ALL_PSYMTABS (objfile, pst)
{
- if (FILENAME_CMP (lbasename (pst->filename), name) == 0)
+ if (pst->filename && FILENAME_CMP (lbasename (pst->filename), name) == 0)
return (pst);
}
>
> Either that, or if you can make the vmlinux/vmcore pair available
> for me to download, I can look at it.
I'll arrange this if the above information is not enough.
- Ville
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