Re: [Crash-utility] [PATCH] x86_64: Fix check for __per_cpu_offset initialisation
-----Original Message-----
-----Original Message-----
> Since at least kernel v2.6.30 the __per_cpu_offset gets initialized to
> __per_cpu_load. So first check if the __per_cpu_offset was set to a
> proper value before reading any per cpu variable to prevent potential
> bugs.
>
> Signed-off-by: Philipp Rudo <prudo(a)redhat.com>
Thanks for the fix.
Acked-by: Kazuhito Hagio <k-hagio-ab(a)nec.com>
Kazu
> ---
> x86_64.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/x86_64.c b/x86_64.c
> index 6eb7d67..0bb8705 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -1327,6 +1327,8 @@ x86_64_per_cpu_init(void)
> ms->stkinfo.isize = 16384;
>
> for (i = cpus = 0; i < NR_CPUS; i++) {
> + if (kt->__per_cpu_offset[i] == symbol_value("__per_cpu_load"))
> + break;
Rethought this, if __per_cpu_load is gone or renamed, crash cannot
even start. This check is not essential, so I will modify both hunks
as follows and apply.
--- a/x86_64.c
+++ b/x86_64.c
@@ -1285,6 +1285,7 @@ x86_64_per_cpu_init(void)
struct machine_specific *ms;
struct syment *irq_sp, *curr_sp, *cpu_sp, *hardirq_stack_ptr_sp;
ulong hardirq_stack_ptr;
+ ulong __per_cpu_load = 0;
ms = machdep->machspec;
@@ -1326,8 +1327,11 @@ x86_64_per_cpu_init(void)
else if (!ms->stkinfo.isize)
ms->stkinfo.isize = 16384;
+ if (kernel_symbol_exists("__per_cpu_load"))
+ __per_cpu_load = symbol_value("__per_cpu_load");
+
for (i = cpus = 0; i < NR_CPUS; i++) {
- if (kt->__per_cpu_offset[i] == symbol_value("__per_cpu_load"))
+ if (__per_cpu_load && kt->__per_cpu_offset[i] == __per_cpu_load)
break;
if (!readmem(cpu_sp->value + kt->__per_cpu_offset[i],
KVADDR, &cpunumber, sizeof(int),
Thanks,
Kazu
> if (!readmem(cpu_sp->value + kt->__per_cpu_offset[i],
> KVADDR, &cpunumber, sizeof(int),
> "cpu number (per_cpu)", QUIET|RETURN_ON_ERROR))
> @@ -5602,7 +5604,7 @@ x86_64_get_smp_cpus(void)
> return 1;
>
> for (i = cpus = 0; i < NR_CPUS; i++) {
> - if (kt->__per_cpu_offset[i] == 0)
> + if (kt->__per_cpu_offset[i] == symbol_value("__per_cpu_load"))
> break;
> if (!readmem(sp->value + kt->__per_cpu_offset[i],
> KVADDR, &cpunumber, sizeof(int),
> --
> 2.31.1
>
> --
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