* [PATCH v2] kdb: Make memory allocations more robust
@ 2021-01-22 10:20 Sumit Garg
2021-01-22 10:33 ` Daniel Thompson
0 siblings, 1 reply; 2+ messages in thread
From: Sumit Garg @ 2021-01-22 10:20 UTC (permalink / raw)
To: kgdb-bugreport
Cc: jason.wessel, daniel.thompson, dianders, linux-kernel, Sumit Garg
Currently kdb uses in_interrupt() to determine whether it's library
code has been called from the kgdb trap handler or from a saner calling
context such as driver init. This approach is broken because
in_interrupt() alone isn't able to determine kgdb trap handler entry via
normal task context such as [1].
We can improve this by adding check for in_dbg_master() instead which
explicitly determines if we are running in debugger context.
[1] $ echo g > /proc/sysrq-trigger
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
---
Changes in v2:
- Get rid of redundant in_atomic() check.
kernel/debug/kdb/kdb_private.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index 7a4a181..344eb0d 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -231,7 +231,7 @@ extern struct task_struct *kdb_curr_task(int);
#define kdb_task_has_cpu(p) (task_curr(p))
-#define GFP_KDB (in_interrupt() ? GFP_ATOMIC : GFP_KERNEL)
+#define GFP_KDB (in_dbg_master() ? GFP_ATOMIC : GFP_KERNEL)
extern void *debug_kmalloc(size_t size, gfp_t flags);
extern void debug_kfree(void *);
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] kdb: Make memory allocations more robust
2021-01-22 10:20 [PATCH v2] kdb: Make memory allocations more robust Sumit Garg
@ 2021-01-22 10:33 ` Daniel Thompson
0 siblings, 0 replies; 2+ messages in thread
From: Daniel Thompson @ 2021-01-22 10:33 UTC (permalink / raw)
To: Sumit Garg; +Cc: kgdb-bugreport, jason.wessel, dianders, linux-kernel
On Fri, Jan 22, 2021 at 03:50:50PM +0530, Sumit Garg wrote:
> Currently kdb uses in_interrupt() to determine whether it's library
Looks like a good change just a few nitpicks with the description:
s/it's/its/
> code has been called from the kgdb trap handler or from a saner calling
> context such as driver init. This approach is broken because
> in_interrupt() alone isn't able to determine kgdb trap handler entry via
> normal task context such as [1].
Why footnote this and aren't breakpoints a far more natural reason to
enter the debugger?
The following will be clearer for backporting, etc:
... detmermine kgdb trap handler entry from normal task context. This
can happen during normal use of basic features such as breakpoints
and can also be trivially reproduced using: echo g > /proc/sysrq-trigger
>
> We can improve this by adding check for in_dbg_master() instead which
> explicitly determines if we are running in debugger context.
>
> [1] $ echo g > /proc/sysrq-trigger
>
Cc: stable@ ?
> Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Daniel.
> ---
>
> Changes in v2:
> - Get rid of redundant in_atomic() check.
>
> kernel/debug/kdb/kdb_private.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
> index 7a4a181..344eb0d 100644
> --- a/kernel/debug/kdb/kdb_private.h
> +++ b/kernel/debug/kdb/kdb_private.h
> @@ -231,7 +231,7 @@ extern struct task_struct *kdb_curr_task(int);
>
> #define kdb_task_has_cpu(p) (task_curr(p))
>
> -#define GFP_KDB (in_interrupt() ? GFP_ATOMIC : GFP_KERNEL)
> +#define GFP_KDB (in_dbg_master() ? GFP_ATOMIC : GFP_KERNEL)
>
> extern void *debug_kmalloc(size_t size, gfp_t flags);
> extern void debug_kfree(void *);
> --
> 2.7.4
>
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