linux-kernel - Re: [PATCH 09/13] powerpc: Disable KMSAN checks on functions which walk the stack

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Date:   Thu, 14 Dec 2023 09:00:40 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Nicholas Miehlbradt <nicholas@...ux.ibm.com>,
        "glider@...gle.com" <glider@...gle.com>,
        "elver@...gle.com" <elver@...gle.com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "npiggin@...il.com" <npiggin@...il.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        "iii@...ux.ibm.com" <iii@...ux.ibm.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/13] powerpc: Disable KMSAN checks on functions which
 walk the stack



Le 14/12/2023 à 06:55, Nicholas Miehlbradt a écrit :
> Functions which walk the stack read parts of the stack which cannot be
> instrumented by KMSAN e.g. the backchain. Disable KMSAN sanitization of
> these functions to prevent false positives.

Do other architectures have to do it as well ?

I don't see it for show_stack(), is that a specific need for powerpc ?

> 
> Signed-off-by: Nicholas Miehlbradt <nicholas@...ux.ibm.com>
> ---
>   arch/powerpc/kernel/process.c    |  6 +++---
>   arch/powerpc/kernel/stacktrace.c | 10 ++++++----
>   arch/powerpc/perf/callchain.c    |  2 +-
>   3 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 392404688cec..3dc88143c3b2 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -2276,9 +2276,9 @@ static bool empty_user_regs(struct pt_regs *regs, struct task_struct *tsk)
>   
>   static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;
>   
> -void __no_sanitize_address show_stack(struct task_struct *tsk,
> -				      unsigned long *stack,
> -				      const char *loglvl)
> +void __no_sanitize_address __no_kmsan_checks show_stack(struct task_struct *tsk,
> +							unsigned long *stack,
> +							const char *loglvl)
>   {
>   	unsigned long sp, ip, lr, newsp;
>   	int count = 0;
> diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
> index e6a958a5da27..369b8b2a1bcd 100644
> --- a/arch/powerpc/kernel/stacktrace.c
> +++ b/arch/powerpc/kernel/stacktrace.c
> @@ -24,8 +24,9 @@
>   
>   #include <asm/paca.h>
>   
> -void __no_sanitize_address arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
> -					   struct task_struct *task, struct pt_regs *regs)
> +void __no_sanitize_address __no_kmsan_checks
> +	arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
> +			struct task_struct *task, struct pt_regs *regs)
>   {
>   	unsigned long sp;
>   
> @@ -62,8 +63,9 @@ void __no_sanitize_address arch_stack_walk(stack_trace_consume_fn consume_entry,
>    *
>    * If the task is not 'current', the caller *must* ensure the task is inactive.
>    */
> -int __no_sanitize_address arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
> -						   void *cookie, struct task_struct *task)
> +int __no_sanitize_address __no_kmsan_checks
> +	arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, void *cookie,
> +				 struct task_struct *task)
>   {
>   	unsigned long sp;
>   	unsigned long newsp;
> diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
> index 6b4434dd0ff3..c7610b38e9b8 100644
> --- a/arch/powerpc/perf/callchain.c
> +++ b/arch/powerpc/perf/callchain.c
> @@ -40,7 +40,7 @@ static int valid_next_sp(unsigned long sp, unsigned long prev_sp)
>   	return 0;
>   }
>   
> -void __no_sanitize_address
> +void __no_sanitize_address __no_kmsan_checks
>   perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
>   {
>   	unsigned long sp, next_sp;