[PATCH] kprobes, x86/ptrace.h: fix regs argument order for i386

[PATCH] kprobes, x86/ptrace.h: fix regs argument order for i386

[Vamshi K Sthambamkadi]

On i386, the order of parameters passed on regs is eax,edx,and ecx
(as per regparm(3) calling conventions).

Change the mapping in regs_get_kernel_argument(), so that arg1=ax
arg2=dx, and arg3=cx.

Running the selftests testcase kprobes_args_use.tc shows the result
as passed.

Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
---
 arch/x86/include/asm/ptrace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 40aa69d..d8324a2 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -327,8 +327,8 @@ static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs,
 	static const unsigned int argument_offs[] = {
 #ifdef __i386__
 		offsetof(struct pt_regs, ax),
-		offsetof(struct pt_regs, cx),
 		offsetof(struct pt_regs, dx),
+		offsetof(struct pt_regs, cx),
 #define NR_REG_ARGUMENTS 3
 #else
 		offsetof(struct pt_regs, di),
-- 
2.7.4

Re: [PATCH] kprobes, x86/ptrace.h: fix regs argument order for i386

[Masami Hiramatsu]

On Fri, 28 Aug 2020 17:02:46 +0530
Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com> wrote:

> On i386, the order of parameters passed on regs is eax,edx,and ecx
> (as per regparm(3) calling conventions).
> 
> Change the mapping in regs_get_kernel_argument(), so that arg1=ax
> arg2=dx, and arg3=cx.
> 
> Running the selftests testcase kprobes_args_use.tc shows the result
> as passed.

Good catch! BTW, this is for tracing (ftrace kprobe events), so the "tracing/kprobes:" tag is better.
Anyway,

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thank you,

> 
> Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
> ---
>  arch/x86/include/asm/ptrace.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
> index 40aa69d..d8324a2 100644
> --- a/arch/x86/include/asm/ptrace.h
> +++ b/arch/x86/include/asm/ptrace.h
> @@ -327,8 +327,8 @@ static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs,
>  	static const unsigned int argument_offs[] = {
>  #ifdef __i386__
>  		offsetof(struct pt_regs, ax),
> -		offsetof(struct pt_regs, cx),
>  		offsetof(struct pt_regs, dx),
> +		offsetof(struct pt_regs, cx),
>  #define NR_REG_ARGUMENTS 3
>  #else
>  		offsetof(struct pt_regs, di),
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH] kprobes, x86/ptrace.h: fix regs argument order for i386

[peterz]

On Fri, Aug 28, 2020 at 05:02:46PM +0530, Vamshi K Sthambamkadi wrote:
> On i386, the order of parameters passed on regs is eax,edx,and ecx
> (as per regparm(3) calling conventions).
> 
> Change the mapping in regs_get_kernel_argument(), so that arg1=ax
> arg2=dx, and arg3=cx.
> 
> Running the selftests testcase kprobes_args_use.tc shows the result
> as passed.
> 
Fixes: 3c88ee194c28 ("x86: ptrace: Add function argument access API")
> Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> ---
>  arch/x86/include/asm/ptrace.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
> index 40aa69d..d8324a2 100644
> --- a/arch/x86/include/asm/ptrace.h
> +++ b/arch/x86/include/asm/ptrace.h
> @@ -327,8 +327,8 @@ static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs,
>  	static const unsigned int argument_offs[] = {
>  #ifdef __i386__
>  		offsetof(struct pt_regs, ax),
> -		offsetof(struct pt_regs, cx),
>  		offsetof(struct pt_regs, dx),
> +		offsetof(struct pt_regs, cx),
>  #define NR_REG_ARGUMENTS 3
>  #else
>  		offsetof(struct pt_regs, di),
> -- 
> 2.7.4
> 

[tip: x86/urgent] tracing/kprobes, x86/ptrace: Fix regs argument order for i386

[tip-bot2 for Vamshi K Sthambamkadi]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     2356bb4b8221d7dc8c7beb810418122ed90254c9
Gitweb:        https://git.kernel.org/tip/2356bb4b8221d7dc8c7beb810418122ed90254c9
Author:        Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
AuthorDate:    Fri, 28 Aug 2020 17:02:46 +05:30
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Fri, 04 Sep 2020 14:40:42 +02:00

tracing/kprobes, x86/ptrace: Fix regs argument order for i386

On i386, the order of parameters passed on regs is eax,edx,and ecx
(as per regparm(3) calling conventions).

Change the mapping in regs_get_kernel_argument(), so that arg1=ax
arg2=dx, and arg3=cx.

Running the selftests testcase kprobes_args_use.tc shows the result
as passed.

Fixes: 3c88ee194c28 ("x86: ptrace: Add function argument access API")
Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200828113242.GA1424@cosmos
---
 arch/x86/include/asm/ptrace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 40aa69d..d8324a2 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -327,8 +327,8 @@ static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs,
 	static const unsigned int argument_offs[] = {
 #ifdef __i386__
 		offsetof(struct pt_regs, ax),
-		offsetof(struct pt_regs, cx),
 		offsetof(struct pt_regs, dx),
+		offsetof(struct pt_regs, cx),
 #define NR_REG_ARGUMENTS 3
 #else
 		offsetof(struct pt_regs, di),