[PATCH 5.8 118/186] tracing/kprobes, x86/ptrace: Fix regs argument order for i386

From: Greg Kroah-Hartman
Date: Tue Sep 08 2020 - 15:18:54 EST

From: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@xxxxxxxxx>

commit 2356bb4b8221d7dc8c7beb810418122ed90254c9 upstream.

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@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200828113242.GA1424@cosmos
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/x86/include/asm/ptrace.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -322,8 +322,8 @@ static inline unsigned long regs_get_ker
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),
offsetof(struct pt_regs, di),