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Re: [PATCH 10/15] riscv: Avoid clobbering register parameters in syscall

From: Palmer Dabbelt <palmerdabbelt at google dot com>
To: dj at redhat dot com
Cc: adhemerval dot zanella at linaro dot org, libc-alpha at sourceware dot org
Date: Mon, 10 Feb 2020 13:27:11 -0800 (PST)
Subject: Re: [PATCH 10/15] riscv: Avoid clobbering register parameters in syscall

On Mon, 10 Feb 2020 11:51:05 PST (-0800), dj@redhat.com wrote:


Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:

 	long int _sys_result;						\
+	long int _arg0 = (long int) (arg0);				\
 									\
 	{								\
 	register long int __a7 asm ("a7") = number;			\
-	register long int __a0 asm ("a0") = (long int) (arg0);		\
+	register long int __a0 asm ("a0") = _arg0;			\

Ok


Ya, thanks -- I found this behavior super surprising.  I'm assuming you're
commiting this one (you is Adhemerval here)?

 	long int _sys_result;						\
+	long int _arg0 = (long int) (arg0);				\
+	long int _arg1 = (long int) (arg1);				\
 									\
 	{								\
 	register long int __a7 asm ("a7") = number;			\
-	register long int __a0 asm ("a0") = (long int) (arg0);		\
-	register long int __a1 asm ("a1") = (long int) (arg1);		\
+	register long int __a0 asm ("a0") = _arg0;			\
+	register long int __a1 asm ("a1") = _arg1;			\

Ok.

 	long int _sys_result;						\
+	long int _arg0 = (long int) (arg0);				\
+	long int _arg1 = (long int) (arg1);				\
+	long int _arg2 = (long int) (arg2);				\
 									\
 	{								\
 	register long int __a7 asm ("a7") = number;			\
-	register long int __a0 asm ("a0") = (long int) (arg0);		\
-	register long int __a1 asm ("a1") = (long int) (arg1);		\
-	register long int __a2 asm ("a2") = (long int) (arg2);		\
+	register long int __a0 asm ("a0") = _arg0;			\
+	register long int __a1 asm ("a1") = _arg1;			\
+	register long int __a2 asm ("a2") = _arg2;			\

Ok.

 	long int _sys_result;						\
+	long int _arg0 = (long int) (arg0);				\
+	long int _arg1 = (long int) (arg1);				\
+	long int _arg2 = (long int) (arg2);				\
+	long int _arg3 = (long int) (arg3);				\
 									\
 	{								\
 	register long int __a7 asm ("a7") = number;			\
-	register long int __a0 asm ("a0") = (long int) (arg0);		\
-	register long int __a1 asm ("a1") = (long int) (arg1);		\
-	register long int __a2 asm ("a2") = (long int) (arg2);		\
-	register long int __a3 asm ("a3") = (long int) (arg3);		\
+	register long int __a0 asm ("a0") = _arg0;			\
+	register long int __a1 asm ("a1") = _arg1;			\
+	register long int __a2 asm ("a2") = _arg2;			\
+	register long int __a3 asm ("a3") = _arg3;			\

Ok.

 	long int _sys_result;						\
+	long int _arg0 = (long int) (arg0);				\
+	long int _arg1 = (long int) (arg1);				\
+	long int _arg2 = (long int) (arg2);				\
+	long int _arg3 = (long int) (arg3);				\
+	long int _arg4 = (long int) (arg4);				\
 									\
 	{								\
 	register long int __a7 asm ("a7") = number;			\
-	register long int __a0 asm ("a0") = (long int) (arg0);		\
-	register long int __a1 asm ("a1") = (long int) (arg1);		\
-	register long int __a2 asm ("a2") = (long int) (arg2);		\
-	register long int __a3 asm ("a3") = (long int) (arg3);		\
-	register long int __a4 asm ("a4") = (long int) (arg4);		\
+	register long int __a0 asm ("a0") = _arg0;			\
+	register long int __a1 asm ("a1") = _arg1;			\
+	register long int __a2 asm ("a2") = _arg2;			\
+	register long int __a3 asm ("a3") = _arg3;			\
+	register long int __a4 asm ("a4") = _arg4;			\

Ok

 ({ 									\
 	long int _sys_result;						\
+	long int _arg0 = (long int) (arg0);				\
+	long int _arg1 = (long int) (arg1);				\
+	long int _arg2 = (long int) (arg2);				\
+	long int _arg3 = (long int) (arg3);				\
+	long int _arg4 = (long int) (arg4);				\
+	long int _arg5 = (long int) (arg5);				\
 									\
 	{								\
 	register long int __a7 asm ("a7") = number;			\
-	register long int __a0 asm ("a0") = (long int) (arg0);		\
-	register long int __a1 asm ("a1") = (long int) (arg1);		\
-	register long int __a2 asm ("a2") = (long int) (arg2);		\
-	register long int __a3 asm ("a3") = (long int) (arg3);		\
-	register long int __a4 asm ("a4") = (long int) (arg4);		\
-	register long int __a5 asm ("a5") = (long int) (arg5);		\
+	register long int __a0 asm ("a0") = _arg0;			\
+	register long int __a1 asm ("a1") = _arg1;			\
+	register long int __a2 asm ("a2") = _arg2;			\
+	register long int __a3 asm ("a3") = _arg3;			\
+	register long int __a4 asm ("a4") = _arg4;			\
+	register long int __a5 asm ("a5") = _arg5;			\

Ok.

 	long int _sys_result;						\
+	long int _arg0 = (long int) (arg0);				\
+	long int _arg1 = (long int) (arg1);				\
+	long int _arg2 = (long int) (arg2);				\
+	long int _arg3 = (long int) (arg3);				\
+	long int _arg4 = (long int) (arg4);				\
+	long int _arg5 = (long int) (arg5);				\
+	long int _arg6 = (long int) (arg6);				\
 									\
 	{								\
 	register long int __a7 asm ("a7") = number;			\
-	register long int __a0 asm ("a0") = (long int) (arg0);		\
-	register long int __a1 asm ("a1") = (long int) (arg1);		\
-	register long int __a2 asm ("a2") = (long int) (arg2);		\
-	register long int __a3 asm ("a3") = (long int) (arg3);		\
-	register long int __a4 asm ("a4") = (long int) (arg4);		\
-	register long int __a5 asm ("a5") = (long int) (arg5);		\
-	register long int __a6 asm ("a6") = (long int) (arg6);		\
+	register long int __a0 asm ("a0") = _arg0;			\
+	register long int __a1 asm ("a1") = _arg1;			\
+	register long int __a2 asm ("a2") = _arg2;			\
+	register long int __a3 asm ("a3") = _arg3;			\
+	register long int __a4 asm ("a4") = _arg4;			\
+	register long int __a5 asm ("a5") = _arg5;			\
+	register long int __a6 asm ("a6") = _arg6;			\


Ok.

Reviewed-by: DJ Delorie <dj@redhat.com>


Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>

Thanks!

Follow-Ups:
- Re: [PATCH 10/15] riscv: Avoid clobbering register parameters in syscall
  - From: Adhemerval Zanella

References:
- Re: [PATCH 10/15] riscv: Avoid clobbering register parameters in syscall
  - From: DJ Delorie

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