Add REGISTERS_CLOBBERED_BY_SYSCALL for x86-64
Commit Message
X86-64 system calls use a different calling convention, which clobbers
CC, %r11 an %rcx registers. Define REGISTERS_CLOBBERED_BY_SYSCALL for
x86-64 inline asm statements.
Tested on x86-64. OK for master?
H.J.
---
* sysdeps/unix/sysv/linux/x86_64/sysdep.h
(REGISTERS_CLOBBERED_BY_SYSCALL): New.
(INTERNAL_SYSCALL_NCS): Use it.
(INTERNAL_SYSCALL_NCS_TYPES): Likewise.
---
sysdeps/unix/sysv/linux/x86_64/sysdep.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
Comments
On 15 Dec 2015 12:57, H.J. Lu wrote:
> X86-64 system calls use a different calling convention, which clobbers
> CC, %r11 an %rcx registers. Define REGISTERS_CLOBBERED_BY_SYSCALL for
> x86-64 inline asm statements.
>
> Tested on x86-64. OK for master?
lgtm
-mike
"H.J. Lu" <hongjiu.lu@intel.com> writes:
> X86-64 system calls use a different calling convention, which clobbers
Different than what?
Andreas.
On Tue, Dec 15, 2015 at 3:32 PM, Andreas Schwab <schwab@linux-m68k.org> wrote:
> "H.J. Lu" <hongjiu.lu@intel.com> writes:
>
>> X86-64 system calls use a different calling convention, which clobbers
>
> Different than what?
>
Different from x86-64 function calls.
On Tue, Dec 15, 2015 at 12:57:25PM -0800, H.J. Lu wrote:
> X86-64 system calls use a different calling convention, which clobbers
> CC, %r11 an %rcx registers. Define REGISTERS_CLOBBERED_BY_SYSCALL for
> x86-64 inline asm statements.
>
> Tested on x86-64. OK for master?
I don't object, but is there a purpose to it? I agree the "different"
wording is confusing since there's normally no reason to expect
syscalls to look anything like function calls.
Rich
@@ -218,6 +218,9 @@
# undef INTERNAL_SYSCALL_DECL
# define INTERNAL_SYSCALL_DECL(err) do { } while (0)
+/* Registers clobbered by syscall. */
+# define REGISTERS_CLOBBERED_BY_SYSCALL "cc", "r11", "cx"
+
# define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \
({ \
unsigned long int resultvar; \
@@ -226,7 +229,7 @@
asm volatile ( \
"syscall\n\t" \
: "=a" (resultvar) \
- : "0" (name) ASM_ARGS_##nr : "memory", "cc", "r11", "cx"); \
+ : "0" (name) ASM_ARGS_##nr : "memory", REGISTERS_CLOBBERED_BY_SYSCALL); \
(long int) resultvar; })
# undef INTERNAL_SYSCALL
# define INTERNAL_SYSCALL(name, err, nr, args...) \
@@ -240,7 +243,7 @@
asm volatile ( \
"syscall\n\t" \
: "=a" (resultvar) \
- : "0" (name) ASM_ARGS_##nr : "memory", "cc", "r11", "cx"); \
+ : "0" (name) ASM_ARGS_##nr : "memory", REGISTERS_CLOBBERED_BY_SYSCALL); \
(long int) resultvar; })
# undef INTERNAL_SYSCALL_TYPES
# define INTERNAL_SYSCALL_TYPES(name, err, nr, args...) \