From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
To: Florian Weimer <fweimer@redhat.com>,
Joe Simmons-Talbott via Libc-alpha <libc-alpha@sourceware.org>
Cc: Joe Simmons-Talbott <josimmon@redhat.com>
Subject: Re: [PATCH 2/2] aarch64: Set the syscall register right before doing the syscall.
Date: Tue, 11 Apr 2023 11:15:28 -0300 [thread overview]
Message-ID: <c8163631-7040-a9ff-2e06-c43ded34ebb7@linaro.org> (raw)
In-Reply-To: <87h6tmil4j.fsf@oldenburg.str.redhat.com>
On 11/04/23 10:50, Florian Weimer via Libc-alpha wrote:
> * Joe Simmons-Talbott via Libc-alpha:
>
>> ({ long _sys_result; \
>> { \
>> LOAD_ARGS_##nr (args) \
>> register long _x8 asm ("x8") = (name); \
>> + if (__builtin_constant_p(name)) \
>> + asm volatile ("mov x8, " MSTR(name) ";" \
>> + : /* no output */ : "i" (name) : "x8"); \
>> asm volatile ("svc 0 // syscall " # name \
>> : "=r" (_x0) : "r"(_x8) ASM_ARGS_##nr : "memory"); \
>> _sys_result = _x0; \
>
> I think you should do this in a single assembler statement, load the
> constant only once.
Is this required because compiler is free to reorganize the argument
list? I think it should me it clear on the commit message.
Using a single assembler would require two inline asm, something like:
diff --git a/sysdeps/unix/sysv/linux/aarch64/sysdep.h b/sysdeps/unix/sysv/linux/aarch64/sysdep.h index e94d1703ad..2a128bb72d 100644 --- a/sysdeps/unix/sysv/linux/aarch64/sysdep.h +++ b/sysdeps/unix/sysv/linux/aarch64/sysdep.h @@ -172,9 +172,19 @@
({ long _sys_result; \
{ \
LOAD_ARGS_##nr (args) \
- register long _x8 asm ("x8") = (name); \
- asm volatile ("svc 0 // syscall " # name \
- : "=r" (_x0) : "r"(_x8) ASM_ARGS_##nr : "memory"); \
+ if (__builtin_constant_p (name)) \
+ asm volatile ("mov x8, %1\n" \
+ "svc 0 // syscall " # name \
+ : "=r" (_x0) \
+ : "i" (name) ASM_ARGS_##nr \
+ : "x8", "memory"); \
+ else \
+ { \
+ register long _x8 asm ("x8") = (name); \
+ asm volatile ("svc 0 // syscall " # name \
+ : "=r" (_x0) \
+ : "r"(_x8) ASM_ARGS_##nr : "memory"); \
+ } \
_sys_result = _x0; \
} \
_sys_result; })
Which really makes me doubt if this extra complexity is really necessary...
next prev parent reply other threads:[~2023-04-11 14:15 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-11 13:30 [PATCH 0/2] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-11 13:30 ` [PATCH 1/2] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-17 22:35 ` Noah Goldstein
2023-04-17 22:36 ` Noah Goldstein
2023-04-11 13:30 ` [PATCH 2/2] aarch64: " Joe Simmons-Talbott
2023-04-11 13:50 ` Florian Weimer
2023-04-11 14:15 ` Adhemerval Zanella Netto [this message]
2023-04-11 15:43 ` Szabolcs Nagy
2023-04-11 16:03 ` Florian Weimer
2023-04-11 16:39 ` Adhemerval Zanella Netto
2023-04-12 15:27 ` Joe Simmons-Talbott
2023-04-12 21:11 ` [PATCH v2 0/2] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-12 21:11 ` [PATCH v2 1/2] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-12 21:11 ` [PATCH v2 2/2] aarch64: " Joe Simmons-Talbott
2023-04-17 15:34 ` [PATCH v3 0/2] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-17 15:34 ` [PATCH v3 1/2] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-17 15:54 ` H.J. Lu
2023-04-17 16:00 ` Joe Simmons-Talbott
2023-04-17 18:38 ` H.J. Lu
2023-04-17 15:34 ` [PATCH v3 2/2] aarch64: " Joe Simmons-Talbott
2023-04-17 21:20 ` [PATCH v4 0/2] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-17 21:20 ` [PATCH v4 1/2] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-17 21:20 ` [PATCH v4 2/2] aarch64: " Joe Simmons-Talbott
2023-04-18 12:57 ` Szabolcs Nagy
2023-04-18 19:33 ` Joe Simmons-Talbott
2023-04-19 13:58 ` [PATCH v5 0/3] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-19 13:58 ` [PATCH v5 1/3] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-19 15:35 ` H.J. Lu
2023-04-19 15:48 ` Joe Simmons-Talbott
2023-04-19 13:58 ` [PATCH v5 2/3] aarch64: " Joe Simmons-Talbott
2023-04-19 14:56 ` Szabolcs Nagy
2023-04-19 15:21 ` Joe Simmons-Talbott
2023-04-19 13:58 ` [PATCH v5 3/3] nptl: Use direct syscall numbers in setxid Joe Simmons-Talbott
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