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arch/x86_64: align the user signal frame and skip the ABI red zone

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The signal frame was built inside the 128 byte red zone of the
interrupted user code and inherited its stack alignment, so a leaf
function could lose live data to the siginfo copy and the handler
could fault on an SSE access. Build the frame below the red zone,
16 byte aligned; the naked trampoline calls the handler itself and
its call provides the return address slot.

Signed-off-by: raiden00pl <raiden00@railab.me>
Assisted-by: Claude Code
This commit is contained in:
raiden00pl 2026-08-10 15:58:58 +02:00 • committed by Xiang Xiao
parent 7c43502613
commit 7815a905af
1 changed files with 17 additions and 7 deletions
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24
arch/x86_64/src/common/x86_64_syscall.c
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@ -39,6 +39,14 @@
#include "x86_64_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Red zone the System V AMD64 ABI reserves below the user stack pointer */
#define X86_64_ABI_RED_ZONE 128
/****************************************************************************
* Private Types
****************************************************************************/
@ -241,16 +249,18 @@ uint64_t *x86_64_syscall(uint64_t *regs)
rtcb->xcp.kstkptr = (uintptr_t *)regs[REG_RSP];
/* Copy "info" into user stack */
/* Create a 16 byte aligned frame for info below the red
* zone of the interrupted user code
*/
usp = rtcb->xcp.saved_ursp - 8;
/* Create a frame for info and copy the kernel info */
usp = usp - sizeof(siginfo_t);
usp = (rtcb->xcp.saved_ursp - X86_64_ABI_RED_ZONE -
sizeof(siginfo_t)) & ~0x0f;
memcpy((void *)usp, (void *)regs[REG_RSI], sizeof(siginfo_t));
/* Now set the updated SP and user copy of "info" to RSI */
/* Set the new SP and the user copy of "info" to RSI.
* The naked trampoline is entered with SP 16 byte
* aligned; its call provides the return address slot.
*/
regs[REG_RSP] = usp;
regs[REG_RSI] = usp;