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hurd: Clear FP exceptions before calling signal handler 

This avoids SIGFPE handlers (or code longjmp-ed to) getting disturbed by the
exception that generated it.

Note: gcc's unwinding depends on the rpc_wait_trampoline/trampoline exact
code, so we here avoid breaking it.
This commit is contained in:
Samuel Thibault 2025-04-21 19:58:04 +02:00
parent 0f2df19d95
commit 0d99714680
1 changed files with 10 additions and 4 deletions
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14
sysdeps/mach/hurd/x86/trampoline.c
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@ -461,7 +461,10 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, const struct sigaction *action
- in gdb: gdb/i386-gnu-tdep.c gnu_sigtramp_code. */ - in gdb: gdb/i386-gnu-tdep.c gnu_sigtramp_code. */
#ifdef __x86_64__ #ifdef __x86_64__
asm ("rpc_wait_trampoline:\n" asm ("trampoline:\n"
"fnclex\n" /* Clear any pending exception. */
"jmp _trampoline\n"
"rpc_wait_trampoline:\n"
/* This is the entry point when we have an RPC reply message to receive /* This is the entry point when we have an RPC reply message to receive
before running the handler. The MACH_MSG_SEND bit has already been before running the handler. The MACH_MSG_SEND bit has already been
cleared in the OPTION argument in our %rsi. The interrupted user cleared in the OPTION argument in our %rsi. The interrupted user
@ -480,7 +483,7 @@ asm ("rpc_wait_trampoline:\n"
/* Switch to the signal stack. */ /* Switch to the signal stack. */
"movq %rbx, %rsp\n" "movq %rbx, %rsp\n"
"trampoline:\n" "_trampoline:\n"
/* Entry point for running the handler normally. The arguments to the /* Entry point for running the handler normally. The arguments to the
handler function are on the top of the stack, same as in the i386 handler function are on the top of the stack, same as in the i386
version: version:
@ -506,7 +509,10 @@ asm ("rpc_wait_trampoline:\n"
"movq 16(%rsp), %rdi\n" "movq 16(%rsp), %rdi\n"
"ret"); "ret");
#else #else
asm ("rpc_wait_trampoline:\n"); asm ("trampoline:\n"
"fnclex\n" /* Clear any pending exception. */
"jmp _trampoline\n"
"rpc_wait_trampoline:\n");
/* This is the entry point when we have an RPC reply message to receive /* This is the entry point when we have an RPC reply message to receive
before running the handler. The MACH_MSG_SEND bit has already been before running the handler. The MACH_MSG_SEND bit has already been
cleared in the OPTION argument on our stack. The interrupted user cleared in the OPTION argument on our stack. The interrupted user
@ -526,7 +532,7 @@ asm (/* Retry the interrupted mach_msg system call. */
/* Switch to the signal stack. */ /* Switch to the signal stack. */
"movl %ebx, %esp\n"); "movl %ebx, %esp\n");
asm ("trampoline:\n"); asm ("_trampoline:\n");
/* Entry point for running the handler normally. The arguments to the /* Entry point for running the handler normally. The arguments to the
handler function are already on the top of the stack: handler function are already on the top of the stack: