From 0d9971468087c77e8727638123ae4aa60724e0ff Mon Sep 17 00:00:00 2001 From: Samuel Thibault Date: Mon, 21 Apr 2025 19:58:04 +0200 Subject: [PATCH] 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. --- sysdeps/mach/hurd/x86/trampoline.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/sysdeps/mach/hurd/x86/trampoline.c b/sysdeps/mach/hurd/x86/trampoline.c index 02510b178c..6f23c567da 100644 --- a/sysdeps/mach/hurd/x86/trampoline.c +++ b/sysdeps/mach/hurd/x86/trampoline.c @@ -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. */ #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 before running the handler. The MACH_MSG_SEND bit has already been 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. */ "movq %rbx, %rsp\n" - "trampoline:\n" + "_trampoline:\n" /* 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 version: @@ -506,7 +509,10 @@ asm ("rpc_wait_trampoline:\n" "movq 16(%rsp), %rdi\n" "ret"); #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 before running the handler. The MACH_MSG_SEND bit has already been 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. */ "movl %ebx, %esp\n"); - asm ("trampoline:\n"); +asm ("_trampoline:\n"); /* Entry point for running the handler normally. The arguments to the handler function are already on the top of the stack: -- 2.47.2