diff options
| -rw-r--r-- | sysdeps/mach/hurd/x86_64/sigreturn.c | 84 |
1 files changed, 46 insertions, 38 deletions
diff --git a/sysdeps/mach/hurd/x86_64/sigreturn.c b/sysdeps/mach/hurd/x86_64/sigreturn.c index f37ae119ca..94a379d382 100644 --- a/sysdeps/mach/hurd/x86_64/sigreturn.c +++ b/sysdeps/mach/hurd/x86_64/sigreturn.c @@ -24,7 +24,7 @@ unlock SS off sigstack. */ void __sigreturn2 (struct hurd_sigstate *ss, uintptr_t *usp, - struct sigcontext *scp) + mach_port_t sc_reply_port) { mach_port_t reply_port; _hurd_sigstate_unlock (ss); @@ -44,7 +44,7 @@ __sigreturn2 (struct hurd_sigstate *ss, uintptr_t *usp, if (__glibc_likely (MACH_PORT_VALID (reply_port))) (void) __mach_port_mod_refs (__mach_task_self (), reply_port, MACH_PORT_RIGHT_RECEIVE, -1); - THREAD_SETMEM (THREAD_SELF, reply_port, scp->sc_reply_port); + THREAD_SETMEM (THREAD_SELF, reply_port, sc_reply_port); asm volatile ( /* Point the stack to the register dump. */ @@ -77,6 +77,8 @@ __sigreturn (struct sigcontext *scp) { struct hurd_sigstate *ss; struct hurd_userlink *link = (void *) &scp[1]; + uintptr_t *usp; + mach_port_t sc_reply_port; if (__glibc_unlikely (scp == NULL || (scp->sc_mask & _SIG_CANT_MASK))) return __hurd_fail (EINVAL); @@ -118,42 +120,48 @@ __sigreturn (struct sigcontext *scp) in the format the i387 `frstor' instruction uses to restore it. */ asm volatile ("frstor %0" : : "m" (scp->sc_fpsave)); - { - /* There are convenient instructions to pop state off the stack, so we - copy the registers onto the user's stack, switch there, pop and - return. */ - - uintptr_t *usp = (uintptr_t *) (scp->sc_ursp - 128); - - *--usp = scp->sc_rip; - *--usp = scp->sc_rfl; - *--usp = scp->sc_rax; - *--usp = scp->sc_rcx; - *--usp = scp->sc_rdx; - *--usp = scp->sc_rbx; - *--usp = scp->sc_rbp; - *--usp = scp->sc_rsi; - *--usp = scp->sc_rdi; - *--usp = scp->sc_r15; - *--usp = scp->sc_r14; - *--usp = scp->sc_r13; - *--usp = scp->sc_r12; - *--usp = scp->sc_r11; - *--usp = scp->sc_r10; - *--usp = scp->sc_r9; - *--usp = scp->sc_r8; - - /* Switch to the user's stack that we have just prepared, and call - __sigreturn2. Clobber "memory" to make sure GCC flushes the stack - setup to actual memory. We align the stack as per the ABI, but pass - the original usp to __sigreturn2 as an argument. */ - asm volatile ("movq %1, %%rsp\n" - "andq $-16, %%rsp\n" - "call __sigreturn2" : - : "D" (ss), "S" (usp), "d" (scp) - : "memory"); - __builtin_unreachable (); - } + /* Copy the registers onto the user's stack, to be able to release the + altstack (by unlocking sigstate). Note that unless an altstack is used, + the sigcontext will itself be located on the user's stack, so we may well + be overwriting it here (or later in __sigreturn2). + + So: do this very carefully. First, load sc_reply_port, which is the only + other bit of sigcontext that __sigreturn2 needs. Then copy the registers + without reordering them, but skipping the ones we won't need. We have to + copy starting from the larger addresses down, since our register dump is + located at a larger address than the sigcontext. */ + + sc_reply_port = scp->sc_reply_port; + usp = (uintptr_t *) (scp->sc_ursp - 128); + + *--usp = scp->sc_rip; + *--usp = scp->sc_rfl; + *--usp = scp->sc_rax; + *--usp = scp->sc_rcx; + *--usp = scp->sc_rdx; + *--usp = scp->sc_rbx; + *--usp = scp->sc_rbp; + *--usp = scp->sc_rsi; + *--usp = scp->sc_rdi; + *--usp = scp->sc_r15; + *--usp = scp->sc_r14; + *--usp = scp->sc_r13; + *--usp = scp->sc_r12; + *--usp = scp->sc_r11; + *--usp = scp->sc_r10; + *--usp = scp->sc_r9; + *--usp = scp->sc_r8; + + /* Switch to the user's stack that we have just prepared, and call + __sigreturn2. Clobber "memory" to make sure GCC flushes the stack + setup to actual memory. We align the stack as per the ABI, but pass + the original usp to __sigreturn2 as an argument. */ + asm volatile ("movq %1, %%rsp\n" + "andq $-16, %%rsp\n" + "call __sigreturn2" : + : "D" (ss), "S" (usp), "d" (sc_reply_port) + : "memory"); + __builtin_unreachable (); } weak_alias (__sigreturn, sigreturn) |