This patch prevents userspace() from incorrectly restoring FPU registers
after a sigreturn or rt_sigreturn system call, which has already restored
FPU registers to the state prior to the signal handler was invoked.
Fixes FPU state corruption after invoking the signal handler.
Signed-off-by: Eli Cooper <elicoo...@gmx.com>
---
arch/um/os-Linux/skas/process.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 23025d6..664f184 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -310,6 +310,8 @@ void userspace(struct uml_pt_regs *regs)
int err, status, op, pid = userspace_pid[0];
/* To prevent races if using_sysemu changes under us.*/
int local_using_sysemu;
+ /* To prevent FPU register restore after sigreturn syscalls. */
+ int skip_fp_restore = 0;
siginfo_t si;
/* Handle any immediate reschedules or signals */
@@ -328,8 +330,9 @@ void userspace(struct uml_pt_regs *regs)
if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
fatal_sigsegv();
- if (put_fp_registers(pid, regs->fp))
- fatal_sigsegv();
+ if (!skip_fp_restore)
+ if (put_fp_registers(pid, regs->fp))
+ fatal_sigsegv();
/* Now we set local_using_sysemu to be used for one loop */
local_using_sysemu = get_using_sysemu();
@@ -351,6 +354,7 @@ void userspace(struct uml_pt_regs *regs)
}
regs->is_user = 1;
+ skip_fp_restore = 0;
if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
"errno = %d\n", errno);
@@ -381,6 +385,12 @@ void userspace(struct uml_pt_regs *regs)
else handle_segv(pid, regs);
break;
case SIGTRAP + 0x80:
+#ifdef __i386__
+ if (PT_SYSCALL_NR(regs->gp) == __NR_sigreturn)
+ skip_fp_restore = 1;
+#endif
+ if (PT_SYSCALL_NR(regs->gp) ==
__NR_rt_sigreturn)
+ skip_fp_restore = 1;
handle_trap(pid, regs, local_using_sysemu);
break;
case SIGTRAP:
--
2.7.2
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