diff mbox

[PULL,04/24] linux-user: Fix syscall instruction usermode emulation on X86_64

Message ID fc40b8c83ca362c4e12a69e415e6864ef88414cb.1408100160.git.riku.voipio@linaro.org
State New
Headers show

Commit Message

Riku Voipio Aug. 15, 2014, 11:01 a.m. UTC 
From: Jincheng Miao <jmiao@redhat.com>

Currently syscall instruction is buggy on user mode X86_64,
the EIP is updated after do_syscall(), that is too late for
clone(). Because clone() will create a thread at the env->EIP
(the address of syscall insn), and then child thread enters
do_syscall() again, that is not expected. Sometimes it is tragic.

User mode syscall insn emulation is not used MSR, so the
action should be same to INT 0x80. INT 0x80 will update EIP in
do_interrupt(), ditto for syscall() for consistency.

Signed-off-by: Jincheng Miao <jmiao@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
---
 linux-user/main.c        | 1 -
 target-i386/seg_helper.c | 4 ++--
 2 files changed, 2 insertions(+), 3 deletions(-)
diff mbox

Patch

diff --git a/linux-user/main.c b/linux-user/main.c
index c5878f9..bc1ff46 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -309,7 +309,6 @@  void cpu_loop(CPUX86State *env)
                                           env->regs[8],
                                           env->regs[9],
                                           0, 0);
-            env->eip = env->exception_next_eip;
             break;
 #endif
         case EXCP0B_NOSEG:
diff --git a/target-i386/seg_helper.c b/target-i386/seg_helper.c
index 2d970d0..13eefba 100644
--- a/target-i386/seg_helper.c
+++ b/target-i386/seg_helper.c
@@ -1127,8 +1127,8 @@  static void do_interrupt_user(CPUX86State *env, int intno, int is_int,
 
     /* Since we emulate only user space, we cannot do more than
        exiting the emulation with the suitable exception and error
-       code */
-    if (is_int) {
+       code. So update EIP for INT 0x80 and EXCP_SYSCALL. */
+    if (is_int || intno == EXCP_SYSCALL) {
         env->eip = next_eip;
     }
 }