On Fri, Aug 08, 2014 at 11:56:54AM +0800, Jincheng Miao wrote:
> 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.
Thanks applied to linux-user tree for next pull request.
Riku
> Signed-off-by: Jincheng Miao <jm...@redhat.com>
> ---
> linux-user/main.c | 1 -
> target-i386/seg_helper.c | 4 ++--
> 2 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/linux-user/main.c b/linux-user/main.c
> index b453a39..472a16d 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;
> }
> }
> --
> 1.7.1
>
