Re: [Qemu-devel] [PATCH 1/1] target-i386: fix crash on x86 32bit linux host with hw breakpoint exceptions

[Aurelien Jarno]

On Tue, Jan 26, 2010 at 04:29:50PM -0600, Jason Wessel wrote:
> If you make use of hw breakpoints on a 32bit x86 linux host, qemu
> will segmentation fault when processing the exception.
> 
> The problem is that the value of env is stored in $ebp in the op_helper
> raise_exception() function, and it can have the wrong value when
> calling it from non generated code.
> 
> It is possible to work around the problem by restoring the value of
> env before calling raise_exception() using a new helper function that
> takes (CPUState *) as one of the arguments.

Thanks, applied.

> Signed-off-by: Jason Wessel <address@hidden>
> ---
>  target-i386/exec.h      |    1 +
>  target-i386/helper.c    |    6 +++---
>  target-i386/op_helper.c |    5 +++++
>  3 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/target-i386/exec.h b/target-i386/exec.h
> index 1fd74fd..4ff3c57 100644
> --- a/target-i386/exec.h
> +++ b/target-i386/exec.h
> @@ -73,6 +73,7 @@ void do_interrupt_user(int intno, int is_int, int 
> error_code,
>                         target_ulong next_eip);
>  void QEMU_NORETURN raise_exception_err(int exception_index, int error_code);
>  void QEMU_NORETURN raise_exception(int exception_index);
> +void QEMU_NORETURN raise_exception_env(int exception_index, CPUState *nenv);
>  void do_smm_enter(void);
>  
>  /* n must be a constant to be efficient */
> diff --git a/target-i386/helper.c b/target-i386/helper.c
> index 70762bb..736ef16 100644
> --- a/target-i386/helper.c
> +++ b/target-i386/helper.c
> @@ -1529,7 +1529,7 @@ int check_hw_breakpoints(CPUState *env, int 
> force_dr6_update)
>  
>  static CPUDebugExcpHandler *prev_debug_excp_handler;
>  
> -void raise_exception(int exception_index);
> +void raise_exception_env(int exception_index, CPUState *env);
>  
>  static void breakpoint_handler(CPUState *env)
>  {
> @@ -1539,7 +1539,7 @@ static void breakpoint_handler(CPUState *env)
>          if (env->watchpoint_hit->flags & BP_CPU) {
>              env->watchpoint_hit = NULL;
>              if (check_hw_breakpoints(env, 0))
> -                raise_exception(EXCP01_DB);
> +                raise_exception_env(EXCP01_DB, env);
>              else
>                  cpu_resume_from_signal(env, NULL);
>          }
> @@ -1548,7 +1548,7 @@ static void breakpoint_handler(CPUState *env)
>              if (bp->pc == env->eip) {
>                  if (bp->flags & BP_CPU) {
>                      check_hw_breakpoints(env, 1);
> -                    raise_exception(EXCP01_DB);
> +                    raise_exception_env(EXCP01_DB, env);
>                  }
>                  break;
>              }
> diff --git a/target-i386/op_helper.c b/target-i386/op_helper.c
> index 5eea322..4bb4347 100644
> --- a/target-i386/op_helper.c
> +++ b/target-i386/op_helper.c
> @@ -1351,6 +1351,11 @@ void raise_exception(int exception_index)
>      raise_interrupt(exception_index, 0, 0, 0);
>  }
>  
> +void raise_exception_env(int exception_index, CPUState *nenv)
> +{
> +    env = nenv;
> +    raise_exception(exception_index);
> +}
>  /* SMM support */
>  
>  #if defined(CONFIG_USER_ONLY)
> -- 
> 1.6.3.3
> 
> 
> 
> 

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net