Re: [Qemu-devel] [PATCH v2 08/27] linux-user/sh4: Notice gUSA regions during signal delivery

[Laurent Vivier]

Le 07/07/2017 à 04:20, Richard Henderson a écrit :
> We translate gUSA regions atomically in a parallel context.
> But in a serial context a gUSA region may be interrupted.
> In that case, restart the region as the kernel would.
> 
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  linux-user/signal.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/linux-user/signal.c b/linux-user/signal.c
> index 3d18d1b..a537778 100644
> --- a/linux-user/signal.c
> +++ b/linux-user/signal.c
> @@ -3471,6 +3471,25 @@ static abi_ulong get_sigframe(struct target_sigaction 
> *ka,
>      return (sp - frame_size) & -8ul;
>  }
>  
> +/* Notice when we're in the middle of a gUSA region and reset.
> +   Note that this will only occur for !parallel_cpus, as we will
> +   translate such sequences differently in a parallel context.  */
> +static void unwind_gusa(CPUSH4State *regs)
> +{
> +    /* If the stack pointer is sufficiently negative ... */
> +    if ((regs->gregs[15] & 0xc0000000u) == 0xc0000000u
> +        /* ... and we haven't completed the sequence ... */
> +        && regs->pc < regs->gregs[0]) {
> +        /* Reset the PC to before the gUSA region, as computed from
> +           R0 = region end, SP = -(region size), plus one more insn
> +           that actually sets SP to the region size.  */
> +        regs->pc = regs->gregs[0] + regs->gregs[15] - 2;
> +
> +        /* Reset the SP to the saved version in R1.  */
> +        regs->gregs[15] = regs->gregs[1];
> +    }
> +}
> +
>  static void setup_sigcontext(struct target_sigcontext *sc,
>                               CPUSH4State *regs, unsigned long mask)
>  {
> @@ -3534,6 +3553,8 @@ static void setup_frame(int sig, struct 
> target_sigaction *ka,
>      abi_ulong frame_addr;
>      int i;
>  
> +    unwind_gusa(regs);
> +
>      frame_addr = get_sigframe(ka, regs->gregs[15], sizeof(*frame));

I think unwind_gusa() should be moved after the get_sigfram() (in both
cases), because r15  can be updated and the sigframe base lost.

@@ -3551,9 +3552,8 @@ static void setup_frame(int sig, struct
target_sigaction *
ka,
     abi_ulong frame_addr;
     int i;

-    unwind_gusa(regs);
-
     frame_addr = get_sigframe(ka, regs->gregs[15], sizeof(*frame));
+    unwind_gusa(regs);
     trace_user_setup_frame(regs, frame_addr);
     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
         goto give_sigsegv;
@@ -3602,9 +3602,8 @@ static void setup_rt_frame(int sig, struct
target_sigaction *ka,
     abi_ulong frame_addr;
     int i;

-    unwind_gusa(regs);
-
     frame_addr = get_sigframe(ka, regs->gregs[15], sizeof(*frame));
+    unwind_gusa(regs);
     trace_user_setup_rt_frame(regs, frame_addr);
     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
         goto give_sigsegv;

Laurent