[Qemu-devel] [PATCH] linux-user: Fix MIPS16/microMIPS signal handling

[Qemu-devel] [PATCH] linux-user: Fix MIPS16/microMIPS signal handling

[Kwok Cheung Yeung]

Signal handlers written using a compressed MIPS instruction
set will segfault when invoked.  This patch fixes this.

Switch the ISA mode on cores supporting the MIPS16/microMIPS
ISAs according to bit 0 of the signal handler address.  Clear
bit 0 of the address assigned to the PC.

Signed-off-by: Kwok Cheung Yeung <kcy@codesourcery.com>
---
 linux-user/signal.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/linux-user/signal.c b/linux-user/signal.c
index 1055507..abfb382 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -2662,6 +2662,11 @@ static void setup_frame(int sig, struct target_sigaction * ka,
     * since it returns to userland using eret
     * we cannot do this here, and we must set PC directly */
     regs->active_tc.PC = regs->active_tc.gpr[25] = ka->_sa_handler;
+    if (regs->insn_flags & (ASE_MIPS16 | ASE_MICROMIPS)) {
+        regs->hflags &= ~MIPS_HFLAG_M16;
+        regs->hflags |= (ka->_sa_handler & 1) << MIPS_HFLAG_M16_SHIFT;
+        regs->active_tc.PC &= ~(target_ulong) 1;
+    }
     unlock_user_struct(frame, frame_addr, 1);
     return;
 
@@ -2771,6 +2776,11 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
     * since it returns to userland using eret
     * we cannot do this here, and we must set PC directly */
     env->active_tc.PC = env->active_tc.gpr[25] = ka->_sa_handler;
+    if (env->insn_flags & (ASE_MIPS16 | ASE_MICROMIPS)) {
+        env->hflags &= ~MIPS_HFLAG_M16;
+        env->hflags |= (ka->_sa_handler & 1) << MIPS_HFLAG_M16_SHIFT;
+        env->active_tc.PC &= ~(target_ulong) 1;
+    }
     unlock_user_struct(frame, frame_addr, 1);
     return;
 
-- 
1.8.2.2

[Qemu-devel] [PATCH] linux-user: Fix MIPS16/microMIPS signal handling

[Kwok Cheung Yeung]

Signal handlers written using a compressed MIPS instruction
set will segfault when invoked.  This patch fixes this.

Switch the ISA mode on cores supporting the MIPS16/microMIPS
ISAs according to bit 0 of the signal handler address.  Clear
bit 0 of the address assigned to the PC.

Signed-off-by: Kwok Cheung Yeung <kcy@codesourcery.com>
---
 linux-user/signal.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/linux-user/signal.c b/linux-user/signal.c
index 1055507..abfb382 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -2662,6 +2662,11 @@ static void setup_frame(int sig, struct target_sigaction * ka,
     * since it returns to userland using eret
     * we cannot do this here, and we must set PC directly */
     regs->active_tc.PC = regs->active_tc.gpr[25] = ka->_sa_handler;
+    if (regs->insn_flags & (ASE_MIPS16 | ASE_MICROMIPS)) {
+        regs->hflags &= ~MIPS_HFLAG_M16;
+        regs->hflags |= (ka->_sa_handler & 1) << MIPS_HFLAG_M16_SHIFT;
+        regs->active_tc.PC &= ~(target_ulong) 1;
+    }
     unlock_user_struct(frame, frame_addr, 1);
     return;
 
@@ -2771,6 +2776,11 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
     * since it returns to userland using eret
     * we cannot do this here, and we must set PC directly */
     env->active_tc.PC = env->active_tc.gpr[25] = ka->_sa_handler;
+    if (env->insn_flags & (ASE_MIPS16 | ASE_MICROMIPS)) {
+        env->hflags &= ~MIPS_HFLAG_M16;
+        env->hflags |= (ka->_sa_handler & 1) << MIPS_HFLAG_M16_SHIFT;
+        env->active_tc.PC &= ~(target_ulong) 1;
+    }
     unlock_user_struct(frame, frame_addr, 1);
     return;
 
-- 
1.8.2.2

Re: [Qemu-devel] [PATCH] linux-user: Fix MIPS16/microMIPS signal handling

[Peter Maydell]

On 30 April 2013 19:09, Kwok Cheung Yeung <kcy@codesourcery.com> wrote:
> Signal handlers written using a compressed MIPS instruction
> set will segfault when invoked.  This patch fixes this.
>
> Switch the ISA mode on cores supporting the MIPS16/microMIPS
> ISAs according to bit 0 of the signal handler address.  Clear
> bit 0 of the address assigned to the PC.

Don't you also need to handle bit-0-set in restore_sigcontext
when returning from the signal? (I guess that might cause
a crash if you have a non-compressed-instruction-set signal
handler invoked while running compressed-instruction--set code.)

>
> Signed-off-by: Kwok Cheung Yeung <kcy@codesourcery.com>
> ---
>  linux-user/signal.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/linux-user/signal.c b/linux-user/signal.c
> index 1055507..abfb382 100644
> --- a/linux-user/signal.c
> +++ b/linux-user/signal.c
> @@ -2662,6 +2662,11 @@ static void setup_frame(int sig, struct target_sigaction * ka,
>      * since it returns to userland using eret
>      * we cannot do this here, and we must set PC directly */
>      regs->active_tc.PC = regs->active_tc.gpr[25] = ka->_sa_handler;
> +    if (regs->insn_flags & (ASE_MIPS16 | ASE_MICROMIPS)) {
> +        regs->hflags &= ~MIPS_HFLAG_M16;
> +        regs->hflags |= (ka->_sa_handler & 1) << MIPS_HFLAG_M16_SHIFT;
> +        regs->active_tc.PC &= ~(target_ulong) 1;
> +    }
>      unlock_user_struct(frame, frame_addr, 1);
>      return;
>
> @@ -2771,6 +2776,11 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
>      * since it returns to userland using eret
>      * we cannot do this here, and we must set PC directly */
>      env->active_tc.PC = env->active_tc.gpr[25] = ka->_sa_handler;
> +    if (env->insn_flags & (ASE_MIPS16 | ASE_MICROMIPS)) {
> +        env->hflags &= ~MIPS_HFLAG_M16;
> +        env->hflags |= (ka->_sa_handler & 1) << MIPS_HFLAG_M16_SHIFT;
> +        env->active_tc.PC &= ~(target_ulong) 1;
> +    }
>      unlock_user_struct(frame, frame_addr, 1);
>      return;
>
> --
> 1.8.2.2
>
>

-- PMM