Re: [PATCH v3 10/27] linux-user/i386: Implement setup_sigtramp

2021-09-27 Thread Philippe Mathieu-Daudé 
On Tue, Sep 28, 2021 at 3:42 AM Richard Henderson
 wrote:
> On 9/24/21 2:01 PM, Philippe Mathieu-Daudé wrote:
> >> +static void install_sigtramp(void *tramp)
> >> +{
> >> +/* This is popl %eax ; movl $syscall,%eax ; int $0x80 */
> >> +__put_user(0xb858, (uint16_t *)(tramp + 0));
> >> +__put_user(TARGET_NR_sigreturn, (int *)(tramp + 2));
> >
> > I know this is mostly code movement, but using uint32_t would
> > make it easier to read.
>
> I'll give you int32_t here, since the value is signed.

Better, thanks.

>
> >> +__put_user(TARGET_NR_rt_sigreturn, (int *)(tramp + 1));
> >
> > and uint32_t.
>
> Likewise.
>
> >> +uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
> >
> > Shouldn't this be 8 + 7?
>
> Does it really matter if we write 15 or 16 bytes of this page?

Certainly not :)

Re: [PATCH v3 10/27] linux-user/i386: Implement setup_sigtramp

2021-09-27 Thread Richard Henderson 

On 9/24/21 2:01 PM, Philippe Mathieu-Daudé wrote:

+static void install_sigtramp(void *tramp)
+{
+    /* This is popl %eax ; movl $syscall,%eax ; int $0x80 */
+    __put_user(0xb858, (uint16_t *)(tramp + 0));
+    __put_user(TARGET_NR_sigreturn, (int *)(tramp + 2));


I know this is mostly code movement, but using uint32_t would
make it easier to read.


I'll give you int32_t here, since the value is signed.


+    __put_user(TARGET_NR_rt_sigreturn, (int *)(tramp + 1));


and uint32_t.


Likewise.


+    uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);


Shouldn't this be 8 + 7?


Does it really matter if we write 15 or 16 bytes of this page?


r~

Re: [PATCH v3 10/27] linux-user/i386: Implement setup_sigtramp

2021-09-24 Thread Philippe Mathieu-Daudé 

On 9/24/21 18:59, Richard Henderson wrote:

Create and record the two signal trampolines.
Use them when the guest does not use SA_RESTORER.
Note that x86_64 does not use this code.

Signed-off-by: Richard Henderson 
---
  linux-user/i386/target_signal.h   |  2 ++
  linux-user/x86_64/target_signal.h |  3 ++
  linux-user/i386/signal.c  | 56 +--
  3 files changed, 43 insertions(+), 18 deletions(-)

diff --git a/linux-user/i386/target_signal.h b/linux-user/i386/target_signal.h
index 50361af874..64d09f2e75 100644
--- a/linux-user/i386/target_signal.h
+++ b/linux-user/i386/target_signal.h
@@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
  #include "../generic/signal.h"
  
  #define TARGET_ARCH_HAS_SETUP_FRAME

+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
  #endif /* I386_TARGET_SIGNAL_H */
diff --git a/linux-user/x86_64/target_signal.h 
b/linux-user/x86_64/target_signal.h
index 4ea74f20dd..4673c5a886 100644
--- a/linux-user/x86_64/target_signal.h
+++ b/linux-user/x86_64/target_signal.h
@@ -21,4 +21,7 @@ typedef struct target_sigaltstack {
  
  #include "../generic/signal.h"
  
+/* For x86_64, use of SA_RESTORER is mandatory. */

+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
+
  #endif /* X86_64_TARGET_SIGNAL_H */
diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c
index 3b4b55fc0a..94ab6396a0 100644
--- a/linux-user/i386/signal.c
+++ b/linux-user/i386/signal.c
@@ -310,6 +310,22 @@ get_sigframe(struct target_sigaction *ka, CPUX86State 
*env, size_t frame_size)
  }
  
  #ifndef TARGET_X86_64

+static void install_sigtramp(void *tramp)
+{
+/* This is popl %eax ; movl $syscall,%eax ; int $0x80 */
+__put_user(0xb858, (uint16_t *)(tramp + 0));
+__put_user(TARGET_NR_sigreturn, (int *)(tramp + 2));


I know this is mostly code movement, but using uint32_t would
make it easier to read.


+__put_user(0x80cd, (uint16_t *)(tramp + 6));
+}
+
+static void install_rt_sigtramp(void *tramp)
+{
+/* This is movl $syscall,%eax ; int $0x80 */
+__put_user(0xb8, (char *)(tramp + 0));


Ditto uint8_t,


+__put_user(TARGET_NR_rt_sigreturn, (int *)(tramp + 1));


and uint32_t.


+__put_user(0x80cd, (uint16_t *)(tramp + 5));
+}
+
  /* compare linux/arch/i386/kernel/signal.c:setup_frame() */
  void setup_frame(int sig, struct target_sigaction *ka,
   target_sigset_t *set, CPUX86State *env)
@@ -338,16 +354,9 @@ void setup_frame(int sig, struct target_sigaction *ka,
  if (ka->sa_flags & TARGET_SA_RESTORER) {
  __put_user(ka->sa_restorer, &frame->pretcode);
  } else {
-uint16_t val16;
-abi_ulong retcode_addr;
-retcode_addr = frame_addr + offsetof(struct sigframe, retcode);
-__put_user(retcode_addr, &frame->pretcode);
-/* This is popl %eax ; movl $,%eax ; int $0x80 */
-val16 = 0xb858;
-__put_user(val16, (uint16_t *)(frame->retcode+0));
-__put_user(TARGET_NR_sigreturn, (int *)(frame->retcode+2));
-val16 = 0x80cd;
-__put_user(val16, (uint16_t *)(frame->retcode+6));
+/* This is no longer used, but is retained for ABI compatibility. */
+install_sigtramp(frame->retcode);
+__put_user(default_sigreturn, &frame->pretcode);
  }
  
  /* Set up registers for signal handler */

@@ -416,14 +425,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
  if (ka->sa_flags & TARGET_SA_RESTORER) {
  __put_user(ka->sa_restorer, &frame->pretcode);
  } else {
-uint16_t val16;
-addr = frame_addr + offsetof(struct rt_sigframe, retcode);
-__put_user(addr, &frame->pretcode);
-/* This is movl $,%eax ; int $0x80 */
-__put_user(0xb8, (char *)(frame->retcode+0));
-__put_user(TARGET_NR_rt_sigreturn, (int *)(frame->retcode+1));
-val16 = 0x80cd;
-__put_user(val16, (uint16_t *)(frame->retcode+5));
+/* This is no longer used, but is retained for ABI compatibility. */
+install_rt_sigtramp(frame->retcode);
+__put_user(default_rt_sigreturn, &frame->pretcode);
  }
  #else
  /* XXX: Would be slightly better to return -EFAULT here if test fails
@@ -592,3 +596,19 @@ badframe:
  force_sig(TARGET_SIGSEGV);
  return -TARGET_QEMU_ESIGRETURN;
  }
+
+#ifndef TARGET_X86_64
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);


Shouldn't this be 8 + 7?


+assert(tramp != NULL);
+
+default_sigreturn = sigtramp_page;
+install_sigtramp(tramp);
+
+default_rt_sigreturn = sigtramp_page + 8;
+install_rt_sigtramp(tramp + 8);
+
+unlock_user(tramp, sigtramp_page, 2 * 8);
+}
+#endif

[PATCH v3 10/27] linux-user/i386: Implement setup_sigtramp

2021-09-24 Thread Richard Henderson 
Create and record the two signal trampolines.
Use them when the guest does not use SA_RESTORER.
Note that x86_64 does not use this code.

Signed-off-by: Richard Henderson 
---
 linux-user/i386/target_signal.h   |  2 ++
 linux-user/x86_64/target_signal.h |  3 ++
 linux-user/i386/signal.c  | 56 +--
 3 files changed, 43 insertions(+), 18 deletions(-)

diff --git a/linux-user/i386/target_signal.h b/linux-user/i386/target_signal.h
index 50361af874..64d09f2e75 100644
--- a/linux-user/i386/target_signal.h
+++ b/linux-user/i386/target_signal.h
@@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
 #include "../generic/signal.h"
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* I386_TARGET_SIGNAL_H */
diff --git a/linux-user/x86_64/target_signal.h 
b/linux-user/x86_64/target_signal.h
index 4ea74f20dd..4673c5a886 100644
--- a/linux-user/x86_64/target_signal.h
+++ b/linux-user/x86_64/target_signal.h
@@ -21,4 +21,7 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+/* For x86_64, use of SA_RESTORER is mandatory. */
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
+
 #endif /* X86_64_TARGET_SIGNAL_H */
diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c
index 3b4b55fc0a..94ab6396a0 100644
--- a/linux-user/i386/signal.c
+++ b/linux-user/i386/signal.c
@@ -310,6 +310,22 @@ get_sigframe(struct target_sigaction *ka, CPUX86State 
*env, size_t frame_size)
 }
 
 #ifndef TARGET_X86_64
+static void install_sigtramp(void *tramp)
+{
+/* This is popl %eax ; movl $syscall,%eax ; int $0x80 */
+__put_user(0xb858, (uint16_t *)(tramp + 0));
+__put_user(TARGET_NR_sigreturn, (int *)(tramp + 2));
+__put_user(0x80cd, (uint16_t *)(tramp + 6));
+}
+
+static void install_rt_sigtramp(void *tramp)
+{
+/* This is movl $syscall,%eax ; int $0x80 */
+__put_user(0xb8, (char *)(tramp + 0));
+__put_user(TARGET_NR_rt_sigreturn, (int *)(tramp + 1));
+__put_user(0x80cd, (uint16_t *)(tramp + 5));
+}
+
 /* compare linux/arch/i386/kernel/signal.c:setup_frame() */
 void setup_frame(int sig, struct target_sigaction *ka,
  target_sigset_t *set, CPUX86State *env)
@@ -338,16 +354,9 @@ void setup_frame(int sig, struct target_sigaction *ka,
 if (ka->sa_flags & TARGET_SA_RESTORER) {
 __put_user(ka->sa_restorer, &frame->pretcode);
 } else {
-uint16_t val16;
-abi_ulong retcode_addr;
-retcode_addr = frame_addr + offsetof(struct sigframe, retcode);
-__put_user(retcode_addr, &frame->pretcode);
-/* This is popl %eax ; movl $,%eax ; int $0x80 */
-val16 = 0xb858;
-__put_user(val16, (uint16_t *)(frame->retcode+0));
-__put_user(TARGET_NR_sigreturn, (int *)(frame->retcode+2));
-val16 = 0x80cd;
-__put_user(val16, (uint16_t *)(frame->retcode+6));
+/* This is no longer used, but is retained for ABI compatibility. */
+install_sigtramp(frame->retcode);
+__put_user(default_sigreturn, &frame->pretcode);
 }
 
 /* Set up registers for signal handler */
@@ -416,14 +425,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 if (ka->sa_flags & TARGET_SA_RESTORER) {
 __put_user(ka->sa_restorer, &frame->pretcode);
 } else {
-uint16_t val16;
-addr = frame_addr + offsetof(struct rt_sigframe, retcode);
-__put_user(addr, &frame->pretcode);
-/* This is movl $,%eax ; int $0x80 */
-__put_user(0xb8, (char *)(frame->retcode+0));
-__put_user(TARGET_NR_rt_sigreturn, (int *)(frame->retcode+1));
-val16 = 0x80cd;
-__put_user(val16, (uint16_t *)(frame->retcode+5));
+/* This is no longer used, but is retained for ABI compatibility. */
+install_rt_sigtramp(frame->retcode);
+__put_user(default_rt_sigreturn, &frame->pretcode);
 }
 #else
 /* XXX: Would be slightly better to return -EFAULT here if test fails
@@ -592,3 +596,19 @@ badframe:
 force_sig(TARGET_SIGSEGV);
 return -TARGET_QEMU_ESIGRETURN;
 }
+
+#ifndef TARGET_X86_64
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
+assert(tramp != NULL);
+
+default_sigreturn = sigtramp_page;
+install_sigtramp(tramp);
+
+default_rt_sigreturn = sigtramp_page + 8;
+install_rt_sigtramp(tramp + 8);
+
+unlock_user(tramp, sigtramp_page, 2 * 8);
+}
+#endif
-- 
2.25.1