[v2,20/28] linux-user: Support for restarting system calls for Microblaze targets

Commit Message

Peter Maydell May 12, 2016, 5:47 p.m. UTC

From: Timothy E Baldwin <[e-mail]>

Update the Microblaze main loop and sigreturn code:
 * on TARGET_ERESTARTSYS, wind guest PC backwards to repeat syscall insn
 * set all guest CPU state within signal.c code on sigreturn
 * handle TARGET_QEMU_ESIGRETURN in the main loop as the indication
   that the main loop should not touch any guest CPU state

Note that this in passing fixes a bug where we were corrupting
the guest r[3] on sigreturn with the guest's r[10] because
do_sigreturn() was returning env->regs[10] but the register for
syscall return values is env->regs[3].

Signed-off-by: Timothy Edward Baldwin <[e-mail]>
Message-id: [e-mail]
Reviewed-by: Edgar E. Iglesias <[e-mail]>
Reviewed-by: Peter Maydell <[e-mail]>
[PMM: Commit message tweaks; drop TARGET_USE_ERESTARTSYS define;
 drop whitespace changes]
Signed-off-by: Peter Maydell <[e-mail]>
---
 linux-user/main.c                     | 7 ++++++-
 linux-user/microblaze/target_signal.h | 1 +
 linux-user/signal.c                   | 2 +-
 3 files changed, 8 insertions(+), 2 deletions(-)

Patch

diff --git a/linux-user/main.c b/linux-user/main.c
index 54db9bb..c7be8e2 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -2981,7 +2981,12 @@  void cpu_loop(CPUMBState *env)
                              env->regs[9], 
                              env->regs[10],
                              0, 0);
-            env->regs[3] = ret;
+            if (ret == -TARGET_ERESTARTSYS) {
+                /* Wind back to before the syscall. */
+                env->sregs[SR_PC] -= 4;
+            } else if (ret != -TARGET_QEMU_ESIGRETURN) {
+                env->regs[3] = ret;
+            }
             /* All syscall exits result in guest r14 being equal to the
              * PC we return to, because the kernel syscall exit "rtbd" does
              * this. (This is true even for sigreturn(); note that r14 is
diff --git a/linux-user/microblaze/target_signal.h b/linux-user/microblaze/target_signal.h
index 3d1f7a7..acdf3b5 100644
--- a/linux-user/microblaze/target_signal.h
+++ b/linux-user/microblaze/target_signal.h
@@ -26,4 +26,5 @@  static inline abi_ulong get_sp_from_cpustate(CPUMBState *state)
     return state->regs[14];
 }
 
+
 #endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/signal.c b/linux-user/signal.c
index b4641df..9e85550 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -3618,7 +3618,7 @@  long do_sigreturn(CPUMBState *env)
     env->regs[14] = env->sregs[SR_PC];
 
     unlock_user_struct(frame, frame_addr, 0);
-    return env->regs[10];
+    return -TARGET_QEMU_ESIGRETURN;
 badframe:
     force_sig(TARGET_SIGSEGV);
 }