[Qemu-devel] [PULL 20/38] linux-user: Support for restarting system calls for Microblaze targets

[riku . voipio]

From: Timothy E Baldwin <address@hidden>

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

diff --git a/linux-user/main.c b/linux-user/main.c
index aa6b414..40aea6e 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -2982,7 +2982,12 @@ 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);
 }
-- 
2.1.4