diff mbox

[PULL,v2,19/38] linux-user: Set r14 on exit from microblaze syscall

Message ID d7749ab770601258be7ae862b5827c42bb35e44c.1464353863.git.riku.voipio@linaro.org
State Accepted
Commit d7749ab770601258be7ae862b5827c42bb35e44c
Headers show

Commit Message

Riku Voipio May 27, 2016, 1 p.m. UTC 
From: Peter Maydell <peter.maydell@linaro.org>


All syscall exits on microblaze result in r14 being equal to the
PC we return to, because the kernel syscall exit instruction "rtbd"
does this. (This is true even for sigreturn(); note that r14 is
not a userspace-usable register as the kernel may clobber it at
any point.)

Emulate the setting of r14 on exit; this isn't really a guest
visible change for valid guest code because r14 isn't reliably
observable anyway. However having the code and the comment helps
to explain why it's ok for the ERESTARTSYS handling not to undo
the changes to r14 that happen on syscall entry.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

---
 linux-user/main.c | 7 +++++++
 1 file changed, 7 insertions(+)

-- 
2.1.4
diff mbox

Patch

diff --git a/linux-user/main.c b/linux-user/main.c
index 4607e48..c5da418 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -2983,6 +2983,13 @@  void cpu_loop(CPUMBState *env)
                              env->regs[10],
                              0, 0);
             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
+             * not a userspace-usable register, as the kernel may clobber it
+             * at any point.)
+             */
+            env->regs[14] = env->sregs[SR_PC];
             break;
         case EXCP_HW_EXCP:
             env->regs[17] = env->sregs[SR_PC] + 4;