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[Qemu-devel] [PATCH v2 19/28] linux-user: Set r14 on exit from microblaz
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PATCH v2 19/28] linux-user: Set r14 on exit from microblaze syscall |
Date: |
Thu, 12 May 2016 18:47:43 +0100 |
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 <address@hidden>
---
I think this is clearer, anyway, but the counterargument is that
the guest can't reliably examine r14 anyway and so setting it
is unnecessary.
---
linux-user/main.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/linux-user/main.c b/linux-user/main.c
index 59b8fd5..54db9bb 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -2982,6 +2982,13 @@ 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;
--
1.9.1
- [Qemu-devel] [PATCH v2 07/28] linux-user: Support for restarting system calls for ARM targets, (continued)
- [Qemu-devel] [PATCH v2 07/28] linux-user: Support for restarting system calls for ARM targets, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 13/28] linux-user: Support for restarting system calls for UniCore32 targets, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 04/28] linux-user: Define TARGET_ERESTART* errno values, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 22/28] linux-user: Provide safe_syscall for fixing races between signals and syscalls, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 06/28] linux-user: Support for restarting system calls for x86 targets, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 02/28] linux-user: Consistently return host errnos from do_openat(), Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 27/28] linux-user: Use safe_syscall for pselect, select syscalls, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 24/28] linux-user: Use safe_syscall for open and openat system calls, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 14/28] linux-user: Support for restarting system calls for OpenRISC targets, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 19/28] linux-user: Set r14 on exit from microblaze syscall,
Peter Maydell <=
- [Qemu-devel] [PATCH v2 12/28] linux-user: Support for restarting system calls for Alpha targets, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 23/28] linux-user: Use safe_syscall for read and write system calls, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 08/28] linux-user: Support for restarting system calls for MIPS targets, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 16/28] linux-user: Support for restarting system calls for S390 targets, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 03/28] linux-user: Reindent signal handling, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 10/28] linux-user: Support for restarting system calls for SPARC targets, Peter Maydell, 2016/05/12
- [Qemu-devel] [PATCH v2 26/28] linux-user: Use safe_syscall for execve syscall, Peter Maydell, 2016/05/12