[Qemu-devel] [RFC] [PATCH] linux-user: implement m68k atomic syscalls

[Qemu-devel] [RFC] [PATCH] linux-user: implement m68k atomic syscalls

[riku.voipio]

From: Riku Voipio <riku.voipio@linaro.org>

With nptl enabled, atomic_cmpxchg_32 and atomic_barrier
system calls are needed. This patch enabled really dummy
versions of the system calls, modeled after the m68k
kernel code.

With this patch I am able to execute m68k binaries
with qemu linux-user (busybox compiled for coldfire).

Cc: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
---
 linux-user/strace.list |  6 ++++++
 linux-user/syscall.c   | 20 ++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/linux-user/strace.list b/linux-user/strace.list
index 08f115d..4377365 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -1524,3 +1524,9 @@
 #ifdef TARGET_NR_pipe2
 { TARGET_NR_pipe2, "pipe2", NULL, NULL, NULL },
 #endif
+#ifdef TARGET_NR_atomic_cmpxchg_32
+{ TARGET_NR_atomic_cmpxchg_32, "atomic_cmpxchg_32", NULL, NULL, NULL },
+#endif
+#ifdef TARGET_NR_atomic_barrier
+{ TARGET_NR_atomic_barrier, "atomic_barrier", NULL, NULL, NULL },
+#endif
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 3f6db4b..a98cec5 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8990,6 +8990,26 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         break;
     }
 #endif
+#ifdef TARGET_NR_atomic_cmpxchg_32
+    case TARGET_NR_atomic_cmpxchg_32:
+    {
+        /* should use start_exclusive from main.c */
+        abi_ulong mem_value;
+        if (get_user_u32(mem_value, arg6))
+            ret = -TARGET_EFAULT;
+        if (mem_value == arg2)
+            put_user_u32(arg1, arg6);
+        ret = mem_value;
+        break;
+    }
+#endif
+#ifdef TARGET_NR_atomic_barrier
+    case TARGET_NR_atomic_barrier:
+    {
+        /* Like the kernel implementation and the qemu arm barrier, no-op this? */
+        break;
+    }
+#endif
     default:
     unimplemented:
         gemu_log("qemu: Unsupported syscall: %d\n", num);
-- 
1.8.1.2

Re: [Qemu-devel] [RFC] [PATCH] linux-user: implement m68k atomic syscalls

[Richard Henderson]

On 07/23/2013 09:10 PM, riku.voipio@linaro.org wrote:
> +#ifdef TARGET_NR_atomic_cmpxchg_32
> +    case TARGET_NR_atomic_cmpxchg_32:
> +    {
> +        /* should use start_exclusive from main.c */
> +        abi_ulong mem_value;
> +        if (get_user_u32(mem_value, arg6))
> +            ret = -TARGET_EFAULT;
> +        if (mem_value == arg2)
> +            put_user_u32(arg1, arg6);
> +        ret = mem_value;
> +        break;
> +    }

The ret = -TARGET_FAULT doesn't do anything useful
without an associated break.

The kernel queues the expected SIGSEGV for this sort
of failure.  Would that happen here?


r~