[Qemu-devel] [PATCH 10/10] alpha-linux-user: Fix the getpriority syscall

[Richard Henderson <rth@twiddle.net>]

Alpha uses unbiased priority values in the syscall, with the a3
return value signaling error conditions.  Therefore, properly
interpret the libc getpriority as needed for the guest rather
than passing the host value through unchanged.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 linux-user/syscall.c |   20 +++++++++++++++-----
 1 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 2e1c1c0..b487635 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -218,7 +218,6 @@ _syscall3(int, sys_getdents, uint, fd, struct linux_dirent *, dirp, uint, count)
 #if defined(TARGET_NR_getdents64) && defined(__NR_getdents64)
 _syscall3(int, sys_getdents64, uint, fd, struct linux_dirent64 *, dirp, uint, count);
 #endif
-_syscall2(int, sys_getpriority, int, which, int, who);
 #if defined(TARGET_NR__llseek) && defined(__NR_llseek)
 _syscall5(int, _llseek,  uint,  fd, ulong, hi, ulong, lo,
           loff_t *, res, uint, wh);
@@ -6445,10 +6444,21 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         break;
 #endif
     case TARGET_NR_getpriority:
-        /* libc does special remapping of the return value of
-         * sys_getpriority() so it's just easiest to call
-         * sys_getpriority() directly rather than through libc. */
-        ret = get_errno(sys_getpriority(arg1, arg2));
+        /* Note that negative values are valid for getpriority, so we must
+           differentiate based on errno settings.  */
+        errno = 0;
+        ret = getpriority(arg1, arg2);
+        if (ret == -1 && errno != 0) {
+            ret = get_errno(errno);
+            break;
+        }
+#ifdef TARGET_ALPHA
+        /* Return value is the unbiased priority.  Signal no error.  */
+        ((CPUAlphaState *)cpu_env)->ir[IR_V0] = 0;
+#else
+        /* Return value is a biased priority to avoid negative numbers.  */
+        ret = 20 - ret;
+#endif
         break;
     case TARGET_NR_setpriority:
         ret = get_errno(setpriority(arg1, arg2, arg3));
-- 
1.7.7.6