When emulating a 32 bit Linux user-mode program on a 64 bit target
we implement the llseek syscall in terms of lseek. Correct a bug
which meant we were silently casting the result of host lseek()
to a 32 bit integer as it passed through get_errno() and thus
throwing away the top half.
We also don't try to store the result back to userspace unless
the seek succeeded; this matches the kernel behaviour.
Thanks to Eoghan Sherry for identifying the problem and suggesting
a solution.
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
linux-user/syscall.c | 16 ++++++++++------
1 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index cf8a4c3..23d7a63 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6127,16 +6127,20 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
#ifdef TARGET_NR__llseek /* Not on alpha */
case TARGET_NR__llseek:
{
+ int64_t res;
#if !defined(__NR_llseek)
- ret = get_errno(lseek(arg1, ((uint64_t )arg2 << 32) | arg3, arg5));
- if (put_user_s64(ret, arg4))
- goto efault;
+ res = lseek(arg1, ((uint64_t)arg2 << 32) | arg3, arg5);
+ if (res == -1) {
+ ret = get_errno(res);
+ } else {
+ ret = 0;
+ }
#else
- int64_t res;
ret = get_errno(_llseek(arg1, arg2, arg3, &res, arg5));
- if (put_user_s64(res, arg4))
- goto efault;
#endif
+ if ((ret == 0) && put_user_s64(res, arg4)) {
+ goto efault;
+ }
}
break;
#endif
--
1.7.1
