| Message ID | 1298379746-18484-1-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | Accepted |
| Commit | 0c1592d93585ddce572a71a77534ca765c5f5d34 |
| Headers | show |
On Tue, Feb 22, 2011 at 01:02:26PM +0000, Peter Maydell wrote: > 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.maydell@linaro.org> > --- > linux-user/syscall.c | 16 ++++++++++------ > 1 files changed, 10 insertions(+), 6 deletions(-) Thanks, applied. > 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 > > >
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
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.maydell@linaro.org> --- linux-user/syscall.c | 16 ++++++++++------ 1 files changed, 10 insertions(+), 6 deletions(-)