[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] syscall: fix special case of write(fd, NULL, 0)
From: |
Oliver Smith |
Subject: |
Re: [Qemu-devel] [PATCH] syscall: fix special case of write(fd, NULL, 0) |
Date: |
Wed, 14 Feb 2018 23:33:00 +0000 |
Hello there,
I'm a little late to the party. But what is necessary to get this
upstreamed, and how can I help?
PS: Sorry if I picked the wrong e-mail addresses, I wasn't subscribed to
the ML at that point and used the addresses I could find for the people
who answered to the original thread here:
https://lists.gnu.org/archive/html/qemu-devel/2017-09/msg08073.html
Thanks,
Oliver
From: Zhuowei Zhang <address@hidden>
> Linux returns success for the special case of calling write with a
> zero-length NULL buffer: compiling and running
>
> ```
>
> int main() {
> ssize_t ret = write(STDOUT_FILENO, NULL, 0);
> fprintf(stderr, "write returned %ld\n", ret);
> return 0;
> }
> ```
> gives "write returned 0" when run directly, but "write returned -1" in
> QEMU.
>
> This commit checks for this situation and returns success if found.
>
> Signed-off-by: Zhuowei Zhang <address@hidden>
> ---
> linux-user/syscall.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 9b6364a..ecadf49 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -7783,6 +7783,11 @@ abi_long do_syscall(void *cpu_env, int num,
abi_long
> arg1,
> }
> break;
> case TARGET_NR_write:
> + if (arg2 == 0 && arg3 == 0) {
> + /* special case: write(fd, NULL, 0) returns success. */
> + ret = 0;
> + break;
> + }
> if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1)))
> goto efault;
> if (fd_trans_target_to_host_data(arg1)) {
> --
> 1.9.1
- Re: [Qemu-devel] [PATCH] syscall: fix special case of write(fd, NULL, 0),
Oliver Smith <=