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From: Laurent Vivier <laurent@vivier.eu>
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Date: Thu, 15 Feb 2018 09:50:20 +0100
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Subject: Re: [Qemu-devel] [PATCH] syscall: fix special case of write(fd, NULL,
 0)
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To: Oliver Smith <ollieparanoid@bitmessage.ch>, qemu-devel@nongnu.org, peter.maydell@linaro.org
Cc: zhuoweizhang@yahoo.com

Le 15/02/2018 à 00:33, Oliver Smith a écrit :
> 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

According to comments in the ML thread, you need to:

- update the patch to call write() with NULL and 0, something like:

--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7912,6 +7912,10 @@ abi_long do_syscall(void *cpu_env, int num,
abi_long arg1,
         }
         break;
     case TARGET_NR_write:
+        if (arg2 == 0 && arg3 == 0) {
+            ret = get_errno(safe_write(arg1, NULL, 0));
+            break;
+        }
         if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1)))
             goto efault;
         if (fd_trans_target_to_host_data(arg1)) {

- change TARGET_NR_read to do the same

- check if we need to do the same for pread64/pwrite64

Thanks,
Laurent