From 976ef444b83d9c2ab1cff5cf95434d349e3c3161 Mon Sep 17 00:00:00 2001
From: Nicolas Derumigny <nderumigny@gmail.com>
Date: Sat, 15 Oct 2016 15:06:24 -0500
Subject: [PATCH] syscall: read() should not write anything if reading EOF.

Read() should not write anything when returning 0 (EOF).
This patch does not correct the same bug occuring for :

nbr_read=read(file, buf, nbytes)

When nbr_read<nbytes, nbytes bytes are copied into the virtual
RAM instead of nbr_read. If buf is smaller than nbytes, a
page fault occurs, even if buf is in fact bigger than nbr_read.

Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
---
 src/sim/syscall_emul.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/sim/syscall_emul.cc b/src/sim/syscall_emul.cc
index 392658c5a..e62a8686a 100644
--- a/src/sim/syscall_emul.cc
+++ b/src/sim/syscall_emul.cc
@@ -245,7 +245,7 @@ readFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 
     int bytes_read = read(sim_fd, bufArg.bufferPtr(), nbytes);
 
-    if (bytes_read != -1)
+    if (bytes_read > 0)
         bufArg.copyOut(tc->getMemProxy());
 
     return bytes_read;
-- 
2.30.2