[Qemu-devel] [PATCH] linux-user: Consistently return host errnos from do_openat()

[Peter Maydell <peter.maydell@linaro.org>]

The function do_openat() is not consistent about whether it is
returning a host errno or a guest errno in case of failure.
Standardise on returning -1 with errno set (ie caller has
to call get_errno()).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reported-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
---
Timothy's patchset for fixing signal races had a patch which also
addressed this bug.  However I preferred to take the opposite tack
and have the callers do get_errno() rather than the callee, because
it means changes in fewer places and it's generally more natural
for the 'fill' functions that do_openat() calls.
---
 linux-user/syscall.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index f9dcdd4..39586e4 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -5557,7 +5557,9 @@ static int open_self_cmdline(void *cpu_env, int fd)
 
         nb_read = read(fd_orig, buf, sizeof(buf));
         if (nb_read < 0) {
+            int e = errno;
             fd_orig = close(fd_orig);
+            errno = e;
             return -1;
         } else if (nb_read == 0) {
             break;
@@ -5577,7 +5579,9 @@ static int open_self_cmdline(void *cpu_env, int fd)
 
         if (word_skipped) {
             if (write(fd, cp_buf, nb_read) != nb_read) {
+                int e = errno;
                 close(fd_orig);
+                errno = e;
                 return -1;
             }
         }
@@ -5597,7 +5601,7 @@ static int open_self_maps(void *cpu_env, int fd)
 
     fp = fopen("/proc/self/maps", "r");
     if (fp == NULL) {
-        return -EACCES;
+        return -1;
     }
 
     while ((read = getline(&line, &len, fp)) != -1) {
@@ -5741,7 +5745,7 @@ static int open_net_route(void *cpu_env, int fd)
 
     fp = fopen("/proc/net/route", "r");
     if (fp == NULL) {
-        return -EACCES;
+        return -1;
     }
 
     /* read header */
@@ -5791,7 +5795,7 @@ static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags,
 
     if (is_proc_myself(pathname, "exe")) {
         int execfd = qemu_getauxval(AT_EXECFD);
-        return execfd ? execfd : get_errno(sys_openat(dirfd, exec_path, flags, mode));
+        return execfd ? execfd : sys_openat(dirfd, exec_path, flags, mode);
     }
 
     for (fake_open = fakes; fake_open->filename; fake_open++) {
@@ -5817,7 +5821,9 @@ static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags,
         unlink(filename);
 
         if ((r = fake_open->fill(cpu_env, fd))) {
+            int e = errno;
             close(fd);
+            errno = e;
             return r;
         }
         lseek(fd, 0, SEEK_SET);
@@ -5825,7 +5831,7 @@ static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags,
         return fd;
     }
 
-    return get_errno(sys_openat(dirfd, path(pathname), flags, mode));
+    return sys_openat(dirfd, path(pathname), flags, mode);
 }
 
 #define TIMER_MAGIC 0x0caf0000
-- 
1.9.1