[Qemu-devel] [PATCH] linux-user: identify running binary in /proc/$$/exe

[Andreas Schwab]

Some applications like to test /proc/$$/exe (where $$ is the own pid) to
find out who they are.  Handle it like /proc/self/exe.

Also, do the same handling in readlinkat.

Signed-off-by: Andreas Schwab <address@hidden>
---
 linux-user/syscall.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 19630ea..3e5a6ae 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6413,7 +6413,10 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
             if (!p || !p2)
                 ret = -TARGET_EFAULT;
             else {
-                if (strncmp((const char *)p, "/proc/self/exe", 14) == 0) {
+                char myself[PATH_MAX];
+                snprintf(myself, sizeof(myself), "/proc/%d/exe", getpid());
+                if (strncmp((const char *)p, "/proc/self/exe", 14) == 0 ||
+                    strcmp((const char *)p, myself) == 0) {
                     char real[PATH_MAX];
                     temp = realpath(exec_path,real);
                     ret = (temp==NULL) ? get_errno(-1) : strlen(real) ;
@@ -6429,13 +6432,24 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
 #if defined(TARGET_NR_readlinkat) && defined(__NR_readlinkat)
     case TARGET_NR_readlinkat:
         {
-            void *p2;
+            void *p2, *temp;
             p  = lock_user_string(arg2);
             p2 = lock_user(VERIFY_WRITE, arg3, arg4, 0);
             if (!p || !p2)
                ret = -TARGET_EFAULT;
-            else
-                ret = get_errno(sys_readlinkat(arg1, path(p), p2, arg4));
+            else {
+                char myself[PATH_MAX];
+                snprintf(myself, sizeof(myself), "/proc/%d/exe", getpid());
+                if (strncmp((const char *)p, "/proc/self/exe", 14) == 0 ||
+                    strcmp((const char *)p, myself) == 0) {
+                    char real[PATH_MAX];
+                    temp = realpath(exec_path,real);
+                    ret = (temp==NULL) ? get_errno(-1) : strlen(real) ;
+                    snprintf((char *)p2, arg3, "%s", real);
+                }
+                else
+                    ret = get_errno(sys_readlinkat(arg1, path(p), p2, arg4));
+            }
             unlock_user(p2, arg3, ret);
             unlock_user(p, arg2, 0);
         }
-- 
1.8.1.5


-- 
Andreas Schwab, SUSE Labs, address@hidden
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."