From: Colin Percival <cperciva@tarsnap.com>

Previously it was impossible to emulate a program with a file name
different from its argv[0].  With this change, you can run
    qemu -0 fakename realname args
which runs the program "realname" with an argv of "fakename args".

Signed-off-by: Colin Percival <cperciva@tarsnap.com>
Signed-off-by: Warner Losh <imp@bsdimp.com>
---
 bsd-user/main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/bsd-user/main.c b/bsd-user/main.c
index 1de5dc189b..c3ecdaf824 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -284,6 +284,7 @@ int main(int argc, char **argv)
     char **target_environ, **wrk;
     envlist_t *envlist = NULL;
     bsd_type = HOST_DEFAULT_BSD_TYPE;
+    char * argv0 = NULL;
 
     adjust_ssize();
 
@@ -405,6 +406,8 @@ int main(int argc, char **argv)
             do_strace = 1;
         } else if (!strcmp(r, "trace")) {
             trace_opt_parse(optarg);
+        } else if (!strcmp(r, "0")) {
+            argv0 = argv[optind++];
         } else {
             usage();
         }
@@ -428,6 +431,8 @@ int main(int argc, char **argv)
         usage();
     }
     filename = argv[optind];
+    if (argv0)
+        argv[optind] = argv0;
 
     if (!trace_init_backends()) {
         exit(1);
-- 
2.32.0

On 8/7/21 11:42 AM, Warner Losh wrote:
> From: Colin Percival<cperciva@tarsnap.com>
> 
> Previously it was impossible to emulate a program with a file name
> different from its argv[0].  With this change, you can run
>      qemu -0 fakename realname args
> which runs the program "realname" with an argv of "fakename args".
> 
> Signed-off-by: Colin Percival<cperciva@tarsnap.com>
> Signed-off-by: Warner Losh<imp@bsdimp.com>
> ---
>   bsd-user/main.c | 5 +++++
>   1 file changed, 5 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~