Le 14/12/2019 à 13:20, Joakim Tjernlund a écrit : > From: Joakim Tjernlund <joakim.tjernl...@infinera.com> > > QEMU can autodetect if it is started from Linux binfmt loader > when binfmt flag O is on. > Use that and require binfmt flag P as well which will enable QEMU > to pass in correct argv0 to the application.
I agree it's a good idea to try to detect the P flag if we use the O but it changes the current behavior and breaks the compatibility with previous version. This will prevent to run old and new version of QEMU on the same system. I already try to find a solution to this problem. The first one is at QEMU level: https://patchew.org/QEMU/20191024153847.31815-1-laur...@vivier.eu/ Another would be at linux level to provide a way to detect binfmt flags (like you try to do with AT_EXECFD): https://lore.kernel.org/patchwork/patch/1158151/ I also found another one from another author: https://patchwork.kernel.org/patch/10902935/ Thanks, Laurent > Signed-off-by: Joakim Tjernlund <joakim.tjernl...@infinera.com> > --- > linux-user/main.c | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) > > diff --git a/linux-user/main.c b/linux-user/main.c > index 6ff7851e86..1b626e5762 100644 > --- a/linux-user/main.c > +++ b/linux-user/main.c > @@ -544,7 +544,7 @@ static void usage(int exitcode) > exit(exitcode); > } > > -static int parse_args(int argc, char **argv) > +static int parse_args(int argc, char **argv, int assume_P_flag) > { > const char *r; > int optind; > @@ -560,7 +560,17 @@ static int parse_args(int argc, char **argv) > arginfo->handle_opt(r); > } > } > - > + if (assume_P_flag) { > + /* Assume started by binmisc and binfmt P flag is set */ > + if (argc < 3) { > + fprintf(stderr, "%s: Please use me through binfmt with P flag\n", > + argv[0]); > + exit(1); > + } > + exec_path = argv[1]; > + /* Next argv must be argv0 for the app */ > + return 2; > + } > optind = 1; > for (;;) { > if (optind >= argc) { > @@ -659,7 +669,8 @@ int main(int argc, char **argv, char **envp) > qemu_add_opts(&qemu_trace_opts); > qemu_plugin_add_opts(); > > - optind = parse_args(argc, argv); > + execfd = qemu_getauxval(AT_EXECFD); > + optind = parse_args(argc, argv, execfd > 0); > > if (!trace_init_backends()) { > exit(1); > @@ -682,7 +693,6 @@ int main(int argc, char **argv, char **envp) > > init_qemu_uname_release(); > > - execfd = qemu_getauxval(AT_EXECFD); > if (execfd == 0) { > execfd = open(exec_path, O_RDONLY); > if (execfd < 0) { >
