On Sun, 2019-12-15 at 17:54 +0100, Laurent Vivier wrote: > > 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.
Only if you already are using O flag only. Distributions can adjust so that O and P are used in tandem. > > I already try to find a solution to this problem. > > The first one is at QEMU level: > > https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchew.org%2FQEMU%2F20191024153847.31815-1-laurent%40vivier.eu%2F&data=02%7C01%7Cjoakim.tjernlund%40infinera.com%7C5c4859947f4949d8824d08d7817f7aef%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C1%7C637120256850791761&sdata=w6YgDlrUPxk7BSPdOVRyyWzb64usUiF9EMSOMonskPY%3D&reserved=0 > > Another would be at linux level to provide a way to detect binfmt flags > (like you try to do with AT_EXECFD): The kernel way to report flags are really the way forward here. There seems to be little interest from QEMU community to fix this though, why is that? Jocke > > https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fpatchwork%2Fpatch%2F1158151%2F&data=02%7C01%7Cjoakim.tjernlund%40infinera.com%7C5c4859947f4949d8824d08d7817f7aef%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C1%7C637120256850791761&sdata=abV%2BELktrjTOCS6gEp38%2BYuj17HQfCclj0YhyN0X7Bg%3D&reserved=0 > > I also found another one from another author: > > https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fpatch%2F10902935%2F&data=02%7C01%7Cjoakim.tjernlund%40infinera.com%7C5c4859947f4949d8824d08d7817f7aef%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C1%7C637120256850791761&sdata=TftL59%2Baj2IAAoQ6Femfb8w%2F6%2FGc%2FjrM49iQvw4b1MM%3D&reserved=0 > > 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) { > >
