Le 22/02/2021 à 11:50, Laurent Vivier a écrit :
> Add --preserve-argv0 in qemu-binfmt-conf.sh to configure the preserve-argv0
> flag.
>
> This patch allows to use new flag in AT_FLAGS to detect if
> preserve-argv0 is configured for this interpreter:
> argv[0] (the full pathname provided by binfmt-misc) is removed and
> replaced by argv[1] (the original argv[0] provided by binfmt-misc when
> 'P'/preserve-arg[0] is set)
>
> For instance with this patch and kernel support for AT_FLAGS:
>
> $ sudo chroot m68k-chroot sh -c 'echo $0'
> sh
>
> without this patch:
>
> $ sudo chroot m68k-chroot sh -c 'echo $0'
> /usr/bin/sh
>
> The new flag is available in kernel (v5.12) since:
> 2347961b11d4 ("binfmt_misc: pass binfmt_misc flags to the interpreter")
>
> This can be tested with something like:
>
> # cp ..../qemu-ppc /chroot/powerpc/jessie
>
> # qemu-binfmt-conf.sh --qemu-path / --systemd ppc --credential yes \
> --persistent no --preserve-argv0 yes
> # systemctl restart systemd-binfmt.service
> # cat /proc/sys/fs/binfmt_misc/qemu-ppc
> enabled
> interpreter //qemu-ppc
> flags: POC
> offset 0
> magic 7f454c4601020100000000000000000000020014
> mask ffffffffffffff00fffffffffffffffffffeffff
> # chroot /chroot/powerpc/jessie sh -c 'echo $0'
> sh
>
> # qemu-binfmt-conf.sh --qemu-path / --systemd ppc --credential yes \
> --persistent no --preserve-argv0 no
> # systemctl restart systemd-binfmt.service
> # cat /proc/sys/fs/binfmt_misc/qemu-ppc
> enabled
> interpreter //qemu-ppc
> flags: OC
> offset 0
> magic 7f454c4601020100000000000000000000020014
> mask ffffffffffffff00fffffffffffffffffffeffff
> # chroot /chroot/powerpc/jessie sh -c 'echo $0'
> /bin/sh
>
> Signed-off-by: Laurent Vivier <laur...@vivier.eu>
> ---
> linux-user/main.c | 24 ++++++++++++++++++++
> scripts/qemu-binfmt-conf.sh | 44 +++++++++++++++++++++++--------------
> 2 files changed, 51 insertions(+), 17 deletions(-)
>
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 81f48ff54ed4..b9015a5dbd3e 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -26,6 +26,7 @@
> #include <sys/syscall.h>
> #include <sys/resource.h>
> #include <sys/shm.h>
> +#include <linux/binfmts.h>
>
> #include "qapi/error.h"
> #include "qemu.h"
> @@ -49,6 +50,11 @@
> #include "cpu_loop-common.h"
> #include "crypto/init.h"
>
> +#ifndef AT_FLAGS_PRESERVE_ARGV0
> +#define AT_FLAGS_PRESERVE_ARGV0_BIT 0
> +#define AT_FLAGS_PRESERVE_ARGV0 (1 << AT_FLAGS_PRESERVE_ARGV0_BIT)
> +#endif
> +
> char *exec_path;
>
> int singlestep;
> @@ -631,6 +637,7 @@ int main(int argc, char **argv, char **envp)
> int execfd;
> int log_mask;
> unsigned long max_reserved_va;
> + bool preserve_argv0;
>
> error_init(argv[0]);
> module_call_init(MODULE_INIT_TRACE);
> @@ -687,6 +694,9 @@ int main(int argc, char **argv, char **envp)
>
> init_qemu_uname_release();
>
> + /*
> + * Manage binfmt-misc open-binary flag
> + */
> execfd = qemu_getauxval(AT_EXECFD);
> if (execfd == 0) {
> execfd = open(exec_path, O_RDONLY);
> @@ -696,6 +706,20 @@ int main(int argc, char **argv, char **envp)
> }
> }
>
> + /*
> + * get binfmt_misc flags
> + */
> + preserve_argv0 = !!(qemu_getauxval(AT_FLAGS) & AT_FLAGS_PRESERVE_ARGV0);
> +
> + /*
> + * Manage binfmt-misc preserve-arg[0] flag
> + * argv[optind] full path to the binary
> + * argv[optind + 1] original argv[0]
> + */
> + if (optind + 1 < argc && preserve_argv0) {
> + optind++;
> + }
> +
> if (cpu_model == NULL) {
> cpu_model = cpu_get_model(get_elf_eflags(execfd));
> }
> diff --git a/scripts/qemu-binfmt-conf.sh b/scripts/qemu-binfmt-conf.sh
> index 7b5d54b88741..573b5dc6acd7 100755
> --- a/scripts/qemu-binfmt-conf.sh
> +++ b/scripts/qemu-binfmt-conf.sh
> @@ -178,25 +178,27 @@ usage() {
> Usage: qemu-binfmt-conf.sh [--qemu-path PATH][--debian][--systemd CPU]
> [--help][--credential yes|no][--exportdir PATH]
> [--persistent yes|no][--qemu-suffix SUFFIX]
> + [--preserve-argv0 yes|no]
>
> Configure binfmt_misc to use qemu interpreter
>
> - --help: display this usage
> - --qemu-path: set path to qemu interpreter ($QEMU_PATH)
> - --qemu-suffix: add a suffix to the default interpreter name
> - --debian: don't write into /proc,
> - instead generate update-binfmts templates
> - --systemd: don't write into /proc,
> - instead generate file for systemd-binfmt.service
> - for the given CPU. If CPU is "ALL", generate a
> - file for all known cpus
> - --exportdir: define where to write configuration files
> - (default: $SYSTEMDDIR or $DEBIANDIR)
> - --credential: if yes, credential and security tokens are
> - calculated according to the binary to interpret
> - --persistent: if yes, the interpreter is loaded when binfmt is
> - configured and remains in memory. All future uses
> - are cloned from the open file.
> + --help: display this usage
> + --qemu-path: set path to qemu interpreter ($QEMU_PATH)
> + --qemu-suffix: add a suffix to the default interpreter name
> + --debian: don't write into /proc,
> + instead generate update-binfmts templates
> + --systemd: don't write into /proc,
> + instead generate file for systemd-binfmt.service
> + for the given CPU. If CPU is "ALL", generate a
> + file for all known cpus
> + --exportdir: define where to write configuration files
> + (default: $SYSTEMDDIR or $DEBIANDIR)
> + --credential: if yes, credential and security tokens are
> + calculated according to the binary to interpret
> + --persistent: if yes, the interpreter is loaded when binfmt is
> + configured and remains in memory. All future uses
> + are cloned from the open file.
> + --preserve-argv0 preserve argv[0]
>
> To import templates with update-binfmts, use :
>
> @@ -269,6 +271,9 @@ qemu_generate_register() {
> if [ "$PERSISTENT" = "yes" ] ; then
> flags="${flags}F"
> fi
> + if [ "$PRESERVE_ARG0" = "yes" ] ; then
> + flags="${flags}P"
> + fi
>
> echo ":qemu-$cpu:M::$magic:$mask:$qemu:$flags"
> }
> @@ -330,9 +335,10 @@ DEBIANDIR="/usr/share/binfmts"
> QEMU_PATH=/usr/local/bin
> CREDENTIAL=no
> PERSISTENT=no
> +PRESERVE_ARG0=no
> QEMU_SUFFIX=""
>
> -options=$(getopt -o ds:Q:S:e:hc:p: -l
> debian,systemd:,qemu-path:,qemu-suffix:,exportdir:,help,credential:,persistent:
> -- "$@")
> +options=$(getopt -o ds:Q:S:e:hc:p:g: -l
> debian,systemd:,qemu-path:,qemu-suffix:,exportdir:,help,credential:,persistent:,preserve-argv0:
> -- "$@")
> eval set -- "$options"
>
> while true ; do
> @@ -388,6 +394,10 @@ while true ; do
> shift
> PERSISTENT="$1"
> ;;
> + -g|--preserve-argv0)
> + shift
> + PRESERVE_ARG0="$1"
> + ;;
> *)
> break
> ;;
>
Applied to my linux-user-for-6.0 branch.
Thanks,
Laurent
