linux-user: manage binfmt-misc preserve-arg[0] flag
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 $0'
/bin/sh
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210222105004.1642234-1-laurent@vivier.eu>
diff --git a/scripts/qemu-binfmt-conf.sh b/scripts/qemu-binfmt-conf.sh
index 7b5d54b..573b5dc 100755
--- a/scripts/qemu-binfmt-conf.sh
+++ b/scripts/qemu-binfmt-conf.sh
@@ -178,25 +178,27 @@
Usage: qemu-binfmt-conf.sh [--qemu-path PATH][--debian][--systemd CPU]
[--help][--credential yes|no][--exportdir PATH]
[--persistent yes|no][--qemu-suffix SUFFIX]
+ [--preserve-argv0 yes|no]
Configure binfmt_misc to use qemu interpreter
- --help: display this usage
- --qemu-path: set path to qemu interpreter ($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 $DEBIANDIR)
+ --credential: if yes, credential and security tokens are
+ calculated according to the binary to interpret
+ --persistent: if yes, the interpreter is loaded when binfmt is
+ configured and remains in memory. All future uses
+ are cloned from the open file.
+ --preserve-argv0 preserve argv[0]
To import templates with update-binfmts, use :
@@ -269,6 +271,9 @@
if [ "$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 @@
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 @@
shift
PERSISTENT="$1"
;;
+ -g|--preserve-argv0)
+ shift
+ PRESERVE_ARG0="$1"
+ ;;
*)
break
;;
