Re: [PATCH v3] binfmt_misc: pass binfmt_misc flags to the interpreter
From: YunQiang Su <hidden>
Date: 2020-03-01 00:47:39
Also in:
linux-arch, linux-fsdevel, lkml
Laurent Vivier [off-list ref] 于2020年1月28日周二 下午9:25写道：
It can be useful to the interpreter to know which flags are in use. For instance, knowing if the preserve-argv[0] is in use would allow to skip the pathname argument. This patch uses an unused auxiliary vector, AT_FLAGS, to add a flag to inform interpreter if the preserve-argv[0] is enabled.
I am suggested to post linux-arch and/or linux-api.
quoted hunk
Signed-off-by: Laurent Vivier <redacted> --- Notes: This can be tested with QEMU from my branch: https://github.com/vivier/qemu/commits/binfmt-argv0 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 v3: mix my patch with one from YunQiang Su and my comments on it introduce a new flag in the uabi for the AT_FLAGS v2: only pass special flags (remove Magic and Enabled flags) fs/binfmt_elf.c | 5 ++++- fs/binfmt_elf_fdpic.c | 5 ++++- fs/binfmt_misc.c | 4 +++- include/linux/binfmts.h | 4 ++++ include/uapi/linux/binfmts.h | 4 ++++ 5 files changed, 19 insertions(+), 3 deletions(-)diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index ecd8d2698515..ff918042ceed 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c@@ -176,6 +176,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, unsigned char k_rand_bytes[16]; int items; elf_addr_t *elf_info; + elf_addr_t flags = 0; int ei_index = 0; const struct cred *cred = current_cred(); struct vm_area_struct *vma;@@ -250,7 +251,9 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, NEW_AUX_ENT(AT_PHENT, sizeof(struct elf_phdr)); NEW_AUX_ENT(AT_PHNUM, exec->e_phnum); NEW_AUX_ENT(AT_BASE, interp_load_addr); - NEW_AUX_ENT(AT_FLAGS, 0); + if (bprm->interp_flags & BINPRM_FLAGS_PRESERVE_ARGV0) + flags |= AT_FLAGS_PRESERVE_ARGV0; + NEW_AUX_ENT(AT_FLAGS, flags); NEW_AUX_ENT(AT_ENTRY, exec->e_entry); NEW_AUX_ENT(AT_UID, from_kuid_munged(cred->user_ns, cred->uid)); NEW_AUX_ENT(AT_EUID, from_kuid_munged(cred->user_ns, cred->euid));diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index 240f66663543..abb90d82aa58 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c@@ -507,6 +507,7 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm, char __user *u_platform, *u_base_platform, *p; int loop; int nr; /* reset for each csp adjustment */ + unsigned long flags = 0; #ifdef CONFIG_MMU /* In some cases (e.g. Hyper-Threading), we want to avoid L1 evictions@@ -647,7 +648,9 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm, NEW_AUX_ENT(AT_PHENT, sizeof(struct elf_phdr)); NEW_AUX_ENT(AT_PHNUM, exec_params->hdr.e_phnum); NEW_AUX_ENT(AT_BASE, interp_params->elfhdr_addr); - NEW_AUX_ENT(AT_FLAGS, 0); + if (bprm->interp_flags & BINPRM_FLAGS_PRESERVE_ARGV0) + flags |= AT_FLAGS_PRESERVE_ARGV0; + NEW_AUX_ENT(AT_FLAGS, flags); NEW_AUX_ENT(AT_ENTRY, exec_params->entry_addr); NEW_AUX_ENT(AT_UID, (elf_addr_t) from_kuid_munged(cred->user_ns, cred->uid)); NEW_AUX_ENT(AT_EUID, (elf_addr_t) from_kuid_munged(cred->user_ns, cred->euid));diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index cdb45829354d..b9acdd26a654 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c@@ -154,7 +154,9 @@ static int load_misc_binary(struct linux_binprm *bprm) if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE) goto ret; - if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) { + if (fmt->flags & MISC_FMT_PRESERVE_ARGV0) { + bprm->interp_flags |= BINPRM_FLAGS_PRESERVE_ARGV0; + } else { retval = remove_arg_zero(bprm); if (retval) goto ret;diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index b40fc633f3be..265b80d5fd6f 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h@@ -78,6 +78,10 @@ struct linux_binprm { #define BINPRM_FLAGS_PATH_INACCESSIBLE_BIT 2 #define BINPRM_FLAGS_PATH_INACCESSIBLE (1 << BINPRM_FLAGS_PATH_INACCESSIBLE_BIT) +/* if preserve the argv0 for the interpreter */ +#define BINPRM_FLAGS_PRESERVE_ARGV0_BIT 3 +#define BINPRM_FLAGS_PRESERVE_ARGV0 (1 << BINPRM_FLAGS_PRESERVE_ARGV0_BIT) + /* Function parameter for binfmt->coredump */ struct coredump_params { const kernel_siginfo_t *siginfo;diff --git a/include/uapi/linux/binfmts.h b/include/uapi/linux/binfmts.h index 689025d9c185..a70747416130 100644 --- a/include/uapi/linux/binfmts.h +++ b/include/uapi/linux/binfmts.h@@ -18,4 +18,8 @@ struct pt_regs; /* sizeof(linux_binprm->buf) */ #define BINPRM_BUF_SIZE 256 +/* if preserve the argv0 for the interpreter */ +#define AT_FLAGS_PRESERVE_ARGV0_BIT 0 +#define AT_FLAGS_PRESERVE_ARGV0 (1 << AT_FLAGS_PRESERVE_ARGV0_BIT) + #endif /* _UAPI_LINUX_BINFMTS_H */ --2.24.1