Le 16/01/2020 à 09:30, YunQiang Su a écrit : > From: YunQiang Su <ysu@xxxxxxxxxxxx> > > Currently program invoked by binfmt_misc cannot be aware about whether > P flag, aka preserve path is enabled. > > Some applications like qemu need to know since it has 2 use case: > 1. call by hand, like: qemu-mipsel-static test.app OPTION > so, qemu have to assume that P option is not enabled. > 2. call by binfmt_misc. If qemu cannot know about whether P flag is > enabled, distribution's have to set qemu without P flag, and > binfmt_misc call qemu like: > qemu-mipsel-static /absolute/path/to/test.app OPTION > even test.app is not called by absoulute path, like > ./relative/path/to/test.app > > This patch passes this information by the 0st bits of unused AT_FLAGS. > Then, in qemu, we can get this info by: > getauxval(AT_FLAGS) & (1<<0) > > v2->v3: > define a new AT_FLAGS_PRESERVE_ARGV0 as (1<<0), so now we use 0st bit. > > v1->v2: > not enable kdebug > > See: https://bugs.launchpad.net/qemu/+bug/1818483 > Signed-off-by: YunQiang Su <ysu@xxxxxxxxxxxx> > --- > fs/binfmt_elf.c | 6 +++++- > fs/binfmt_elf_fdpic.c | 6 +++++- > fs/binfmt_misc.c | 2 ++ > include/linux/binfmts.h | 4 ++++ > 4 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index f4713ea76e82..c4efff74223f 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -178,6 +178,7 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec, > unsigned char k_rand_bytes[16]; > int items; > elf_addr_t *elf_info; > + elf_addr_t flags = 0; > int ei_index; > const struct cred *cred = current_cred(); > struct vm_area_struct *vma; > @@ -252,7 +253,10 @@ create_elf_tables(struct linux_binprm *bprm, const 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, 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..c89a4630efad 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 +648,10 @@ 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..cb14e9bbf00f 100644 > --- a/fs/binfmt_misc.c > +++ b/fs/binfmt_misc.c > @@ -158,6 +158,8 @@ static int load_misc_binary(struct linux_binprm *bprm) > retval = remove_arg_zero(bprm); > if (retval) > goto ret; > + } else { > + bprm->interp_flags |= AT_FLAGS_PRESERVE_ARGV0; Keep BINPRM_FLAGS_PRESERVE_ARGV0 here. > } > > if (fmt->flags & MISC_FMT_OPEN_BINARY) { > diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h > index b40fc633f3be..380a30a46db1 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 AT_FLAGS_PRESERVE_ARGV0_BIT 0 > +#define AT_FLAGS_PRESERVE_ARGV0 (1 << AT_FLAGS_PRESERVE_ARGV0_BIT) > + I think it should be added in include/uapi/linux/binfmts.h to be shared with user space (external API- Where is defined BINPRM_FLAGS_PRESERVE_ARGV0 now? It should be here (internal ABI) Thanks, Laurent
