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 3rd bits of unused AT_FLAGS.
Then, in qemu, we can get this info by:
getauxval(AT_FLAGS) & (1<<3)
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 | 9 +++++++--
fs/binfmt_misc.c | 2 ++
include/linux/binfmts.h | 4 ++++
4 files changed, 18 insertions(+), 3 deletions(-)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 09e76b25d833..30688fbad615 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -175,6 +175,7 @@ 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;
@@ -249,7 +250,10 @@ 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 |= BINPRM_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 b53bb3729ac1..ba3385be00fb 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -46,7 +46,7 @@
typedef char *elf_caddr_t;
-#if 0
+#if 1
#define kdebug(fmt, ...) printk("FDPIC "fmt"\n" ,##__VA_ARGS__ )
#else
#define kdebug(fmt, ...) do {} while(0)
@@ -511,6 +511,7 @@ 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
@@ -651,7 +652,11 @@ 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 |= BINPRM_FLAGS_PRESERVE_ARGV0;
+ }
+ kdebug("AT_FLAGS %ld\n", flags);
+ 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 aa4a7a23ff99..46c509cd096e 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -156,6 +156,8 @@ static int load_misc_binary(struct linux_binprm *bprm)
retval = remove_arg_zero(bprm);
if (retval)
goto ret;
+ } else {
+ bprm->interp_flags |= BINPRM_FLAGS_PRESERVE_ARGV0;
}
if (fmt->flags & MISC_FMT_OPEN_BINARY) {
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 688ab0de7810..c082650a0310 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -77,6 +77,10 @@ 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;
--
2.20.1
