binfmt_misc: pass binfmt_misc flags to the interpreter

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.

Note by Helge Deller:
The real-world user of this patch is qemu-user, which needs to know
if it has to preserve the argv[0]. See Debian bug #970460.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: YunQiang Su <ysu@wavecomp.com>
URL: http://bugs.debian.org/970460
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 950bc177238ac77ad10137385a1e290cf20a9151..11fb68e68f656028c943a990f00f8622439507f1 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -186,6 +186,7 @@ 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;
@@ -260,7 +261,9 @@ 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 be4062b8ba75eef23d71b19de1c52a9e65efd064..7a78c91bc1c15fe42a20bb58e856e19be977a989 100644 (file)
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -506,6 +506,7 @@ 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
@@ -648,7 +649,9 @@ 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 3880a82da1dc507a4b4efd02a8d6a2db79b40ef4..c457334de43f8709cc5ee162d2382ebb3fb4f199 100644 (file)
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -153,7 +153,9 @@ 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 0571701ab1c57cc0d3dcddb119ea0c503e1ba641..0abd93efc18106437448e94e225de28407ea7880 100644 (file)
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -73,6 +73,10 @@ struct linux_binprm {
 #define BINPRM_FLAGS_PATH_INACCESSIBLE_BIT 2
 #define BINPRM_FLAGS_PATH_INACCESSIBLE (1 << BINPRM_FLAGS_PATH_INACCESSIBLE_BIT)
 
+/* preserve 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 689025d9c185b06abe50e36161c88ca263bba7cf..c6f9450efc120af7f82a3615e8f2aeed5d4924d9 100644 (file)
--- 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
 
+/* preserve 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 */