Commit 2347961b authored by Laurent Vivier's avatar Laurent Vivier Committed by Helge Deller
Browse files

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: default avatarLaurent Vivier <laurent@vivier.eu>
Reviewed-by: default avatarYunQiang Su <ysu@wavecomp.com>
URL: http://bugs.debian.org/970460


Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent b7795074

fs/binfmt_elf.c

+4 −1
Original line number Diff line number Diff line
@@ -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));

fs/binfmt_elf_fdpic.c

+4 −1
Original line number Diff line number Diff line
@@ -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));

fs/binfmt_misc.c

+3 −1
Original line number Diff line number Diff line
@@ -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;

include/linux/binfmts.h

+4 −0
Original line number Diff line number Diff line
@@ -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;

include/uapi/linux/binfmts.h

+4 −0
Original line number Diff line number Diff line
@@ -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 */