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John Reiser 6519108746 execve filename: document and export via auxiliary vector 
The Linux kernel puts the filename argument of execve() into the new
address space.  Many developers are surprised to learn this.  Those who
know and could use it, object "But it's not documented."

Those who want to use it dislike the expression
  (char *)(1+ strlen(env[-1+ n_env]) + env[-1+ n_env])
because it requires locating the last original environment variable,
and assumes that the filename follows the characters.

This patch documents the insertion of the filename, and makes it easier
to find by adding a new tag AT_EXECFN in the ElfXX_auxv_t; see <elf.h>.

In many cases readlink("/proc/self/exe",) gives the same answer.  But if
all the original pages get unmapped, then the kernel erases the symlink
for /proc/self/exe.  This can happen when a program decompressor does a
good job of cleaning up after uncompressing directly to memory, so that
the address space of the target program looks the same as if compression
had never happened.  One example is http://upx.sourceforge.net .

One notable use of the underlying concept (what path containED the
executable) is glibc expanding $ORIGIN in DT_RUNPATH.  In practice for
the near term, it may be a good idea for user-mode code to use both
/proc/self/exe and AT_EXECFN as fall-back methods for each other.
/proc/self/exe can fail due to unmapping, AT_EXECFN can fail because it
won't be present on non-new systems.  The auxvec or {AT_EXECFN}.d_val
also can get overwritten, although in nearly all cases this would be the
result of a bug.

The runtime cost is one NEW_AUX_ENT using two words of stack space.  The
underlying value is maintained already as bprm->exec; setup_arg_pages()
in fs/exec.c slides it for stack_shift, etc.

Signed-off-by: John Reiser <jreiser@BitWagon.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-22 09:59:40 -07:00
..
9p 9p: fix O_APPEND in legacy mode 2008-07-03 09:59:03 -05:00
adfs fs: replace remaining __FUNCTION__ occurrences 2008-04-30 08:29:54 -07:00
affs [PATCH] fix reservation discarding in affs 2008-05-06 13:45:33 -04:00
afs Fix various old email addresses for dwmw2 2008-06-06 11:29:10 -07:00
autofs mount options: fix autofs 2008-02-08 09:22:40 -08:00
autofs4 autofs: path_{get,put}() cleanups 2008-05-01 08:04:01 -07:00
befs byteorder: don't directly include linux/byteorder/generic.h 2008-05-16 12:01:45 -07:00
bfs fs: replace remaining __FUNCTION__ occurrences 2008-04-30 08:29:54 -07:00
cifs Merge commit 'v2.6.26' into bkl-removal 2008-07-14 15:29:34 -06:00
coda codafs: fix build warning 2008-04-29 08:06:04 -07:00
configfs configfs: Allow ->make_item() and ->make_group() to return detailed errors. 2008-07-17 15:21:29 -07:00
cramfs fs: Remove unnecessary inclusions of asm/semaphore.h 2008-04-18 22:16:44 -04:00
debugfs DEBUGFS: Correct location of debugfs API documentation. 2008-04-30 16:52:47 -07:00
devpts devpts: factor out PTY index allocation 2008-04-30 08:29:48 -07:00
dlm configfs: Allow ->make_item() and ->make_group() to return detailed errors. 2008-07-17 15:21:29 -07:00
ecryptfs Merge commit 'v2.6.26' into bkl-removal 2008-07-14 15:29:34 -06:00
efs efs: update error msg to not refer to deleted read_inode() 2008-04-02 15:28:19 -07:00
exportfs fs: replace remaining __FUNCTION__ occurrences 2008-04-30 08:29:54 -07:00
ext2 ext2: retry block allocation if new blocks are allocated from system zone 2008-04-28 08:58:43 -07:00
ext3 ext3: add missing unlock to error path in ext3_quota_write() 2008-07-04 10:40:05 -07:00
ext4 ext4: do not set extents feature from the kernel 2008-07-11 19:27:31 -04:00
fat Merge commit 'v2.6.26' into bkl-removal 2008-07-14 15:29:34 -06:00
freevxfs fs/freevxfs/: proper externs 2008-04-29 08:06:00 -07:00
fuse fuse: fix thinko in max I/O size calucation 2008-06-17 18:08:10 -07:00
gfs2 Merge git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6-nmw 2008-07-15 10:38:46 -07:00
hfs hfs: fix warning with 64k PAGE_SIZE 2008-04-30 08:29:52 -07:00
hfsplus Fix hfsplus oops on image without extents 2008-05-13 08:02:24 -07:00
hostfs uml: fix hostfs tv_usec calculations 2008-02-05 09:44:30 -08:00
hpfs mount options: fix hpfs 2008-02-08 09:22:40 -08:00
hppfs fix hppfs Makefile breakage 2008-05-21 16:55:58 -07:00
hugetlbfs mm: bdi: add separate writeback accounting capability 2008-04-30 08:29:50 -07:00
isofs isofs: fix access to unallocated memory when reading corrupted filesystem 2008-04-30 08:29:33 -07:00
jbd jbd: need to hold j_state_lock to updates to transaction t_state to T_COMMIT 2008-05-14 19:11:14 -07:00
jbd2 ext4: Add ordered mode support for delalloc 2008-07-11 19:27:31 -04:00
jffs2 Merge git://git.infradead.org/mtd-2.6 2008-05-01 11:15:28 -07:00
jfs jfs: remove DIRENTSIZ 2008-06-10 15:12:58 -05:00
lockd Merge branch 'for-2.6.27' of git://linux-nfs.org/~bfields/linux 2008-07-20 21:21:46 -07:00
minix iget: stop the MINIX filesystem from using iget() and read_inode() 2008-02-07 08:42:28 -08:00
msdos Replace BKL with superblock lock in fat/msdos/vfat 2008-06-20 14:05:54 -06:00
ncpfs Remove BKL from remote_llseek v2 2008-07-02 15:06:27 -06:00
nfs Merge branch 'bkl-removal' into next 2008-07-15 18:34:58 -04:00
nfs_common
nfsd Merge branch 'for-2.6.27' of git://linux-nfs.org/~bfields/linux 2008-07-20 21:21:46 -07:00
nls
ntfs ntfs: le*_add_cpu conversion 2008-05-24 09:56:08 -07:00
ocfs2 configfs: Allow ->make_item() and ->make_group() to return detailed errors. 2008-07-17 15:21:29 -07:00
openpromfs iget: stop OPENPROMFS from using iget() and read_inode() 2008-02-07 08:42:29 -08:00
partitions fs: replace remaining __FUNCTION__ occurrences 2008-04-30 08:29:54 -07:00
proc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2008-07-20 17:43:29 -07:00
qnx4 iget: stop QNX4 from using iget() and read_inode() 2008-02-07 08:42:28 -08:00
ramfs ramfs: enable splice write 2008-07-04 09:52:14 +02:00
reiserfs reiserfs: discard prealloc in reiserfs_delete_inode 2008-07-08 12:39:31 -07:00
romfs ROMFS: Fix up an error in iget removal 2008-03-19 18:53:36 -07:00
smbfs Remove BKL from remote_llseek v2 2008-07-02 15:06:27 -06:00
sysfs sysfs: remove error messages for -EEXIST case 2008-05-14 22:34:16 -07:00
sysv sysv: [bl]e*_add_cpu conversion 2008-04-30 08:29:52 -07:00
ubifs UBIFS: include to compilation 2008-07-15 17:35:24 +03:00
udf udf: Fix regression in UDF anchor block detection 2008-06-24 11:38:03 +02:00
ufs ufs: remove unneeded ufs_put_inode prototype 2008-05-13 08:02:23 -07:00
vfat Replace BKL with superblock lock in fat/msdos/vfat 2008-06-20 14:05:54 -06:00
xfs Fix reference counting race on log buffers 2008-07-11 11:37:18 -07:00
aio.c uml: activate_mm: remove the dead PF_BORROWED_MM check 2008-06-06 11:36:22 -07:00
anon_inodes.c [PATCH] sanitize anon_inode_getfd() 2008-05-01 13:08:50 -04:00
attr.c
bad_inode.c iget: introduce a function to register iget failure 2008-02-07 08:42:26 -08:00
binfmt_aout.c fs/binfmt_aout.c: use printk_ratelimit() 2008-04-29 08:06:04 -07:00
binfmt_elf_fdpic.c nommu: fix ksize() abuse 2008-06-06 11:29:13 -07:00
binfmt_elf.c execve filename: document and export via auxiliary vector 2008-07-22 09:59:40 -07:00
binfmt_em86.c binfmt_misc.c: avoid potential kernel stack overflow 2008-04-29 08:06:04 -07:00
binfmt_flat.c nommu: fix ksize() abuse 2008-06-06 11:29:13 -07:00
binfmt_misc.c binfmt_misc.c: avoid potential kernel stack overflow 2008-04-29 08:06:04 -07:00
binfmt_script.c binfmt_misc.c: avoid potential kernel stack overflow 2008-04-29 08:06:04 -07:00
binfmt_som.c [PATCH] sanitize handling of shared descriptor tables in failing execve() 2008-04-25 09:23:53 -04:00
bio-integrity.c block: integrity checkpatch cleanups 2008-07-03 13:21:13 +02:00
bio.c Add bvec_merge_data to handle stacked devices and ->merge_bvec() 2008-07-03 13:21:15 +02:00
block_dev.c [PATCH] fix cgroup-inflicted breakage in block_dev.c 2008-06-23 08:30:55 -04:00
buffer.c Merge branch 'generic-ipi' into generic-ipi-for-linus 2008-07-15 21:55:59 +02:00
char_dev.c Remove the lock_kernel() call from chrdev_open() 2008-06-20 14:05:53 -06:00
compat_binfmt_elf.c x86: compat_binfmt_elf 2008-01-30 13:31:46 +01:00
compat_ioctl.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/holtmann/bluetooth-2.6 2008-07-19 00:30:39 -07:00
compat.c [PATCH] get rid of leak in compat_execve() 2008-05-16 17:23:05 -04:00
dcache.c [patch 2/3] vfs: dcache cleanups 2008-06-23 13:07:00 -04:00
dcookies.c d_path: Make d_path() use a struct path 2008-02-14 21:17:09 -08:00
direct-io.c Pagecache zeroing: zero_user_segment, zero_user_segments and zero_user 2008-02-05 09:44:13 -08:00
dnotify.c [PATCH] split linux/file.h 2008-05-01 13:08:16 -04:00
dquot.c quota: don't call sync_fs() from vfs_quota_off() when there's no quota turn off 2008-05-13 08:02:23 -07:00
drop_caches.c vfs: skip inodes without pages to free in drop_pagecache_sb() 2008-04-29 08:06:05 -07:00
eventfd.c [PATCH] sanitize anon_inode_getfd() 2008-05-01 13:08:50 -04:00
eventpoll.c [PATCH] sanitize anon_inode_getfd() 2008-05-01 13:08:50 -04:00
exec.c exec: fix stack excutability without PT_GNU_STACK 2008-07-10 13:25:43 -07:00
fcntl.c Call fasync() functions without the BKL 2008-07-02 15:06:28 -06:00
fifo.c
file_table.c [PATCH] split linux/file.h 2008-05-01 13:08:16 -04:00
file.c [PATCH] avoid multiplication overflows and signedness issues for max_fds 2008-05-16 17:22:52 -04:00
filesystems.c
fs-writeback.c VFS: export sync_sb_inodes 2008-07-14 19:10:52 +03:00
generic_acl.c
inode.c VFS: fix unused variable warning 2008-05-06 13:13:37 -07:00
inotify_user.c Remove duplicated unlikely() in IS_ERR() 2008-04-29 08:06:25 -07:00
inotify.c inotify: remove debug code 2008-02-06 10:41:07 -08:00
internal.h [PATCH] move a bunch of declarations to fs/internal.h 2008-04-21 23:11:01 -04:00
ioctl.c make vfs_ioctl() static 2008-04-29 08:06:00 -07:00
ioprio.c
Kconfig Merge branch 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mfasheh/ocfs2 2008-07-17 10:55:51 -07:00
Kconfig.binfmt frv: don't offer BINFMT_FLAT 2008-06-06 11:29:08 -07:00
libfs.c add kernel-doc for simple_read_from_buffer and memory_read_from_buffer 2008-07-04 10:40:07 -07:00
locks.c [patch 4/4] flock: remove unused fields from file_lock_operations 2008-06-23 11:52:30 -04:00
Makefile Merge branch 'for_linus' of git://git.infradead.org/~dedekind/ubifs-2.6 2008-07-16 15:02:57 -07:00
mbcache.c vfs: fix possible deadlock in ext2, ext3, ext4 when using xattrs 2008-04-15 19:35:41 -07:00
mpage.c vfs: add hooks for ext4's delayed allocation support 2008-07-11 19:27:31 -04:00
namei.c [patch 3/4] vfs: fix ERR_PTR abuse in generic_readlink 2008-06-23 11:52:30 -04:00
namespace.c LSM/SELinux: show LSM mount options in /proc/mounts 2008-07-14 15:02:05 +10:00
nfsctl.c Introduce path_put() 2008-02-14 21:13:33 -08:00
no-block.c
open.c security: filesystem capabilities: fix fragile setuid fixup code 2008-07-04 10:40:08 -07:00
pipe.c [patch 1/4] vfs: path_{get,put}() cleanups 2008-06-23 11:52:29 -04:00
pnode.c [patch 7/7] vfs: mountinfo: show dominating group id 2008-04-23 00:05:09 -04:00
pnode.h [patch 7/7] vfs: mountinfo: show dominating group id 2008-04-23 00:05:09 -04:00
posix_acl.c
quota_v1.c quota: do not allow setting of quota limits to too high values 2008-04-28 08:58:32 -07:00
quota_v2.c quota: le*_add_cpu conversion 2008-04-30 08:29:51 -07:00
quota.c quota: quota core changes for quotaon on remount 2008-04-28 08:58:33 -07:00
read_write.c Remove BKL from remote_llseek v2 2008-07-02 15:06:27 -06:00
read_write.h
readdir.c
select.c Fix performance regression on lmbench select benchmark 2008-06-22 12:23:15 -07:00
seq_file.c [patch 2/7] vfs: mountinfo: add seq_file_root() 2008-04-23 00:04:38 -04:00
signalfd.c [PATCH] sanitize anon_inode_getfd() 2008-05-01 13:08:50 -04:00
splice.c splice: fix generic_file_splice_read() race with page invalidation 2008-07-04 09:52:14 +02:00
stack.c
stat.c Introduce path_put() 2008-02-14 21:13:33 -08:00
super.c make __put_super() static 2008-04-29 08:06:00 -07:00
sync.c vfs: fix unconditional write_super() call in file_fsync() 2008-04-29 08:06:06 -07:00
timerfd.c [PATCH] sanitize anon_inode_getfd() 2008-05-01 13:08:50 -04:00
utimes.c [patch for 2.6.26 4/4] vfs: utimensat(): fix write access check for futimens() 2008-06-23 08:43:52 -04:00
xattr_acl.c
xattr.c xattr: add missing consts to function arguments 2008-04-29 08:06:06 -07:00