The patch titled execve filename: document and export via auxiliary vector has been added to the -mm tree. Its filename is execve-filename-document-and-export-via-auxiliary-vector.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: execve filename: document and export via auxiliary vector From: John Reiser <jreiser@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> Cc: Roland McGrath <roland@xxxxxxxxxx> Cc: Jakub Jelinek <jakub@xxxxxxxxxx> Cc: Ulrich Drepper <drepper@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/binfmt_elf.c | 1 + include/linux/auxvec.h | 4 +++- 2 files changed, 4 insertions(+), 1 deletion(-) diff -puN fs/binfmt_elf.c~execve-filename-document-and-export-via-auxiliary-vector fs/binfmt_elf.c --- a/fs/binfmt_elf.c~execve-filename-document-and-export-via-auxiliary-vector +++ a/fs/binfmt_elf.c @@ -205,6 +205,7 @@ create_elf_tables(struct linux_binprm *b NEW_AUX_ENT(AT_GID, tsk->gid); NEW_AUX_ENT(AT_EGID, tsk->egid); NEW_AUX_ENT(AT_SECURE, security_bprm_secureexec(bprm)); + NEW_AUX_ENT(AT_EXECFN, bprm->exec); if (k_platform) { NEW_AUX_ENT(AT_PLATFORM, (elf_addr_t)(unsigned long)u_platform); diff -puN include/linux/auxvec.h~execve-filename-document-and-export-via-auxiliary-vector include/linux/auxvec.h --- a/include/linux/auxvec.h~execve-filename-document-and-export-via-auxiliary-vector +++ a/include/linux/auxvec.h @@ -26,8 +26,10 @@ #define AT_SECURE 23 /* secure mode boolean */ +#define AT_EXECFN 31 /* filename of program */ #ifdef __KERNEL__ -#define AT_VECTOR_SIZE_BASE (14 + 2) /* NEW_AUX_ENT entries in auxiliary table */ +#define AT_VECTOR_SIZE_BASE 17 /* NEW_AUX_ENT entries in auxiliary table */ + /* number of "#define AT_.*" above, minus {AT_NULL, AT_IGNORE, AT_NOTELF} */ #endif #endif /* _LINUX_AUXVEC_H */ _ Patches currently in -mm which might be from jreiser@xxxxxxxxxxxx are execve-filename-document-and-export-via-auxiliary-vector.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html