>From c14eab222c5208ec0650292c3771a3ee632fdb0d Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Sun, 11 Nov 2018 22:18:47 -0800 Subject: [PATCH] Fix dumping on GNU/Linux ppc64le Problem reported by Thomas Fitzsimmons (Bug#33174). * src/emacs.c (main): Adjust to sysdep.c changes. * src/sysdep.c (exec_personality): New static var. (disable_address_randomization): Remove, replacing with ... (maybe_disable_address_randomization): ... this new function. Do not set or use an environment variable; use a command-line argument instead, and set the new static var. Migrate the emacs.c personality-change code to here, where it belongs. (emacs_exec_file): Simplify by using new static var. --- src/emacs.c | 23 +---------------- src/lisp.h | 7 +++-- src/sysdep.c | 73 +++++++++++++++++++++++++++++++++------------------- 3 files changed, 53 insertions(+), 50 deletions(-) diff --git a/src/emacs.c b/src/emacs.c index 07df191035..512174d562 100644 --- a/src/emacs.c +++ b/src/emacs.c @@ -706,28 +706,7 @@ main (int argc, char **argv) dumping = false; #endif - /* True if address randomization interferes with memory allocation. */ -# ifdef __PPC64__ - bool disable_aslr = true; -# else - bool disable_aslr = dumping; -# endif - - if (disable_aslr && disable_address_randomization () - && !getenv ("EMACS_HEAP_EXEC")) - { - /* Set this so the personality will be reverted before execs - after this one, and to work around an re-exec loop on buggy - kernels (Bug#32083). */ - xputenv ("EMACS_HEAP_EXEC=true"); - - /* Address randomization was enabled, but is now disabled. - Re-execute Emacs to get a clean slate. */ - execvp (argv[0], argv); - - /* If the exec fails, warn and then try anyway. */ - perror (argv[0]); - } + argc = maybe_disable_address_randomization (dumping, argc, argv); #ifndef CANNOT_DUMP might_dump = !initialized; diff --git a/src/lisp.h b/src/lisp.h index eb6762678c..383d61274c 100644 --- a/src/lisp.h +++ b/src/lisp.h @@ -4325,9 +4325,12 @@ struct tty_display_info; /* Defined in sysdep.c. */ #ifdef HAVE_PERSONALITY_ADDR_NO_RANDOMIZE -extern bool disable_address_randomization (void); +extern int maybe_disable_address_randomization (bool, int, char **); #else -INLINE bool disable_address_randomization (void) { return false; } +INLINE void +maybe_disable_address_randomization (bool dumping, int argc, char **argv) +{ +} #endif extern int emacs_exec_file (char const *, char *const *, char *const *); extern void init_standard_fds (void); diff --git a/src/sysdep.c b/src/sysdep.c index 7a0c8a8ab8..ddcb594f66 100644 --- a/src/sysdep.c +++ b/src/sysdep.c @@ -150,22 +150,52 @@ static const int baud_convert[] = #ifdef HAVE_PERSONALITY_ADDR_NO_RANDOMIZE # include -/* Disable address randomization in the current process. Return true - if addresses were randomized but this has been disabled, false - otherwise. */ -bool -disable_address_randomization (void) +/* If not -1, the personality that should be restored before exec. */ +static int exec_personality; + +/* Try to disable randomization if the current process needs it and + does not appear to have it already. */ +int +maybe_disable_address_randomization (bool dumping, int argc, char **argv) { - int pers = personality (0xffffffff); - if (pers < 0) - return false; - int desired_pers = pers | ADDR_NO_RANDOMIZE; + /* Undocumented Emacs option used only by this function. */ + static char const aslr_disabled_option[] = "--__aslr-disabled"; - /* Call 'personality' twice, to detect buggy platforms like WSL - where 'personality' always returns 0. */ - return (pers != desired_pers - && personality (desired_pers) == pers - && personality (0xffffffff) == desired_pers); + if (argc < 2 || strcmp (argv[1], aslr_disabled_option) != 0) + { + bool disable_aslr = dumping; +# ifdef __PPC64__ + disable_aslr = true; +# endif + exec_personality = disable_aslr ? personality (0xffffffff) : -1; + if (exec_personality & ADDR_NO_RANDOMIZE) + exec_personality = -1; + if (exec_personality != -1 + && personality (exec_personality | ADDR_NO_RANDOMIZE) != -1) + { + char **newargv = malloc ((argc + 2) * sizeof *newargv); + if (newargv) + { + /* Invoke self with undocumented option. */ + newargv[0] = argv[0]; + newargv[1] = (char *) aslr_disabled_option; + memcpy (&newargv[2], &argv[1], argc * sizeof *newargv); + execvp (newargv[0], newargv); + } + + /* If malloc or execvp fails, warn and then try anyway. */ + perror (argv[0]); + free (newargv); + } + } + else + { + /* Our earlier incarnation already disabled ASLR. */ + argc--; + memmove (&argv[1], &argv[2], argc * sizeof *argv); + } + + return argc; } #endif @@ -177,21 +207,12 @@ int emacs_exec_file (char const *file, char *const *argv, char *const *envp) { #ifdef HAVE_PERSONALITY_ADDR_NO_RANDOMIZE - int pers = getenv ("EMACS_HEAP_EXEC") ? personality (0xffffffff) : -1; - bool change_personality = 0 <= pers && pers & ADDR_NO_RANDOMIZE; - if (change_personality) - personality (pers & ~ADDR_NO_RANDOMIZE); + if (exec_personality != -1) + personality (exec_personality); #endif execve (file, argv, envp); - int err = errno; - -#ifdef HAVE_PERSONALITY_ADDR_NO_RANDOMIZE - if (change_personality) - personality (pers); -#endif - - return err; + return errno; } /* If FD is not already open, arrange for it to be open with FLAGS. */ -- 2.17.1