diff options
Diffstat (limited to 'src/sysdep.c')
| -rw-r--r-- | src/sysdep.c | 73 |
1 files changed, 47 insertions, 26 deletions
diff --git a/src/sysdep.c b/src/sysdep.c index 7a0c8a8ab85..ddcb594f668 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 <sys/personality.h> -/* 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. */ |