From f9fb20b42da0e755d93de229a5a737d79a0e8f60 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Fri, 1 Nov 2013 20:34:05 -0400 Subject: [PATCH] simplify faccessat AT_EACCESS path and eliminate resource dependence now that we're waiting for the exit status of the child process, the result can be conveyed in the exit status rather than via a pipe. since the error value might not fit in 7 bits, a table is used to translate possible meaningful error values to small integers. --- src/unistd/faccessat.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/src/unistd/faccessat.c b/src/unistd/faccessat.c index 76bbd4c7..33478959 100644 --- a/src/unistd/faccessat.c +++ b/src/unistd/faccessat.c @@ -1,5 +1,6 @@ #include #include +#include #include #include "syscall.h" #include "pthread_impl.h" @@ -8,19 +9,26 @@ struct ctx { int fd; const char *filename; int amode; - int p; +}; + +static const int errors[] = { + 0, -EACCES, -ELOOP, -ENAMETOOLONG, -ENOENT, -ENOTDIR, + -EROFS, -EBADF, -EINVAL, -ETXTBSY, + -EFAULT, -EIO, -ENOMEM, + -EBUSY }; static int checker(void *p) { struct ctx *c = p; int ret; + int i; if (__syscall(SYS_setregid, __syscall(SYS_getegid), -1) || __syscall(SYS_setreuid, __syscall(SYS_geteuid), -1)) __syscall(SYS_exit, 1); ret = __syscall(SYS_faccessat, c->fd, c->filename, c->amode, 0); - __syscall(SYS_write, c->p, &ret, sizeof ret); - return 0; + for (i=0; i < sizeof errors/sizeof *errors - 1 && ret!=errors[i]; i++); + return i; } int faccessat(int fd, const char *filename, int amode, int flag) @@ -34,21 +42,20 @@ int faccessat(int fd, const char *filename, int amode, int flag) char stack[1024]; sigset_t set; pid_t pid; - int status; - int ret, p[2]; - - if (pipe2(p, O_CLOEXEC)) return __syscall_ret(-EBUSY); - struct ctx c = { .fd = fd, .filename = filename, .amode = amode, .p = p[1] }; + int ret = -EBUSY; + struct ctx c = { .fd = fd, .filename = filename, .amode = amode }; __block_all_sigs(&set); pid = __clone(checker, stack+sizeof stack, 0, &c); - __syscall(SYS_close, p[1]); - - if (pid<0 || __syscall(SYS_read, p[0], &ret, sizeof ret) != sizeof(ret)) - ret = -EBUSY; - __syscall(SYS_close, p[0]); - __syscall(SYS_wait4, pid, &status, __WCLONE, 0); + if (pid > 0) { + int status; + do { + __syscall(SYS_wait4, pid, &status, __WCLONE, 0); + } while (!WIFEXITED(status) && !WIFSIGNALED(status)); + if (WIFEXITED(status)) + ret = errors[WEXITSTATUS(status)]; + } __restore_sigs(&set); -- 2.25.1