diff options
| -rw-r--r-- | src/misc/realpath.c | 159 |
1 files changed, 136 insertions, 23 deletions
diff --git a/src/misc/realpath.c b/src/misc/realpath.c index d2708e59..db8b74dc 100644 --- a/src/misc/realpath.c +++ b/src/misc/realpath.c @@ -1,43 +1,156 @@ #include <stdlib.h> #include <limits.h> -#include <sys/stat.h> -#include <fcntl.h> #include <errno.h> #include <unistd.h> #include <string.h> -#include "syscall.h" + +static size_t slash_len(const char *s) +{ + const char *s0 = s; + while (*s == '/') s++; + return s-s0; +} char *realpath(const char *restrict filename, char *restrict resolved) { - int fd; - ssize_t r; - struct stat st1, st2; - char buf[15+3*sizeof(int)]; - char tmp[PATH_MAX]; + char stack[PATH_MAX+1]; + char output[PATH_MAX]; + size_t p, q, l, l0, cnt=0, nup=0; + int check_dir=0; if (!filename) { errno = EINVAL; return 0; } + l = strnlen(filename, sizeof stack); + if (!l) { + errno = ENOENT; + return 0; + } + if (l >= PATH_MAX) goto toolong; + p = sizeof stack - l - 1; + q = 0; + memcpy(stack+p, filename, l+1); + + /* Main loop. Each iteration pops the next part from stack of + * remaining path components and consumes any slashes that follow. + * If not a link, it's moved to output; if a link, contents are + * pushed to the stack. */ +restart: + for (; ; p+=slash_len(stack+p)) { + /* If stack starts with /, the whole component is / or // + * and the output state must be reset. */ + if (stack[p] == '/') { + check_dir=0; + nup=0; + q=0; + output[q++] = '/'; + p++; + /* Initial // is special. */ + if (stack[p] == '/' && stack[p+1] != '/') + output[q++] = '/'; + continue; + } + + char *z = __strchrnul(stack+p, '/'); + l0 = l = z-(stack+p); - fd = sys_open(filename, O_PATH|O_NONBLOCK|O_CLOEXEC); - if (fd < 0) return 0; - __procfdname(buf, fd); + if (!l && !check_dir) break; - r = readlink(buf, tmp, sizeof tmp - 1); - if (r < 0) goto err; - tmp[r] = 0; + /* Skip any . component but preserve check_dir status. */ + if (l==1 && stack[p]=='.') { + p += l; + continue; + } - fstat(fd, &st1); - r = stat(tmp, &st2); - if (r<0 || st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino) { - if (!r) errno = ELOOP; - goto err; + /* Copy next component onto output at least temporarily, to + * call readlink, but wait to advance output position until + * determining it's not a link. */ + if (q && output[q-1] != '/') { + if (!p) goto toolong; + stack[--p] = '/'; + l++; + } + if (q+l >= PATH_MAX) goto toolong; + memcpy(output+q, stack+p, l); + output[q+l] = 0; + p += l; + + int up = 0; + if (l0==2 && stack[p-2]=='.' && stack[p-1]=='.') { + up = 1; + /* Any non-.. path components we could cancel start + * after nup repetitions of the 3-byte string "../"; + * if there are none, accumulate .. components to + * later apply to cwd, if needed. */ + if (q <= 3*nup) { + nup++; + q += l; + continue; + } + /* When previous components are already known to be + * directories, processing .. can skip readlink. */ + if (!check_dir) goto skip_readlink; + } + ssize_t k = readlink(output, stack, p); + if (k==p) goto toolong; + if (!k) { + errno = ENOENT; + return 0; + } + if (k<0) { + if (errno != EINVAL) return 0; +skip_readlink: + check_dir = 0; + if (up) { + while(q && output[q-1]!='/') q--; + if (q>1 && (q>2 || output[0]!='/')) q--; + continue; + } + if (l0) q += l; + check_dir = stack[p]; + continue; + } + if (++cnt == SYMLOOP_MAX) { + errno = ELOOP; + return 0; + } + + /* If link contents end in /, strip any slashes already on + * stack to avoid /->// or //->/// or spurious toolong. */ + if (stack[k-1]=='/') while (stack[p]=='/') p++; + p -= k; + memmove(stack+p, stack, k); + + /* Skip the stack advancement in case we have a new + * absolute base path. */ + goto restart; } - __syscall(SYS_close, fd); - return resolved ? strcpy(resolved, tmp) : strdup(tmp); -err: - __syscall(SYS_close, fd); + output[q] = 0; + + if (output[0] != '/') { + if (!getcwd(stack, sizeof stack)) return 0; + l = strlen(stack); + /* Cancel any initial .. components. */ + p = 0; + while (nup--) { + while(l>1 && stack[l-1]!='/') l--; + if (l>1) l--; + p += 2; + if (p<q) p++; + } + if (q-p && stack[l-1]!='/') stack[l++] = '/'; + if (l + (q-p) + 1 >= PATH_MAX) goto toolong; + memmove(output + l, output + p, q - p + 1); + memcpy(output, stack, l); + q = l + q-p; + } + + if (resolved) return memcpy(resolved, output, q+1); + else return strdup(output); + +toolong: + errno = ENAMETOOLONG; return 0; } |