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authorSamuel Holland <samuel@sholland.org>2018-09-11 22:28:24 -0500
committerSamuel Holland <samuel@sholland.org>2018-09-11 22:50:44 -0500
commite9224395eba97e86d8d411f016972b2d70cd6ff3 (patch)
tree3298e2079d913f7742016220c1d2145e8c401804
parent71d20ba411d3923934409936ba20f6ead8a6cbcd (diff)
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realpath: Intercept realpath(/proc/self/exe)
Reuse the machinery from readlink Signed-off-by: Samuel Holland <samuel@sholland.org>
-rw-r--r--CHANGELOG.rst5
-rw-r--r--Makefile1
-rw-r--r--libgcompat/realpath.c51
3 files changed, 55 insertions, 2 deletions
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 2a4b1d3..188d75c 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -35,9 +35,10 @@ math
* Add most __*_finite functions, courtesy of Elizabeth Myers.
-readlink
---------
+readlink/realpath
+-----------------
+* Intercept realpath as well as readlink.
* Report ENOSYS on dlsym failure.
diff --git a/Makefile b/Makefile
index 272bfd9..934422f 100644
--- a/Makefile
+++ b/Makefile
@@ -16,6 +16,7 @@ LIBGCOMPAT_SRC = \
libgcompat/pthread.c \
libgcompat/pwd.c \
libgcompat/readlink.c \
+ libgcompat/realpath.c \
libgcompat/resolv.c \
libgcompat/resource.c \
libgcompat/setjmp.c \
diff --git a/libgcompat/realpath.c b/libgcompat/realpath.c
new file mode 100644
index 0000000..ab68cc4
--- /dev/null
+++ b/libgcompat/realpath.c
@@ -0,0 +1,51 @@
+#include <dlfcn.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#ifndef LINKER
+#error LINKER must be defined
+#endif
+
+static char *(*real_realpath)(const char *restrict, char *restrict);
+
+char *realpath(const char *restrict path, char *restrict resolved)
+{
+ if (real_realpath == NULL) {
+ real_realpath = dlsym(RTLD_NEXT, "realpath");
+ if (real_realpath == NULL) {
+ errno = ENOSYS;
+ return NULL;
+ }
+ }
+
+ if (!strcmp(path, "/proc/self/exe")) {
+ char *fixed = resolved;
+
+ if (fixed == NULL) {
+ fixed = malloc(PATH_MAX);
+ if (fixed == NULL) {
+ errno = ENOMEM;
+ return NULL;
+ }
+ }
+
+ /* If passed in, the buffer is at least PATH_MAX per POSIX. */
+ ssize_t written = readlink(path, fixed, PATH_MAX - 1);
+ if (written == -1) {
+ /* Free the buffer iff we allocated it. */
+ if (fixed != resolved)
+ free(fixed);
+ return NULL;
+ }
+ fixed[written] = '\0';
+
+ return fixed;
+ }
+
+ return real_realpath(path, resolved);
+}