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-rw-r--r--libc/unistd/exec.c94
1 files changed, 57 insertions, 37 deletions
diff --git a/libc/unistd/exec.c b/libc/unistd/exec.c
index 11807a8a7..1006ac3c4 100644
--- a/libc/unistd/exec.c
+++ b/libc/unistd/exec.c
@@ -42,47 +42,66 @@ libc_hidden_proto(munmap)
libc_hidden_proto(getenv)
/**********************************************************************/
-#if defined(__ARCH_USE_MMU__) || defined(__UCLIBC_UCLINUX_BROKEN_MUNMAP__)
+#define EXEC_FUNC_COMMON 0
+#define EXEC_FUNC_EXECVP 1
+#if defined(__ARCH_USE_MMU__)
-/* We have an MMU, so use alloca() to grab space for buffers and
- * arg lists. Also fall back to alloca() if munmap() is broken. */
+/* We have an MMU, so use alloca() to grab space for buffers and arg lists. */
-# define EXEC_ALLOC_SIZE(VAR) /* nothing to do */
-# define EXEC_ALLOC(SIZE,VAR) alloca((SIZE))
-# define EXEC_FREE(PTR,VAR) ((void)0)
+# define EXEC_ALLOC_SIZE(VAR) /* nothing to do */
+# define EXEC_ALLOC(SIZE,VAR,FUNC) alloca((SIZE))
+# define EXEC_FREE(PTR,VAR) ((void)0)
#else
-/* We do not have an MMU, so using alloca() is not an option.
- * Less obviously, using malloc() is not an option either since
- * malloc()ed memory can leak in a vfork() and exec*() situation.
- * Therefore, we must use mmap() and unmap() directly, caching
- * the result as we go. This way we minimize the leak to 1
- * allocation.
+/* We do not have an MMU, so using alloca() is not an option (as this will
+ * easily overflow the stack in most setups). Less obviously, using malloc()
+ * is not an option either since malloc()ed memory can leak in from a vfork()ed
+ * child into the parent as no one is around after the child calls exec*() to
+ * free() the memory. Therefore, we must use mmap() and unmap() directly,
+ * caching the result as we go. This way we minimize the leak by reusing the
+ * memory with every call to an exec*().
+ *
+ * To prevent recursive use of the same cached memory, we have to give execvp()
+ * its own cache. Here are the nested exec calls (a/-: alloc/no-alloc):
+ * execve(-) -> calls straight to kernel
+ * execl(a) -> execve(-)
+ * execlp(a) -> execvp(a) !! recursive usage !!
+ * execle(a) -> execve(-)
+ * execv(-) -> execve(-)
+ * execvp(a) -> execve(-)
*/
-# define EXEC_ALLOC_SIZE(VAR) size_t VAR; /* Semicolon included! */
-# define EXEC_ALLOC(SIZE,VAR) __exec_alloc((VAR = (SIZE)))
-# define EXEC_FREE(PTR,VAR) ((void)0)
+# define EXEC_ALLOC_SIZE(VAR) /* nothing to do */
+# define EXEC_ALLOC(SIZE,VAR,FUNC) __exec_alloc((SIZE), FUNC)
+# define EXEC_FREE(PTR,VAR) ((void)0)
-extern void *__exec_alloc(size_t size) attribute_hidden;
+extern void *__exec_alloc(size_t size, int func) attribute_hidden;
# ifdef L___exec_alloc
-void attribute_hidden *__exec_alloc(size_t size)
+void attribute_hidden *__exec_alloc(size_t size, int func)
{
- static void *p;
- static size_t old_size;
-
- if (old_size >= size)
- return p;
- else if (p)
- munmap(p, old_size);
-
- old_size = size;
- p = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
-
- return (p != MAP_FAILED) ? p : NULL;
+ static void *common_cache, *execvp_cache;
+ static size_t common_size, execvp_size;
+
+ void **cache = (func ? &execvp_cache : &common_cache);
+ size_t *cache_size = (func ? &execvp_size : &common_size);
+
+ if (*cache_size >= size)
+ return *cache;
+ else if (*cache)
+ munmap(*cache, *cache_size);
+
+ *cache_size = size;
+ return *cache = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
+
+ /* We don't actually handle OOM in the exec funcs ...
+ if (*cache != MAP_FAILED)
+ return *cache;
+ else
+ return (*cache = NULL);
+ */
}
# endif
@@ -98,7 +117,7 @@ int execl(const char *path, const char *arg, ...)
char **argv;
char **p;
va_list args;
-
+
n = 0;
va_start(args, arg);
do {
@@ -106,7 +125,7 @@ int execl(const char *path, const char *arg, ...)
} while (va_arg(args, char *));
va_end(args);
- p = argv = (char **) EXEC_ALLOC((n+1) * sizeof(char *), size);
+ p = argv = (char **) EXEC_ALLOC((n+1) * sizeof(char *), size, EXEC_FUNC_COMMON);
p[0] = (char *)arg;
@@ -146,7 +165,7 @@ int execle(const char *path, const char *arg, ...)
char **p;
char *const *envp;
va_list args;
-
+
n = 0;
va_start(args, arg);
do {
@@ -155,7 +174,7 @@ int execle(const char *path, const char *arg, ...)
envp = va_arg(args, char *const *); /* Varies from execl and execlp. */
va_end(args);
- p = argv = (char **) EXEC_ALLOC((n+1) * sizeof(char *), size);
+ p = argv = (char **) EXEC_ALLOC((n+1) * sizeof(char *), size, EXEC_FUNC_COMMON);
p[0] = (char *)arg;
@@ -184,7 +203,7 @@ int execlp(const char *file, const char *arg, ...)
char **argv;
char **p;
va_list args;
-
+
n = 0;
va_start(args, arg);
do {
@@ -192,7 +211,7 @@ int execlp(const char *file, const char *arg, ...)
} while (va_arg(args, char *));
va_end(args);
- p = argv = (char **) EXEC_ALLOC((n+1) * sizeof(char *), size);
+ p = argv = (char **) EXEC_ALLOC((n+1) * sizeof(char *), size, EXEC_FUNC_COMMON);
p[0] = (char *)arg;
@@ -248,7 +267,7 @@ int execvp(const char *path, char *const argv[])
/* Need the dimension - 1. We omit counting the trailing
* NULL but we actually omit the first entry. */
for (n=0 ; argv[n] ; n++) {}
- nargv = (char **) EXEC_ALLOC((n+2) * sizeof(char *), size2);
+ nargv = (char **) EXEC_ALLOC((n+2) * sizeof(char *), size2, EXEC_FUNC_EXECVP);
nargv[0] = argv[0];
nargv[1] = (char *)path;
memcpy(nargv+2, argv+1, n*sizeof(char *));
@@ -272,7 +291,8 @@ int execvp(const char *path, char *const argv[])
}
len = (FILENAME_MAX - 1) - plen;
- if ((buf = EXEC_ALLOC(FILENAME_MAX, size)) != NULL) {
+ buf = EXEC_ALLOC(FILENAME_MAX, size, EXEC_FUNC_EXECVP);
+ {
int seen_small = 0;
s0 = buf + len;
memcpy(s0, path, plen+1);