From: Tulio A M Mendes <tadryanom@hotmail.com>
Date: Sun, 19 Apr 2026 17:55:59 +0000 (-0300)
Subject: Fix getcwd(NULL, 0): allocate buffer when buf is NULL (glibc extension)
X-Git-Url: https://projects.tadryanom.me/?a=commitdiff_plain;h=13b43e0ea66930cee10969fd9c70bdf0de500e30;p=AdrOS.git

Fix getcwd(NULL, 0): allocate buffer when buf is NULL (glibc extension)

Bash calls getcwd(NULL, 0) — a glibc extension where NULL means
"allocate a buffer for me". Both ulibc and newlib wrappers passed
NULL straight to the kernel syscall, which returned -EFAULT because
the kernel rejects user_buf == NULL.

This caused:
  shell-init: error retrieving current directory: getcwd:
  cannot access parent directories: Bad address

Now both wrappers handle NULL buf by malloc'ing a buffer (4096 bytes
if size is 0), passing it to the kernel, and returning the allocated
pointer on success (or freeing it on error). This matches glibc
behavior and unblocks bash and other ported software.
---

diff --git a/newlib/libgloss/adros/posix_stubs.c b/newlib/libgloss/adros/posix_stubs.c
index 75459089..c796b0b6 100644
--- a/newlib/libgloss/adros/posix_stubs.c
+++ b/newlib/libgloss/adros/posix_stubs.c
@@ -176,8 +176,19 @@ int chdir(const char *path) {
 }
 
 char *getcwd(char *buf, size_t size) {
+    int allocated = 0;
+    if (!buf) {
+        if (size == 0) size = 4096;
+        buf = (char *)malloc(size);
+        if (!buf) { errno = ENOMEM; return 0; }
+        allocated = 1;
+    }
     int r = _sc2(SYS_GETCWD, (int)buf, (int)size);
-    if (r < 0) { errno = -r; return 0; }
+    if (r < 0) {
+        errno = -r;
+        if (allocated) free(buf);
+        return 0;
+    }
     return buf;
 }
 
diff --git a/user/ulibc/src/unistd.c b/user/ulibc/src/unistd.c
index 34c6ac94..6dcadb35 100644
--- a/user/ulibc/src/unistd.c
+++ b/user/ulibc/src/unistd.c
@@ -11,6 +11,7 @@
 #include "syscall.h"
 #include "errno.h"
 #include "termios.h"
+#include "stdlib.h"
 
 int read(int fd, void* buf, size_t count) {
     return __syscall_ret(_syscall3(SYS_READ, fd, (int)buf, (int)count));
@@ -70,8 +71,19 @@ int chdir(const char* path) {
 }
 
 char* getcwd(char* buf, size_t size) {
+    int allocated = 0;
+    if (!buf) {
+        if (size == 0) size = 4096;
+        buf = (char*)malloc(size);
+        if (!buf) { errno = ENOMEM; return NULL; }
+        allocated = 1;
+    }
     int r = _syscall2(SYS_GETCWD, (int)buf, (int)size);
-    if (r < 0) { errno = -r; return NULL; }
+    if (r < 0) {
+        errno = -r;
+        if (allocated) free(buf);
+        return NULL;
+    }
     return buf;
 }