[RFC PATCH v2 8/8] tools/include/string: Implement `strdup()` and `strndup()`

From: Ammar Faizi
Date: Tue Mar 22 2022 - 06:22:18 EST


These functions are currently only available on architectures that have
my_syscall6() macro implemented. Since these functions use malloc(),
malloc() uses mmap(), mmap() depends on my_syscall6() macro.

On architectures that don't support my_syscall6(), these function will
always return NULL with errno set to ENOSYS.

Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
---

@@ Changelog:

Link RFC v1: https://lore.kernel.org/lkml/20220320093750.159991-7-ammarfaizi2@xxxxxxxxxxx/
RFC v1 -> RFC v2:
- Update strdup and strndup implementation, use strlen and strnlen to get
the string length first (comment from Willy and Alviro).
- Fix the subject line prefix, it was "tools/include/string: ", it should be
"tools/nolibc/string: ".
- Update the commit message.
---
tools/include/nolibc/string.h | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)

diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h
index 1426eefc1ef2..bcc76f89199e 100644
--- a/tools/include/nolibc/string.h
+++ b/tools/include/nolibc/string.h
@@ -9,6 +9,8 @@

#include "std.h"

+static void *malloc(size_t len);
+
/*
* As much as possible, please keep functions alphabetically sorted.
*/
@@ -147,6 +149,36 @@ size_t strnlen(const char *str, size_t maxlen)
return len;
}

+static __attribute__((unused))
+char *strdup(const char *str)
+{
+ size_t len;
+ char *ret;
+
+ len = strlen(str);
+ ret = malloc(len + 1);
+ if (__builtin_expect(ret != NULL, 1))
+ memcpy(ret, str, len + 1);
+
+ return ret;
+}
+
+static __attribute__((unused))
+char *strndup(const char *str, size_t maxlen)
+{
+ size_t len;
+ char *ret;
+
+ len = strnlen(str, maxlen);
+ ret = malloc(len + 1);
+ if (__builtin_expect(ret != NULL, 1)) {
+ memcpy(ret, str, len);
+ ret[len] = '\0';
+ }
+
+ return ret;
+}
+
static __attribute__((unused))
size_t strlcat(char *dst, const char *src, size_t size)
{
--
Ammar Faizi