linux-kernel - [PATCH nolibc 61/61] tools/nolibc/string: Implement `strdup()` and `strndup()`

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Date:   Mon, 18 Apr 2022 17:42:25 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     gwml@...r.gnuweeb.org, kernel-team@...com, w@....eu,
        Ammar Faizi <ammarfaizi2@...weeb.org>,
        Willy Tarreau <w@....eu>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH nolibc 61/61] tools/nolibc/string: Implement `strdup()` and `strndup()`

From: Ammar Faizi <ammarfaizi2@...weeb.org>

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.

Acked-by: Willy Tarreau <w@....eu>
Signed-off-by: Ammar Faizi <ammarfaizi2@...weeb.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 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 f43d52a44d09..bef35bee9c44 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.
  */
@@ -156,6 +158,36 @@ 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)
 {
-- 
2.31.1.189.g2e36527f23