Re: [PATCH bpf v2 14/15] selftests/bpf: Check BPFTOOL env var in detect_bpftool_path()

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 2/18/26 10:17 AM, Ihor Solodrai wrote:
> On 2/18/26 9:38 AM, Alexei Starovoitov wrote:
>> On Tue, Feb 17, 2026 at 4:31 PM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>>>
>>> [...]
>>>
>>>         /* Check default bpftool location (will work if we are running the
>>>          * default flavor of test_progs)
>>>          */
>>>         snprintf(tmp, BPFTOOL_PATH_MAX_LEN, "./%s", BPFTOOL_DEFAULT_PATH);
>>>         if (access(tmp, X_OK) == 0) {
>>> -               strncpy(buffer, tmp, BPFTOOL_PATH_MAX_LEN);
>>> +               snprintf(buffer, BPFTOOL_PATH_MAX_LEN, "%s", tmp);
>>
>> I guess it's ok for user space, but
>>
>> git log --oneline|grep "snprintf with strscpy"
>> ad789a85b163 mm/cma: replace snprintf with strscpy in cma_new_area
>> 674fb053e95d sparc: vio: Replace snprintf with strscpy in vio_create_one
>> 2dfc417414c6 genirq/proc: Replace snprintf with strscpy in register_handler_proc
>> f46ebb910989 block: Replace snprintf with strscpy in check_partition
>> b66215e7b780 media: verisilicon: replace snprintf with strscpy+strlcat
>> a86028f8e3ee staging: most: sound: replace snprintf with strscpy
>>
>> and many others...
>> So.. should we introduce strscpy() in selftests/bpf ?
> 
> I guess we can, but:
> 
> $ grep -r 'snprintf(' --include="*.[ch]" tools/testing/selftests/bpf/ | wc -l
> 238
> 
> The reason to prefer strscpy() is speed, right?
> Can we use kernel implementation in userspace directly?
> 
> In tools/include I only see this:
> 
> 	#define strscpy strcpy
> 

I think we can add a simple implementation to tools/lib/string.c
See a diff below: essentially a copy from arch/s390/boot/string.c [1]

I suppose it's faster than snprintf(). However I am not sure about
going through all 238 usages, as that would touch many files. But at
least we can make actual strscpy available in selftests.

I can add this in v3. Alexei, wdyt?

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/s390/boot/string.c?h=v6.19#n32

diff --git a/tools/include/linux/string.h b/tools/include/linux/string.h
index 51ad3cf4fa82..ca183a0e846a 100644
--- a/tools/include/linux/string.h
+++ b/tools/include/linux/string.h
@@ -3,6 +3,7 @@
 #define _TOOLS_LINUX_STRING_H_
 
 #include <linux/types.h>	/* for size_t */
+#include <sys/types.h>		/* for ssize_t */
 #include <string.h>
 
 void *memdup(const void *src, size_t len);
@@ -12,7 +13,7 @@ void argv_free(char **argv);
 
 int strtobool(const char *s, bool *res);
 
-#define strscpy strcpy
+ssize_t strscpy(char *dest, const char *src, size_t count);
 
 /*
  * glibc based builds needs the extern while uClibc doesn't.
diff --git a/tools/lib/string.c b/tools/lib/string.c
index 3126d2cff716..54c9163fa2b0 100644
--- a/tools/lib/string.c
+++ b/tools/lib/string.c
@@ -239,3 +239,17 @@ void *memchr_inv(const void *start, int c, size_t bytes)
 
 	return check_bytes8(start, value, bytes % 8);
 }
+
+ssize_t strscpy(char *dst, const char *src, size_t count)
+{
+	size_t len;
+
+	if (count == 0)
+		return -E2BIG;
+
+	len = strnlen(src, count - 1);
+	memcpy(dst, src, len);
+	dst[len] = '\0';
+
+	return src[len] ? -E2BIG : len;
+}