Re: [PATCHv4 3/8] efi/x86: Implement support for unaccepted memory

[Dave Hansen <dave.hansen@intel.com>]

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On 4/19/22 08:30, Kirill A. Shutemov wrote:
>> I think the stuff coming from the linux/ namespace you can simply copy
>> into a header in compressed/, like I've done with efi.h.
> Hm. Dave was worried about having copies of _find_next_bit() and
> __bitmap_*() inside compressed/.
> 
> How do we rectify code duplication and making decompresser self-contained?
> Do we care about multiple copies of the same code in the kernel?
> Do we care about keeping them in sync?

Would it be feasible to have the common code defined as a 'static
inline' in a header that both the main kernel and the decompressor could
include?  Something like the attached patch.

I'd much rather duplicate something like this:

int strncasecmp(const char *s1, const char *s2, size_t len)
{
        return __lib_strncasecmp(s1, s1, len);
}

in the decompressor versus a real full implementation.

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commit d94fa6842b25809958903fdd33d498bb622695a5
Author: Dave Hansen <dave.hansen@linux.intel.com>
Date:   Tue Apr 19 09:31:07 2022 -0700

    foo
    
    bar1

diff --git a/lib/string-internal.h b/lib/string-internal.h
new file mode 100644
index 000000000000..230c22864b75
--- /dev/null
+++ b/lib/string-internal.h
@@ -0,0 +1,31 @@
+#include <linux/ctype.h>
+
+/**
+ * strncasecmp - Case insensitive, length-limited string comparison
+ * @s1: One string
+ * @s2: The other string
+ * @len: the maximum number of characters to compare
+ */
+static inline int __lib_strncasecmp(const char *s1, const char *s2, size_t len)
+{
+	/* Yes, Virginia, it had better be unsigned */
+	unsigned char c1, c2;
+
+	if (!len)
+		return 0;
+
+	do {
+		c1 = *s1++;
+		c2 = *s2++;
+		if (!c1 || !c2)
+			break;
+		if (c1 == c2)
+			continue;
+		c1 = tolower(c1);
+		c2 = tolower(c2);
+		if (c1 != c2)
+			break;
+	} while (--len);
+	return (int)c1 - (int)c2;
+}
+#endif
diff --git a/lib/string.c b/lib/string.c
index 485777c9da83..705b799e3b5c 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -29,6 +29,7 @@
 #include <asm/word-at-a-time.h>
 #include <asm/page.h>
 
+#include "string-internal.h"
 #ifndef __HAVE_ARCH_STRNCASECMP
 /**
  * strncasecmp - Case insensitive, length-limited string comparison
@@ -38,25 +39,7 @@
  */
 int strncasecmp(const char *s1, const char *s2, size_t len)
 {
-	/* Yes, Virginia, it had better be unsigned */
-	unsigned char c1, c2;
-
-	if (!len)
-		return 0;
-
-	do {
-		c1 = *s1++;
-		c2 = *s2++;
-		if (!c1 || !c2)
-			break;
-		if (c1 == c2)
-			continue;
-		c1 = tolower(c1);
-		c2 = tolower(c2);
-		if (c1 != c2)
-			break;
-	} while (--len);
-	return (int)c1 - (int)c2;
+	return __lib_strncasecmp(s1, s1, len);
 }
 EXPORT_SYMBOL(strncasecmp);
 #endif