[xen staging-4.14] xen/lib: Fix strcmp() and strncmp()

[patchbot@xxxxxxx]

commit 8df03ef746dec2d4612ef7ea1933e8066783ad27
Author:     Jane Malalane <jane.malalane@xxxxxxxxxx>
AuthorDate: Wed Aug 25 15:10:32 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Aug 25 15:10:32 2021 +0200

    xen/lib: Fix strcmp() and strncmp()
    
    The C standard requires that each character be compared as unsigned
    char. Xen's current behaviour compares as signed char, which changes
    the answer when chars with a value greater than 0x7f are used.
    
    Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Jane Malalane <jane.malalane@xxxxxxxxxx>
    Reviewed-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
    master commit: 3747a2bb67daa5a8baeff6cda57dc98a5ef79c3e
    master date: 2021-07-30 10:52:46 +0100
---
 xen/common/string.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/xen/common/string.c b/xen/common/string.c
index af3d96ad0f..43624b1b45 100644
--- a/xen/common/string.c
+++ b/xen/common/string.c
@@ -119,14 +119,16 @@ EXPORT_SYMBOL(strlcat);
  */
 int (strcmp)(const char *cs, const char *ct)
 {
-       register signed char __res;
+       unsigned char *csu = (unsigned char *)cs;
+       unsigned char *ctu = (unsigned char *)ct;
+       int res;
 
        while (1) {
-               if ((__res = *cs - *ct++) != 0 || !*cs++)
+               if ((res = *csu - *ctu++) != 0 || !*csu++)
                        break;
        }
 
-       return __res;
+       return res;
 }
 #endif
 
@@ -139,15 +141,17 @@ int (strcmp)(const char *cs, const char *ct)
  */
 int (strncmp)(const char *cs, const char *ct, size_t count)
 {
-       register signed char __res = 0;
+       unsigned char *csu = (unsigned char *)cs;
+       unsigned char *ctu = (unsigned char *)ct;
+       int res = 0;
 
        while (count) {
-               if ((__res = *cs - *ct++) != 0 || !*cs++)
+               if ((res = *csu - *ctu++) != 0 || !*csu++)
                        break;
                count--;
        }
 
-       return __res;
+       return res;
 }
 #endif
 
--
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