[Xen-devel] [PATCH] xen: Introduce separator modifiers for the %ph custom printk

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The printk formats %*ph{C,D,N} are chosen to be compatible with their Linux
counterparts.

Sample:

  (XEN) buf: 00 01 03 07 78 65 6e 00
  (XEN) buf: 00:01:03:07:78:65:6e:00
  (XEN) buf: 00-01-03-07-78-65-6e-00
  (XEN) buf: 0001030778656e00

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 docs/misc/printk-formats.txt |  9 +++++++--
 xen/common/vsprintf.c        | 32 +++++++++++++++++++++++++++++---
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/docs/misc/printk-formats.txt b/docs/misc/printk-formats.txt
index dee0f3e..525108f 100644
--- a/docs/misc/printk-formats.txt
+++ b/docs/misc/printk-formats.txt
@@ -5,8 +5,13 @@ pointers are fine.  Numbers should make use of the _p() macro.
 
 Raw buffer as hex string:
 
-       %*ph    Up to 64 characters, printed as "00 01 02 ... ff".  Buffer 
length
-               expected via the field_width paramter. i.e. printk("%*ph", 8, 
buffer);
+       %*ph    00 01 02  ...  3f
+       %*phC   00:01:02: ... :3f
+       %*phD   00-01-02- ... -3f
+       %*phN   000102 ... 3f
+
+       Up to 64 characters.  Buffer length expected via the field_width
+       paramter. i.e. printk("%*ph", 8, buffer);
 
 Symbol/Function pointers:
 
diff --git a/xen/common/vsprintf.c b/xen/common/vsprintf.c
index 51b5e4e..18d2634 100644
--- a/xen/common/vsprintf.c
+++ b/xen/common/vsprintf.c
@@ -275,6 +275,7 @@ static char *pointer(char *str, char *end, const char 
**fmt_ptr,
     case 'h': /* Raw buffer as hex string. */
     {
         const uint8_t *hex_buffer = arg;
+        char sep = ' '; /* Separator character. */
         unsigned int i;
 
         /* Consumed 'h' from the format string. */
@@ -286,6 +287,28 @@ static char *pointer(char *str, char *end, const char 
**fmt_ptr,
         if ( field_width > 64 )
             field_width = 64;
 
+        /*
+         * Peek ahead in the format string to see if a recognised separator
+         * modifier is present.
+         */
+        switch ( fmt[2] )
+        {
+        case 'C': /* Colons. */
+            ++*fmt_ptr;
+            sep = ':';
+            break;
+
+        case 'D': /* Dashes. */
+            ++*fmt_ptr;
+            sep = '-';
+            break;
+
+        case 'N': /* No separator. */
+            ++*fmt_ptr;
+            sep = 0;
+            break;
+        }
+
         for ( i = 0; ; )
         {
             /* Each byte: 2 chars, 0-padded, base 16, no hex prefix. */
@@ -294,9 +317,12 @@ static char *pointer(char *str, char *end, const char 
**fmt_ptr,
             if ( ++i == field_width )
                 return str;
 
-            if ( str < end )
-                *str = ' ';
-            ++str;
+            if ( sep )
+            {
+                if ( str < end )
+                    *str = sep;
+                ++str;
+            }
         }
     }
 
-- 
2.1.4


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