[Xen-devel] [PATCH 3/7] common/vsprintf: Add %ps and %pS format specifier support

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Introduce the %ps and %pS format options for printing a symbol.

  %ps will print the symbol name alone
  %pS will print the symbol name + offset / size

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
 docs/misc/printk-formats.txt |   11 ++++++++
 xen/common/vsprintf.c        |   58 +++++++++++++++++++++++++++++++++++++-----
 2 files changed, 62 insertions(+), 7 deletions(-)
 create mode 100644 docs/misc/printk-formats.txt

diff --git a/docs/misc/printk-formats.txt b/docs/misc/printk-formats.txt
new file mode 100644
index 0000000..ef25e16
--- /dev/null
+++ b/docs/misc/printk-formats.txt
@@ -0,0 +1,11 @@
+Xen custom %p format options.  A subset, borrowed from Linux.
+
+All parameters to a %p option should be enclosed with the _p() macro
+
+Symbol/Function pointers:
+
+       %ps     Symbol name only
+       %pS     Symbol name + offset / function length
+
+       In the case that an appropriate symbol name can't be found, %p[sS] will
+       fall back to '%p' and print the address in hex.
diff --git a/xen/common/vsprintf.c b/xen/common/vsprintf.c
index 5fdd391..5ac5b9b 100644
--- a/xen/common/vsprintf.c
+++ b/xen/common/vsprintf.c
@@ -17,6 +17,7 @@
  */
 
 #include <xen/ctype.h>
+#include <xen/symbols.h>
 #include <xen/lib.h>
 #include <asm/div64.h>
 #include <asm/page.h>
@@ -261,19 +262,61 @@ static char *string(char *str, char *end, const char *s,
     return str;
 }
 
-static char *pointer(char *str, char *end,
+static char *pointer(char *str, char *end, const char **fmt_ptr,
                      unsigned long val, int field_width, int precision,
                      int flags)
 {
-    if ( field_width == -1 )
+    const char *fmt = *fmt_ptr, *s;
+
+    /*
+     * Custom %p suffixes, compatible with Linux.
+     * See XEN_ROOT/docs/misc/printk-formats.txt
+     */
+    switch ( fmt[1] )
     {
-        field_width = 2 * sizeof(void *);
-        flags |= ZEROPAD;
+    case 's': /* Symbol name */
+    case 'S': /* Symbol name with offset and size */
+    {
+        unsigned long sym_size, sym_offset;
+        char namebuf[KSYM_NAME_LEN+1];
+
+        /* Advance fmt pointer, as we have consumed 's' or 'S'.  Leave fmt
+         * along for consistency. */
+        (*fmt_ptr)++;
+
+        s = symbols_lookup(val, &sym_size, &sym_offset, namebuf);
+
+        /* If the symbol is not found, fall back to printing the address */
+        if ( !s )
+            goto regular_pointer;
+
+        /* Print symbol name */
+        str = string(str, end, s, -1, -1, 0);
+
+        if ( fmt[1] == 'S' )
+        {
+            /* Print '+0x<offset>/0x<len>' */
+            str = string(str, end, "+0x", -1, -1, 0);
+            str = number(str, end, sym_offset, 16, -1, -1, 0);
+            str = string(str, end, "/0x", -1, -1, 0);
+            str = number(str, end, sym_size, 16, -1, -1, 0);
+        }
+
+        return str;
     }
 
-    str = number(str, end, val, 16, field_width, precision, flags);
+    default:
+    regular_pointer:
+
+        if ( field_width == -1 )
+        {
+            field_width = 2 * sizeof(void *);
+            flags |= ZEROPAD;
+        }
+
+        return number(str, end, val, 16, field_width, precision, flags);
+    }
 
-    return str;
 }
 
 /**
@@ -414,7 +457,8 @@ int vsnprintf(char *buf, size_t size, const char *fmt, 
va_list args)
             continue;
 
         case 'p':
-            str = pointer(str, end, (unsigned long) va_arg(args, void *),
+            /* pointer() might advance fmt (%pS for example) */
+            str = pointer(str, end, &fmt, (unsigned long) va_arg(args, void *),
                           field_width, precision, flags);
             continue;
 
-- 
1.7.10.4


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