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authorNamhyung Kim <namhyung@gmail.com>2011-03-24 11:42:29 +0900
committerIngo Molnar <mingo@elte.hu>2011-03-24 08:36:10 +0100
commit0f77a8d378254f27df4a114a5da67223af1fe93f (patch)
treeedc37c211adce744100d4776e4a28fb868c8b3c0 /kernel
parentdec2960827c85253d76938dbfa909df3be34958b (diff)
vsprintf: Introduce %pB format specifier
The %pB format specifier is for stack backtrace. Its handler sprint_backtrace() does symbol lookup using (address-1) to ensure the address will not point outside of the function. If there is a tail-call to the function marked "noreturn", gcc optimized out the code after the call then causes saved return address points outside of the function (i.e. the start of the next function), so pollutes call trace somewhat. This patch adds the %pB printk mechanism that allows architecture call-trace printout functions to improve backtrace printouts. Signed-off-by: Namhyung Kim <namhyung@gmail.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: linux-arch@vger.kernel.org LKML-Reference: <1300934550-21394-1-git-send-email-namhyung@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kallsyms.c44
1 files changed, 41 insertions, 3 deletions
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 6f6d091b575..59e879929b1 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -342,13 +342,15 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
}
/* Look up a kernel symbol and return it in a text buffer. */
-int sprint_symbol(char *buffer, unsigned long address)
+static int __sprint_symbol(char *buffer, unsigned long address,
+ int symbol_offset)
{
char *modname;
const char *name;
unsigned long offset, size;
int len;
+ address += symbol_offset;
name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
if (!name)
return sprintf(buffer, "0x%lx", address);
@@ -357,17 +359,53 @@ int sprint_symbol(char *buffer, unsigned long address)
strcpy(buffer, name);
len = strlen(buffer);
buffer += len;
+ offset -= symbol_offset;
if (modname)
- len += sprintf(buffer, "+%#lx/%#lx [%s]",
- offset, size, modname);
+ len += sprintf(buffer, "+%#lx/%#lx [%s]", offset, size, modname);
else
len += sprintf(buffer, "+%#lx/%#lx", offset, size);
return len;
}
+
+/**
+ * sprint_symbol - Look up a kernel symbol and return it in a text buffer
+ * @buffer: buffer to be stored
+ * @address: address to lookup
+ *
+ * This function looks up a kernel symbol with @address and stores its name,
+ * offset, size and module name to @buffer if possible. If no symbol was found,
+ * just saves its @address as is.
+ *
+ * This function returns the number of bytes stored in @buffer.
+ */
+int sprint_symbol(char *buffer, unsigned long address)
+{
+ return __sprint_symbol(buffer, address, 0);
+}
+
EXPORT_SYMBOL_GPL(sprint_symbol);
+/**
+ * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
+ * @buffer: buffer to be stored
+ * @address: address to lookup
+ *
+ * This function is for stack backtrace and does the same thing as
+ * sprint_symbol() but with modified/decreased @address. If there is a
+ * tail-call to the function marked "noreturn", gcc optimized out code after
+ * the call so that the stack-saved return address could point outside of the
+ * caller. This function ensures that kallsyms will find the original caller
+ * by decreasing @address.
+ *
+ * This function returns the number of bytes stored in @buffer.
+ */
+int sprint_backtrace(char *buffer, unsigned long address)
+{
+ return __sprint_symbol(buffer, address, -1);
+}
+
/* Look up a kernel symbol and print it to the kernel messages. */
void __print_symbol(const char *fmt, unsigned long address)
{