From 0f77a8d378254f27df4a114a5da67223af1fe93f Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Thu, 24 Mar 2011 11:42:29 +0900 Subject: 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 Acked-by: Steven Rostedt Acked-by: Frederic Weisbecker Cc: Linus Torvalds Cc: Andrew Morton Cc: linux-arch@vger.kernel.org LKML-Reference: <1300934550-21394-1-git-send-email-namhyung@gmail.com> Signed-off-by: Ingo Molnar --- kernel/kallsyms.c | 44 +++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 41 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 6f6d091b5757..59e879929b17 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) { -- cgit v1.2.3