[PATCH v2] vsprintf: introduce %pf

Frederic Weisbecker
2009-04-15T15:48:33Z

On Tue, Apr 14, 2009 at 10:38:36PM -0400, Steven Rostedt wrote:
>
> On Tue, 14 Apr 2009, Mike Frysinger wrote:
>
> > On Tue, Apr 14, 2009 at 20:00, Frederic Weisbecker wrote:
> > > - * - 'F' For symbolic function descriptor pointers
> > > + * - 'F' For symbolic function descriptor pointers with asm offset
> > > + * - 'f' For simple function symbol
> >
> > "asm" is weird here as it isnt an assembly offset (not that i have any
> > idea what an "assembly offset" even means). just say "offset".
>
> Or perhaps better: function offset, as it ususally means the offset into
> the function.
>
> -- Steve
>

Ok, I've tried to keep a balance between all your comments.
Tell me what your think about this v2:

--
>From 302d8752d1734242ab1eb7d9e5df637bcba3f4a9 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Wed, 15 Apr 2009 17:41:56 +0200
Subject: [PATCH v2] vsprintf: introduce %pf

If I remember well, a format which could let us to print a pure
function name has been suggested by Andrew Morton some monthes ago.

The current %pF is very convenient to print a function symbol, but
often we only want to print the name of the function, without
its asm offset.

That's what does %pf in this patch.
The lowecase f has been chosen for its intuitive sense of a weak kind
of %pF

The support for this new format would be welcome for the tracing tree
where the need to print pure function names is often needed and also
on other parts:

$ git-grep -E "kallsyms_lookup\(.+?\)"
arch/blackfin/kernel/traps.c: symname = kallsyms_lookup(address, &symsize, &offset, &modname, namebuf);
arch/powerpc/xmon/xmon.c: name = kallsyms_lookup(pc, &size, &offset, NULL, tmpstr);
arch/sh/kernel/cpu/sh5/unwind.c: sym = kallsyms_lookup(pc, NULL, &offset, NULL, namebuf);
arch/x86/kernel/ftrace.c: kallsyms_lookup((unsigned long) syscall, NULL, NULL, NULL, str);
kernel/kprobes.c: sym = kallsyms_lookup((unsigned long)p->addr, NULL,
kernel/lockdep.c: return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
kernel/trace/ftrace.c: kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
kernel/trace/ftrace.c: kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
kernel/trace/ftrace.c: kallsyms_lookup((unsigned long)rec->ops->func, NULL, NULL, NULL, str);
kernel/trace/ftrace.c: kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
kernel/trace/ftrace.c: kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
kernel/trace/ftrace.c: kallsyms_lookup(rec->ip, NULL, NULL, &modname, str);
kernel/trace/ftrace.c: kallsyms_lookup(*ptr, NULL, NULL, NULL, str);
kernel/trace/trace_functions.c: kallsyms_lookup(ip, NULL, NULL, NULL, str);
kernel/trace/trace_output.c: kallsyms_lookup(address, NULL, NULL, NULL, str);

Changes in v2:

- Add the explanations of the %pf role for vsnprintf() and bstr_printf()
- Change the comments by dropping the "asm offset" notion and only
define the %pf against the actual function offset notion.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
lib/vsprintf.c | 19 +++++++++++++------
1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index b56f6d0..756ccaf 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -575,12 +575,15 @@ static char *string(char *buf, char *end, char *s, struct printf_spec spec)
}

static char *symbol_string(char *buf, char *end, void *ptr,
- struct printf_spec spec)
+ struct printf_spec spec, char ext)
{
unsigned long value = (unsigned long) ptr;
#ifdef CONFIG_KALLSYMS
char sym[KSYM_SYMBOL_LEN];
- sprint_symbol(sym, value);
+ if (ext != 'f')
+ sprint_symbol(sym, value);
+ else
+ kallsyms_lookup(value, NULL, NULL, NULL, sym);
return string(buf, end, sym, spec);
#else
spec.field_width = 2*sizeof(void *);
@@ -692,7 +695,8 @@ static char *ip4_addr_string(char *buf, char *end, u8 *addr,
*
* Right now we handle:
*
- * - 'F' For symbolic function descriptor pointers
+ * - 'F' For symbolic function descriptor pointers with offset
+ * - 'f' For simple symbolic function names without offset
* - 'S' For symbolic direct pointers
* - 'R' For a struct resource pointer, it prints the range of
* addresses (not the name nor the flags)
@@ -715,10 +719,11 @@ static char *pointer(const char *fmt, char *buf, char *end, void *ptr,

switch (*fmt) {
case 'F':
+ case 'f':
ptr = dereference_function_descriptor(ptr);
/* Fallthrough */
case 'S':
- return symbol_string(buf, end, ptr, spec);
+ return symbol_string(buf, end, ptr, spec, *fmt);
case 'R':
return resource_string(buf, end, ptr, spec);
case 'm':
@@ -954,7 +959,8 @@ qualifier:
*
* This function follows C99 vsnprintf, but has some extensions:
* %pS output the name of a text symbol
- * %pF output the name of a function pointer
+ * %pF output the name of a function pointer with its offset
+ * %pf output the name of a function pointer without its offset
* %pR output the address range in a struct resource
*
* The return value is the number of characters which would
@@ -1412,7 +1418,8 @@ EXPORT_SYMBOL_GPL(vbin_printf);
*
* The format follows C99 vsnprintf, but has some extensions:
* %pS output the name of a text symbol
- * %pF output the name of a function pointer
+ * %pF output the name of a function pointer with its offset
+ * %pf output the name of a function pointer without its offset
* %pR output the address range in a struct resource
* %n is ignored
*
--
1.6.1