linux-kernel - Re: [PATCHv3 01/50] kallsyms/printk: Add loglvl to print_ip

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Date:   Sat, 18 Apr 2020 13:40:45 -0700
From:   Joe Perches <joe@...ches.com>
To:     Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>, Jiri Slaby <jslaby@...e.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Albert Ou <aou@...s.berkeley.edu>,
        Ben Segall <bsegall@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Greentime Hu <green.hu@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Hogan <jhogan@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Mel Gorman <mgorman@...e.de>, Michal Simek <monstr@...str.eu>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Burton <paulburton@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincent Chen <deanbo422@...il.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Will Deacon <will@...nel.org>, linux-mips@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCHv3 01/50] kallsyms/printk: Add loglvl to print_ip_sym()

On Sat, 2020-04-18 at 21:18 +0100, Dmitry Safonov wrote:
> print_ip_sym() needs to have a log level parameter to comply with other
> parts being printed. Otherwise, half of the expected backtrace would be
> printed and other may be missing with some logging level.

I'd rather create another extension to %ps that also emits
the [<address>] along with the symbol lookup and retire
print_ip_sym altogether.

Something like:
---
 lib/vsprintf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 7c488a..8fce8f 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2072,6 +2072,8 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
  * - 'S' For symbolic direct pointers (or function descriptors) with offset
  * - 's' For symbolic direct pointers (or function descriptors) without offset
  * - '[Ss]R' as above with __builtin_extract_return_addr() translation
+ * - '[Ss]B' [<address>] and symbolic direct pointers as above
+ *	     (was used previously used as print_ip_sym)
  * - '[Ff]' %pf and %pF were obsoleted and later removed in favor of
  *	    %ps and %pS. Be careful when re-using these specifiers.
  * - 'B' For backtraced symbolic direct pointers with offset
@@ -2183,6 +2185,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 	case 'S':
 	case 's':
 		ptr = dereference_symbol_descriptor(ptr);
+		if (fmt[1] == 'B')
+			buf += vsprintf(buf, end, "[<%px>] ", ptr);
 		/* Fallthrough */
 	case 'B':
 		return symbol_string(buf, end, ptr, spec, fmt);