Quoting Rasmus Villemoes (2021-03-24 15:21:34)

On 24/03/2021 20.11, Stephen Boyd wrote:

quoted

Quoting Rasmus Villemoes (2021-03-24 02:57:13)

quoted

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Is there any reason you didn't just make b an optional flag that could
be specified with or without R? I suppose the parsing is more difficult
with several orthogonal flags (see escaped_string()), but it's a little
easier to understand. Dunno, it's not like we're gonna think of 10 other
things that could be printed for a symbol, so perhaps it's fine.

I think I follow. So %pSb or %pSRb? If it's easier to understand then
sure. I was trying to avoid checking another character beyond fmt[1] but
it should be fine if fmt[1] is already 'R'.

I don't know. On the one hand, it seems sensible to allow such "flag"
modifiers to appear independently and in any order. Because what if some
day we think of some other property of the symbol we might want to
provide access to via a "z" flag; when to allow all combinations of the
R, b and z functionality we'd have to use four more random letters to
stand for various combinations of those flags. On the other hand,
vsprintf.c is already a complete wild west of odd conventions for
%p<foo>, and it's not like symbol_string() gets extended every other
release, and I can certainly understand the desire to keep the parsing
of fmt minimal. So 'r' to mean 'Rb' is ok by me if you prefer that.

I'm inclined to use %pSb and %pSRb. The code looks to simpler and I
suppose we can worry about different ordering/combination problems if it
comes to it.

---8<---

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 41ddc353ebb8..0e94cba5ba20 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c

@@ -968,6 +968,8 @@ char *symbol_string(char *buf, char *end, void *ptr,
 #ifdef CONFIG_KALLSYMS
        if (*fmt == 'B')
                sprint_backtrace(sym, value);
+       else if (*fmt == 'S' && (fmt[1] == 'b' || (fmt[1] == 'R' && fmt[2] == 'b')))
+               sprint_symbol_stacktrace(sym, value);
        else if (*fmt != 's')
                sprint_symbol(sym, value);
        else