From 0fe1ef24f7bd0020f29ffe287dfdb9ead33ca0b2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 6 Jul 2008 16:43:12 -0700 Subject: [PATCH] vsprintf: add support for '%pS' and '%pF' pointer formats They print out a pointer in symbolic format, if possible (ie using symbolic KALLSYMS information). The '%pS' format is for regular direct pointers (which can point to data or code and that you find on the stack during backtraces etc), while '%pF' is for C function pointer types. On most architectures, the two mean exactly the same thing, but some architectures use an indirect pointer for C function pointers, where the function pointer points to a function descriptor (which in turn contains the actual pointer to the code). The '%pF' code automatically does the appropriate function descriptor dereference on such architectures. Signed-off-by: Linus Torvalds --- lib/vsprintf.c | 41 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 40 insertions(+), 1 deletion(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 5d6f0718b6d..1dc2d1d18fa 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -22,6 +22,8 @@ #include #include #include +#include +#include #include /* for PAGE_SIZE */ #include @@ -511,15 +513,52 @@ static char *string(char *buf, char *end, char *s, int field_width, int precisio return buf; } +static inline void *dereference_function_descriptor(void *ptr) +{ +#if defined(CONFIG_IA64) || defined(CONFIG_PPC64) + void *p; + if (!probe_kernel_address(ptr, p)) + ptr = p; +#endif + return ptr; +} + +static char *symbol_string(char *buf, char *end, void *ptr, int field_width, int precision, int flags) +{ + unsigned long value = (unsigned long) ptr; +#ifdef CONFIG_KALLSYMS + char sym[KSYM_SYMBOL_LEN]; + sprint_symbol(sym, value); + return string(buf, end, sym, field_width, precision, flags); +#else + field_width = 2*sizeof(void *); + flags |= SPECIAL | SMALL | ZEROPAD; + return number(buf, end, value, 16, field_width, precision, flags); +#endif +} + /* * Show a '%p' thing. A kernel extension is that the '%p' is followed * by an extra set of alphanumeric characters that are extended format * specifiers. * - * Right now don't actually handle any such, but we will.. + * Right now we just handle 'F' (for symbolic Function descriptor pointers) + * and 'S' (for Symbolic direct pointers), but this can easily be + * extended in the future (network address types etc). + * + * The difference between 'S' and 'F' is that on ia64 and ppc64 function + * pointers are really function descriptors, which contain a pointer the + * real address. */ static char *pointer(const char *fmt, char *buf, char *end, void *ptr, int field_width, int precision, int flags) { + switch (*fmt) { + case 'F': + ptr = dereference_function_descriptor(ptr); + /* Fallthrough */ + case 'S': + return symbol_string(buf, end, ptr, field_width, precision, flags); + } flags |= SMALL; if (field_width == -1) { field_width = 2*sizeof(void *); -- 2.41.1