From: Masami Hiramatsu (Google) <[email protected]> Function profiler shows the hit count of each function using its symbol name. However, there are some same-name local symbols, which we can not distinguish. To solve this issue, this introduces an option to show the symbols in "_text+OFFSET" format. This can avoid exposing the random shift of KASLR. The functions in modules are shown as "MODNAME+OFFSET" where the offset is from ".text".
E.g. for the kernel text symbols, specify vmlinux and the output to addr2line, you can find the actual function and source info; $ addr2line -fie vmlinux _text+3078208 __balance_callbacks kernel/sched/core.c:5064 for modules, specify the module file and .text+OFFSET; $ addr2line -fie samples/trace_events/trace-events-sample.ko .text+8224 do_simple_thread_func samples/trace_events/trace-events-sample.c:23 Suggested-by: Steven Rostedt (Google) <[email protected]> Signed-off-by: Masami Hiramatsu (Google) <[email protected]> --- Changes in v2: - Define a dummy TRACE_ITER_PROF_TEXT_OFFSET if CONFIG_FUNCTION_PROFILER=n. --- kernel/trace/ftrace.c | 26 +++++++++++++++++++++++++- kernel/trace/trace.c | 5 +++-- kernel/trace/trace.h | 11 ++++++++++- 3 files changed, 38 insertions(+), 4 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 00b76d450a89..d4802bb93793 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -534,7 +534,9 @@ static int function_stat_headers(struct seq_file *m) static int function_stat_show(struct seq_file *m, void *v) { + struct trace_array *tr = trace_get_global_array(); struct ftrace_profile *rec = v; + const char *refsymbol = NULL; char str[KSYM_SYMBOL_LEN]; #ifdef CONFIG_FUNCTION_GRAPH_TRACER static struct trace_seq s; @@ -554,7 +556,29 @@ static int function_stat_show(struct seq_file *m, void *v) return 0; #endif - kallsyms_lookup(rec->ip, NULL, NULL, NULL, str); + if (tr->trace_flags & TRACE_ITER_PROF_TEXT_OFFSET) { + long offset; + + if (core_kernel_text(rec->ip)) { + refsymbol = "_text"; + offset = rec->ip - (unsigned long)_text; + } else { + struct module *mod; + + guard(rcu)(); + mod = __module_text_address(rec->ip); + if (mod) { + refsymbol = mod->name; + /* Calculate offset from module's text entry address. */ + offset = rec->ip - (unsigned long)mod->mem[MOD_TEXT].base; + } + } + if (refsymbol) + snprintf(str, sizeof(str), " %s%+ld", refsymbol, offset); + } + if (!refsymbol) + kallsyms_lookup(rec->ip, NULL, NULL, NULL, str); + seq_printf(m, " %-30.30s %10lu", str, rec->counter); #ifdef CONFIG_FUNCTION_GRAPH_TRACER diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 652b7dd34c25..3c39b7c68742 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -527,7 +527,8 @@ EXPORT_SYMBOL_GPL(unregister_ftrace_export); /* trace_options that are only supported by global_trace */ #define TOP_LEVEL_TRACE_FLAGS (TRACE_ITER_PRINTK | \ - TRACE_ITER_PRINTK_MSGONLY | TRACE_ITER_RECORD_CMD) + TRACE_ITER_PRINTK_MSGONLY | TRACE_ITER_RECORD_CMD | \ + TRACE_ITER_PROF_TEXT_OFFSET) /* trace_flags that are default zero for instances */ #define ZEROED_TRACE_FLAGS \ @@ -11111,7 +11112,7 @@ __init static int tracer_alloc_buffers(void) #ifdef CONFIG_FUNCTION_TRACER /* Used to set module cached ftrace filtering at boot up */ -__init struct trace_array *trace_get_global_array(void) +struct trace_array *trace_get_global_array(void) { return &global_trace; } diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 41c613ea0b4d..b64f322d8c52 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1353,6 +1353,14 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf, # define STACK_FLAGS #endif +#ifdef CONFIG_FUNCTION_PROFILER +# define PROFILER_FLAGS \ + C(PROF_TEXT_OFFSET, "prof-text-offset") +#else +# define PROFILER_FLAGS +# define TRACE_ITER_PROF_TEXT_OFFSET 0UL +#endif + /* * trace_iterator_flags is an enumeration that defines bit * positions into trace_flags that controls the output. @@ -1391,7 +1399,8 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf, FUNCTION_FLAGS \ FGRAPH_FLAGS \ STACK_FLAGS \ - BRANCH_FLAGS + BRANCH_FLAGS \ + PROFILER_FLAGS /* * By defining C, we can make TRACE_FLAGS a list of bit names
