From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx> Currently, trace-cmd has a tracecmd_parse_ftrace_printk() function that reads a string that holds the content of printk_formats from the tracefs file system, and then passes the address of the printk strings mappings to the tep handler. There's no reason for this to be specific to trace-cmd as other applications can easily read the printk_formats with the tracefs API and then pass it to the tep handler. Add the same functionality to libtraceevent as tep_parse_printk_formats(). Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> --- Documentation/libtraceevent-parse-files.txt | 30 +++++++++++- src/event-parse.c | 51 +++++++++++++++++++++ src/event-parse.h | 1 + 3 files changed, 80 insertions(+), 2 deletions(-) diff --git a/Documentation/libtraceevent-parse-files.txt b/Documentation/libtraceevent-parse-files.txt index 594cef2..211f4f4 100644 --- a/Documentation/libtraceevent-parse-files.txt +++ b/Documentation/libtraceevent-parse-files.txt @@ -3,7 +3,7 @@ libtraceevent(3) NAME ---- -tep_parse_saved_cmdlines, tep_parse_kallsyms +tep_parse_saved_cmdlines, tep_parse_printk_formats, tep_parse_kallsyms - Parsing functions to load mappings SYNOPSIS @@ -13,6 +13,7 @@ SYNOPSIS *#include <event-parse.h>* int *tep_parse_saved_cmdlines*(struct tep_handle pass:[*]_tep_, const char pass:[*]_buf_); +int *tep_parse_printk_formats*(struct tep_handle pass:[*]_tep_, const char pass:[*]_buf_); int *tep_parse_kallsyms*(struct tep_handle pass:[*]_tep_, const char pass:[*]_buf_); -- @@ -25,6 +26,14 @@ _tep_ handler. The events store the pid and this is used to be able to show the process names associated to those process ids. It parses the string _buf_ that holds the content of saved_cmdlines and ends with a nul character ('\0'). +*tep_parse_printk_formats* is a helper function to parse content in the tracefs +file system of the "printk_formats" file (stored in a string buffer passed in by _buf_) +and loads the mapping of addresses of strings that may be referenced by events. +Events only store the address of constant strings in the kernel, and the mapping +of their address to the string is exported to user space in the printk_formats +file. It parses the string _buf_ that holds the content of printk_formats and +ends with a nul character ('\0'). + *tep_parse_kallsyms* is a helper function to parse the Linux kernel /proc/kallsyms format (stored in a string buffer passed in by _buf_) and load the functions into the _tep_ handler such that function IP addresses can be mapped to their name when @@ -36,6 +45,9 @@ RETURN VALUE The *tep_parse_saved_cmdlines*() function returns 0 in case of success, or -1 in case of an error. +The *tep_parse_printk_formats*() function returns 0 in case of success, or -1 +in case of an error. + The *tep_parse_kallsyms*() function returns 0 in case of success, or -1 in case of an error. @@ -61,6 +73,19 @@ int load_cmdlines(struct tep_handle *tep) return r; } +int load_print_strings(struct tep_handle *tep) +{ + char *buf = NULL; + int r; + + buf = tracefs_instance_file_read(NULL, "printk_formats", NULL); + if (!buf) + return -1; + r = tep_parse_printk_formats(tep, buf); + free(buf); + return r; +} + int load_kallsyms(struct tep_handle *tep) { char *line = NULL; @@ -101,7 +126,8 @@ FILES SEE ALSO -------- -_libtraceevent(3)_, _trace-cmd(1)_, _tep_register_comm(3)_, _tep_register_function(3)_ +_libtraceevent(3)_, _trace-cmd(1)_, _tep_register_comm(3)_, _tep_register_function(3)_, +_tep_register_print_string_(3) AUTHOR ------ diff --git a/src/event-parse.c b/src/event-parse.c index 0d12ec4..cec4ad1 100644 --- a/src/event-parse.c +++ b/src/event-parse.c @@ -913,6 +913,57 @@ void tep_print_printk(struct tep_handle *tep) } } +/** + * tep_parse_printk_formats - Parse the address to strings + * @tep: a handle to the trace event parser + * @buf: A string buffer that holds the content of printk_formats and ends with '\0' + * + * This is a helper function to parse the address to printk formats in + * the kernel. Some events use %s to a kernel address that holds a constant + * string. The printk_formats file has a mapping of these addresses to the + * strings that are in the kernel. This parses the content of that file + * and registers those strings and their addresses so that the parsing of + * events can display the string as the event only has the address of the string. + * + * Returns 0 on success, and -1 on error. + */ +int tep_parse_printk_formats(struct tep_handle *tep, const char *buf) +{ + unsigned long long addr; + char *copy; + char *printk; + char *line; + char *next = NULL; + char *addr_str; + char *fmt; + int ret = -1; + + copy = strdup(buf); + if (!copy) + return -1; + + line = strtok_r(copy, "\n", &next); + while (line) { + addr_str = strtok_r(line, ":", &fmt); + if (!addr_str) { + tep_warning("printk format with empty entry"); + break; + } + addr = strtoull(addr_str, NULL, 16); + /* fmt still has a space, skip it */ + printk = strdup(fmt+1); + if (!printk) + goto out; + line = strtok_r(NULL, "\n", &next); + tep_register_print_string(tep, printk, addr); + free(printk); + } + ret = 0; + out: + free(copy); + return ret; +} + static struct tep_event *alloc_event(void) { return calloc(1, sizeof(struct tep_event)); diff --git a/src/event-parse.h b/src/event-parse.h index 078b202..05b156b 100644 --- a/src/event-parse.h +++ b/src/event-parse.h @@ -443,6 +443,7 @@ int tep_parse_saved_cmdlines(struct tep_handle *tep, const char *buf); int tep_parse_kallsyms(struct tep_handle *tep, const char *kallsyms); int tep_register_function(struct tep_handle *tep, char *name, unsigned long long addr, char *mod); +int tep_parse_printk_formats(struct tep_handle *tep, const char *buf); int tep_register_print_string(struct tep_handle *tep, const char *fmt, unsigned long long addr); bool tep_is_pid_registered(struct tep_handle *tep, int pid); -- 2.29.2