Commit 011ea050 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
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tracing: Display some syscall arrays as strings 

Some of the system calls that read a fixed length of memory from the user
space address are not arrays but strings. Take a bit away from the nb_args
field in the syscall meta data to use as a flag to denote that the system
call's user_arg_size is being used as a string. The nb_args should never
be more than 6, so 7 bits is plenty to hold that number. When the
user_arg_is_str flag that, when set, will display the data array from the
user space address as a string and not an array.

This will allow the output to look like this:

  sys_sethostname(name: 0x5584310eb2a0 "debian", len: 6)

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231147.930550359@kernel.org


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent b4f7624c

include/trace/syscall.h

+3 −1
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
 * @name: name of the syscall

 * @syscall_nr: number of the syscall

 * @nb_args: number of parameters it takes

 * @user_arg_is_str: set if the arg for @user_arg_size is a string

 * @user_arg_size: holds @arg that has size of the user space to read

 * @user_mask: mask of @args that will read user space

 * @types: list of types as strings
@@ -27,7 +28,8 @@ 
struct syscall_metadata {

	const char	*name;

	int		syscall_nr;

	u8		nb_args;

	u8		nb_args:7;

	u8		user_arg_is_str:1;

	s8		user_arg_size;

	short		user_mask;

	const char	**types;

kernel/trace/trace_syscalls.c

+19 −3
Original line number Diff line number Diff line
@@ -184,7 +184,7 @@ print_syscall_enter(struct trace_iterator *iter, int flags, 
		ptr = (void *)ent + (val & 0xffff);

		len = val >> 16;



		if (entry->user_arg_size < 0) {

		if (entry->user_arg_size < 0 || entry->user_arg_is_str) {

			trace_seq_printf(s, " \"%.*s\"", len, ptr);

			continue;

		}
@@ -249,6 +249,7 @@ print_syscall_exit(struct trace_iterator *iter, int flags, 
static int __init

__set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)

{

	bool is_string = entry->user_arg_is_str;

	int i;

	int pos = 0;
@@ -266,7 +267,7 @@ __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len) 
			continue;



		/* Add the format for the user space string or array */

		if (entry->user_arg_size < 0)

		if (entry->user_arg_size < 0 || is_string)

			pos += snprintf(buf + pos, LEN_OR_ZERO, " \\\"%%s\\\"");

		else

			pos += snprintf(buf + pos, LEN_OR_ZERO, " (%%s)");
@@ -279,7 +280,7 @@ __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len) 
		if (!(BIT(i) & entry->user_mask))

			continue;

		/* The user space data for arg has name __<arg>_val */

		if (entry->user_arg_size < 0) {

		if (entry->user_arg_size < 0 || is_string) {

			pos += snprintf(buf + pos, LEN_OR_ZERO, ", __get_str(__%s_val)",

					entry->args[i]);

		} else {
@@ -781,6 +782,21 @@ static void check_faultable_syscall(struct trace_event_call *call, int nr) 
		sys_data->user_mask = BIT(1);

		sys_data->user_arg_size = 2;

		break;

	/* user arg 0 with size arg at 1 as string */

	case __NR_setdomainname:

	case __NR_sethostname:

		sys_data->user_mask = BIT(0);

		sys_data->user_arg_size = 1;

		sys_data->user_arg_is_str = 1;

		break;

#ifdef __NR_kexec_file_load

	/* user arg 4 with size arg at 3 as string */

	case __NR_kexec_file_load:

		sys_data->user_mask = BIT(4);

		sys_data->user_arg_size = 3;

		sys_data->user_arg_is_str = 1;

		break;

#endif

	/* user arg at position 0 */

#ifdef __NR_access

	case __NR_access: