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tracing/probes: Support BTF field access from $retval

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Support BTF argument on '$retval' for function return events including
kretprobe and fprobe for accessing the return value.
This also allows user to access its fields if the return value is a
pointer of a data structure.

E.g.
 # echo 'f getname_flags%return +0($retval->name):string' \
   > dynamic_events
 # echo 1 > events/fprobes/getname_flags__exit/enable
 # ls > /dev/null
 # head -n 40 trace | tail
              ls-87      [000] ...1.  8067.616101: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./function_profile_enabled"
              ls-87      [000] ...1.  8067.616108: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./trace_stat"
              ls-87      [000] ...1.  8067.616115: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_graph_notrace"
              ls-87      [000] ...1.  8067.616122: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_graph_function"
              ls-87      [000] ...1.  8067.616129: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_notrace"
              ls-87      [000] ...1.  8067.616135: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_filter"
              ls-87      [000] ...1.  8067.616143: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./touched_functions"
              ls-87      [000] ...1.  8067.616237: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./enabled_functions"
              ls-87      [000] ...1.  8067.616245: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./available_filter_functions"
              ls-87      [000] ...1.  8067.616253: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_notrace_pid"


Link: https://lore.kernel.org/all/169272158234.160970.2446691104240645205.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu (Google) 2023-08-23 01:26:22 +09:00
parent c440adfbe3
commit d157d76944
2 changed files with 86 additions and 102 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

187
kernel/trace/trace_probe.c
View file

@ -364,38 +364,46 @@ static const char *fetch_type_from_btf_type(struct btf *btf,
return NULL; return NULL;
} }
static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr, static int query_btf_context(struct traceprobe_parse_context *ctx)
struct btf **btf_p, bool tracepoint)
{ {
const struct btf_param *param; const struct btf_param *param;
const struct btf_type *t; const struct btf_type *type;
struct btf *btf; struct btf *btf;
s32 nr;
if (!funcname || !nr) if (ctx->btf)
return ERR_PTR(-EINVAL); return 0;
t = btf_find_func_proto(funcname, &btf); if (!ctx->funcname)
if (!t) return -EINVAL;
return (const struct btf_param *)t;
param = btf_get_func_param(t, nr); type = btf_find_func_proto(ctx->funcname, &btf);
if (IS_ERR_OR_NULL(param)) if (!type)
goto err; return -ENOENT;
/* Hide the first 'data' argument of tracepoint */ ctx->btf = btf;
if (tracepoint) { ctx->proto = type;
(*nr)--;
param++; /* ctx->params is optional, since func(void) will not have params. */
nr = 0;
param = btf_get_func_param(type, &nr);
if (!IS_ERR_OR_NULL(param)) {
/* Hide the first 'data' argument of tracepoint */
if (ctx->flags & TPARG_FL_TPOINT) {
nr--;
param++;
}
} }
if (*nr > 0) { if (nr > 0) {
*btf_p = btf; ctx->nr_params = nr;
return param; ctx->params = param;
} else {
ctx->nr_params = 0;
ctx->params = NULL;
} }
err: return 0;
btf_put(btf);
return NULL;
} }
static void clear_btf_context(struct traceprobe_parse_context *ctx) static void clear_btf_context(struct traceprobe_parse_context *ctx)
@ -403,6 +411,7 @@ static void clear_btf_context(struct traceprobe_parse_context *ctx)
if (ctx->btf) { if (ctx->btf) {
btf_put(ctx->btf); btf_put(ctx->btf);
ctx->btf = NULL; ctx->btf = NULL;
ctx->proto = NULL;
ctx->params = NULL; ctx->params = NULL;
ctx->nr_params = 0; ctx->nr_params = 0;
} }
@ -522,7 +531,7 @@ static int parse_btf_arg(char *varname,
const struct btf_param *params; const struct btf_param *params;
const struct btf_type *type; const struct btf_type *type;
char *field = NULL; char *field = NULL;
int i, is_ptr; int i, is_ptr, ret;
u32 tid; u32 tid;
if (WARN_ON_ONCE(!ctx->funcname)) if (WARN_ON_ONCE(!ctx->funcname))
@ -538,17 +547,37 @@ static int parse_btf_arg(char *varname,
return -EOPNOTSUPP; return -EOPNOTSUPP;
} }
if (!ctx->params) { if (ctx->flags & TPARG_FL_RETURN) {
params = find_btf_func_param(ctx->funcname, if (strcmp(varname, "$retval") != 0) {
&ctx->nr_params, &ctx->btf, trace_probe_log_err(ctx->offset, NO_BTFARG);
ctx->flags & TPARG_FL_TPOINT); return -ENOENT;
if (IS_ERR_OR_NULL(params)) { }
code->op = FETCH_OP_RETVAL;
/* Check whether the function return type is not void */
if (query_btf_context(ctx) == 0) {
if (ctx->proto->type == 0) {
trace_probe_log_err(ctx->offset, NO_RETVAL);
return -ENOENT;
}
tid = ctx->proto->type;
goto found;
}
if (field) {
trace_probe_log_err(ctx->offset + field - varname,
NO_BTF_ENTRY);
return -ENOENT;
}
return 0;
}
if (!ctx->btf) {
ret = query_btf_context(ctx);
if (ret < 0 || ctx->nr_params == 0) {
trace_probe_log_err(ctx->offset, NO_BTF_ENTRY); trace_probe_log_err(ctx->offset, NO_BTF_ENTRY);
return PTR_ERR(params); return PTR_ERR(params);
} }
ctx->params = params; }
} else params = ctx->params;
params = ctx->params;
for (i = 0; i < ctx->nr_params; i++) { for (i = 0; i < ctx->nr_params; i++) {
const char *name = btf_name_by_offset(ctx->btf, params[i].name_off); const char *name = btf_name_by_offset(ctx->btf, params[i].name_off);
@ -559,7 +588,6 @@ static int parse_btf_arg(char *varname,
code->param = i + 1; code->param = i + 1;
else else
code->param = i; code->param = i;
tid = params[i].type; tid = params[i].type;
goto found; goto found;
} }
@ -584,7 +612,7 @@ static int parse_btf_arg(char *varname,
return 0; return 0;
} }
static const struct fetch_type *parse_btf_arg_type( static const struct fetch_type *find_fetch_type_from_btf_type(
struct traceprobe_parse_context *ctx) struct traceprobe_parse_context *ctx)
{ {
struct btf *btf = ctx->btf; struct btf *btf = ctx->btf;
@ -596,27 +624,6 @@ static const struct fetch_type *parse_btf_arg_type(
return find_fetch_type(typestr, ctx->flags); return find_fetch_type(typestr, ctx->flags);
} }
static const struct fetch_type *parse_btf_retval_type(
struct traceprobe_parse_context *ctx)
{
const char *typestr = NULL;
const struct btf_type *type;
struct btf *btf;
if (ctx->funcname) {
/* Do not use ctx->btf, because it must be used with ctx->param */
type = btf_find_func_proto(ctx->funcname, &btf);
if (type) {
type = btf_type_skip_modifiers(btf, type->type, NULL);
if (!IS_ERR_OR_NULL(type))
typestr = fetch_type_from_btf_type(btf, type, ctx);
btf_put(btf);
}
}
return find_fetch_type(typestr, ctx->flags);
}
static int parse_btf_bitfield(struct fetch_insn **pcode, static int parse_btf_bitfield(struct fetch_insn **pcode,
struct traceprobe_parse_context *ctx) struct traceprobe_parse_context *ctx)
{ {
@ -639,30 +646,15 @@ static int parse_btf_bitfield(struct fetch_insn **pcode,
return 0; return 0;
} }
static bool is_btf_retval_void(const char *funcname)
{
const struct btf_type *t;
struct btf *btf;
bool ret;
t = btf_find_func_proto(funcname, &btf);
if (!t)
return false;
ret = (t->type == 0);
btf_put(btf);
return ret;
}
#else #else
static void clear_btf_context(struct traceprobe_parse_context *ctx) static void clear_btf_context(struct traceprobe_parse_context *ctx)
{ {
ctx->btf = NULL; ctx->btf = NULL;
} }
static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr, static int query_btf_context(struct traceprobe_parse_context *ctx)
struct btf **btf_p, bool tracepoint)
{ {
return ERR_PTR(-EOPNOTSUPP); return -EOPNOTSUPP;
} }
static int parse_btf_arg(char *varname, static int parse_btf_arg(char *varname,
@ -680,24 +672,23 @@ static int parse_btf_bitfield(struct fetch_insn **pcode,
return -EOPNOTSUPP; return -EOPNOTSUPP;
} }
#define parse_btf_arg_type(ctx) \ #define find_fetch_type_from_btf_type(ctx) \
find_fetch_type(NULL, ctx->flags) find_fetch_type(NULL, ctx->flags)
#define parse_btf_retval_type(ctx) \
find_fetch_type(NULL, ctx->flags)
#define is_btf_retval_void(funcname) (false)
#endif #endif
#define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long)) #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
static int parse_probe_vars(char *arg, const struct fetch_type *t, /* Parse $vars. @orig_arg points '$', which syncs to @ctx->offset */
struct fetch_insn *code, static int parse_probe_vars(char *orig_arg, const struct fetch_type *t,
struct fetch_insn **pcode,
struct fetch_insn *end,
struct traceprobe_parse_context *ctx) struct traceprobe_parse_context *ctx)
{ {
unsigned long param; struct fetch_insn *code = *pcode;
int err = TP_ERR_BAD_VAR; int err = TP_ERR_BAD_VAR;
char *arg = orig_arg + 1;
unsigned long param;
int ret = 0; int ret = 0;
int len; int len;
@ -716,18 +707,17 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
goto inval; goto inval;
} }
if (strcmp(arg, "retval") == 0) { if (str_has_prefix(arg, "retval")) {
if (ctx->flags & TPARG_FL_RETURN) { if (!(ctx->flags & TPARG_FL_RETURN)) {
if ((ctx->flags & TPARG_FL_KERNEL) && err = TP_ERR_RETVAL_ON_PROBE;
is_btf_retval_void(ctx->funcname)) { goto inval;
err = TP_ERR_NO_RETVAL; }
goto inval; if (!(ctx->flags & TPARG_FL_KERNEL) ||
} !IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS)) {
code->op = FETCH_OP_RETVAL; code->op = FETCH_OP_RETVAL;
return 0; return 0;
} }
err = TP_ERR_RETVAL_ON_PROBE; return parse_btf_arg(orig_arg, pcode, end, ctx);
goto inval;
} }
len = str_has_prefix(arg, "stack"); len = str_has_prefix(arg, "stack");
@ -829,7 +819,7 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
switch (arg[0]) { switch (arg[0]) {
case '$': case '$':
ret = parse_probe_vars(arg + 1, type, code, ctx); ret = parse_probe_vars(arg, type, pcode, end, ctx);
break; break;
case '%': /* named register */ case '%': /* named register */
@ -1126,12 +1116,9 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
goto fail; goto fail;
/* Update storing type if BTF is available */ /* Update storing type if BTF is available */
if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && !t) { if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) &&
if (ctx->last_type) !t && ctx->last_type)
parg->type = parse_btf_arg_type(ctx); parg->type = find_fetch_type_from_btf_type(ctx);
else if (ctx->flags & TPARG_FL_RETURN)
parg->type = parse_btf_retval_type(ctx);
}
ret = -EINVAL; ret = -EINVAL;
/* Store operation */ /* Store operation */
@ -1420,7 +1407,6 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
const struct btf_param *params = NULL; const struct btf_param *params = NULL;
int i, j, n, used, ret, args_idx = -1; int i, j, n, used, ret, args_idx = -1;
const char **new_argv = NULL; const char **new_argv = NULL;
int nr_params;
ret = argv_has_var_arg(argc, argv, &args_idx, ctx); ret = argv_has_var_arg(argc, argv, &args_idx, ctx);
if (ret < 0) if (ret < 0)
@ -1431,9 +1417,8 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
return NULL; return NULL;
} }
params = find_btf_func_param(ctx->funcname, &nr_params, &ctx->btf, ret = query_btf_context(ctx);
ctx->flags & TPARG_FL_TPOINT); if (ret < 0 || ctx->nr_params == 0) {
if (IS_ERR_OR_NULL(params)) {
if (args_idx != -1) { if (args_idx != -1) {
/* $arg* requires BTF info */ /* $arg* requires BTF info */
trace_probe_log_err(0, NOSUP_BTFARG); trace_probe_log_err(0, NOSUP_BTFARG);
@ -1442,8 +1427,6 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
*new_argc = argc; *new_argc = argc;
return NULL; return NULL;
} }
ctx->params = params;
ctx->nr_params = nr_params;
if (args_idx >= 0) if (args_idx >= 0)
*new_argc = argc + ctx->nr_params - 1; *new_argc = argc + ctx->nr_params - 1;
@ -1458,7 +1441,7 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
for (i = 0, j = 0; i < argc; i++) { for (i = 0, j = 0; i < argc; i++) {
trace_probe_log_set_index(i + 2); trace_probe_log_set_index(i + 2);
if (i == args_idx) { if (i == args_idx) {
for (n = 0; n < nr_params; n++) { for (n = 0; n < ctx->nr_params; n++) {
ret = sprint_nth_btf_arg(n, "", buf + used, ret = sprint_nth_btf_arg(n, "", buf + used,
bufsize - used, ctx); bufsize - used, ctx);
if (ret < 0) if (ret < 0)

1
kernel/trace/trace_probe.h
View file

@ -385,6 +385,7 @@ struct traceprobe_parse_context {
struct trace_event_call *event; struct trace_event_call *event;
/* BTF related parameters */ /* BTF related parameters */
const char *funcname; /* Function name in BTF */ const char *funcname; /* Function name in BTF */
const struct btf_type *proto; /* Prototype of the function */
const struct btf_param *params; /* Parameter of the function */ const struct btf_param *params; /* Parameter of the function */
s32 nr_params; /* The number of the parameters */ s32 nr_params; /* The number of the parameters */
struct btf *btf; /* The BTF to be used */ struct btf *btf; /* The BTF to be used */