[PATCH v3 6/8] tracing/probes: Support $argN in return probe (kprobe and fprobe)

Masami Hiramatsu (Google)
2024-03-04T03:40:59Z

Support accessing $argN in the return probe events. This will help users to
record entry data in function return (exit) event for simplfing the function
entry/exit information in one event, and record the result values (e.g.
allocated object/initialized object) at function exit.

For example, if we have a function `int init_foo(struct foo *obj, int param)`
sometimes we want to check how `obj` is initialized. In such case, we can
define a new return event like below;

# echo 'r init_foo retval=$retval param=$arg2 field1=+0($arg1)' >> kprobe_events

Thus it records the function parameter `param` and its result `obj->field1`
(the dereference will be done in the function exit timing) value at once.

This also support fprobe, BTF args and'$arg*'. So if CONFIG_DEBUG_INFO_BTF
is enabled, we can trace both function parameters and the return value
by following command.

# echo 'f target_function%return $arg* $retval' >> dynamic_events

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v3:
- Fix syntax error check selftests because now some syntax error
will not happen.
Changes in v2:
- Update README message
---
kernel/trace/trace.c | 1
kernel/trace/trace_eprobe.c | 6 -
kernel/trace/trace_fprobe.c | 55 ++++--
kernel/trace/trace_kprobe.c | 56 +++++-
kernel/trace/trace_probe.c | 177 ++++++++++++++++++--
kernel/trace/trace_probe.h | 28 +++
kernel/trace/trace_probe_tmpl.h | 10 +
kernel/trace/trace_uprobe.c | 12 +
.../ftrace/test.d/dynevent/fprobe_syntax_errors.tc | 4
.../ftrace/test.d/kprobe/kprobe_syntax_errors.tc | 2
10 files changed, 289 insertions(+), 62 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 516c585f5879..71a96decc276 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5755,6 +5755,7 @@ static const char readme_msg[] =
"\t $stack<index>, $stack, $retval, $comm,\n"
#endif
"\t +|-[u]<offset>(<fetcharg>), \\imm-value, \\\"imm-string\"\n"
+ "\t kernel return probes support: $retval, $arg<N>, $comm\n"
"\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, char, string, symbol,\n"
"\t b<bit-width>@<bit-offset>/<container-size>, ustring,\n"
"\t symstr, <type>\\[<array-size>\\]\n"
diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index eb72def7410f..b0e0ec85912e 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -390,8 +390,8 @@ static int get_eprobe_size(struct trace_probe *tp, void *rec)

/* Note that we don't verify it, since the code does not come from user space */
static int
-process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
- void *base)
+process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
+ void *dest, void *base)
{
unsigned long val;
int ret;
@@ -438,7 +438,7 @@ __eprobe_trace_func(struct eprobe_data *edata, void *rec)
return;

entry = fbuffer.entry = ring_buffer_event_data(fbuffer.event);
- store_trace_args(&entry[1], &edata->ep->tp, rec, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &edata->ep->tp, rec, NULL, sizeof(*entry), dsize);

trace_event_buffer_commit(&fbuffer);
}
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 5109650b0d82..4f4280815522 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -4,6 +4,7 @@
* Copyright (C) 2022 Google LLC.
*/
#define pr_fmt(fmt) "trace_fprobe: " fmt
+#include <asm/ptrace.h>

#include <linux/fprobe.h>
#include <linux/module.h>
@@ -129,8 +130,8 @@ static bool trace_fprobe_is_registered(struct trace_fprobe *tf)
* from user space.
*/
static int
-process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
- void *base)
+process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
+ void *dest, void *base)
{
struct pt_regs *regs = rec;
unsigned long val;
@@ -152,6 +153,9 @@ process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
case FETCH_OP_ARG:
val = regs_get_kernel_argument(regs, code->param);
break;
+ case FETCH_OP_EDATA:
+ val = *(unsigned long *)((unsigned long)edata + code->offset);
+ break;
#endif
case FETCH_NOP_SYMBOL: /* Ignore a place holder */
code++;
@@ -184,7 +188,7 @@ __fentry_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
if (trace_trigger_soft_disabled(trace_file))
return;

- dsize = __get_data_size(&tf->tp, regs);
+ dsize = __get_data_size(&tf->tp, regs, NULL);

entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + tf->tp.size + dsize);
@@ -194,7 +198,7 @@ __fentry_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
fbuffer.regs = regs;
entry = fbuffer.entry = ring_buffer_event_data(fbuffer.event);
entry->ip = entry_ip;
- store_trace_args(&entry[1], &tf->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, regs, NULL, sizeof(*entry), dsize);

trace_event_buffer_commit(&fbuffer);
}
@@ -211,10 +215,23 @@ fentry_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
NOKPROBE_SYMBOL(fentry_trace_func);

/* function exit handler */
+static int trace_fprobe_entry_handler(struct fprobe *fp, unsigned long entry_ip,
+ unsigned long ret_ip, struct pt_regs *regs,
+ void *entry_data)
+{
+ struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);
+
+ if (tf->tp.entry_arg)
+ store_trace_entry_data(entry_data, &tf->tp, regs);
+
+ return 0;
+}
+NOKPROBE_SYMBOL(trace_fprobe_entry_handler)
+
static nokprobe_inline void
__fexit_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
unsigned long ret_ip, struct pt_regs *regs,
- struct trace_event_file *trace_file)
+ void *entry_data, struct trace_event_file *trace_file)
{
struct fexit_trace_entry_head *entry;
struct trace_event_buffer fbuffer;
@@ -227,7 +244,7 @@ __fexit_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
if (trace_trigger_soft_disabled(trace_file))
return;

- dsize = __get_data_size(&tf->tp, regs);
+ dsize = __get_data_size(&tf->tp, regs, entry_data);

entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + tf->tp.size + dsize);
@@ -238,19 +255,19 @@ __fexit_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
entry = fbuffer.entry = ring_buffer_event_data(fbuffer.event);
entry->func = entry_ip;
entry->ret_ip = ret_ip;
- store_trace_args(&entry[1], &tf->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, regs, entry_data, sizeof(*entry), dsize);

trace_event_buffer_commit(&fbuffer);
}

static void
fexit_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs)
+ unsigned long ret_ip, struct pt_regs *regs, void *entry_data)
{
struct event_file_link *link;

trace_probe_for_each_link_rcu(link, &tf->tp)
- __fexit_trace_func(tf, entry_ip, ret_ip, regs, link->file);
+ __fexit_trace_func(tf, entry_ip, ret_ip, regs, entry_data, link->file);
}
NOKPROBE_SYMBOL(fexit_trace_func);

@@ -269,7 +286,7 @@ static int fentry_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
if (hlist_empty(head))
return 0;

- dsize = __get_data_size(&tf->tp, regs);
+ dsize = __get_data_size(&tf->tp, regs, NULL);
__size = sizeof(*entry) + tf->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
size -= sizeof(u32);
@@ -280,7 +297,7 @@ static int fentry_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,

entry->ip = entry_ip;
memset(&entry[1], 0, dsize);
- store_trace_args(&entry[1], &tf->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, regs, NULL, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
return 0;
@@ -289,7 +306,8 @@ NOKPROBE_SYMBOL(fentry_perf_func);

static void
fexit_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs)
+ unsigned long ret_ip, struct pt_regs *regs,
+ void *entry_data)
{
struct trace_event_call *call = trace_probe_event_call(&tf->tp);
struct fexit_trace_entry_head *entry;
@@ -301,7 +319,7 @@ fexit_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
if (hlist_empty(head))
return;

- dsize = __get_data_size(&tf->tp, regs);
+ dsize = __get_data_size(&tf->tp, regs, entry_data);
__size = sizeof(*entry) + tf->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
size -= sizeof(u32);
@@ -312,7 +330,7 @@ fexit_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,

entry->func = entry_ip;
entry->ret_ip = ret_ip;
- store_trace_args(&entry[1], &tf->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, regs, entry_data, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
}
@@ -343,10 +361,10 @@ static void fexit_dispatcher(struct fprobe *fp, unsigned long entry_ip,
struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);

if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
- fexit_trace_func(tf, entry_ip, ret_ip, regs);
+ fexit_trace_func(tf, entry_ip, ret_ip, regs, entry_data);
#ifdef CONFIG_PERF_EVENTS
if (trace_probe_test_flag(&tf->tp, TP_FLAG_PROFILE))
- fexit_perf_func(tf, entry_ip, ret_ip, regs);
+ fexit_perf_func(tf, entry_ip, ret_ip, regs, entry_data);
#endif
}
NOKPROBE_SYMBOL(fexit_dispatcher);
@@ -1109,6 +1127,11 @@ static int __trace_fprobe_create(int argc, const char *argv[])
goto error; /* This can be -ENOMEM */
}

+ if (is_return && tf->tp.entry_arg) {
+ tf->fp.entry_handler = trace_fprobe_entry_handler;
+ tf->fp.entry_data_size = traceprobe_get_entry_data_size(&tf->tp);
+ }
+
ret = traceprobe_set_print_fmt(&tf->tp,
is_return ? PROBE_PRINT_RETURN : PROBE_PRINT_NORMAL);
if (ret < 0)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 843f13f839df..14099cc17fc9 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -740,6 +740,9 @@ static unsigned int number_of_same_symbols(char *func_name)
return ctx.count;
}

+static int trace_kprobe_entry_handler(struct kretprobe_instance *ri,
+ struct pt_regs *regs);
+
static int __trace_kprobe_create(int argc, const char *argv[])
{
/*
@@ -948,6 +951,11 @@ static int __trace_kprobe_create(int argc, const char *argv[])
if (ret)
goto error; /* This can be -ENOMEM */
}
+ /* entry handler for kretprobe */
+ if (is_return && tk->tp.entry_arg) {
+ tk->rp.entry_handler = trace_kprobe_entry_handler;
+ tk->rp.data_size = traceprobe_get_entry_data_size(&tk->tp);
+ }

ptype = is_return ? PROBE_PRINT_RETURN : PROBE_PRINT_NORMAL;
ret = traceprobe_set_print_fmt(&tk->tp, ptype);
@@ -1303,8 +1311,8 @@ static const struct file_operations kprobe_profile_ops = {

/* Note that we don't verify it, since the code does not come from user space */
static int
-process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
- void *base)
+process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
+ void *dest, void *base)
{
struct pt_regs *regs = rec;
unsigned long val;
@@ -1329,6 +1337,9 @@ process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
case FETCH_OP_ARG:
val = regs_get_kernel_argument(regs, code->param);
break;
+ case FETCH_OP_EDATA:
+ val = *(unsigned long *)((unsigned long)edata + code->offset);
+ break;
#endif
case FETCH_NOP_SYMBOL: /* Ignore a place holder */
code++;
@@ -1359,7 +1370,7 @@ __kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs,
if (trace_trigger_soft_disabled(trace_file))
return;

- dsize = __get_data_size(&tk->tp, regs);
+ dsize = __get_data_size(&tk->tp, regs, NULL);

entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + tk->tp.size + dsize);
@@ -1368,7 +1379,7 @@ __kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs,

fbuffer.regs = regs;
entry->ip = (unsigned long)tk->rp.kp.addr;
- store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tk->tp, regs, NULL, sizeof(*entry), dsize);

trace_event_buffer_commit(&fbuffer);
}
@@ -1384,6 +1395,31 @@ kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs)
NOKPROBE_SYMBOL(kprobe_trace_func);

/* Kretprobe handler */
+
+static int trace_kprobe_entry_handler(struct kretprobe_instance *ri,
+ struct pt_regs *regs)
+{
+ struct kretprobe *rp = get_kretprobe(ri);
+ struct trace_kprobe *tk;
+
+ /*
+ * There is a small chance that get_kretprobe(ri) returns NULL when
+ * the kretprobe is unregister on another CPU between kretprobe's
+ * trampoline_handler and this function.
+ */
+ if (unlikely(!rp))
+ return -ENOENT;
+
+ tk = container_of(rp, struct trace_kprobe, rp);
+
+ /* store argument values into ri->data as entry data */
+ if (tk->tp.entry_arg)
+ store_trace_entry_data(ri->data, &tk->tp, regs);
+
+ return 0;
+}
+
+
static nokprobe_inline void
__kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
struct pt_regs *regs,
@@ -1399,7 +1435,7 @@ __kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
if (trace_trigger_soft_disabled(trace_file))
return;

- dsize = __get_data_size(&tk->tp, regs);
+ dsize = __get_data_size(&tk->tp, regs, ri->data);

entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + tk->tp.size + dsize);
@@ -1409,7 +1445,7 @@ __kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
fbuffer.regs = regs;
entry->func = (unsigned long)tk->rp.kp.addr;
entry->ret_ip = get_kretprobe_retaddr(ri);
- store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tk->tp, regs, ri->data, sizeof(*entry), dsize);

trace_event_buffer_commit(&fbuffer);
}
@@ -1557,7 +1593,7 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
if (hlist_empty(head))
return 0;

- dsize = __get_data_size(&tk->tp, regs);
+ dsize = __get_data_size(&tk->tp, regs, NULL);
__size = sizeof(*entry) + tk->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
size -= sizeof(u32);
@@ -1568,7 +1604,7 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)

entry->ip = (unsigned long)tk->rp.kp.addr;
memset(&entry[1], 0, dsize);
- store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tk->tp, regs, NULL, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
return 0;
@@ -1593,7 +1629,7 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
if (hlist_empty(head))
return;

- dsize = __get_data_size(&tk->tp, regs);
+ dsize = __get_data_size(&tk->tp, regs, ri->data);
__size = sizeof(*entry) + tk->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
size -= sizeof(u32);
@@ -1604,7 +1640,7 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,

entry->func = (unsigned long)tk->rp.kp.addr;
entry->ret_ip = get_kretprobe_retaddr(ri);
- store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tk->tp, regs, ri->data, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
}
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 93f36f8a108e..217169de0920 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -594,6 +594,8 @@ static int parse_btf_field(char *fieldname, const struct btf_type *type,
return 0;
}

+static int __store_entry_arg(struct trace_probe *tp, int argnum);
+
static int parse_btf_arg(char *varname,
struct fetch_insn **pcode, struct fetch_insn *end,
struct traceprobe_parse_context *ctx)
@@ -618,11 +620,7 @@ static int parse_btf_arg(char *varname,
return -EOPNOTSUPP;
}

- if (ctx->flags & TPARG_FL_RETURN) {
- if (strcmp(varname, "$retval") != 0) {
- trace_probe_log_err(ctx->offset, NO_BTFARG);
- return -ENOENT;
- }
+ if (ctx->flags & TPARG_FL_RETURN && !strcmp(varname, "$retval")) {
code->op = FETCH_OP_RETVAL;
/* Check whether the function return type is not void */
if (query_btf_context(ctx) == 0) {
@@ -654,11 +652,21 @@ static int parse_btf_arg(char *varname,
const char *name = btf_name_by_offset(ctx->btf, params[i].name_off);

if (name && !strcmp(name, varname)) {
- code->op = FETCH_OP_ARG;
- if (ctx->flags & TPARG_FL_TPOINT)
- code->param = i + 1;
- else
- code->param = i;
+ if (tparg_is_function_entry(ctx->flags)) {
+ code->op = FETCH_OP_ARG;
+ if (ctx->flags & TPARG_FL_TPOINT)
+ code->param = i + 1;
+ else
+ code->param = i;
+ } else if (tparg_is_function_return(ctx->flags)) {
+ code->op = FETCH_OP_EDATA;
+ ret = __store_entry_arg(ctx->tp, i);
+ if (ret < 0) {
+ /* internal error */
+ return ret;
+ }
+ code->offset = ret;
+ }
tid = params[i].type;
goto found;
}
@@ -755,6 +763,110 @@ static int check_prepare_btf_string_fetch(char *typename,

#endif

+#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
+
+static int __store_entry_arg(struct trace_probe *tp, int argnum)
+{
+ struct probe_entry_arg *earg = tp->entry_arg;
+ bool match = false;
+ int i, offset;
+
+ if (!earg) {
+ earg = kzalloc(sizeof(*tp->entry_arg), GFP_KERNEL);
+ if (!earg)
+ return -ENOMEM;
+ earg->size = 2 * tp->nr_args + 1;
+ earg->code = kcalloc(earg->size, sizeof(struct fetch_insn),
+ GFP_KERNEL);
+ if (!earg->code) {
+ kfree(earg);
+ return -ENOMEM;
+ }
+ /* Fill the code buffer with 'end' to simplify it */
+ for (i = 0; i < earg->size; i++)
+ earg->code[i].op = FETCH_OP_END;
+ tp->entry_arg = earg;
+ }
+
+ offset = 0;
+ for (i = 0; i < earg->size - 1; i++) {
+ switch (earg->code[i].op) {
+ case FETCH_OP_END:
+ earg->code[i].op = FETCH_OP_ARG;
+ earg->code[i].param = argnum;
+ earg->code[i + 1].op = FETCH_OP_ST_EDATA;
+ earg->code[i + 1].offset = offset;
+ return offset;
+ case FETCH_OP_ARG:
+ match = (earg->code[i].param == argnum);
+ break;
+ case FETCH_OP_ST_EDATA:
+ offset = earg->code[i].offset;
+ if (match)
+ return offset;
+ offset += sizeof(unsigned long);
+ break;
+ default:
+ break;
+ }
+ }
+ return -ENOSPC;
+}
+
+int traceprobe_get_entry_data_size(struct trace_probe *tp)
+{
+ struct probe_entry_arg *earg = tp->entry_arg;
+ int i, size = 0;
+
+ if (!earg)
+ return 0;
+
+ for (i = 0; i < earg->size; i++) {
+ switch (earg->code[i].op) {
+ case FETCH_OP_END:
+ goto out;
+ case FETCH_OP_ST_EDATA:
+ size = earg->code[i].offset + sizeof(unsigned long);
+ break;
+ default:
+ break;
+ }
+ }
+out:
+ return size;
+}
+
+void store_trace_entry_data(void *edata, struct trace_probe *tp, struct pt_regs *regs)
+{
+ struct probe_entry_arg *earg = tp->entry_arg;
+ unsigned long val;
+ int i;
+
+ if (!earg)
+ return;
+
+ for (i = 0; i < earg->size; i++) {
+ struct fetch_insn *code = &earg->code[i];
+
+ switch (code->op) {
+ case FETCH_OP_ARG:
+ val = regs_get_kernel_argument(regs, code->param);
+ break;
+ case FETCH_OP_ST_EDATA:
+ *(unsigned long *)((unsigned long)edata + code->offset) = val;
+ break;
+ case FETCH_OP_END:
+ goto end;
+ default:
+ break;
+ }
+ }
+end:
+ return;
+}
+NOKPROBE_SYMBOL(store_trace_entry_data)
+#endif
+
#define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))

/* Parse $vars. @orig_arg points '$', which syncs to @ctx->offset */
@@ -830,7 +942,7 @@ static int parse_probe_vars(char *orig_arg, const struct fetch_type *t,

#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
len = str_has_prefix(arg, "arg");
- if (len && tparg_is_function_entry(ctx->flags)) {
+ if (len) {
ret = kstrtoul(arg + len, 10, &param);
if (ret)
goto inval;
@@ -839,15 +951,29 @@ static int parse_probe_vars(char *orig_arg, const struct fetch_type *t,
err = TP_ERR_BAD_ARG_NUM;
goto inval;
}
+ param--; /* argN starts from 1, but internal arg[N] starts from 0 */

- code->op = FETCH_OP_ARG;
- code->param = (unsigned int)param - 1;
- /*
- * The tracepoint probe will probe a stub function, and the
- * first parameter of the stub is a dummy and should be ignored.
- */
- if (ctx->flags & TPARG_FL_TPOINT)
- code->param++;
+ if (tparg_is_function_entry(ctx->flags)) {
+ code->op = FETCH_OP_ARG;
+ code->param = (unsigned int)param;
+ /*
+ * The tracepoint probe will probe a stub function, and the
+ * first parameter of the stub is a dummy and should be ignored.
+ */
+ if (ctx->flags & TPARG_FL_TPOINT)
+ code->param++;
+ } else if (tparg_is_function_return(ctx->flags)) {
+ /* function entry argument access from return probe */
+ ret = __store_entry_arg(ctx->tp, param);
+ if (ret < 0) /* This error should be an internal error */
+ return ret;
+
+ code->op = FETCH_OP_EDATA;
+ code->offset = ret;
+ } else {
+ err = TP_ERR_NOFENTRY_ARGS;
+ goto inval;
+ }
return 0;
}
#endif
@@ -1037,7 +1163,8 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
break;
default:
if (isalpha(arg[0]) || arg[0] == '_') { /* BTF variable */
- if (!tparg_is_function_entry(ctx->flags)) {
+ if (!tparg_is_function_entry(ctx->flags) &&
+ !tparg_is_function_return(ctx->flags)) {
trace_probe_log_err(ctx->offset, NOSUP_BTFARG);
return -EINVAL;
}
@@ -1423,6 +1550,7 @@ int traceprobe_parse_probe_arg(struct trace_probe *tp, int i, const char *arg,
struct probe_arg *parg = &tp->args[i];
const char *body;

+ ctx->tp = tp;
body = strchr(arg, '=');
if (body) {
if (body - arg > MAX_ARG_NAME_LEN) {
@@ -1479,7 +1607,8 @@ static int argv_has_var_arg(int argc, const char *argv[], int *args_idx,
if (str_has_prefix(argv[i], "$arg")) {
trace_probe_log_set_index(i + 2);

- if (!tparg_is_function_entry(ctx->flags)) {
+ if (!tparg_is_function_entry(ctx->flags) &&
+ !tparg_is_function_return(ctx->flags)) {
trace_probe_log_err(0, NOFENTRY_ARGS);
return -EINVAL;
}
@@ -1802,6 +1931,12 @@ void trace_probe_cleanup(struct trace_probe *tp)
for (i = 0; i < tp->nr_args; i++)
traceprobe_free_probe_arg(&tp->args[i]);

+ if (tp->entry_arg) {
+ kfree(tp->entry_arg->code);
+ kfree(tp->entry_arg);
+ tp->entry_arg = NULL;
+ }
+
if (tp->event)
trace_probe_unlink(tp);
}
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index ed8d1052f8a7..cef3a50628a3 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -92,6 +92,7 @@ enum fetch_op {
FETCH_OP_ARG, /* Function argument : .param */
FETCH_OP_FOFFS, /* File offset: .immediate */
FETCH_OP_DATA, /* Allocated data: .data */
+ FETCH_OP_EDATA, /* Entry data: .offset */
// Stage 2 (dereference) op
FETCH_OP_DEREF, /* Dereference: .offset */
FETCH_OP_UDEREF, /* User-space Dereference: .offset */
@@ -102,6 +103,7 @@ enum fetch_op {
FETCH_OP_ST_STRING, /* String: .offset, .size */
FETCH_OP_ST_USTRING, /* User String: .offset, .size */
FETCH_OP_ST_SYMSTR, /* Kernel Symbol String: .offset, .size */
+ FETCH_OP_ST_EDATA, /* Store Entry Data: .offset */
// Stage 4 (modify) op
FETCH_OP_MOD_BF, /* Bitfield: .basesize, .lshift, .rshift */
// Stage 5 (loop) op
@@ -232,6 +234,11 @@ struct probe_arg {
const struct fetch_type *type; /* Type of this argument */
};

+struct probe_entry_arg {
+ struct fetch_insn *code;
+ unsigned int size; /* The entry data size */
+};
+
struct trace_uprobe_filter {
rwlock_t rwlock;
int nr_systemwide;
@@ -253,6 +260,7 @@ struct trace_probe {
struct trace_probe_event *event;
ssize_t size; /* trace entry size */
unsigned int nr_args;
+ struct probe_entry_arg *entry_arg; /* This is only for return probe */
struct probe_arg args[];
};

@@ -355,6 +363,18 @@ int trace_probe_create(const char *raw_command, int (*createfn)(int, const char
int trace_probe_print_args(struct trace_seq *s, struct probe_arg *args, int nr_args,
u8 *data, void *field);

+#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
+int traceprobe_get_entry_data_size(struct trace_probe *tp);
+/* This is a runtime function to store entry data */
+void store_trace_entry_data(void *edata, struct trace_probe *tp, struct pt_regs *regs);
+#else /* !CONFIG_HAVE_FUNCTION_ARG_ACCESS_API */
+static inline int traceprobe_get_entry_data_size(struct trace_probe *tp)
+{
+ return 0;
+}
+#define store_trace_entry_data(edata, tp, regs) do { } while (0)
+#endif
+
#define trace_probe_for_each_link(pos, tp) \
list_for_each_entry(pos, &(tp)->event->files, list)
#define trace_probe_for_each_link_rcu(pos, tp) \
@@ -381,6 +401,11 @@ static inline bool tparg_is_function_entry(unsigned int flags)
return (flags & TPARG_FL_LOC_MASK) == (TPARG_FL_KERNEL | TPARG_FL_FENTRY);
}

+static inline bool tparg_is_function_return(unsigned int flags)
+{
+ return (flags & TPARG_FL_LOC_MASK) == (TPARG_FL_KERNEL | TPARG_FL_RETURN);
+}
+
struct traceprobe_parse_context {
struct trace_event_call *event;
/* BTF related parameters */
@@ -392,6 +417,7 @@ struct traceprobe_parse_context {
const struct btf_type *last_type; /* Saved type */
u32 last_bitoffs; /* Saved bitoffs */
u32 last_bitsize; /* Saved bitsize */
+ struct trace_probe *tp;
unsigned int flags;
int offset;
};
@@ -506,7 +532,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
C(NO_BTFARG, "This variable is not found at this probe point"),\
C(NO_BTF_ENTRY, "No BTF entry for this probe point"), \
C(BAD_VAR_ARGS, "$arg* must be an independent parameter without name etc."),\
- C(NOFENTRY_ARGS, "$arg* can be used only on function entry"), \
+ C(NOFENTRY_ARGS, "$arg* can be used only on function entry or exit"), \
C(DOUBLE_ARGS, "$arg* can be used only once in the parameters"), \
C(ARGS_2LONG, "$arg* failed because the argument list is too long"), \
C(ARGIDX_2BIG, "$argN index is too big"), \
diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index 3935b347f874..2caf0d2afb32 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -54,7 +54,7 @@ fetch_apply_bitfield(struct fetch_insn *code, void *buf)
* If dest is NULL, don't store result and return required dynamic data size.
*/
static int
-process_fetch_insn(struct fetch_insn *code, void *rec,
+process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
void *dest, void *base);
static nokprobe_inline int fetch_store_strlen(unsigned long addr);
static nokprobe_inline int
@@ -232,7 +232,7 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,

/* Sum up total data length for dynamic arrays (strings) */
static nokprobe_inline int
-__get_data_size(struct trace_probe *tp, struct pt_regs *regs)
+__get_data_size(struct trace_probe *tp, struct pt_regs *regs, void *edata)
{
struct probe_arg *arg;
int i, len, ret = 0;
@@ -240,7 +240,7 @@ __get_data_size(struct trace_probe *tp, struct pt_regs *regs)
for (i = 0; i < tp->nr_args; i++) {
arg = tp->args + i;
if (unlikely(arg->dynamic)) {
- len = process_fetch_insn(arg->code, regs, NULL, NULL);
+ len = process_fetch_insn(arg->code, regs, edata, NULL, NULL);
if (len > 0)
ret += len;
}
@@ -251,7 +251,7 @@ __get_data_size(struct trace_probe *tp, struct pt_regs *regs)

/* Store the value of each argument */
static nokprobe_inline void
-store_trace_args(void *data, struct trace_probe *tp, void *rec,
+store_trace_args(void *data, struct trace_probe *tp, void *rec, void *edata,
int header_size, int maxlen)
{
struct probe_arg *arg;
@@ -266,7 +266,7 @@ store_trace_args(void *data, struct trace_probe *tp, void *rec,
/* Point the dynamic data area if needed */
if (unlikely(arg->dynamic))
*dl = make_data_loc(maxlen, dyndata - base);
- ret = process_fetch_insn(arg->code, rec, dl, base);
+ ret = process_fetch_insn(arg->code, rec, edata, dl, base);
if (arg->dynamic && likely(ret > 0)) {
dyndata += ret;
maxlen -= ret;
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 796ebcae9b38..9e461362450a 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -211,8 +211,8 @@ static unsigned long translate_user_vaddr(unsigned long file_offset)

/* Note that we don't verify it, since the code does not come from user space */
static int
-process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
- void *base)
+process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
+ void *dest, void *base)
{
struct pt_regs *regs = rec;
unsigned long val;
@@ -1490,11 +1490,11 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
if (WARN_ON_ONCE(!uprobe_cpu_buffer))
return 0;

- dsize = __get_data_size(&tu->tp, regs);
+ dsize = __get_data_size(&tu->tp, regs, NULL);
esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));

ucb = uprobe_buffer_get();
- store_trace_args(ucb->buf, &tu->tp, regs, esize, dsize);
+ store_trace_args(ucb->buf, &tu->tp, regs, NULL, esize, dsize);

if (trace_probe_test_flag(&tu->tp, TP_FLAG_TRACE))
ret |= uprobe_trace_func(tu, regs, ucb, dsize);
@@ -1525,11 +1525,11 @@ static int uretprobe_dispatcher(struct uprobe_consumer *con,
if (WARN_ON_ONCE(!uprobe_cpu_buffer))
return 0;

- dsize = __get_data_size(&tu->tp, regs);
+ dsize = __get_data_size(&tu->tp, regs, NULL);
esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));

ucb = uprobe_buffer_get();
- store_trace_args(ucb->buf, &tu->tp, regs, esize, dsize);
+ store_trace_args(ucb->buf, &tu->tp, regs, NULL, esize, dsize);

if (trace_probe_test_flag(&tu->tp, TP_FLAG_TRACE))
uretprobe_trace_func(tu, func, regs, ucb, dsize);
diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
index 20e42c030095..61877d166451 100644
--- a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
@@ -34,7 +34,9 @@ check_error 'f vfs_read ^$stack10000' # BAD_STACK_NUM

check_error 'f vfs_read ^$arg10000' # BAD_ARG_NUM

+if !grep -q 'kernel return probes support:' README; then
check_error 'f vfs_read $retval ^$arg1' # BAD_VAR
+fi
check_error 'f vfs_read ^$none_var' # BAD_VAR
check_error 'f vfs_read ^'$REG # BAD_VAR

@@ -99,7 +101,9 @@ if grep -q "<argname>" README; then
check_error 'f vfs_read args=^$arg*' # BAD_VAR_ARGS
check_error 'f vfs_read +0(^$arg*)' # BAD_VAR_ARGS
check_error 'f vfs_read $arg* ^$arg*' # DOUBLE_ARGS
+if !grep -q 'kernel return probes support:' README; then
check_error 'f vfs_read%return ^$arg*' # NOFENTRY_ARGS
+fi
check_error 'f vfs_read ^hoge' # NO_BTFARG
check_error 'f kfree ^$arg10' # NO_BTFARG (exceed the number of parameters)
check_error 'f kfree%return ^$retval' # NO_RETVAL
diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
index 65fbb26fd58c..a16c6a6f6055 100644
--- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
@@ -108,7 +108,9 @@ if grep -q "<argname>" README; then
check_error 'p vfs_read args=^$arg*' # BAD_VAR_ARGS
check_error 'p vfs_read +0(^$arg*)' # BAD_VAR_ARGS
check_error 'p vfs_read $arg* ^$arg*' # DOUBLE_ARGS
+if !grep -q 'kernel return probes support:' README; then
check_error 'r vfs_read ^$arg*' # NOFENTRY_ARGS
+fi
check_error 'p vfs_read+8 ^$arg*' # NOFENTRY_ARGS
check_error 'p vfs_read ^hoge' # NO_BTFARG
check_error 'p kfree ^$arg10' # NO_BTFARG (exceed the number of parameters)