[PATCH v9 28/36] tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS

From: Masami Hiramatsu (Google)
Date: Mon Apr 15 2024 - 09:14:23 EST

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From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

Allow fprobe events to be enabled with CONFIG_DYNAMIC_FTRACE_WITH_ARGS.
With this change, fprobe events mostly use ftrace_regs instead of pt_regs.
Note that if the arch doesn't enable HAVE_PT_REGS_COMPAT_FTRACE_REGS,
fprobe events will not be able to be used from perf.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
---
Changes in v9:
- Copy store_trace_entry_data() as store_fprobe_entry_data() for
fprobe.
Chagnes in v3:
- Use ftrace_regs_get_return_value().
Changes in v2:
- Define ftrace_regs_get_kernel_stack_nth() for
!CONFIG_HAVE_REGS_AND_STACK_ACCESS_API.
Changes from previous series: Update against the new series.
---
include/linux/ftrace.h | 17 ++++++
kernel/trace/Kconfig | 1
kernel/trace/trace_fprobe.c | 107 +++++++++++++++++++++++++--------------
kernel/trace/trace_probe_tmpl.h | 2 -
4 files changed, 86 insertions(+), 41 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 71dd25afdb1c..d845a80a3d56 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -256,6 +256,23 @@ static __always_inline bool ftrace_regs_has_args(struct ftrace_regs *fregs)
frame_pointer(&(fregs)->regs)
#endif

+#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API
+static __always_inline unsigned long
+ftrace_regs_get_kernel_stack_nth(struct ftrace_regs *fregs, unsigned int nth)
+{
+ unsigned long *stackp;
+
+ stackp = (unsigned long *)ftrace_regs_get_stack_pointer(fregs);
+ if (((unsigned long)(stackp + nth) & ~(THREAD_SIZE - 1)) ==
+ ((unsigned long)stackp & ~(THREAD_SIZE - 1)))
+ return *(stackp + nth);
+
+ return 0;
+}
+#else /* !CONFIG_HAVE_REGS_AND_STACK_ACCESS_API */
+#define ftrace_regs_get_kernel_stack_nth(fregs, nth) (0L)
+#endif /* CONFIG_HAVE_REGS_AND_STACK_ACCESS_API */
+
typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs);

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index d818ba3ff943..e2fc600f0ef2 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -680,7 +680,6 @@ config FPROBE_EVENTS
select TRACING
select PROBE_EVENTS
select DYNAMIC_EVENTS
- depends on DYNAMIC_FTRACE_WITH_REGS
default y
help
This allows user to add tracing events on the function entry and
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 273cdf3cf70c..86cd6a8c806a 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -133,7 +133,7 @@ static int
process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
void *dest, void *base)
{
- struct pt_regs *regs = rec;
+ struct ftrace_regs *fregs = rec;
unsigned long val;
int ret;

@@ -141,17 +141,17 @@ process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
/* 1st stage: get value from context */
switch (code->op) {
case FETCH_OP_STACK:
- val = regs_get_kernel_stack_nth(regs, code->param);
+ val = ftrace_regs_get_kernel_stack_nth(fregs, code->param);
break;
case FETCH_OP_STACKP:
- val = kernel_stack_pointer(regs);
+ val = ftrace_regs_get_stack_pointer(fregs);
break;
case FETCH_OP_RETVAL:
- val = regs_return_value(regs);
+ val = ftrace_regs_get_return_value(fregs);
break;
#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
case FETCH_OP_ARG:
- val = regs_get_kernel_argument(regs, code->param);
+ val = ftrace_regs_get_argument(fregs, code->param);
break;
case FETCH_OP_EDATA:
val = *(unsigned long *)((unsigned long)edata + code->offset);
@@ -174,7 +174,7 @@ NOKPROBE_SYMBOL(process_fetch_insn)
/* function entry handler */
static nokprobe_inline void
__fentry_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
- struct pt_regs *regs,
+ struct ftrace_regs *fregs,
struct trace_event_file *trace_file)
{
struct fentry_trace_entry_head *entry;
@@ -188,41 +188,71 @@ __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, NULL);
+ dsize = __get_data_size(&tf->tp, fregs, NULL);

entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + tf->tp.size + dsize);
if (!entry)
return;

- fbuffer.regs = regs;
+ fbuffer.regs = ftrace_get_regs(fregs);
entry = fbuffer.entry = ring_buffer_event_data(fbuffer.event);
entry->ip = entry_ip;
- store_trace_args(&entry[1], &tf->tp, regs, NULL, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, fregs, NULL, sizeof(*entry), dsize);

trace_event_buffer_commit(&fbuffer);
}

static void
fentry_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
- struct pt_regs *regs)
+ struct ftrace_regs *fregs)
{
struct event_file_link *link;

trace_probe_for_each_link_rcu(link, &tf->tp)
- __fentry_trace_func(tf, entry_ip, regs, link->file);
+ __fentry_trace_func(tf, entry_ip, fregs, link->file);
}
NOKPROBE_SYMBOL(fentry_trace_func);

+static nokprobe_inline
+void store_fprobe_entry_data(void *edata, struct trace_probe *tp, struct ftrace_regs *fregs)
+{
+ struct probe_entry_arg *earg = tp->entry_arg;
+ unsigned long val = 0;
+ 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 = ftrace_regs_get_argument(fregs, 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;
+}
+
/* function exit handler */
static int trace_fprobe_entry_handler(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
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);
+ store_fprobe_entry_data(entry_data, &tf->tp, fregs);

return 0;
}
@@ -230,7 +260,7 @@ 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,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *entry_data, struct trace_event_file *trace_file)
{
struct fexit_trace_entry_head *entry;
@@ -244,60 +274,63 @@ __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, entry_data);
+ dsize = __get_data_size(&tf->tp, fregs, entry_data);

entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + tf->tp.size + dsize);
if (!entry)
return;

- fbuffer.regs = regs;
+ fbuffer.regs = ftrace_get_regs(fregs);
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, entry_data, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, fregs, 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, void *entry_data)
+ unsigned long ret_ip, struct ftrace_regs *fregs, 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, entry_data, link->file);
+ __fexit_trace_func(tf, entry_ip, ret_ip, fregs, entry_data, link->file);
}
NOKPROBE_SYMBOL(fexit_trace_func);

#ifdef CONFIG_PERF_EVENTS

static int fentry_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
- struct pt_regs *regs)
+ struct ftrace_regs *fregs)
{
struct trace_event_call *call = trace_probe_event_call(&tf->tp);
struct fentry_trace_entry_head *entry;
struct hlist_head *head;
int size, __size, dsize;
+ struct pt_regs *regs;
int rctx;

head = this_cpu_ptr(call->perf_events);
if (hlist_empty(head))
return 0;

- dsize = __get_data_size(&tf->tp, regs, NULL);
+ dsize = __get_data_size(&tf->tp, fregs, NULL);
__size = sizeof(*entry) + tf->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
size -= sizeof(u32);

- entry = perf_trace_buf_alloc(size, NULL, &rctx);
+ entry = perf_trace_buf_alloc(size, &regs, &rctx);
if (!entry)
return 0;

+ regs = ftrace_fill_perf_regs(fregs, regs);
+
entry->ip = entry_ip;
memset(&entry[1], 0, dsize);
- store_trace_args(&entry[1], &tf->tp, regs, NULL, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, fregs, NULL, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
return 0;
@@ -306,31 +339,34 @@ 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 ftrace_regs *fregs,
void *entry_data)
{
struct trace_event_call *call = trace_probe_event_call(&tf->tp);
struct fexit_trace_entry_head *entry;
struct hlist_head *head;
int size, __size, dsize;
+ struct pt_regs *regs;
int rctx;

head = this_cpu_ptr(call->perf_events);
if (hlist_empty(head))
return;

- dsize = __get_data_size(&tf->tp, regs, entry_data);
+ dsize = __get_data_size(&tf->tp, fregs, entry_data);
__size = sizeof(*entry) + tf->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
size -= sizeof(u32);

- entry = perf_trace_buf_alloc(size, NULL, &rctx);
+ entry = perf_trace_buf_alloc(size, &regs, &rctx);
if (!entry)
return;

+ regs = ftrace_fill_perf_regs(fregs, regs);
+
entry->func = entry_ip;
entry->ret_ip = ret_ip;
- store_trace_args(&entry[1], &tf->tp, regs, entry_data, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, fregs, entry_data, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
}
@@ -342,17 +378,14 @@ static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip,
void *entry_data)
{
struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);
- struct pt_regs *regs = ftrace_get_regs(fregs);
int ret = 0;

- if (!regs)
- return 0;
-
if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
- fentry_trace_func(tf, entry_ip, regs);
+ fentry_trace_func(tf, entry_ip, fregs);
+
#ifdef CONFIG_PERF_EVENTS
if (trace_probe_test_flag(&tf->tp, TP_FLAG_PROFILE))
- ret = fentry_perf_func(tf, entry_ip, regs);
+ ret = fentry_perf_func(tf, entry_ip, fregs);
#endif
return ret;
}
@@ -363,16 +396,12 @@ static void fexit_dispatcher(struct fprobe *fp, unsigned long entry_ip,
void *entry_data)
{
struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);
- struct pt_regs *regs = ftrace_get_regs(fregs);
-
- if (!regs)
- return;

if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
- fexit_trace_func(tf, entry_ip, ret_ip, regs, entry_data);
+ fexit_trace_func(tf, entry_ip, ret_ip, fregs, 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, entry_data);
+ fexit_perf_func(tf, entry_ip, ret_ip, fregs, entry_data);
#endif
}
NOKPROBE_SYMBOL(fexit_dispatcher);
diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index 2caf0d2afb32..f39b37fcdb3b 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -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, void *edata)
+__get_data_size(struct trace_probe *tp, void *regs, void *edata)
{
struct probe_arg *arg;
int i, len, ret = 0;

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