[PATCH v11 07/18] fprobe: Use ftrace_regs in fprobe exit handler

Masami Hiramatsu (Google)
2024-06-17T01:47:55Z

Change the fprobe exit handler to use ftrace_regs structure instead of
pt_regs. This also introduce HAVE_PT_REGS_TO_FTRACE_REGS_CAST which means
the ftrace_regs's memory layout is equal to the pt_regs so that those are
able to cast. Fprobe introduces a new dependency with that.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v3:
- Use ftrace_regs_get_return_value()
Changes from previous series: NOTHING, just forward ported.
---
arch/loongarch/Kconfig | 1 +
arch/s390/Kconfig | 1 +
arch/x86/Kconfig | 1 +
include/linux/fprobe.h | 2 +-
include/linux/ftrace.h | 6 ++++++
kernel/trace/Kconfig | 8 ++++++++
kernel/trace/bpf_trace.c | 6 +++++-
kernel/trace/fprobe.c | 3 ++-
kernel/trace/trace_fprobe.c | 6 +++++-
lib/test_fprobe.c | 6 +++---
samples/fprobe/fprobe_example.c | 2 +-
11 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 23014d5f0047..0f1b2057507b 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -119,6 +119,7 @@ config LOONGARCH
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ select HAVE_PT_REGS_TO_FTRACE_REGS_CAST
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EBPF_JIT
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 33688d43fd14..adc8f6620525 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -173,6 +173,7 @@ config S390
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ select HAVE_PT_REGS_TO_FTRACE_REGS_CAST
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EBPF_JIT if HAVE_MARCH_Z196_FEATURES
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5fc3a2997977..d4655b72e6d7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -218,6 +218,7 @@ config X86
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
+ select HAVE_PT_REGS_TO_FTRACE_REGS_CAST if X86_64
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index ca64ee5e45d2..ef609bcca0f9 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h
@@ -14,7 +14,7 @@ typedef int (*fprobe_entry_cb)(struct fprobe *fp, unsigned long entry_ip,
void *entry_data);

typedef void (*fprobe_exit_cb)(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *regs,
void *entry_data);

/**
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 85394b9fb630..fa578748f7d2 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -162,6 +162,12 @@ struct ftrace_regs {
#define ftrace_regs_set_instruction_pointer(fregs, ip) do { } while (0)
#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */

+#ifdef CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST
+
+static_assert(sizeof(struct pt_regs) == sizeof(struct ftrace_regs));
+
+#endif /* CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST */
+
static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)
{
if (!fregs)
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 78b0da6fda1a..15e340a865f5 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -57,6 +57,13 @@ config HAVE_DYNAMIC_FTRACE_WITH_ARGS
This allows for use of ftrace_regs_get_argument() and
ftrace_regs_get_stack_pointer().

+config HAVE_PT_REGS_TO_FTRACE_REGS_CAST
+ bool
+ help
+ If this is set, the memory layout of the ftrace_regs data structure
+ is the same as the pt_regs. So the pt_regs is possible to be casted
+ to ftrace_regs.
+
config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
bool
help
@@ -288,6 +295,7 @@ config FPROBE
bool "Kernel Function Probe (fprobe)"
depends on FUNCTION_TRACER
depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
+ depends on HAVE_PT_REGS_TO_FTRACE_REGS_CAST || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
depends on HAVE_RETHOOK
select RETHOOK
default n
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 7e782a58ca6d..f72b421abe9b 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2871,10 +2871,14 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,

static void
kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *data)
{
struct bpf_kprobe_multi_link *link;
+ struct pt_regs *regs = ftrace_get_regs(fregs);
+
+ if (!regs)
+ return;

link = container_of(fp, struct bpf_kprobe_multi_link, fp);
kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs, true, data);
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 3d3789283873..90a3c8e2bbdf 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -124,6 +124,7 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data,
{
struct fprobe *fp = (struct fprobe *)data;
struct fprobe_rethook_node *fpr;
+ struct ftrace_regs *fregs = (struct ftrace_regs *)regs;
int bit;

if (!fp || fprobe_disabled(fp))
@@ -141,7 +142,7 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data,
return;
}

- fp->exit_handler(fp, fpr->entry_ip, ret_ip, regs,
+ fp->exit_handler(fp, fpr->entry_ip, ret_ip, fregs,
fp->entry_data_size ? (void *)fpr->data : NULL);
ftrace_test_recursion_unlock(bit);
}
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index b2c20d4fdfd7..273cdf3cf70c 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -359,10 +359,14 @@ static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip,
NOKPROBE_SYMBOL(fentry_dispatcher);

static void fexit_dispatcher(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);
+ 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);
diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
index ff607babba18..271ce0caeec0 100644
--- a/lib/test_fprobe.c
+++ b/lib/test_fprobe.c
@@ -59,9 +59,9 @@ static notrace int fp_entry_handler(struct fprobe *fp, unsigned long ip,

static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
- unsigned long ret = regs_return_value(regs);
+ unsigned long ret = ftrace_regs_get_return_value(fregs);

KUNIT_EXPECT_FALSE(current_test, preemptible());
if (ip != target_ip) {
@@ -89,7 +89,7 @@ static notrace int nest_entry_handler(struct fprobe *fp, unsigned long ip,

static notrace void nest_exit_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
KUNIT_EXPECT_FALSE(current_test, preemptible());
KUNIT_EXPECT_EQ(current_test, ip, target_nest_ip);
diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c
index 1545a1aac616..d476d1f07538 100644
--- a/samples/fprobe/fprobe_example.c
+++ b/samples/fprobe/fprobe_example.c
@@ -67,7 +67,7 @@ static int sample_entry_handler(struct fprobe *fp, unsigned long ip,
}

static void sample_exit_handler(struct fprobe *fp, unsigned long ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *regs,
void *data)
{
unsigned long rip = ret_ip;