[PATCH v16 03/18] function_graph: Pass ftrace_regs to entryfunc

Masami Hiramatsu (Google)
2024-10-15T01:29:11Z

Pass ftrace_regs to the fgraph_ops::entryfunc(). If ftrace_regs is not
available, it passes a NULL instead. User callback function can access
some registers (including return address) via this ftrace_regs.

Note that the ftrace_regs can be NULL when the arch does NOT define:
HAVE_DYNAMIC_FTRACE_WITH_ARGS or HAVE_DYNAMIC_FTRACE_WITH_REGS.
More specifically, if HAVE_DYNAMIC_FTRACE_WITH_REGS is defined but
not the HAVE_DYNAMIC_FTRACE_WITH_ARGS, and the ftrace ops used to
register the function callback does not set FTRACE_OPS_FL_SAVE_REGS.
In this case, ftrace_regs can be NULL in user callback.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Naveen N Rao <naveen@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

---
Changes in v16:
- Add a note when the ftrace_regs can be NULL.
- Update against for the latest kernel.
Changes in v11:
- Update for the latest for-next branch.
Changes in v8:
- Just pass ftrace_regs to the handler instead of adding a new
entryregfunc.
- Update riscv ftrace_graph_func().
Changes in v3:
- Update for new multiple fgraph.
---
arch/arm64/kernel/ftrace.c | 20 +++++++++++-
arch/loongarch/kernel/ftrace_dyn.c | 10 +++++-
arch/powerpc/kernel/trace/ftrace.c | 2 +
arch/powerpc/kernel/trace/ftrace_64_pg.c | 10 ++++--
arch/riscv/kernel/ftrace.c | 17 ++++++++++
arch/x86/kernel/ftrace.c | 50 +++++++++++++++++++++---------
include/linux/ftrace.h | 17 ++++++++--
kernel/trace/fgraph.c | 25 +++++++++------
kernel/trace/ftrace.c | 3 +-
kernel/trace/trace.h | 3 +-
kernel/trace/trace_functions_graph.c | 3 +-
kernel/trace/trace_irqsoff.c | 3 +-
kernel/trace/trace_sched_wakeup.c | 3 +-
kernel/trace/trace_selftest.c | 8 +++--
14 files changed, 129 insertions(+), 45 deletions(-)

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index b2d947175cbe..a5a285f8a7ef 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -481,7 +481,25 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs)
{
- prepare_ftrace_return(ip, &arch_ftrace_regs(fregs)->lr, arch_ftrace_regs(fregs)->fp);
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+ unsigned long frame_pointer = arch_ftrace_regs(fregs)->fp;
+ unsigned long *parent = &arch_ftrace_regs(fregs)->lr;
+ unsigned long old;
+
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ return;
+
+ /*
+ * Note:
+ * No protection against faulting at *parent, which may be seen
+ * on other archs. It's unlikely on AArch64.
+ */
+ old = *parent;
+
+ if (!function_graph_enter_regs(old, ip, frame_pointer,
+ (void *)frame_pointer, fregs)) {
+ *parent = return_hooker;
+ }
}
#else
/*
diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
index 18056229e22e..25c9a4cfd5fa 100644
--- a/arch/loongarch/kernel/ftrace_dyn.c
+++ b/arch/loongarch/kernel/ftrace_dyn.c
@@ -243,8 +243,16 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
{
struct pt_regs *regs = &arch_ftrace_regs(fregs)->regs;
unsigned long *parent = (unsigned long *)&regs->regs[1];
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+ unsigned long old;
+
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ return;
+
+ old = *parent;

- prepare_ftrace_return(ip, (unsigned long *)parent);
+ if (!function_graph_enter_regs(old, ip, 0, parent, fregs))
+ *parent = return_hooker;
}
#else
static int ftrace_modify_graph_caller(bool enable)
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index df41f4a7c738..c3ec437b530d 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -434,7 +434,7 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
if (bit < 0)
goto out;

- if (!function_graph_enter(parent_ip, ip, 0, (unsigned long *)sp))
+ if (!function_graph_enter_regs(parent_ip, ip, 0, (unsigned long *)sp, fregs))
parent_ip = ppc_function_entry(return_to_handler);

ftrace_test_recursion_unlock(bit);
diff --git a/arch/powerpc/kernel/trace/ftrace_64_pg.c b/arch/powerpc/kernel/trace/ftrace_64_pg.c
index d3c5552e4984..7964d632d13d 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_pg.c
+++ b/arch/powerpc/kernel/trace/ftrace_64_pg.c
@@ -800,7 +800,8 @@ int ftrace_disable_ftrace_graph_caller(void)
* in current thread info. Return the address we want to divert to.
*/
static unsigned long
-__prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp)
+__prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp,
+ struct ftrace_regs *fregs)
{
unsigned long return_hooker;
int bit;
@@ -817,7 +818,7 @@ __prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp

return_hooker = ppc_function_entry(return_to_handler);

- if (!function_graph_enter(parent, ip, 0, (unsigned long *)sp))
+ if (!function_graph_enter_regs(parent, ip, 0, (unsigned long *)sp, fregs))
parent = return_hooker;

ftrace_test_recursion_unlock(bit);
@@ -829,13 +830,14 @@ __prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp
void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs)
{
- arch_ftrace_regs(fregs)->regs.link = __prepare_ftrace_return(parent_ip, ip, arch_ftrace_regs(fregs)->regs.gpr[1]);
+ arch_ftrace_regs(fregs)->regs.link = __prepare_ftrace_return(parent_ip, ip,
+ arch_ftrace_regs(fregs)->regs.gpr[1], fregs);
}
#else
unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
unsigned long sp)
{
- return __prepare_ftrace_return(parent, ip, sp);
+ return __prepare_ftrace_return(parent, ip, sp, NULL);
}
#endif
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 5081ad886841..d6ebdb5d7537 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -214,7 +214,22 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs)
{
- prepare_ftrace_return(&arch_ftrace_regs(fregs)->ra, ip, arch_ftrace_regs(fregs)->s0);
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+ unsigned long frame_pointer = arch_ftrace_regs(fregs)->s0;
+ unsigned long *parent = &arch_ftrace_regs(fregs)->ra;
+ unsigned long old;
+
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ return;
+
+ /*
+ * We don't suffer access faults, so no extra fault-recovery assembly
+ * is needed here.
+ */
+ old = *parent;
+
+ if (!function_graph_enter_regs(old, ip, frame_pointer, parent, fregs))
+ *parent = return_hooker;
}
#else /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */
extern void ftrace_graph_call(void);
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index adb09f78edb2..be224f1c2078 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -605,16 +605,8 @@ int ftrace_disable_ftrace_graph_caller(void)
}
#endif /* CONFIG_DYNAMIC_FTRACE && !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */

-/*
- * Hook the return address and push it in the stack of return addrs
- * in current thread info.
- */
-void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
- unsigned long frame_pointer)
+static inline bool skip_ftrace_return(void)
{
- unsigned long return_hooker = (unsigned long)&return_to_handler;
- int bit;
-
/*
* When resuming from suspend-to-ram, this function can be indirectly
* called from early CPU startup code while the CPU is in real mode,
@@ -624,13 +616,28 @@ void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
* This check isn't as accurate as virt_addr_valid(), but it should be
* good enough for this purpose, and it's fast.
*/
- if (unlikely((long)__builtin_frame_address(0) >= 0))
- return;
+ if ((long)__builtin_frame_address(0) >= 0)
+ return true;

- if (unlikely(ftrace_graph_is_dead()))
- return;
+ if (ftrace_graph_is_dead())
+ return true;
+
+ if (atomic_read(&current->tracing_graph_pause))
+ return true;
+ return false;
+}
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
+ unsigned long frame_pointer)
+{
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+ int bit;

- if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ if (unlikely(skip_ftrace_return()))
return;

bit = ftrace_test_recursion_trylock(ip, *parent);
@@ -649,8 +656,21 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
{
struct pt_regs *regs = &arch_ftrace_regs(fregs)->regs;
unsigned long *stack = (unsigned long *)kernel_stack_pointer(regs);
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+ unsigned long *parent = (unsigned long *)stack;
+ int bit;

- prepare_ftrace_return(ip, (unsigned long *)stack, 0);
+ if (unlikely(skip_ftrace_return()))
+ return;
+
+ bit = ftrace_test_recursion_trylock(ip, *parent);
+ if (bit < 0)
+ return;
+
+ if (!function_graph_enter_regs(*parent, ip, 0, parent, fregs))
+ *parent = return_hooker;
+
+ ftrace_test_recursion_unlock(bit);
}
#endif

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index aa9ddd1e4bb6..c86ac786da3d 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1071,10 +1071,12 @@ struct fgraph_ops;
typedef void (*trace_func_graph_ret_t)(struct ftrace_graph_ret *,
struct fgraph_ops *); /* return */
typedef int (*trace_func_graph_ent_t)(struct ftrace_graph_ent *,
- struct fgraph_ops *); /* entry */
+ struct fgraph_ops *,
+ struct ftrace_regs *); /* entry */

extern int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops);
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs);
bool ftrace_pids_enabled(struct ftrace_ops *ops);

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -1114,8 +1116,15 @@ struct ftrace_ret_stack {
extern void return_to_handler(void);

extern int
-function_graph_enter(unsigned long ret, unsigned long func,
- unsigned long frame_pointer, unsigned long *retp);
+function_graph_enter_regs(unsigned long ret, unsigned long func,
+ unsigned long frame_pointer, unsigned long *retp,
+ struct ftrace_regs *fregs);
+
+static inline int function_graph_enter(unsigned long ret, unsigned long func,
+ unsigned long fp, unsigned long *retp)
+{
+ return function_graph_enter_regs(ret, func, fp, retp, NULL);
+}

struct ftrace_ret_stack *
ftrace_graph_get_ret_stack(struct task_struct *task, int skip);
diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index ee829d65f301..3eda5880f883 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -290,7 +290,8 @@ static inline unsigned long make_data_type_val(int idx, int size, int offset)
}

/* ftrace_graph_entry set to this to tell some archs to run function graph */
-static int entry_run(struct ftrace_graph_ent *trace, struct fgraph_ops *ops)
+static int entry_run(struct ftrace_graph_ent *trace, struct fgraph_ops *ops,
+ struct ftrace_regs *fregs)
{
return 0;
}
@@ -518,7 +519,8 @@ int __weak ftrace_disable_ftrace_graph_caller(void)
#endif

int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops)
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs)
{
return 0;
}
@@ -642,8 +644,9 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
#endif

/* If the caller does not use ftrace, call this function. */
-int function_graph_enter(unsigned long ret, unsigned long func,
- unsigned long frame_pointer, unsigned long *retp)
+int function_graph_enter_regs(unsigned long ret, unsigned long func,
+ unsigned long frame_pointer, unsigned long *retp,
+ struct ftrace_regs *fregs)
{
struct ftrace_graph_ent trace;
unsigned long bitmap = 0;
@@ -661,7 +664,7 @@ int function_graph_enter(unsigned long ret, unsigned long func,
if (static_branch_likely(&fgraph_do_direct)) {
int save_curr_ret_stack = current->curr_ret_stack;

- if (static_call(fgraph_func)(&trace, fgraph_direct_gops))
+ if (static_call(fgraph_func)(&trace, fgraph_direct_gops, fregs))
bitmap |= BIT(fgraph_direct_gops->idx);
else
/* Clear out any saved storage */
@@ -679,7 +682,7 @@ int function_graph_enter(unsigned long ret, unsigned long func,

save_curr_ret_stack = current->curr_ret_stack;
if (ftrace_ops_test(&gops->ops, func, NULL) &&
- gops->entryfunc(&trace, gops))
+ gops->entryfunc(&trace, gops, fregs))
bitmap |= BIT(i);
else
/* Clear out any saved storage */
@@ -977,7 +980,7 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,

static struct ftrace_ops graph_ops = {
.func = ftrace_graph_func,
- .flags = FTRACE_OPS_GRAPH_STUB,
+ .flags = FTRACE_OPS_GRAPH_STUB | FTRACE_OPS_FL_SAVE_ARGS,
#ifdef FTRACE_GRAPH_TRAMP_ADDR
.trampoline = FTRACE_GRAPH_TRAMP_ADDR,
/* trampoline_size is only needed for dynamically allocated tramps */
@@ -987,7 +990,8 @@ static struct ftrace_ops graph_ops = {
void fgraph_init_ops(struct ftrace_ops *dst_ops,
struct ftrace_ops *src_ops)
{
- dst_ops->flags = FTRACE_OPS_FL_PID | FTRACE_OPS_GRAPH_STUB;
+ dst_ops->flags = FTRACE_OPS_FL_PID | FTRACE_OPS_GRAPH_STUB |
+ FTRACE_OPS_FL_SAVE_ARGS;

#ifdef CONFIG_DYNAMIC_FTRACE
if (src_ops) {
@@ -1159,7 +1163,8 @@ void ftrace_graph_exit_task(struct task_struct *t)

#ifdef CONFIG_DYNAMIC_FTRACE
static int fgraph_pid_func(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops)
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs)
{
struct trace_array *tr = gops->ops.private;
int pid;
@@ -1173,7 +1178,7 @@ static int fgraph_pid_func(struct ftrace_graph_ent *trace,
return 0;
}

- return gops->saved_func(trace, gops);
+ return gops->saved_func(trace, gops, fregs);
}

void fgraph_update_pid_func(void)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index e9fd4fb2769e..6346fe37f2f6 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -827,7 +827,8 @@ struct profile_fgraph_data {
};

static int profile_graph_entry(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops)
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs)
{
struct profile_fgraph_data *profile_data;

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ec99b630eb11..c1d4d5a3469c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -695,7 +695,8 @@ void trace_default_header(struct seq_file *m);
void print_trace_header(struct seq_file *m, struct trace_iterator *iter);

void trace_graph_return(struct ftrace_graph_ret *trace, struct fgraph_ops *gops);
-int trace_graph_entry(struct ftrace_graph_ent *trace, struct fgraph_ops *gops);
+int trace_graph_entry(struct ftrace_graph_ent *trace, struct fgraph_ops *gops,
+ struct ftrace_regs *fregs);

void tracing_start_cmdline_record(void);
void tracing_stop_cmdline_record(void);
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 5504b5e4e7b4..b62ad912d84f 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -175,7 +175,8 @@ struct fgraph_times {
};

int trace_graph_entry(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops)
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs)
{
unsigned long *task_var = fgraph_get_task_var(gops);
struct trace_array *tr = gops->private;
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index fce064e20570..ad739d76fc86 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -176,7 +176,8 @@ static int irqsoff_display_graph(struct trace_array *tr, int set)
}

static int irqsoff_graph_entry(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops)
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs)
{
struct trace_array *tr = irqsoff_trace;
struct trace_array_cpu *data;
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index d6c7f18daa15..0d9e1075d815 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -113,7 +113,8 @@ static int wakeup_display_graph(struct trace_array *tr, int set)
}

static int wakeup_graph_entry(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops)
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs)
{
struct trace_array *tr = wakeup_trace;
struct trace_array_cpu *data;
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index d3a14ae47e26..137c13de5731 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -774,7 +774,8 @@ struct fgraph_fixture {
};

static __init int store_entry(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops)
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs)
{
struct fgraph_fixture *fixture = container_of(gops, struct fgraph_fixture, gops);
const char *type = fixture->store_type_name;
@@ -1025,7 +1026,8 @@ static unsigned int graph_hang_thresh;

/* Wrap the real function entry probe to avoid possible hanging */
static int trace_graph_entry_watchdog(struct ftrace_graph_ent *trace,
- struct fgraph_ops *gops)
+ struct fgraph_ops *gops,
+ struct ftrace_regs *fregs)
{
/* This is harmlessly racy, we want to approximately detect a hang */
if (unlikely(++graph_hang_thresh > GRAPH_MAX_FUNC_TEST)) {
@@ -1039,7 +1041,7 @@ static int trace_graph_entry_watchdog(struct ftrace_graph_ent *trace,
return 0;
}

- return trace_graph_entry(trace, gops);
+ return trace_graph_entry(trace, gops, fregs);
}

static struct fgraph_ops fgraph_ops __initdata = {