Re: [PATCH v5 11/34] function_graph: Have the instances use their own ftrace_ops for filtering

From: Mark Rutland
Date: Fri Jan 05 2024 - 12:09:33 EST

On Mon, Dec 18, 2023 at 10:13:46PM +0900, Masami Hiramatsu (Google) wrote:
> From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
>
> Allow for instances to have their own ftrace_ops part of the fgraph_ops
> that makes the funtion_graph tracer filter on the set_ftrace_filter file
> of the instance and not the top instance.
>
> This also change how the function_graph handles multiple instances on the
> shadow stack. Previously we use ARRAY type entries to record which one
> is enabled, and this makes it a bitmap of the fgraph_array's indexes.
> Previous function_graph_enter() expects calling back from
> prepare_ftrace_return() function which is called back only once if it is
> enabled. But this introduces different ftrace_ops for each fgraph
> instance and those are called from ftrace_graph_func() one by one. Thus
> we can not loop on the fgraph_array(), and need to reuse the ret_stack
> pushed by the previous instance. Finding the ret_stack is easy because
> we can check the ret_stack->func. But that is not enough for the self-
> recursive tail-call case. Thus fgraph uses the bitmap entry to find it
> is already set (this means that entry is for previous tail call).
>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

As a heads-up, while testing the topic/fprobe-on-fgraph branch on arm64, I get
a warning which bisets down to this commit:

| Testing tracer function_graph:
| ------------[ cut here ]------------
| WARNING: CPU: 2 PID: 0 at arch/arm64/kernel/stacktrace.c:84 arch_stack_walk+0x3c0/0x3d8
| Modules linked in:
| CPU: 2 PID: 0 Comm: swapper/2 Not tainted 6.7.0-rc2-00026-gea1e68a341c2 #12
| Hardware name: linux,dummy-virt (DT)
| pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
| pc : arch_stack_walk+0x3c0/0x3d8
| lr : arch_stack_walk+0x260/0x3d8
| sp : ffff80008318be00
| x29: ffff80008318be00 x28: ffff000003c0ae80 x27: 0000000000000000
| x26: 0000000000000000 x25: ffff000003c0ae80 x24: 0000000000000000
| x23: ffff8000800234c8 x22: ffff80008002dc30 x21: ffff800080035d10
| x20: ffff80008318bee8 x19: ffff800080023460 x18: ffff800083453c68
| x17: 0000000000000000 x16: ffff800083188000 x15: 000000008ccc5058
| x14: 0000000000000004 x13: ffff800082b8c4f0 x12: 0000000000000000
| x11: ffff800081fba9b0 x10: ffff80008318bff0 x9 : ffff800080010798
| x8 : ffff80008002dc30 x7 : ffff000003c0ae80 x6 : 00000000ffffffff
| x5 : 0000000000000000 x4 : ffff8000832a3c18 x3 : ffff80008318bff0
| x2 : ffff80008002dc30 x1 : ffff80008002dc30 x0 : ffff80008002dc30
| Call trace:
| arch_stack_walk+0x3c0/0x3d8
| return_address+0x40/0x80
| trace_hardirqs_on+0x8c/0x198
| __do_softirq+0xe8/0x440
| ---[ end trace 0000000000000000 ]---

That's a warning in arm64's unwind_recover_return_address() function, which
fires when ftrace_graph_ret_addr() finds return_to_handler:

if (state->task->ret_stack &&
(state->pc == (unsigned long)return_to_handler)) {
unsigned long orig_pc;
orig_pc = ftrace_graph_ret_addr(state->task, NULL, state->pc,
(void *)state->fp);
if (WARN_ON_ONCE(state->pc == orig_pc))
return -EINVAL;
state->pc = orig_pc;
}

The rationale there is that since tail calls are (currently) disabled on arm64,
the only reason for ftrace_graph_ret_addr() to return return_to_handler is when
it fails to find the original return address.

Does this change make it legitimate for ftrace_graph_ret_addr() to return
return_to_handler in other cases, or is that a bug?

Either way, we'll need *some* way to recover the original return addresss...

Mark.

> ---
> Changes in v4:
> - Simplify get_ret_stack() sanity check and use WARN_ON_ONCE() for
> obviously wrong value.
> - Do not check ret == return_to_handler but always read the previous
> ret_stack in ftrace_push_return_trace() to check it is reusable.
> - Set the bit 0 of the bitmap entry always in function_graph_enter()
> because it uses bit 0 to check re-usability.
> - Fix to ensure the ret_stack entry is bitmap type when checking the
> bitmap.
> Changes in v3:
> - Pass current fgraph_ops to the new entry handler
> (function_graph_enter_ops) if fgraph use ftrace.
> - Add fgraph_ops::idx in this patch.
> - Replace the array type with the bitmap type so that it can record
> which fgraph is called.
> - Fix some helper function to use passed task_struct instead of current.
> - Reduce the ret-index size to 1024 words.
> - Make the ret-index directly points the ret_stack.
> - Fix ftrace_graph_ret_addr() to handle tail-call case correctly.
> Changes in v2:
> - Use ftrace_graph_func and FTRACE_OPS_GRAPH_STUB instead of
> ftrace_stub and FTRACE_OPS_FL_STUB for new ftrace based fgraph.
> ---
> arch/arm64/kernel/ftrace.c | 19 ++
> arch/x86/kernel/ftrace.c | 19 ++
> include/linux/ftrace.h | 7 +
> kernel/trace/fgraph.c | 369 ++++++++++++++++++++--------------
> kernel/trace/ftrace.c | 6 -
> kernel/trace/trace.h | 16 +
> kernel/trace/trace_functions.c | 2
> kernel/trace/trace_functions_graph.c | 8 +
> 8 files changed, 277 insertions(+), 169 deletions(-)
>
> diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
> index a650f5e11fc5..205937e04ece 100644
> --- a/arch/arm64/kernel/ftrace.c
> +++ b/arch/arm64/kernel/ftrace.c
> @@ -481,7 +481,24 @@ 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, &fregs->lr, fregs->fp);
> + unsigned long *parent = &fregs->lr;
> + struct fgraph_ops *gops = container_of(op, struct fgraph_ops, ops);
> + int bit;
> +
> + if (unlikely(ftrace_graph_is_dead()))
> + return;
> +
> + if (unlikely(atomic_read(&current->tracing_graph_pause)))
> + return;
> +
> + bit = ftrace_test_recursion_trylock(ip, *parent);
> + if (bit < 0)
> + return;
> +
> + if (!function_graph_enter_ops(*parent, ip, fregs->fp, parent, gops))
> + *parent = (unsigned long)&return_to_handler;
> +
> + ftrace_test_recursion_unlock(bit);
> }
> #else
> /*
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index 12df54ff0e81..845e29b4254f 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -657,9 +657,24 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
> struct ftrace_ops *op, struct ftrace_regs *fregs)
> {
> struct pt_regs *regs = &fregs->regs;
> - unsigned long *stack = (unsigned long *)kernel_stack_pointer(regs);
> + unsigned long *parent = (unsigned long *)kernel_stack_pointer(regs);
> + struct fgraph_ops *gops = container_of(op, struct fgraph_ops, ops);
> + int bit;
> +
> + if (unlikely(ftrace_graph_is_dead()))
> + return;
> +
> + if (unlikely(atomic_read(&current->tracing_graph_pause)))
> + return;
>
> - prepare_ftrace_return(ip, (unsigned long *)stack, 0);
> + bit = ftrace_test_recursion_trylock(ip, *parent);
> + if (bit < 0)
> + return;
> +
> + if (!function_graph_enter_ops(*parent, ip, 0, parent, gops))
> + *parent = (unsigned long)&return_to_handler;
> +
> + ftrace_test_recursion_unlock(bit);
> }
> #endif
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 7b08169aa51d..c431a33fe789 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -1070,7 +1070,9 @@ extern int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace, struct fgraph
> struct fgraph_ops {
> trace_func_graph_ent_t entryfunc;
> trace_func_graph_ret_t retfunc;
> + struct ftrace_ops ops; /* for the hash lists */
> void *private;
> + int idx;
> };
>
> /*
> @@ -1104,6 +1106,11 @@ extern int
> function_graph_enter(unsigned long ret, unsigned long func,
> unsigned long frame_pointer, unsigned long *retp);
>
> +extern int
> +function_graph_enter_ops(unsigned long ret, unsigned long func,
> + unsigned long frame_pointer, unsigned long *retp,
> + struct fgraph_ops *gops);
> +
> struct ftrace_ret_stack *
> ftrace_graph_get_ret_stack(struct task_struct *task, int idx);
>
> diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> index 62c35d6d95f9..6f537ebd3ed7 100644
> --- a/kernel/trace/fgraph.c
> +++ b/kernel/trace/fgraph.c
> @@ -7,6 +7,7 @@
> *
> * Highly modified by Steven Rostedt (VMware).
> */
> +#include <linux/bits.h>
> #include <linux/jump_label.h>
> #include <linux/suspend.h>
> #include <linux/ftrace.h>
> @@ -17,22 +18,15 @@
> #include "ftrace_internal.h"
> #include "trace.h"
>
> -#ifdef CONFIG_DYNAMIC_FTRACE
> -#define ASSIGN_OPS_HASH(opsname, val) \
> - .func_hash = val, \
> - .local_hash.regex_lock = __MUTEX_INITIALIZER(opsname.local_hash.regex_lock),
> -#else
> -#define ASSIGN_OPS_HASH(opsname, val)
> -#endif
> -
> #define FGRAPH_RET_SIZE sizeof(struct ftrace_ret_stack)
> #define FGRAPH_RET_INDEX (FGRAPH_RET_SIZE / sizeof(long))
>
> /*
> * On entry to a function (via function_graph_enter()), a new ftrace_ret_stack
> - * is allocated on the task's ret_stack, then each fgraph_ops on the
> - * fgraph_array[]'s entryfunc is called and if that returns non-zero, the
> - * index into the fgraph_array[] for that fgraph_ops is added to the ret_stack.
> + * is allocated on the task's ret_stack with indexes entry, then each
> + * fgraph_ops on the fgraph_array[]'s entryfunc is called and if that returns
> + * non-zero, the index into the fgraph_array[] for that fgraph_ops is recorded
> + * on the indexes entry as a bit flag.
> * As the associated ftrace_ret_stack saved for those fgraph_ops needs to
> * be found, the index to it is also added to the ret_stack along with the
> * index of the fgraph_array[] to each fgraph_ops that needs their retfunc
> @@ -42,61 +36,59 @@
> * to the last ftrace_ret_stack saved. All references to the
> * ftrace_ret_stack has the format of:
> *
> - * bits: 0 - 13 Index in words from the previous ftrace_ret_stack
> - * bits: 14 - 15 Type of storage
> + * bits: 0 - 9 offset in words from the previous ftrace_ret_stack
> + * (bitmap type should have FGRAPH_RET_INDEX always)
> + * bits: 10 - 11 Type of storage
> * 0 - reserved
> - * 1 - fgraph_array index
> - * For fgraph_array_index:
> - * bits: 16 - 23 The fgraph_ops fgraph_array index
> + * 1 - bitmap of fgraph_array index
> + *
> + * For bitmap of fgraph_array index
> + * bits: 12 - 27 The bitmap of fgraph_ops fgraph_array index
> *
> * That is, at the end of function_graph_enter, if the first and forth
> * fgraph_ops on the fgraph_array[] (index 0 and 3) needs their retfunc called
> * on the return of the function being traced, this is what will be on the
> * task's shadow ret_stack: (the stack grows upward)
> *
> - * | | <- task->curr_ret_stack
> - * +----------------------------------+
> - * | (3 << FGRAPH_ARRAY_SHIFT)|(2) | ( 3 for index of fourth fgraph_ops)
> - * +----------------------------------+
> - * | (0 << FGRAPH_ARRAY_SHIFT)|(1) | ( 0 for index of first fgraph_ops)
> - * +----------------------------------+
> - * | struct ftrace_ret_stack |
> - * | (stores the saved ret pointer) |
> - * +----------------------------------+
> - * | (X) | (N) | ( N words away from previous ret_stack)
> - * | |
> + * | | <- task->curr_ret_stack
> + * +--------------------------------------------+
> + * | bitmap_type(bitmap:(BIT(3)|BIT(0)), |
> + * | offset:FGRAPH_RET_INDEX) | <- the offset is from here
> + * +--------------------------------------------+
> + * | struct ftrace_ret_stack |
> + * | (stores the saved ret pointer) | <- the offset points here
> + * +--------------------------------------------+
> + * | (X) | (N) | ( N words away from
> + * | | previous ret_stack)
> *
> * If a backtrace is required, and the real return pointer needs to be
> * fetched, then it looks at the task's curr_ret_stack index, if it
> - * is greater than zero, it would subtact one, and then mask the value
> - * on the ret_stack by FGRAPH_RET_INDEX_MASK and subtract FGRAPH_RET_INDEX
> - * from that, to get the index of the ftrace_ret_stack structure stored
> - * on the shadow stack.
> + * is greater than zero (reserved, or right before poped), it would mask
> + * the value by FGRAPH_RET_INDEX_MASK to get the offset index of the
> + * ftrace_ret_stack structure stored on the shadow stack.
> */
>
> -#define FGRAPH_RET_INDEX_SIZE 14
> -#define FGRAPH_RET_INDEX_MASK ((1 << FGRAPH_RET_INDEX_SIZE) - 1)
> -
> +#define FGRAPH_RET_INDEX_SIZE 10
> +#define FGRAPH_RET_INDEX_MASK GENMASK(FGRAPH_RET_INDEX_SIZE - 1, 0)
>
> #define FGRAPH_TYPE_SIZE 2
> -#define FGRAPH_TYPE_MASK ((1 << FGRAPH_TYPE_SIZE) - 1)
> +#define FGRAPH_TYPE_MASK GENMASK(FGRAPH_TYPE_SIZE - 1, 0)
> #define FGRAPH_TYPE_SHIFT FGRAPH_RET_INDEX_SIZE
>
> enum {
> FGRAPH_TYPE_RESERVED = 0,
> - FGRAPH_TYPE_ARRAY = 1,
> + FGRAPH_TYPE_BITMAP = 1,
> };
>
> -#define FGRAPH_ARRAY_SIZE 16
> -#define FGRAPH_ARRAY_MASK ((1 << FGRAPH_ARRAY_SIZE) - 1)
> -#define FGRAPH_ARRAY_SHIFT (FGRAPH_TYPE_SHIFT + FGRAPH_TYPE_SIZE)
> +#define FGRAPH_INDEX_SIZE 16
> +#define FGRAPH_INDEX_MASK GENMASK(FGRAPH_INDEX_SIZE - 1, 0)
> +#define FGRAPH_INDEX_SHIFT (FGRAPH_TYPE_SHIFT + FGRAPH_TYPE_SIZE)
>
> /* Currently the max stack index can't be more than register callers */
> -#define FGRAPH_MAX_INDEX FGRAPH_ARRAY_SIZE
> +#define FGRAPH_MAX_INDEX (FGRAPH_INDEX_SIZE + FGRAPH_RET_INDEX)
> +
> +#define FGRAPH_ARRAY_SIZE FGRAPH_INDEX_SIZE
>
> -#define FGRAPH_FRAME_SIZE (FGRAPH_RET_SIZE + FGRAPH_ARRAY_SIZE * (sizeof(long)))
> -#define FGRAPH_FRAME_INDEX (ALIGN(FGRAPH_FRAME_SIZE, \
> - sizeof(long)) / sizeof(long))
> #define SHADOW_STACK_SIZE (PAGE_SIZE)
> #define SHADOW_STACK_INDEX (SHADOW_STACK_SIZE / sizeof(long))
> /* Leave on a buffer at the end */
> @@ -113,19 +105,36 @@ static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE];
>
> static inline int get_ret_stack_index(struct task_struct *t, int offset)
> {
> - return current->ret_stack[offset] & FGRAPH_RET_INDEX_MASK;
> + return t->ret_stack[offset] & FGRAPH_RET_INDEX_MASK;
> }
>
> static inline int get_fgraph_type(struct task_struct *t, int offset)
> {
> - return (current->ret_stack[offset] >> FGRAPH_TYPE_SHIFT) &
> - FGRAPH_TYPE_MASK;
> + return (t->ret_stack[offset] >> FGRAPH_TYPE_SHIFT) & FGRAPH_TYPE_MASK;
> +}
> +
> +static inline unsigned long
> +get_fgraph_index_bitmap(struct task_struct *t, int offset)
> +{
> + return (t->ret_stack[offset] >> FGRAPH_INDEX_SHIFT) & FGRAPH_INDEX_MASK;
> }
>
> -static inline int get_fgraph_array(struct task_struct *t, int offset)
> +static inline void
> +set_fgraph_index_bitmap(struct task_struct *t, int offset, unsigned long bitmap)
> {
> - return (current->ret_stack[offset] >> FGRAPH_ARRAY_SHIFT) &
> - FGRAPH_ARRAY_MASK;
> + t->ret_stack[offset] = (bitmap << FGRAPH_INDEX_SHIFT) |
> + (FGRAPH_TYPE_BITMAP << FGRAPH_TYPE_SHIFT) | FGRAPH_RET_INDEX;
> +}
> +
> +static inline bool is_fgraph_index_set(struct task_struct *t, int offset, int idx)
> +{
> + return !!(get_fgraph_index_bitmap(t, offset) & BIT(idx));
> +}
> +
> +static inline void
> +add_fgraph_index_bitmap(struct task_struct *t, int offset, unsigned long bitmap)
> +{
> + t->ret_stack[offset] |= (bitmap << FGRAPH_INDEX_SHIFT);
> }
>
> /* ftrace_graph_entry set to this to tell some archs to run function graph */
> @@ -160,17 +169,14 @@ get_ret_stack(struct task_struct *t, int offset, int *index)
>
> BUILD_BUG_ON(FGRAPH_RET_SIZE % sizeof(long));
>
> - if (offset <= 0)
> + if (unlikely(offset <= 0))
> return NULL;
>
> - idx = get_ret_stack_index(t, offset - 1);
> -
> - if (idx <= 0 || idx > FGRAPH_MAX_INDEX)
> + idx = get_ret_stack_index(t, --offset);
> + if (WARN_ON_ONCE(idx <= 0 || idx > offset))
> return NULL;
>
> - offset -= idx + FGRAPH_RET_INDEX;
> - if (offset < 0)
> - return NULL;
> + offset -= idx;
>
> *index = offset;
> return RET_STACK(t, offset);
> @@ -231,10 +237,12 @@ void ftrace_graph_stop(void)
> /* Add a function return address to the trace stack on thread info.*/
> static int
> ftrace_push_return_trace(unsigned long ret, unsigned long func,
> - unsigned long frame_pointer, unsigned long *retp)
> + unsigned long frame_pointer, unsigned long *retp,
> + int fgraph_idx)
> {
> struct ftrace_ret_stack *ret_stack;
> unsigned long long calltime;
> + unsigned long val;
> int index;
>
> if (unlikely(ftrace_graph_is_dead()))
> @@ -243,6 +251,21 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
> if (!current->ret_stack)
> return -EBUSY;
>
> + /*
> + * At first, check whether the previous fgraph callback is pushed by
> + * the fgraph on the same function entry.
> + * But if @func is the self tail-call function, we also need to ensure
> + * the ret_stack is not for the previous call by checking whether the
> + * bit of @fgraph_idx is set or not.
> + */
> + ret_stack = get_ret_stack(current, current->curr_ret_stack, &index);
> + if (ret_stack && ret_stack->func == func &&
> + get_fgraph_type(current, index + FGRAPH_RET_INDEX) == FGRAPH_TYPE_BITMAP &&
> + !is_fgraph_index_set(current, index + FGRAPH_RET_INDEX, fgraph_idx))
> + return index + FGRAPH_RET_INDEX;
> +
> + val = (FGRAPH_TYPE_RESERVED << FGRAPH_TYPE_SHIFT) | FGRAPH_RET_INDEX;
> +
> BUILD_BUG_ON(SHADOW_STACK_SIZE % sizeof(long));
>
> /*
> @@ -252,17 +275,19 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
> smp_rmb();
>
> /* The return trace stack is full */
> - if (current->curr_ret_stack >= SHADOW_STACK_MAX_INDEX) {
> + if (current->curr_ret_stack + FGRAPH_RET_INDEX >= SHADOW_STACK_MAX_INDEX) {
> atomic_inc(&current->trace_overrun);
> return -EBUSY;
> }
>
> calltime = trace_clock_local();
>
> - index = current->curr_ret_stack;
> - /* ret offset = 1 ; type = reserved */
> - current->ret_stack[index + FGRAPH_RET_INDEX] = 1;
> + index = READ_ONCE(current->curr_ret_stack);
> ret_stack = RET_STACK(current, index);
> + index += FGRAPH_RET_INDEX;
> +
> + /* ret offset = FGRAPH_RET_INDEX ; type = reserved */
> + current->ret_stack[index] = val;
> ret_stack->ret = ret;
> /*
> * The unwinders expect curr_ret_stack to point to either zero
> @@ -278,7 +303,7 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
> * at least a correct index!
> */
> barrier();
> - current->curr_ret_stack += FGRAPH_RET_INDEX + 1;
> + current->curr_ret_stack = index + 1;
> /*
> * This next barrier is to ensure that an interrupt coming in
> * will not corrupt what we are about to write.
> @@ -286,7 +311,7 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
> barrier();
>
> /* Still keep it reserved even if an interrupt came in */
> - current->ret_stack[index + FGRAPH_RET_INDEX] = 1;
> + current->ret_stack[index] = val;
>
> ret_stack->ret = ret;
> ret_stack->func = func;
> @@ -297,7 +322,7 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
> #ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
> ret_stack->retp = retp;
> #endif
> - return 0;
> + return index;
> }
>
> /*
> @@ -314,15 +339,13 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
> # define MCOUNT_INSN_SIZE 0
> #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)
> {
> struct ftrace_graph_ent trace;
> - int offset;
> - int start;
> - int type;
> - int val;
> - int cnt = 0;
> + unsigned long bitmap = 0;
> + int index;
> int i;
>
> #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
> @@ -337,69 +360,33 @@ int function_graph_enter(unsigned long ret, unsigned long func,
> return -EBUSY;
> #endif
>
> - if (!ftrace_ops_test(&global_ops, func, NULL))
> - return -EBUSY;
> -
> trace.func = func;
> trace.depth = ++current->curr_ret_depth;
>
> - if (ftrace_push_return_trace(ret, func, frame_pointer, retp))
> + index = ftrace_push_return_trace(ret, func, frame_pointer, retp, 0);
> + if (index < 0)
> goto out;
>
> - /* Use start for the distance to ret_stack (skipping over reserve) */
> - start = offset = current->curr_ret_stack - 2;
> -
> for (i = 0; i < fgraph_array_cnt; i++) {
> struct fgraph_ops *gops = fgraph_array[i];
>
> if (gops == &fgraph_stub)
> continue;
>
> - if ((offset == start) &&
> - (current->curr_ret_stack >= SHADOW_STACK_INDEX - 1)) {
> - atomic_inc(&current->trace_overrun);
> - break;
> - }
> - if (fgraph_array[i]->entryfunc(&trace, fgraph_array[i])) {
> - offset = current->curr_ret_stack;
> - /* Check the top level stored word */
> - type = get_fgraph_type(current, offset - 1);
> -
> - val = (i << FGRAPH_ARRAY_SHIFT) |
> - (FGRAPH_TYPE_ARRAY << FGRAPH_TYPE_SHIFT) |
> - ((offset - start) - 1);
> -
> - /* We can reuse the top word if it is reserved */
> - if (type == FGRAPH_TYPE_RESERVED) {
> - current->ret_stack[offset - 1] = val;
> - cnt++;
> - continue;
> - }
> - val++;
> -
> - current->ret_stack[offset] = val;
> - /*
> - * Write the value before we increment, so that
> - * if an interrupt comes in after we increment
> - * it will still see the value and skip over
> - * this.
> - */
> - barrier();
> - current->curr_ret_stack++;
> - /*
> - * Have to write again, in case an interrupt
> - * came in before the increment and after we
> - * wrote the value.
> - */
> - barrier();
> - current->ret_stack[offset] = val;
> - cnt++;
> - }
> + if (ftrace_ops_test(&gops->ops, func, NULL) &&
> + gops->entryfunc(&trace, gops))
> + bitmap |= BIT(i);
> }
>
> - if (!cnt)
> + if (!bitmap)
> goto out_ret;
>
> + /*
> + * Since this function uses fgraph_idx = 0 as a tail-call checking
> + * flag, set that bit always.
> + */
> + set_fgraph_index_bitmap(current, index, bitmap | BIT(0));
> +
> return 0;
> out_ret:
> current->curr_ret_stack -= FGRAPH_RET_INDEX + 1;
> @@ -408,15 +395,51 @@ int function_graph_enter(unsigned long ret, unsigned long func,
> return -EBUSY;
> }
>
> +/* This is called from ftrace_graph_func() via ftrace */
> +int function_graph_enter_ops(unsigned long ret, unsigned long func,
> + unsigned long frame_pointer, unsigned long *retp,
> + struct fgraph_ops *gops)
> +{
> + struct ftrace_graph_ent trace;
> + int index;
> + int type;
> +
> +
> + /* Use start for the distance to ret_stack (skipping over reserve) */
> + index = ftrace_push_return_trace(ret, func, frame_pointer, retp, gops->idx);
> + if (index < 0)
> + return index;
> + type = get_fgraph_type(current, index);
> +
> + /* This is the first ret_stack for this fentry */
> + if (type == FGRAPH_TYPE_RESERVED)
> + ++current->curr_ret_depth;
> +
> + trace.func = func;
> + trace.depth = current->curr_ret_depth;
> + if (gops->entryfunc(&trace, gops)) {
> + if (type == FGRAPH_TYPE_RESERVED)
> + set_fgraph_index_bitmap(current, index, BIT(gops->idx));
> + else
> + add_fgraph_index_bitmap(current, index, BIT(gops->idx));
> + return 0;
> + }
> +
> + if (type == FGRAPH_TYPE_RESERVED) {
> + current->curr_ret_stack -= FGRAPH_RET_INDEX + 1;
> + current->curr_ret_depth--;
> + }
> + return -EBUSY;
> +}
> +
> /* Retrieve a function return address to the trace stack on thread info.*/
> static struct ftrace_ret_stack *
> ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
> - unsigned long frame_pointer)
> + unsigned long frame_pointer, int *index)
> {
> struct ftrace_ret_stack *ret_stack;
> - int index;
>
> - ret_stack = get_ret_stack(current, current->curr_ret_stack, &index);
> + ret_stack = get_ret_stack(current, current->curr_ret_stack, index);
>
> if (unlikely(!ret_stack)) {
> ftrace_graph_stop();
> @@ -455,6 +478,7 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
> }
> #endif
>
> + *index += FGRAPH_RET_INDEX;
> *ret = ret_stack->ret;
> trace->func = ret_stack->func;
> trace->calltime = ret_stack->calltime;
> @@ -507,13 +531,12 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
> {
> struct ftrace_ret_stack *ret_stack;
> struct ftrace_graph_ret trace;
> + unsigned long bitmap;
> unsigned long ret;
> - int offset;
> int index;
> - int idx;
> int i;
>
> - ret_stack = ftrace_pop_return_trace(&trace, &ret, frame_pointer);
> + ret_stack = ftrace_pop_return_trace(&trace, &ret, frame_pointer, &index);
>
> if (unlikely(!ret_stack)) {
> ftrace_graph_stop();
> @@ -527,16 +550,17 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
> trace.retval = fgraph_ret_regs_return_value(ret_regs);
> #endif
>
> - offset = current->curr_ret_stack - 1;
> - index = get_ret_stack_index(current, offset);
> + bitmap = get_fgraph_index_bitmap(current, index);
> + for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) {
> + struct fgraph_ops *gops = fgraph_array[i];
>
> - /* index has to be at least one! Optimize for it */
> - i = 0;
> - do {
> - idx = get_fgraph_array(current, offset - i);
> - fgraph_array[idx]->retfunc(&trace, fgraph_array[idx]);
> - i++;
> - } while (i < index);
> + if (!(bitmap & BIT(i)))
> + continue;
> + if (gops == &fgraph_stub)
> + continue;
> +
> + gops->retfunc(&trace, gops);
> + }
>
> /*
> * The ftrace_graph_return() may still access the current
> @@ -544,7 +568,7 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
> * curr_ret_stack is after that.
> */
> barrier();
> - current->curr_ret_stack -= index + FGRAPH_RET_INDEX;
> + current->curr_ret_stack -= FGRAPH_RET_INDEX + 1;
> current->curr_ret_depth--;
> return ret;
> }
> @@ -622,7 +646,17 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
> ret_stack = get_ret_stack(current, i, &i);
> if (!ret_stack)
> break;
> - if (ret_stack->retp == retp)
> + /*
> + * For the tail-call, there would be 2 or more ftrace_ret_stacks on
> + * the ret_stack, which records "return_to_handler" as the return
> + * address excpt for the last one.
> + * But on the real stack, there should be 1 entry because tail-call
> + * reuses the return address on the stack and jump to the next function.
> + * Thus we will continue to find real return address.
> + */
> + if (ret_stack->retp == retp &&
> + ret_stack->ret !=
> + (unsigned long)dereference_kernel_function_descriptor(return_to_handler))
> return ret_stack->ret;
> }
>
> @@ -645,6 +679,9 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
> i = *idx;
> do {
> ret_stack = get_ret_stack(task, task_idx, &task_idx);
> + if (ret_stack && ret_stack->ret ==
> + (unsigned long)dereference_kernel_function_descriptor(return_to_handler))
> + continue;
> i--;
> } while (i >= 0 && ret_stack);
>
> @@ -655,17 +692,25 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
> }
> #endif /* HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
>
> -static struct ftrace_ops graph_ops = {
> - .func = ftrace_graph_func,
> - .flags = FTRACE_OPS_FL_INITIALIZED |
> - FTRACE_OPS_FL_PID |
> - FTRACE_OPS_GRAPH_STUB,
> +void fgraph_init_ops(struct ftrace_ops *dst_ops,
> + struct ftrace_ops *src_ops)
> +{
> + dst_ops->func = ftrace_graph_func;
> + dst_ops->flags = FTRACE_OPS_FL_PID | FTRACE_OPS_GRAPH_STUB;
> +
> #ifdef FTRACE_GRAPH_TRAMP_ADDR
> - .trampoline = FTRACE_GRAPH_TRAMP_ADDR,
> + dst_ops->trampoline = FTRACE_GRAPH_TRAMP_ADDR;
> /* trampoline_size is only needed for dynamically allocated tramps */
> #endif
> - ASSIGN_OPS_HASH(graph_ops, &global_ops.local_hash)
> -};
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE
> + if (src_ops) {
> + dst_ops->func_hash = &src_ops->local_hash;
> + mutex_init(&dst_ops->local_hash.regex_lock);
> + dst_ops->flags |= FTRACE_OPS_FL_INITIALIZED;
> + }
> +#endif
> +}
>
> void ftrace_graph_sleep_time_control(bool enable)
> {
> @@ -869,11 +914,20 @@ static int start_graph_tracing(void)
>
> int register_ftrace_graph(struct fgraph_ops *gops)
> {
> + int command = 0;
> int ret = 0;
> int i;
>
> mutex_lock(&ftrace_lock);
>
> + if (!gops->ops.func) {
> + gops->ops.flags |= FTRACE_OPS_GRAPH_STUB;
> + gops->ops.func = ftrace_graph_func;
> +#ifdef FTRACE_GRAPH_TRAMP_ADDR
> + gops->ops.trampoline = FTRACE_GRAPH_TRAMP_ADDR;
> +#endif
> + }
> +
> if (!fgraph_array[0]) {
> /* The array must always have real data on it */
> for (i = 0; i < FGRAPH_ARRAY_SIZE; i++)
> @@ -893,6 +947,7 @@ int register_ftrace_graph(struct fgraph_ops *gops)
> fgraph_array[i] = gops;
> if (i + 1 > fgraph_array_cnt)
> fgraph_array_cnt = i + 1;
> + gops->idx = i;
>
> ftrace_graph_active++;
>
> @@ -909,9 +964,10 @@ int register_ftrace_graph(struct fgraph_ops *gops)
> */
> ftrace_graph_return = return_run;
> ftrace_graph_entry = entry_run;
> -
> - ret = ftrace_startup(&graph_ops, FTRACE_START_FUNC_RET);
> + command = FTRACE_START_FUNC_RET;
> }
> +
> + ret = ftrace_startup(&gops->ops, command);
> out:
> mutex_unlock(&ftrace_lock);
> return ret;
> @@ -919,6 +975,7 @@ int register_ftrace_graph(struct fgraph_ops *gops)
>
> void unregister_ftrace_graph(struct fgraph_ops *gops)
> {
> + int command = 0;
> int i;
>
> mutex_lock(&ftrace_lock);
> @@ -926,25 +983,29 @@ void unregister_ftrace_graph(struct fgraph_ops *gops)
> if (unlikely(!ftrace_graph_active))
> goto out;
>
> - for (i = 0; i < fgraph_array_cnt; i++)
> - if (gops == fgraph_array[i])
> - break;
> - if (i >= fgraph_array_cnt)
> + if (unlikely(gops->idx < 0 || gops->idx >= fgraph_array_cnt))
> goto out;
>
> - fgraph_array[i] = &fgraph_stub;
> - if (i + 1 == fgraph_array_cnt) {
> - for (; i >= 0; i--)
> - if (fgraph_array[i] != &fgraph_stub)
> - break;
> + WARN_ON_ONCE(fgraph_array[gops->idx] != gops);
> +
> + fgraph_array[gops->idx] = &fgraph_stub;
> + if (gops->idx + 1 == fgraph_array_cnt) {
> + i = gops->idx;
> + while (i >= 0 && fgraph_array[i] == &fgraph_stub)
> + i--;
> fgraph_array_cnt = i + 1;
> }
>
> ftrace_graph_active--;
> +
> + if (!ftrace_graph_active)
> + command = FTRACE_STOP_FUNC_RET;
> +
> + ftrace_shutdown(&gops->ops, command);
> +
> if (!ftrace_graph_active) {
> ftrace_graph_return = ftrace_stub_graph;
> ftrace_graph_entry = ftrace_graph_entry_stub;
> - ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET);
> unregister_pm_notifier(&ftrace_suspend_notifier);
> unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
> }
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 83fbfb7b48f8..c4cc2a9d0047 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3050,6 +3050,8 @@ int ftrace_startup(struct ftrace_ops *ops, int command)
> if (unlikely(ftrace_disabled))
> return -ENODEV;
>
> + ftrace_ops_init(ops);
> +
> ret = __register_ftrace_function(ops);
> if (ret)
> return ret;
> @@ -7319,7 +7321,7 @@ __init void ftrace_init_global_array_ops(struct trace_array *tr)
> tr->ops = &global_ops;
> tr->ops->private = tr;
> ftrace_init_trace_array(tr);
> - init_array_fgraph_ops(tr);
> + init_array_fgraph_ops(tr, tr->ops);
> }
>
> void ftrace_init_array_ops(struct trace_array *tr, ftrace_func_t func)
> @@ -8051,7 +8053,7 @@ static int register_ftrace_function_nolock(struct ftrace_ops *ops)
> */
> int register_ftrace_function(struct ftrace_ops *ops)
> {
> - int ret;
> + int ret = -1;
>
> lock_direct_mutex();
> ret = prepare_direct_functions_for_ipmodify(ops);
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 16948c0ed00a..02edfdb68933 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -890,8 +890,8 @@ extern int __trace_graph_entry(struct trace_array *tr,
> extern void __trace_graph_return(struct trace_array *tr,
> struct ftrace_graph_ret *trace,
> unsigned int trace_ctx);
> -extern void init_array_fgraph_ops(struct trace_array *tr);
> -extern int allocate_fgraph_ops(struct trace_array *tr);
> +extern void init_array_fgraph_ops(struct trace_array *tr, struct ftrace_ops *ops);
> +extern int allocate_fgraph_ops(struct trace_array *tr, struct ftrace_ops *ops);
> extern void free_fgraph_ops(struct trace_array *tr);
>
> #ifdef CONFIG_DYNAMIC_FTRACE
> @@ -974,6 +974,7 @@ static inline int ftrace_graph_notrace_addr(unsigned long addr)
> preempt_enable_notrace();
> return ret;
> }
> +
> #else
> static inline int ftrace_graph_addr(struct ftrace_graph_ent *trace)
> {
> @@ -999,18 +1000,19 @@ static inline bool ftrace_graph_ignore_func(struct ftrace_graph_ent *trace)
> (fgraph_max_depth && trace->depth >= fgraph_max_depth);
> }
>
> +void fgraph_init_ops(struct ftrace_ops *dst_ops,
> + struct ftrace_ops *src_ops);
> +
> #else /* CONFIG_FUNCTION_GRAPH_TRACER */
> static inline enum print_line_t
> print_graph_function_flags(struct trace_iterator *iter, u32 flags)
> {
> return TRACE_TYPE_UNHANDLED;
> }
> -static inline void init_array_fgraph_ops(struct trace_array *tr) { }
> -static inline int allocate_fgraph_ops(struct trace_array *tr)
> -{
> - return 0;
> -}
> static inline void free_fgraph_ops(struct trace_array *tr) { }
> +/* ftrace_ops may not be defined */
> +#define init_array_fgraph_ops(tr, ops) do { } while (0)
> +#define allocate_fgraph_ops(tr, ops) ({ 0; })
> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>
> extern struct list_head ftrace_pids;
> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> index 8e8da0d0ee52..13bf2415245d 100644
> --- a/kernel/trace/trace_functions.c
> +++ b/kernel/trace/trace_functions.c
> @@ -91,7 +91,7 @@ int ftrace_create_function_files(struct trace_array *tr,
> if (!tr->ops)
> return -EINVAL;
>
> - ret = allocate_fgraph_ops(tr);
> + ret = allocate_fgraph_ops(tr, tr->ops);
> if (ret) {
> kfree(tr->ops);
> return ret;
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index 9ccc904a7703..7f30652f0e97 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -288,7 +288,7 @@ static struct fgraph_ops funcgraph_ops = {
> .retfunc = &trace_graph_return,
> };
>
> -int allocate_fgraph_ops(struct trace_array *tr)
> +int allocate_fgraph_ops(struct trace_array *tr, struct ftrace_ops *ops)
> {
> struct fgraph_ops *gops;
>
> @@ -301,6 +301,9 @@ int allocate_fgraph_ops(struct trace_array *tr)
>
> tr->gops = gops;
> gops->private = tr;
> +
> + fgraph_init_ops(&gops->ops, ops);
> +
> return 0;
> }
>
> @@ -309,10 +312,11 @@ void free_fgraph_ops(struct trace_array *tr)
> kfree(tr->gops);
> }
>
> -__init void init_array_fgraph_ops(struct trace_array *tr)
> +__init void init_array_fgraph_ops(struct trace_array *tr, struct ftrace_ops *ops)
> {
> tr->gops = &funcgraph_ops;
> funcgraph_ops.private = tr;
> + fgraph_init_ops(&tr->gops->ops, ops);
> }
>
> static int graph_trace_init(struct trace_array *tr)
>