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Message-Id: <20240108101436.07509def635fbecf80a59ae6@kernel.org>
Date: Mon, 8 Jan 2024 10:14:36 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Mark Rutland <mark.rutland@....com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, Steven Rostedt
<rostedt@...dmis.org>, Florent Revest <revest@...omium.org>,
linux-trace-kernel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>, bpf <bpf@...r.kernel.org>, Sven
Schnelle <svens@...ux.ibm.com>, Alexei Starovoitov <ast@...nel.org>, Jiri
Olsa <jolsa@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, Daniel
Borkmann <daniel@...earbox.net>, Alan Maguire <alan.maguire@...cle.com>,
Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner
<tglx@...utronix.de>, Guo Ren <guoren@...nel.org>
Subject: Re: [PATCH v5 11/34] function_graph: Have the instances use their
own ftrace_ops for filtering
On Fri, 5 Jan 2024 17:09:10 +0000
Mark Rutland <mark.rutland@....com> wrote:
> On Mon, Dec 18, 2023 at 10:13:46PM +0900, Masami Hiramatsu (Google) wrote:
> > From: Steven Rostedt (VMware) <rostedt@...dmis.org>
> >
> > 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@...dmis.org>
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
>
> As a heads-up, while testing the topic/fprobe-on-fgraph branch on arm64, I get
> a warning which bisets down to this commit:
Hmm, so does this happen when enabling function graph tracer?
>
> | 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.
Yes. what about FP check?
>
> Does this change make it legitimate for ftrace_graph_ret_addr() to return
> return_to_handler in other cases, or is that a bug?
It should be a bug to be fixed.
>
> Either way, we'll need *some* way to recover the original return addresss...
At least it needs to dump the shadow stack so that we can analyze what
happened.
Thank you!
>
> 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(¤t->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(¤t->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(¤t->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(¤t->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)
> >
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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