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function_graph: Implement fgraph_reserve_data() and fgraph_retrieve_data()

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Added functions that can be called by a fgraph_ops entryfunc and retfunc to
store state between the entry of the function being traced to the exit of
the same function. The fgraph_ops entryfunc() may call
fgraph_reserve_data() to store up to 32 words onto the task's shadow
ret_stack and this then can be retrieved by fgraph_retrieve_data() called
by the corresponding retfunc().

Co-developed with Masami Hiramatsu:
Link: https://lore.kernel.org/linux-trace-kernel/171509109089.162236.11372474169781184034.stgit@devnote2
Link: https://lore.kernel.org/linux-trace-kernel/20240603190823.959703050@goodmis.org

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Guo Ren <guoren@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2024-06-03 15:07:23 -04:00 committed by Steven Rostedt (Google)
parent b84214890a
commit 91c46b0aa9
2 changed files with 186 additions and 8 deletions
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3
include/linux/ftrace.h
View File

@ -1053,6 +1053,9 @@ struct fgraph_ops {
int idx;
};
void *fgraph_reserve_data(int idx, int size_bytes);
void *fgraph_retrieve_data(int idx, int *size_bytes);
/*
* Stack of return addresses for functions
* of a thread.

191
kernel/trace/fgraph.c
View File

@ -31,12 +31,11 @@
* holds a bitmask and a type (called "bitmap"). The bitmap is defined as:
*
* bits: 0 - 9 offset in words from the previous ftrace_ret_stack
* Currently, this will always be set to FGRAPH_FRAME_OFFSET
* to get to the fgraph frame.
*
* bits: 10 - 11 Type of storage
* 0 - reserved
* 1 - bitmap of fgraph_array index
* 2 - reserved data
*
* For type with "bitmap of fgraph_array index" (FGRAPH_TYPE_BITMAP):
* bits: 12 - 27 The bitmap of fgraph_ops fgraph_array index
@ -49,10 +48,15 @@
* The top of the ret_stack (when not empty) will always have a reference
* word that points to the last fgraph frame that was saved.
*
* For reserved data:
* bits: 12 - 17 The size in words that is stored
* bits: 18 - 23 The index of fgraph_array, which shows who is stored
*
* 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)
* on the return of the function being traced, and the forth fgraph_ops
* stored two words of data, this is what will be on the task's shadow
* ret_stack: (the stack grows upward)
*
* ret_stack[SHADOW_STACK_OFFSET]
* | SHADOW_STACK_TASK_VARS(ret_stack)[15] |
@ -62,11 +66,21 @@
* ...
* | | <- task->curr_ret_stack
* +--------------------------------------------+
* | (3 << 12) | (3 << 10) | FGRAPH_FRAME_OFFSET|
* | *or put another way* |
* | (3 << FGRAPH_DATA_INDEX_SHIFT)| \ | This is for fgraph_ops[3].
* | ((2 - 1) << FGRAPH_DATA_SHIFT)| \ | The data size is 2 words.
* | (FGRAPH_TYPE_DATA << FGRAPH_TYPE_SHIFT)| \ |
* | (offset2:FGRAPH_FRAME_OFFSET+3) | <- the offset2 is from here
* +--------------------------------------------+ ( It is 4 words from the ret_stack)
* | STORED DATA WORD 2 |
* | STORED DATA WORD 1 |
* +--------------------------------------------+
* | (9 << 12) | (1 << 10) | FGRAPH_FRAME_OFFSET|
* | *or put another way* |
* | (BIT(3)|BIT(0)) << FGRAPH_INDEX_SHIFT | \ |
* | FGRAPH_TYPE_BITMAP << FGRAPH_TYPE_SHIFT| \ |
* | (offset:FGRAPH_FRAME_OFFSET) | <- the offset is from here
* | (offset1:FGRAPH_FRAME_OFFSET) | <- the offset1 is from here
* +--------------------------------------------+
* | struct ftrace_ret_stack |
* | (stores the saved ret pointer) | <- the offset points here
@ -100,6 +114,7 @@
enum {
FGRAPH_TYPE_RESERVED = 0,
FGRAPH_TYPE_BITMAP = 1,
FGRAPH_TYPE_DATA = 2,
};
/*
@ -110,6 +125,26 @@ enum {
#define FGRAPH_INDEX_MASK GENMASK(FGRAPH_INDEX_BITS - 1, 0)
#define FGRAPH_INDEX_SHIFT (FGRAPH_TYPE_SHIFT + FGRAPH_TYPE_BITS)
/*
* For DATA type:
* FGRAPH_DATA (12-17) bits hold the size of data (in words)
* FGRAPH_INDEX (18-23) bits hold the index for which gops->idx the data is for
*
* Note:
* data_size == 0 means 1 word, and 31 (=2^5 - 1) means 32 words.
*/
#define FGRAPH_DATA_BITS 5
#define FGRAPH_DATA_MASK GENMASK(FGRAPH_DATA_BITS - 1, 0)
#define FGRAPH_DATA_SHIFT (FGRAPH_TYPE_SHIFT + FGRAPH_TYPE_BITS)
#define FGRAPH_MAX_DATA_SIZE (sizeof(long) * (1 << FGRAPH_DATA_BITS))
#define FGRAPH_DATA_INDEX_BITS 4
#define FGRAPH_DATA_INDEX_MASK GENMASK(FGRAPH_DATA_INDEX_BITS - 1, 0)
#define FGRAPH_DATA_INDEX_SHIFT (FGRAPH_DATA_SHIFT + FGRAPH_DATA_BITS)
#define FGRAPH_MAX_INDEX \
((FGRAPH_INDEX_SIZE << FGRAPH_DATA_BITS) + FGRAPH_RET_INDEX)
#define FGRAPH_ARRAY_SIZE FGRAPH_INDEX_BITS
/*
@ -178,16 +213,46 @@ static int fgraph_lru_alloc_index(void)
return idx;
}
/* Get the offset to the fgraph frame from a ret_stack value */
static inline int __get_offset(unsigned long val)
{
return val & FGRAPH_FRAME_OFFSET_MASK;
}
/* Get the type of word from a ret_stack value */
static inline int __get_type(unsigned long val)
{
return (val >> FGRAPH_TYPE_SHIFT) & FGRAPH_TYPE_MASK;
}
/* Get the data_index for a DATA type ret_stack word */
static inline int __get_data_index(unsigned long val)
{
return (val >> FGRAPH_DATA_INDEX_SHIFT) & FGRAPH_DATA_INDEX_MASK;
}
/* Get the data_size for a DATA type ret_stack word */
static inline int __get_data_size(unsigned long val)
{
return ((val >> FGRAPH_DATA_SHIFT) & FGRAPH_DATA_MASK) + 1;
}
/* Get the word from the ret_stack at @offset */
static inline unsigned long get_fgraph_entry(struct task_struct *t, int offset)
{
return t->ret_stack[offset];
}
/* Get the FRAME_OFFSET from the word from the @offset on ret_stack */
static inline int get_frame_offset(struct task_struct *t, int offset)
{
return t->ret_stack[offset] & FGRAPH_FRAME_OFFSET_MASK;
return __get_offset(t->ret_stack[offset]);
}
/* Get FGRAPH_TYPE from the word from the @offset at ret_stack */
static inline int get_fgraph_type(struct task_struct *t, int offset)
{
return (t->ret_stack[offset] >> FGRAPH_TYPE_SHIFT) & FGRAPH_TYPE_MASK;
return __get_type(t->ret_stack[offset]);
}
/* For BITMAP type: get the bitmask from the @offset at ret_stack */
@ -212,6 +277,25 @@ set_bitmap(struct task_struct *t, int offset, unsigned long bitmap)
(FGRAPH_TYPE_BITMAP << FGRAPH_TYPE_SHIFT) | FGRAPH_FRAME_OFFSET;
}
/* For DATA type: get the data saved under the ret_stack word at @offset */
static inline void *get_data_type_data(struct task_struct *t, int offset)
{
unsigned long val = t->ret_stack[offset];
if (__get_type(val) != FGRAPH_TYPE_DATA)
return NULL;
offset -= __get_data_size(val);
return (void *)&t->ret_stack[offset];
}
/* Create the ret_stack word for a DATA type */
static inline unsigned long make_data_type_val(int idx, int size, int offset)
{
return (idx << FGRAPH_DATA_INDEX_SHIFT) |
((size - 1) << FGRAPH_DATA_SHIFT) |
(FGRAPH_TYPE_DATA << FGRAPH_TYPE_SHIFT) | 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)
{
@ -245,6 +329,91 @@ static void ret_stack_init_task_vars(unsigned long *ret_stack)
memset(gvals, 0, sizeof(*gvals) * FGRAPH_ARRAY_SIZE);
}
/**
* fgraph_reserve_data - Reserve storage on the task's ret_stack
* @idx: The index of fgraph_array
* @size_bytes: The size in bytes to reserve
*
* Reserves space of up to FGRAPH_MAX_DATA_SIZE bytes on the
* task's ret_stack shadow stack, for a given fgraph_ops during
* the entryfunc() call. If entryfunc() returns zero, the storage
* is discarded. An entryfunc() can only call this once per iteration.
* The fgraph_ops retfunc() can retrieve this stored data with
* fgraph_retrieve_data().
*
* Returns: On success, a pointer to the data on the stack.
* Otherwise, NULL if there's not enough space left on the
* ret_stack for the data, or if fgraph_reserve_data() was called
* more than once for a single entryfunc() call.
*/
void *fgraph_reserve_data(int idx, int size_bytes)
{
unsigned long val;
void *data;
int curr_ret_stack = current->curr_ret_stack;
int data_size;
if (size_bytes > FGRAPH_MAX_DATA_SIZE)
return NULL;
/* Convert the data size to number of longs. */
data_size = (size_bytes + sizeof(long) - 1) >> (sizeof(long) == 4 ? 2 : 3);
val = get_fgraph_entry(current, curr_ret_stack - 1);
data = &current->ret_stack[curr_ret_stack];
curr_ret_stack += data_size + 1;
if (unlikely(curr_ret_stack >= SHADOW_STACK_MAX_OFFSET))
return NULL;
val = make_data_type_val(idx, data_size, __get_offset(val) + data_size + 1);
/* Set the last word to be reserved */
current->ret_stack[curr_ret_stack - 1] = val;
/* Make sure interrupts see this */
barrier();
current->curr_ret_stack = curr_ret_stack;
/* Again sync with interrupts, and reset reserve */
current->ret_stack[curr_ret_stack - 1] = val;
return data;
}
/**
* fgraph_retrieve_data - Retrieve stored data from fgraph_reserve_data()
* @idx: the index of fgraph_array (fgraph_ops::idx)
* @size_bytes: pointer to retrieved data size.
*
* This is to be called by a fgraph_ops retfunc(), to retrieve data that
* was stored by the fgraph_ops entryfunc() on the function entry.
* That is, this will retrieve the data that was reserved on the
* entry of the function that corresponds to the exit of the function
* that the fgraph_ops retfunc() is called on.
*
* Returns: The stored data from fgraph_reserve_data() called by the
* matching entryfunc() for the retfunc() this is called from.
* Or NULL if there was nothing stored.
*/
void *fgraph_retrieve_data(int idx, int *size_bytes)
{
int offset = current->curr_ret_stack - 1;
unsigned long val;
val = get_fgraph_entry(current, offset);
while (__get_type(val) == FGRAPH_TYPE_DATA) {
if (__get_data_index(val) == idx)
goto found;
offset -= __get_data_size(val) + 1;
val = get_fgraph_entry(current, offset);
}
return NULL;
found:
if (size_bytes)
*size_bytes = __get_data_size(val) * sizeof(long);
return get_data_type_data(current, offset);
}
/**
* fgraph_get_task_var - retrieve a task specific state variable
* @gops: The ftrace_ops that owns the task specific variable
@ -464,13 +633,18 @@ int function_graph_enter(unsigned long ret, unsigned long func,
for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) {
struct fgraph_ops *gops = fgraph_array[i];
int save_curr_ret_stack;
if (gops == &fgraph_stub)
continue;
save_curr_ret_stack = current->curr_ret_stack;
if (ftrace_ops_test(&gops->ops, func, NULL) &&
gops->entryfunc(&trace, gops))
bitmap |= BIT(i);
else
/* Clear out any saved storage */
current->curr_ret_stack = save_curr_ret_stack;
}
if (!bitmap)
@ -626,7 +800,8 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
* curr_ret_stack is after that.
*/
barrier();
current->curr_ret_stack -= FGRAPH_FRAME_OFFSET + 1;
current->curr_ret_stack = offset - FGRAPH_FRAME_OFFSET;
current->curr_ret_depth--;
return ret;
}