From patchwork Wed Nov 8 14:27:38 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13450176 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C29A91A594; Wed, 8 Nov 2023 14:27:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZbP5Fdsv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 695B6C433C8; Wed, 8 Nov 2023 14:27:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699453663; bh=I8UydbwX5CwVQj9WY1DEcYvDCyrAse7mJMsY4uzWdyg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZbP5Fdsv1d16LPM45rr11gylGYgQcX88GBLE8lzTOcizOUnEIMZIzGXZqh1e5+Eul 4jn75DnXOkKOHUfNlC4VHbdA9onvAyL87RkSqMqh5JUEUCSBPov7yA8Y6kncS5TfKa xanY8SIEa97WTqDG+CGmhohQVwXG7GKgXwRqCjXeB3hjsjycIxcATuUrxtNi856vJE 8T/kQAXWI38drS+GjrSx1QtwPfnd5GVFUSa+46Rsi/tHoImkKiayUlhOPMm++TNzSN 1rySsuu+rG7QBt4Mb3NlSvVMZE4mBA9iHogvLH5wX9WceVGkg7CeeRXkjzmu3QAAHV UNjGm5WTuhxNA== From: "Masami Hiramatsu (Google)" To: Alexei Starovoitov , Steven Rostedt , Florent Revest Cc: linux-trace-kernel@vger.kernel.org, LKML , Martin KaFai Lau , bpf , Sven Schnelle , Alexei Starovoitov , Jiri Olsa , Arnaldo Carvalho de Melo , Daniel Borkmann , Alan Maguire , Mark Rutland , Peter Zijlstra , Thomas Gleixner , Guo Ren Subject: [RFC PATCH v2 17/31] function_graph: Implement fgraph_reserve_data() and fgraph_retrieve_data() Date: Wed, 8 Nov 2023 23:27:38 +0900 Message-Id: <169945365765.55307.4129860949245209954.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169945345785.55307.5003201137843449313.stgit@devnote2> References: <169945345785.55307.5003201137843449313.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-State: RFC From: Steven Rostedt (VMware) 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(). Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Masami Hiramatsu (Google) --- Changes in v2: - Retrieve the reserved size by fgraph_retrieve_data(). - Expand the maximum data size to 32 words. - Update stack index with __get_index(val) if FGRAPH_TYPE_ARRAY entry. - fix typos and make description lines shorter than 76 chars. --- include/linux/ftrace.h | 3 + kernel/trace/fgraph.c | 248 +++++++++++++++++++++++++++++++++++++++++------- 2 files changed, 217 insertions(+), 34 deletions(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 3f9f1f48e8fd..3bc01329548b 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -1074,6 +1074,9 @@ struct fgraph_ops { int idx; }; +void *fgraph_reserve_data(int size_bytes); +void *fgraph_retrieve_data(int *size_bytes); + /* * Stack of return addresses for functions * of a thread. diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index 79bdd3c775dd..4d8664942335 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -38,25 +38,36 @@ * bits: 14 - 15 Type of storage * 0 - reserved * 1 - fgraph_array index + * 2 - reservered data * For fgraph_array_index: * bits: 16 - 23 The fgraph_ops fgraph_array index * + * For reserved data: + * bits: 16 - 17 The size in words that 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) + * + * | | <- task->curr_ret_stack + * +-------------------------------------+ + * | (3 << FGRAPH_ARRAY_SHIFT)|type:1|(5)| ( 3 for index of fourth fgraph_ops) + * +-------------------------------------+ + * | (3 << FGRAPH_DATA_SHIFT)|type:2|(4) | ( Data with size of 2 words) + * +-------------------------------------+ ( It is 4 words from the ret_stack) + * | STORED DATA WORD 2 | + * | STORED DATA WORD 1 | + * +-------------------------------------+ + * | (0 << FGRAPH_ARRAY_SHIFT)|type:1|(1)| ( 0 for index of first fgraph_ops) + * +-------------------------------------+ + * | struct ftrace_ret_stack | + * | (stores the saved ret pointer) | + * +-------------------------------------+ + * | (X) | (N) | ( N words away from last ret_stack) + * | | * - * | | <- 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) - * | | * * 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 @@ -77,12 +88,17 @@ enum { FGRAPH_TYPE_RESERVED = 0, FGRAPH_TYPE_ARRAY = 1, + FGRAPH_TYPE_DATA = 2, }; #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_DATA_SIZE 5 +#define FGRAPH_DATA_MASK ((1 << FGRAPH_DATA_SIZE) - 1) +#define FGRAPH_DATA_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 @@ -97,6 +113,8 @@ enum { #define RET_STACK(t, index) ((struct ftrace_ret_stack *)(&(t)->ret_stack[index])) +#define FGRAPH_MAX_DATA_SIZE (sizeof(long) * (1 << FGRAPH_DATA_SIZE)) + /* * Each fgraph_ops has a reservered unsigned long at the end (top) of the * ret_stack to store task specific state. @@ -111,21 +129,44 @@ static int fgraph_array_cnt; static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE]; +static inline int __get_index(unsigned long val) +{ + return val & FGRAPH_RET_INDEX_MASK; +} + +static inline int __get_type(unsigned long val) +{ + return (val >> FGRAPH_TYPE_SHIFT) & FGRAPH_TYPE_MASK; +} + +static inline int __get_array(unsigned long val) +{ + return (val >> FGRAPH_ARRAY_SHIFT) & FGRAPH_ARRAY_MASK; +} + +static inline int __get_data(unsigned long val) +{ + return (val >> FGRAPH_DATA_SHIFT) & FGRAPH_DATA_MASK; +} + static inline int get_ret_stack_index(struct task_struct *t, int offset) { - return current->ret_stack[offset] & FGRAPH_RET_INDEX_MASK; + return __get_index(current->ret_stack[offset]); } static inline int get_fgraph_type(struct task_struct *t, int offset) { - return (current->ret_stack[offset] >> FGRAPH_TYPE_SHIFT) & - FGRAPH_TYPE_MASK; + return __get_type(current->ret_stack[offset]); } static inline int get_fgraph_array(struct task_struct *t, int offset) { - return (current->ret_stack[offset] >> FGRAPH_ARRAY_SHIFT) & - FGRAPH_ARRAY_MASK; + return __get_array(current->ret_stack[offset]); +} + +static inline int get_data_idx(struct task_struct *t, int offset) +{ + return __get_data(current->ret_stack[offset]); } /* ftrace_graph_entry set to this to tell some archs to run function graph */ @@ -161,6 +202,124 @@ 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 + * @size_bytes: The size in bytes to reserve (max of 4 words in size) + * + * Reserves space of up to 4 words (in word increments) 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 size_bytes) +{ + unsigned long val; + void *data; + int curr_ret_stack = current->curr_ret_stack; + int data_size; + int size; + + if (size_bytes > FGRAPH_MAX_DATA_SIZE) + return NULL; + + /* Convert to number of longs + data word */ + data_size = ALIGN(size_bytes, sizeof(long)) / sizeof(long) + 1; + + /* The size to add to ret_stack (including the reserve word) */ + size = data_size + 1; + + val = current->ret_stack[curr_ret_stack - 1]; + + switch (__get_type(val)) { + case FGRAPH_TYPE_RESERVED: + /* + * A reserve word is only saved after the ret_stack + * or after a data storage, not after an fgraph_array + * entry. It's OK if its after the ret_stack in which + * case the index will be one, but if the index is + * greater than 1 it means it's a double call to + * fgraph_reserve_data() + */ + if (__get_index(val) > 1) + return NULL; + /* + * Leave the reserve in case the entryfunc() doesn't + * want to be recorded. + */ + break; + case FGRAPH_TYPE_ARRAY: + break; + default: + return NULL; + } + data = ¤t->ret_stack[curr_ret_stack]; + + curr_ret_stack += size; + if (unlikely(curr_ret_stack >= SHADOW_STACK_MAX_INDEX)) + return NULL; + + val = __get_index(val) + size; + + /* 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; + + val = (data_size << FGRAPH_DATA_SHIFT) | + (FGRAPH_TYPE_DATA << FGRAPH_TYPE_SHIFT) | + (val - 1); + + /* Save the data header */ + current->ret_stack[curr_ret_stack - 2] = val; + + return data; +} + +/** + * fgraph_retrieve_data - Retrieve stored data from fgraph_reserve_data() + * @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 *size_bytes) +{ + unsigned long val; + int curr_ret_stack = current->curr_ret_stack; + + /* Top of stack is the fgraph_ops */ + val = current->ret_stack[curr_ret_stack - 1]; + /* Check if there's nothing between the fgraph_ops and ret_stack */ + if (__get_index(val) == 1) + return NULL; + val = current->ret_stack[curr_ret_stack - 2]; + if (__get_type(val) != FGRAPH_TYPE_DATA) + return NULL; + if (size_bytes) + *size_bytes = (__get_data(val) - 1) * sizeof(long); + + return ¤t->ret_stack[curr_ret_stack - + (__get_data(val) + 1)]; +} + /** * fgraph_get_task_var - retrieve a task specific state variable * @gops: The ftrace_ops that owns the task specific variable @@ -356,6 +515,7 @@ int function_graph_enter(unsigned long ret, unsigned long func, unsigned long frame_pointer, unsigned long *retp) { struct ftrace_graph_ent trace; + int save_curr_ret_stack; int offset; int start; int type; @@ -395,8 +555,10 @@ int function_graph_enter(unsigned long ret, unsigned long func, atomic_inc(¤t->trace_overrun); break; } + save_curr_ret_stack = current->curr_ret_stack; if (ftrace_ops_test(&gops->ops, func, NULL) && gops->entryfunc(&trace, gops)) { + /* Note, curr_ret_stack could change by enryfunc() */ offset = current->curr_ret_stack; /* Check the top level stored word */ type = get_fgraph_type(current, offset - 1); @@ -430,6 +592,9 @@ int function_graph_enter(unsigned long ret, unsigned long func, barrier(); current->ret_stack[offset] = val; cnt++; + } else { + /* Clear out any saved storage */ + current->curr_ret_stack = save_curr_ret_stack; } } @@ -544,10 +709,10 @@ 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 ret; - int offset; + int curr_ret_stack; + int stop_at; int index; int idx; - int i; ret_stack = ftrace_pop_return_trace(&trace, &ret, frame_pointer); @@ -563,24 +728,39 @@ 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); + curr_ret_stack = current->curr_ret_stack; + index = get_ret_stack_index(current, curr_ret_stack - 1); + + stop_at = curr_ret_stack - index; /* 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); + unsigned long val; + + val = current->ret_stack[curr_ret_stack - 1]; + switch (__get_type(val)) { + case FGRAPH_TYPE_ARRAY: + idx = __get_array(val); + fgraph_array[idx]->retfunc(&trace, fgraph_array[idx]); + curr_ret_stack -= __get_index(val); + break; + case FGRAPH_TYPE_RESERVED: + curr_ret_stack--; + break; + case FGRAPH_TYPE_DATA: + curr_ret_stack -= __get_data(val); + break; + default: + WARN_ONCE(1, "Bad fgraph ret_stack data type %d", + __get_type(val)); + curr_ret_stack--; + } + /* Make sure interrupts see the update after the above */ + barrier(); + current->curr_ret_stack = curr_ret_stack; + } while (curr_ret_stack > stop_at); - /* - * The ftrace_graph_return() may still access the current - * ret_stack structure, we need to make sure the update of - * curr_ret_stack is after that. - */ - barrier(); - current->curr_ret_stack -= index + FGRAPH_RET_INDEX; + current->curr_ret_stack -= FGRAPH_RET_INDEX; current->curr_ret_depth--; return ret; }