From: Steven Rostedt <rost...@goodmis.org> Use the unwind_deferred_*() interface to be able to trace deferred user space stacks. This creates two new ftrace events:
user_unwind_cookie user_unwind_stack The user_unwind_cookie will record into the ring buffer the cookie given from unwind_deferred_request(), and the user_unwind_stack will record into the ring buffer the user space stack as well as the cookie associated with it. Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org> --- Changes since v5: https://lore.kernel.org/20250424192613.356969...@goodmis.org - Have the userstacktrace_delay option not depend on the userstacktrace option. - Do not expose the userstacktrace_delay option if it's not supported. kernel/trace/trace.c | 91 ++++++++++++++++++++++++++++++++++-- kernel/trace/trace.h | 20 ++++++++ kernel/trace/trace_entries.h | 24 ++++++++++ kernel/trace/trace_export.c | 23 +++++++++ kernel/trace/trace_output.c | 72 ++++++++++++++++++++++++++++ 5 files changed, 227 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2cca29c9863d..e5b7db19aa53 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3128,6 +3128,66 @@ EXPORT_SYMBOL_GPL(trace_dump_stack); #ifdef CONFIG_USER_STACKTRACE_SUPPORT static DEFINE_PER_CPU(int, user_stack_count); +static void trace_user_unwind_callback(struct unwind_work *unwind, + struct unwind_stacktrace *trace, + u64 ctx_cookie) +{ + struct trace_array *tr = container_of(unwind, struct trace_array, unwinder); + struct trace_buffer *buffer = tr->array_buffer.buffer; + struct userunwind_stack_entry *entry; + struct ring_buffer_event *event; + unsigned int trace_ctx; + unsigned long *caller; + unsigned int offset; + int len; + int i; + + if (!(tr->trace_flags & TRACE_ITER_USERSTACKTRACE_DELAY)) + return; + + len = trace->nr * sizeof(unsigned long) + sizeof(*entry); + + trace_ctx = tracing_gen_ctx(); + event = __trace_buffer_lock_reserve(buffer, TRACE_USER_UNWIND_STACK, + len, trace_ctx); + if (!event) + return; + + entry = ring_buffer_event_data(event); + + entry->cookie = ctx_cookie; + + offset = sizeof(*entry); + len = sizeof(unsigned long) * trace->nr; + + entry->__data_loc_stack = offset | (len << 16); + caller = (void *)entry + offset; + + for (i = 0; i < trace->nr; i++) { + caller[i] = trace->entries[i]; + } + + __buffer_unlock_commit(buffer, event); +} + +static void +ftrace_trace_userstack_delay(struct trace_array *tr, + struct trace_buffer *buffer, unsigned int trace_ctx) +{ + struct userunwind_cookie_entry *entry; + struct ring_buffer_event *event; + + event = __trace_buffer_lock_reserve(buffer, TRACE_USER_UNWIND_COOKIE, + sizeof(*entry), trace_ctx); + if (!event) + return; + entry = ring_buffer_event_data(event); + + unwind_deferred_request(&tr->unwinder, &entry->cookie); + + __buffer_unlock_commit(buffer, event); +} + static void ftrace_trace_userstack(struct trace_array *tr, struct trace_buffer *buffer, unsigned int trace_ctx) @@ -3135,13 +3195,18 @@ ftrace_trace_userstack(struct trace_array *tr, struct ring_buffer_event *event; struct userstack_entry *entry; - if (!(tr->trace_flags & TRACE_ITER_USERSTACKTRACE)) - return; - /* No point doing user space stacktraces on kernel threads */ if (current->flags & (PF_KTHREAD | PF_USER_WORKER)) return; + if (tr->trace_flags & TRACE_ITER_USERSTACKTRACE_DELAY) { + ftrace_trace_userstack_delay(tr, buffer, trace_ctx); + return; + } + + if (!(tr->trace_flags & TRACE_ITER_USERSTACKTRACE)) + return; + /* * NMIs can not handle page faults, even with fix ups. * The save user stack can (and often does) fault. @@ -5215,6 +5280,17 @@ int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set) return 0; } +static int update_unwind_deferred(struct trace_array *tr, int enabled) +{ + if (enabled) { + return unwind_deferred_init(&tr->unwinder, + trace_user_unwind_callback); + } else { + unwind_deferred_cancel(&tr->unwinder); + return 0; + } +} + int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled) { if ((mask == TRACE_ITER_RECORD_TGID) || @@ -5251,6 +5327,12 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled) } } + if (mask == TRACE_ITER_USERSTACKTRACE_DELAY) { + int ret = update_unwind_deferred(tr, enabled); + if (ret < 0) + return ret; + } + if (mask == TRACE_ITER_COPY_MARKER) update_marker_trace(tr, enabled); @@ -10002,6 +10084,9 @@ static int __remove_instance(struct trace_array *tr) if (tr->ref > 1 || (tr->current_trace && tr->trace_ref)) return -EBUSY; + if ((tr->flags & TRACE_ITER_USERSTACKTRACE_DELAY)) + unwind_deferred_cancel(&tr->unwinder); + list_del(&tr->list); /* Disable all the flags that were enabled coming in */ diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 0fd2559ff119..940107ba618a 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -8,6 +8,7 @@ #include <linux/sched.h> #include <linux/clocksource.h> #include <linux/ring_buffer.h> +#include <linux/unwind_deferred.h> #include <linux/mmiotrace.h> #include <linux/tracepoint.h> #include <linux/ftrace.h> @@ -49,7 +50,10 @@ enum trace_type { TRACE_GRAPH_ENT, TRACE_GRAPH_RETADDR_ENT, TRACE_USER_STACK, + /* trace-cmd manually adds blktrace after USER_STACK */ TRACE_BLK, + TRACE_USER_UNWIND_STACK, + TRACE_USER_UNWIND_COOKIE, TRACE_BPUTS, TRACE_HWLAT, TRACE_OSNOISE, @@ -92,6 +96,9 @@ enum trace_type { #undef __array_desc #define __array_desc(type, container, item, size) +#undef __dynamic_array +#define __dynamic_array(type, item) u32 __data_loc_##item; + #undef __dynamic_field #define __dynamic_field(type, item) type item[]; @@ -435,6 +442,7 @@ struct trace_array { struct cond_snapshot *cond_snapshot; #endif struct trace_func_repeats __percpu *last_func_repeats; + struct unwind_work unwinder; /* * On boot up, the ring buffer is set to the minimum size, so that * we do not waste memory on systems that are not using tracing. @@ -526,6 +534,9 @@ extern void __ftrace_bad_type(void); IF_ASSIGN(var, ent, struct ctx_switch_entry, 0); \ IF_ASSIGN(var, ent, struct stack_entry, TRACE_STACK); \ IF_ASSIGN(var, ent, struct userstack_entry, TRACE_USER_STACK);\ + IF_ASSIGN(var, ent, struct userunwind_stack_entry, TRACE_USER_UNWIND_STACK);\ + IF_ASSIGN(var, ent, struct userunwind_cookie_entry, TRACE_USER_UNWIND_COOKIE);\ + IF_ASSIGN(var, ent, struct userstack_entry, TRACE_USER_STACK);\ IF_ASSIGN(var, ent, struct print_entry, TRACE_PRINT); \ IF_ASSIGN(var, ent, struct bprint_entry, TRACE_BPRINT); \ IF_ASSIGN(var, ent, struct bputs_entry, TRACE_BPUTS); \ @@ -1359,6 +1370,14 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf, # define STACK_FLAGS #endif +#ifdef CONFIG_UNWIND_USER +# define USERSTACK_DELAY \ + C(USERSTACKTRACE_DELAY, "userstacktrace_delay"), +#else +# define USERSTACK_DELAY +# define TRACE_ITER_USERSTACKTRACE_DELAY 0 +#endif + /* * trace_iterator_flags is an enumeration that defines bit * positions into trace_flags that controls the output. @@ -1379,6 +1398,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf, C(PRINTK, "trace_printk"), \ C(ANNOTATE, "annotate"), \ C(USERSTACKTRACE, "userstacktrace"), \ + USERSTACK_DELAY \ C(SYM_USEROBJ, "sym-userobj"), \ C(PRINTK_MSGONLY, "printk-msg-only"), \ C(CONTEXT_INFO, "context-info"), /* Print pid/cpu/time */ \ diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h index 5cf80f6c704a..40dc53ead0a8 100644 --- a/kernel/trace/trace_entries.h +++ b/kernel/trace/trace_entries.h @@ -249,6 +249,30 @@ FTRACE_ENTRY(user_stack, userstack_entry, (void *)__entry->caller[6], (void *)__entry->caller[7]) ); +FTRACE_ENTRY(user_unwind_stack, userunwind_stack_entry, + + TRACE_USER_UNWIND_STACK, + + F_STRUCT( + __field( u64, cookie ) + __dynamic_array( unsigned long, stack ) + ), + + F_printk("cookie=%lld\n%s", __entry->cookie, + __print_dynamic_array(stack, sizeof(unsigned long))) +); + +FTRACE_ENTRY(user_unwind_cookie, userunwind_cookie_entry, + + TRACE_USER_UNWIND_COOKIE, + + F_STRUCT( + __field( u64, cookie ) + ), + + F_printk("cookie=%lld", __entry->cookie) +); + /* * trace_printk entry: */ diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c index d9d41e3ba379..831999f84e2c 100644 --- a/kernel/trace/trace_export.c +++ b/kernel/trace/trace_export.c @@ -57,6 +57,9 @@ static int ftrace_event_register(struct trace_event_call *call, #undef __array_desc #define __array_desc(type, container, item, size) type item[size]; +#undef __dynamic_array +#define __dynamic_array(type, item) u32 __data_loc_##item; + #undef __dynamic_field #define __dynamic_field(type, item) type item[]; @@ -66,6 +69,16 @@ static int ftrace_event_register(struct trace_event_call *call, #undef F_printk #define F_printk(fmt, args...) fmt, args +/* Only used for ftrace event format output */ +static inline char * __print_dynamic_array(int array, size_t size) +{ + return NULL; +} + +#undef __print_dynamic_array +#define __print_dynamic_array(array, el_size) \ + __print_dynamic_array(__entry->__data_loc_##array, el_size) + #undef FTRACE_ENTRY #define FTRACE_ENTRY(name, struct_name, id, tstruct, print) \ struct ____ftrace_##name { \ @@ -74,6 +87,7 @@ struct ____ftrace_##name { \ static void __always_unused ____ftrace_check_##name(void) \ { \ struct ____ftrace_##name *__entry = NULL; \ + struct trace_seq __maybe_unused *p = NULL; \ \ /* force compile-time check on F_printk() */ \ printk(print); \ @@ -123,6 +137,12 @@ static void __always_unused ____ftrace_check_##name(void) \ #undef __array_desc #define __array_desc(_type, _container, _item, _len) __array(_type, _item, _len) +#undef __dynamic_array +#define __dynamic_array(_type, _item) { \ + .type = "__data_loc " #_type "[]", .name = #_item, \ + .size = 4, .align = __alignof__(4), \ + is_signed_type(_type), .filter_type = FILTER_OTHER }, + #undef __dynamic_field #define __dynamic_field(_type, _item) { \ .type = #_type "[]", .name = #_item, \ @@ -161,6 +181,9 @@ static struct trace_event_fields ftrace_event_fields_##name[] = { \ #undef __array_desc #define __array_desc(type, container, item, len) +#undef __dynamic_array +#define __dynamic_array(type, item) + #undef __dynamic_field #define __dynamic_field(type, item) diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 97db0b0ccf3e..9489537533f7 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -1404,6 +1404,58 @@ static struct trace_event trace_stack_event = { }; /* TRACE_USER_STACK */ +static enum print_line_t trace_user_unwind_stack_print(struct trace_iterator *iter, + int flags, struct trace_event *event) +{ + struct userunwind_stack_entry *field; + struct trace_seq *s = &iter->seq; + unsigned long *caller; + unsigned int offset; + unsigned int len; + unsigned int caller_cnt; + unsigned int i; + + trace_assign_type(field, iter->ent); + + trace_seq_puts(s, "<user stack unwind>\n"); + + trace_seq_printf(s, "cookie=%llx\n", field->cookie); + + /* The stack field is a dynamic pointer */ + offset = field->__data_loc_stack; + len = offset >> 16; + offset = offset & 0xffff; + caller_cnt = len / sizeof(*caller); + + caller = (void *)iter->ent + offset; + + for (i = 0; i < caller_cnt; i++) { + unsigned long ip = caller[i]; + + if (!ip || trace_seq_has_overflowed(s)) + break; + + trace_seq_puts(s, " => "); + seq_print_user_ip(s, NULL, ip, flags); + trace_seq_putc(s, '\n'); + } + + return trace_handle_return(s); +} + +static enum print_line_t trace_user_unwind_cookie_print(struct trace_iterator *iter, + int flags, struct trace_event *event) +{ + struct userunwind_cookie_entry *field; + struct trace_seq *s = &iter->seq; + + trace_assign_type(field, iter->ent); + + trace_seq_printf(s, "cookie=%llx\n", field->cookie); + + return trace_handle_return(s); +} + static enum print_line_t trace_user_stack_print(struct trace_iterator *iter, int flags, struct trace_event *event) { @@ -1447,6 +1499,24 @@ static enum print_line_t trace_user_stack_print(struct trace_iterator *iter, return trace_handle_return(s); } +static struct trace_event_functions trace_userunwind_stack_funcs = { + .trace = trace_user_unwind_stack_print, +}; + +static struct trace_event trace_userunwind_stack_event = { + .type = TRACE_USER_UNWIND_STACK, + .funcs = &trace_userunwind_stack_funcs, +}; + +static struct trace_event_functions trace_userunwind_cookie_funcs = { + .trace = trace_user_unwind_cookie_print, +}; + +static struct trace_event trace_userunwind_cookie_event = { + .type = TRACE_USER_UNWIND_COOKIE, + .funcs = &trace_userunwind_cookie_funcs, +}; + static struct trace_event_functions trace_user_stack_funcs = { .trace = trace_user_stack_print, }; @@ -1846,6 +1916,8 @@ static struct trace_event *events[] __initdata = { &trace_ctx_event, &trace_wake_event, &trace_stack_event, + &trace_userunwind_cookie_event, + &trace_userunwind_stack_event, &trace_user_stack_event, &trace_bputs_event, &trace_bprint_event, -- 2.50.1
