Kernel/linux-next
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git synced 2025-01-01 10:42:11 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

ftrace: Show a list of all functions that have ever been enabled

Browse Source 
When debugging a crash that appears to be related to ftrace, but not for
sure, it is useful to know if a function was ever enabled by ftrace or
not. It could be that a BPF program was attached to it, or possibly a live
patch.

We are having crashes in the field where this information is not always
known. But having ftrace set a flag if a function has ever been attached
since boot up helps tremendously in trying to know if a crash had to do
with something using ftrace.

For analyzing crashes, the use of a kdump image can have access to the
flags. When looking at issues where the kernel did not panic, the
touched_functions file can simply be used.

Link: https://lore.kernel.org/linux-trace-kernel/20230124095653.6fd1640e@gandalf.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Chris Li <chriscli@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2023-01-24 09:56:53 -05:00
parent 8328e36da9
commit e11b521a7b
2 changed files with 50 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/ftrace.h
View File

@ -548,6 +548,7 @@ bool is_ftrace_trampoline(unsigned long addr);
* DIRECT - there is a direct function to call
* CALL_OPS - the record can use callsite-specific ops
* CALL_OPS_EN - the function is set up to use callsite-specific ops
* TOUCHED - A callback was added since boot up
*
* When a new ftrace_ops is registered and wants a function to save
* pt_regs, the rec->flags REGS is set. When the function has been
@ -567,9 +568,10 @@ enum {
FTRACE_FL_DIRECT_EN = (1UL << 23),
FTRACE_FL_CALL_OPS = (1UL << 22),
FTRACE_FL_CALL_OPS_EN = (1UL << 21),
FTRACE_FL_TOUCHED = (1UL << 20),
};
#define FTRACE_REF_MAX_SHIFT 21
#define FTRACE_REF_MAX_SHIFT 20
#define FTRACE_REF_MAX ((1UL << FTRACE_REF_MAX_SHIFT) - 1)
#define ftrace_rec_count(rec) ((rec)->flags & FTRACE_REF_MAX)
@ -628,6 +630,7 @@ enum {
FTRACE_ITER_PROBE = (1 << 4),
FTRACE_ITER_MOD = (1 << 5),
FTRACE_ITER_ENABLED = (1 << 6),
FTRACE_ITER_TOUCHED = (1 << 7),
};
void arch_ftrace_update_code(int command);

51
kernel/trace/ftrace.c
View File

@ -45,6 +45,9 @@
#include "trace_output.h"
#include "trace_stat.h"
/* Flags that do not get reset */
#define FTRACE_NOCLEAR_FLAGS (FTRACE_FL_DISABLED | FTRACE_FL_TOUCHED)
#define FTRACE_INVALID_FUNCTION "__ftrace_invalid_address__"
#define FTRACE_WARN_ON(cond) \
@ -2256,7 +2259,7 @@ static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update)
flag ^= rec->flags & FTRACE_FL_ENABLED;
if (update) {
rec->flags |= FTRACE_FL_ENABLED;
rec->flags |= FTRACE_FL_ENABLED | FTRACE_FL_TOUCHED;
if (flag & FTRACE_FL_REGS) {
if (rec->flags & FTRACE_FL_REGS)
rec->flags |= FTRACE_FL_REGS_EN;
@ -2326,7 +2329,7 @@ static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update)
if (update) {
/* If there's no more users, clear all flags */
if (!ftrace_rec_count(rec))
rec->flags &= FTRACE_FL_DISABLED;
rec->flags &= FTRACE_NOCLEAR_FLAGS;
else
/*
* Just disable the record, but keep the ops TRAMP
@ -3147,7 +3150,7 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
struct dyn_ftrace *rec;
do_for_each_ftrace_rec(pg, rec) {
if (FTRACE_WARN_ON_ONCE(rec->flags & ~FTRACE_FL_DISABLED))
if (FTRACE_WARN_ON_ONCE(rec->flags & ~FTRACE_NOCLEAR_FLAGS))
pr_warn(" %pS flags:%lx\n",
(void *)rec->ip, rec->flags);
} while_for_each_ftrace_rec();
@ -3598,7 +3601,10 @@ t_func_next(struct seq_file *m, loff_t *pos)
!ftrace_lookup_ip(iter->hash, rec->ip)) ||
((iter->flags & FTRACE_ITER_ENABLED) &&
!(rec->flags & FTRACE_FL_ENABLED))) {
!(rec->flags & FTRACE_FL_ENABLED)) ||
((iter->flags & FTRACE_ITER_TOUCHED) &&
!(rec->flags & FTRACE_FL_TOUCHED))) {
rec = NULL;
goto retry;
@ -3857,7 +3863,7 @@ static int t_show(struct seq_file *m, void *v)
return 0;
}
if (iter->flags & FTRACE_ITER_ENABLED) {
if (iter->flags & (FTRACE_ITER_ENABLED | FTRACE_ITER_TOUCHED)) {
struct ftrace_ops *ops;
seq_printf(m, " (%ld)%s%s%s%s",
@ -3959,6 +3965,31 @@ ftrace_enabled_open(struct inode *inode, struct file *file)
return 0;
}
static int
ftrace_touched_open(struct inode *inode, struct file *file)
{
struct ftrace_iterator *iter;
/*
* This shows us what functions have ever been enabled
* (traced, direct, patched, etc). Not sure if we want lockdown
* to hide such critical information for an admin.
* Although, perhaps it can show information we don't
* want people to see, but if something had traced
* something, we probably want to know about it.
*/
iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
if (!iter)
return -ENOMEM;
iter->pg = ftrace_pages_start;
iter->flags = FTRACE_ITER_TOUCHED;
iter->ops = &global_ops;
return 0;
}
/**
* ftrace_regex_open - initialize function tracer filter files
* @ops: The ftrace_ops that hold the hash filters
@ -5872,6 +5903,13 @@ static const struct file_operations ftrace_enabled_fops = {
.release = seq_release_private,
};
static const struct file_operations ftrace_touched_fops = {
.open = ftrace_touched_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release_private,
};
static const struct file_operations ftrace_filter_fops = {
.open = ftrace_filter_open,
.read = seq_read,
@ -6336,6 +6374,9 @@ static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer)
trace_create_file("enabled_functions", TRACE_MODE_READ,
d_tracer, NULL, &ftrace_enabled_fops);
trace_create_file("touched_functions", TRACE_MODE_READ,
d_tracer, NULL, &ftrace_touched_fops);
ftrace_create_filter_files(&global_ops, d_tracer);
#ifdef CONFIG_FUNCTION_GRAPH_TRACER