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ftrace: Add MODIFIED flag to show if IPMODIFY or direct was attached

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If a function had ever had IPMODIFY or DIRECT attached to it, where this
is how live kernel patching and BPF overrides work, mark them and display
an "M" in the enabled_functions and touched_functions files. This can be
used for debugging. If a function had been modified and later there's a bug
in the code related to that function, this can be used to know if the cause
is possibly from a live kernel patch or a BPF program that changed the
behavior of the code.

Also update the documentation on the enabled_functions and
touched_functions output, as it was missing direct callers and CALL_OPS.
And include this new modify attribute.

Link: https://lore.kernel.org/linux-trace-kernel/20230502213233.004e3ae4@gandalf.local.home

Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google)
2023-05-02 21:32:33 -04:00
parent 4f94559f40
commit 6ce2c04fcb
3 changed files with 37 additions and 4 deletions
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12
kernel/trace/ftrace.c
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@@ -46,7 +46,8 @@
#include "trace_stat.h"
/* Flags that do not get reset */
#define FTRACE_NOCLEAR_FLAGS (FTRACE_FL_DISABLED | FTRACE_FL_TOUCHED)
#define FTRACE_NOCLEAR_FLAGS (FTRACE_FL_DISABLED | FTRACE_FL_TOUCHED | \
FTRACE_FL_MODIFIED)
#define FTRACE_INVALID_FUNCTION "__ftrace_invalid_address__"
@@ -2273,6 +2274,10 @@ static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update)
rec->flags &= ~FTRACE_FL_TRAMP_EN;
}
/* Keep track of anything that modifies the function */
if (rec->flags & (FTRACE_FL_DIRECT | FTRACE_FL_IPMODIFY))
rec->flags |= FTRACE_FL_MODIFIED;
if (flag & FTRACE_FL_DIRECT) {
/*
* If there's only one user (direct_ops helper)
@@ -3866,12 +3871,13 @@ static int t_show(struct seq_file *m, void *v)
if (iter->flags & (FTRACE_ITER_ENABLED | FTRACE_ITER_TOUCHED)) {
struct ftrace_ops *ops;
seq_printf(m, " (%ld)%s%s%s%s",
seq_printf(m, " (%ld)%s%s%s%s%s",
ftrace_rec_count(rec),
rec->flags & FTRACE_FL_REGS ? " R" : " ",
rec->flags & FTRACE_FL_IPMODIFY ? " I" : " ",
rec->flags & FTRACE_FL_DIRECT ? " D" : " ",
rec->flags & FTRACE_FL_CALL_OPS ? " O" : " ");
rec->flags & FTRACE_FL_CALL_OPS ? " O" : " ",
rec->flags & FTRACE_FL_MODIFIED ? " M " : " ");
if (rec->flags & FTRACE_FL_TRAMP_EN) {
ops = ftrace_find_tramp_ops_any(rec);
if (ops) {