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>
an 'I' will be displayed on the same line as the function that
can be overridden.
+ If a non ftrace trampoline is attached (BPF) a 'D' will be displayed.
+ Note, normal ftrace trampolines can also be attached, but only one
+ "direct" trampoline can be attached to a given function at a time.
+
+ Some architectures can not call direct trampolines, but instead have
+ the ftrace ops function located above the function entry point. In
+ such cases an 'O' will be displayed.
+
+ If a function had either the "ip modify" or a "direct" call attached to
+ it in the past, a 'M' will be shown. This flag is never cleared. It is
+ used to know if a function was every modified by the ftrace infrastructure,
+ and can be used for debugging.
+
If the architecture supports it, it will also show what callback
is being directly called by the function. If the count is greater
than 1 it most likely will be ftrace_ops_list_func().
its address will be printed as well as the function that the
trampoline calls.
+ touched_functions:
+
+ This file contains all the functions that ever had a function callback
+ to it via the ftrace infrastructure. It has the same format as
+ enabled_functions but shows all functions that have every been
+ traced.
+
+ To see any function that has every been modified by "ip modify" or a
+ direct trampoline, one can perform the following command:
+
+ grep ' M ' /sys/kernel/tracing/touched_functions
+
function_profile_enabled:
When set it will enable all functions with either the function
* 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
+ * MODIFIED - The function had IPMODIFY or DIRECT attached to it
*
* 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
FTRACE_FL_CALL_OPS = (1UL << 22),
FTRACE_FL_CALL_OPS_EN = (1UL << 21),
FTRACE_FL_TOUCHED = (1UL << 20),
+ FTRACE_FL_MODIFIED = (1UL << 19),
};
-#define FTRACE_REF_MAX_SHIFT 20
+#define FTRACE_REF_MAX_SHIFT 19
#define FTRACE_REF_MAX ((1UL << FTRACE_REF_MAX_SHIFT) - 1)
#define ftrace_rec_count(rec) ((rec)->flags & FTRACE_REF_MAX)
#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__"
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)
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) {