summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2023-05-05 13:11:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2023-05-05 13:11:02 -0700
commite919a3f7057b5ca918dea98826b39a38eff9bebb (patch)
tree614e799fb722519f7e0a43890ced165b4d825664
parentb115d85a9584c98f9a7dec209d835462aa1adc09 (diff)
parent6ce2c04fcbcaa5eb086e5142ab359be306cbc3e1 (diff)
Merge tag 'trace-v6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull more tracing updates from Steven Rostedt: - Make buffer_percent read/write. The buffer_percent file is how users can state how long to block on the tracing buffer depending on how much is in the buffer. When it hits the "buffer_percent" it will wake the task waiting on the buffer. For some reason it was set to read-only. This was not noticed because testing was done as root without SELinux, but with SELinux it will prevent even root to write to it without having CAP_DAC_OVERRIDE. - The "touched_functions" was added this merge window, but one of the reasons for adding it was not implemented. That was to show what functions were not only touched, but had either a direct trampoline attached to it, or a kprobe or live kernel patching that can "hijack" the function to run a different function. The point is to know if there's functions in the kernel that may not be behaving as the kernel code shows. This can be used for debugging. TODO: Add this information to kernel oops too. * tag 'trace-v6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ftrace: Add MODIFIED flag to show if IPMODIFY or direct was attached tracing: Fix permissions for the buffer_percent file
-rw-r--r--Documentation/trace/ftrace.rst25
-rw-r--r--include/linux/ftrace.h4
-rw-r--r--kernel/trace/ftrace.c12
-rw-r--r--kernel/trace/trace.c2
4 files changed, 38 insertions, 5 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index a9c8bce4bc7b..027437b745a0 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -350,6 +350,19 @@ of ftrace. Here is a list of some of the key files:
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().
@@ -359,6 +372,18 @@ of ftrace. Here is a list of some of the key files:
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
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 6954e4ed5bbf..b23bdd414394 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -549,6 +549,7 @@ bool is_ftrace_trampoline(unsigned long addr);
* 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
@@ -569,9 +570,10 @@ enum {
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)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 76973a70ab9d..764668467155 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -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) {
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 427da2341bf0..ebc59781456a 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9661,7 +9661,7 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
tr->buffer_percent = 50;
- trace_create_file("buffer_percent", TRACE_MODE_READ, d_tracer,
+ trace_create_file("buffer_percent", TRACE_MODE_WRITE, d_tracer,
tr, &buffer_percent_fops);
create_trace_options_dir(tr);