[PATCH 4/8] tracing: Have persistent trace instances save KASLR offset
From: Steven Rostedt
Date: Wed Feb 05 2025 - 17:50:44 EST
From: Steven Rostedt <rostedt@xxxxxxxxxxx>
There's no reason to save the KASLR offset for the ring buffer itself.
That is used by the tracer. Now that the tracer has a way to save data in
the persistent memory of the ring buffer, have the tracing infrastructure
take care of the saving of the KASLR offset.
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
include/linux/ring_buffer.h | 1 -
kernel/trace/ring_buffer.c | 47 -------------------------------------
kernel/trace/trace.c | 38 ++++++++++++++++++++++++++----
kernel/trace/trace.h | 6 +++--
4 files changed, 38 insertions(+), 54 deletions(-)
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index b95f940fd07a..d6d9c94e8d8a 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -94,7 +94,6 @@ struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flag
unsigned long range_size,
struct lock_class_key *key);
-bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, unsigned long *kaslr_addr);
void *ring_buffer_meta_scratch(struct trace_buffer *buffer, unsigned int *size);
/*
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 5a81ff785665..a42406287281 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -55,7 +55,6 @@ struct ring_buffer_meta {
};
struct ring_buffer_cpu_meta {
- unsigned long kaslr_addr;
unsigned long first_buffer;
unsigned long head_buffer;
unsigned long commit_buffer;
@@ -557,8 +556,6 @@ struct trace_buffer {
struct ring_buffer_meta *meta;
- unsigned long kaslr_addr;
-
unsigned int subbuf_size;
unsigned int subbuf_order;
unsigned int max_data_size;
@@ -1931,15 +1928,6 @@ static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer)
}
}
-static void rb_meta_init_text_addr(struct ring_buffer_cpu_meta *meta)
-{
-#ifdef CONFIG_RANDOMIZE_BASE
- meta->kaslr_addr = kaslr_offset();
-#else
- meta->kaslr_addr = 0;
-#endif
-}
-
static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
{
struct ring_buffer_cpu_meta *meta;
@@ -1967,7 +1955,6 @@ static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
meta->first_buffer += delta;
meta->head_buffer += delta;
meta->commit_buffer += delta;
- buffer->kaslr_addr = meta->kaslr_addr;
continue;
}
@@ -1984,7 +1971,6 @@ static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
subbuf = rb_subbufs_from_meta(meta);
meta->first_buffer = (unsigned long)subbuf;
- rb_meta_init_text_addr(meta);
/*
* The buffers[] array holds the order of the sub-buffers
@@ -2514,27 +2500,6 @@ struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flag
return alloc_buffer(size, flags, order, start, start + range_size, key);
}
-/**
- * ring_buffer_last_boot_delta - return the delta offset from last boot
- * @buffer: The buffer to return the delta from
- * @text: Return text delta
- * @data: Return data delta
- *
- * Returns: The true if the delta is non zero
- */
-bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, unsigned long *kaslr_addr)
-{
- if (!buffer)
- return false;
-
- if (!buffer->kaslr_addr)
- return false;
-
- *kaslr_addr = buffer->kaslr_addr;
-
- return true;
-}
-
void *ring_buffer_meta_scratch(struct trace_buffer *buffer, unsigned int *size)
{
if (!buffer || !buffer->meta)
@@ -6098,7 +6063,6 @@ static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
- struct ring_buffer_cpu_meta *meta;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
@@ -6117,11 +6081,6 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
atomic_dec(&cpu_buffer->record_disabled);
atomic_dec(&cpu_buffer->resize_disabled);
- /* Make sure persistent meta now uses this buffer's addresses */
- meta = rb_range_meta(buffer, 0, cpu_buffer->cpu);
- if (meta)
- rb_meta_init_text_addr(meta);
-
mutex_unlock(&buffer->mutex);
}
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
@@ -6136,7 +6095,6 @@ EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
- struct ring_buffer_cpu_meta *meta;
int cpu;
/* prevent another thread from changing buffer sizes */
@@ -6164,11 +6122,6 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
reset_disabled_cpu_buffer(cpu_buffer);
- /* Make sure persistent meta now uses this buffer's addresses */
- meta = rb_range_meta(buffer, 0, cpu_buffer->cpu);
- if (meta)
- rb_meta_init_text_addr(meta);
-
atomic_dec(&cpu_buffer->record_disabled);
atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
}
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a9e8eaf1d47e..cb9f8e6878a0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5994,8 +5994,14 @@ ssize_t tracing_resize_ring_buffer(struct trace_array *tr,
return ret;
}
+struct trace_scratch {
+ unsigned long kaslr_addr;
+};
+
static void update_last_data(struct trace_array *tr)
{
+ struct trace_scratch *tscratch;
+
if (!(tr->flags & TRACE_ARRAY_FL_LAST_BOOT))
return;
@@ -6010,6 +6016,17 @@ static void update_last_data(struct trace_array *tr)
/* Using current data now */
tr->text_delta = 0;
+ if (!tr->scratch)
+ return;
+
+ tscratch = tr->scratch;
+
+ /* Set the persistent ring buffer meta data to this address */
+#ifdef CONFIG_RANDOMIZE_BASE
+ tscratch->kaslr_addr = kaslr_offset();
+#else
+ tscratch->kaslr_addr = 0;
+#endif
tr->flags &= ~TRACE_ARRAY_FL_LAST_BOOT;
}
@@ -6823,6 +6840,7 @@ static ssize_t
tracing_last_boot_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
{
struct trace_array *tr = filp->private_data;
+ struct trace_scratch *tscratch = tr->scratch;
struct seq_buf seq;
char buf[64];
@@ -6835,10 +6853,10 @@ tracing_last_boot_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t
* Otherwise it shows the KASLR address from the previous boot which
* should not be the same as the current boot.
*/
- if (!(tr->flags & TRACE_ARRAY_FL_LAST_BOOT))
+ if (!tscratch || !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT))
seq_buf_puts(&seq, "Offset: current\n");
else
- seq_buf_printf(&seq, "Offset: %lx\n", tr->kaslr_addr);
+ seq_buf_printf(&seq, "Offset: %lx\n", tscratch->kaslr_addr);
return simple_read_from_buffer(ubuf, cnt, ppos, buf, seq_buf_used(&seq));
}
@@ -9212,6 +9230,8 @@ static int
allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, int size)
{
enum ring_buffer_flags rb_flags;
+ unsigned int scratch_size;
+ void *scratch;
rb_flags = tr->trace_flags & TRACE_ITER_OVERWRITE ? RB_FL_OVERWRITE : 0;
@@ -9222,10 +9242,20 @@ allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, int size
tr->range_addr_start,
tr->range_addr_size);
+ scratch = ring_buffer_meta_scratch(buf->buffer, &scratch_size);
+ if (scratch) {
+ tr->scratch = scratch;
+ tr->scratch_size = scratch_size;
+
#ifdef CONFIG_RANDOMIZE_BASE
- if (ring_buffer_last_boot_delta(buf->buffer, &tr->kaslr_addr))
- tr->text_delta = kaslr_offset() - tr->kaslr_addr;
+ {
+ struct trace_scratch *tscratch = tr->scratch;
+
+ if (tscratch->kaslr_addr)
+ tr->text_delta = kaslr_offset() - tscratch->kaslr_addr;
+ }
#endif
+ }
/*
* This is basically the same as a mapped buffer,
* with the same restrictions.
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index abe8169c3e87..3a020fb82a34 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -348,8 +348,11 @@ struct trace_array {
unsigned int mapped;
unsigned long range_addr_start;
unsigned long range_addr_size;
- unsigned long kaslr_addr;
long text_delta;
+ void *scratch; /* pointer in persistent memory */
+ int scratch_size;
+
+ int buffer_disabled;
struct trace_pid_list __rcu *filtered_pids;
struct trace_pid_list __rcu *filtered_no_pids;
@@ -367,7 +370,6 @@ struct trace_array {
* CONFIG_TRACER_MAX_TRACE.
*/
arch_spinlock_t max_lock;
- int buffer_disabled;
#ifdef CONFIG_FTRACE_SYSCALLS
int sys_refcount_enter;
int sys_refcount_exit;
--
2.45.2