On Wed, 05 Feb 2025 17:50:35 -0500 Steven Rostedt <[email protected]> wrote:
> From: Steven Rostedt <[email protected]> > > 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. > Looks good to me. But note that the scratchpad size may not enough for module table later, because 1 module requires at least the name[] (64byte - sizeof(ulong)) and the base address (ulong). This means 1 entry consumes 64byte. Thus there can be only 63 entries + meta data in 4K page. My ubuntu loads 189(!) modules; $ lsmod | wc -l 190 so we want 255 entries, which requires 16KB. Thank you, > Signed-off-by: Steven Rostedt (Google) <[email protected]> > --- > 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 > > -- Masami Hiramatsu (Google) <[email protected]>
