[PATCH v2 09/12] KVM: arm64: Add raw interface for hyp tracefs

[Vincent Donnefort]

The raw interface enables userspace tools such as trace-cmd to directly
read the ring-buffer without any decoding by the kernel.

Signed-off-by: Vincent Donnefort <vdonnef...@google.com>

diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c
index 78193dbd8a33..3d2a58977442 100644
--- a/arch/arm64/kvm/hyp_trace.c
+++ b/arch/arm64/kvm/hyp_trace.c
@@ -749,6 +749,85 @@ static const struct file_operations hyp_trace_pipe_fops = {
        .release        = hyp_trace_pipe_release,
 };
 
+static ssize_t
+hyp_trace_raw_read(struct file *file, char __user *ubuf,
+                  size_t cnt, loff_t *ppos)
+{
+       struct ht_iterator *iter = (struct ht_iterator *)file->private_data;
+       size_t size;
+       int ret;
+
+       if (iter->copy_leftover)
+               goto read;
+
+again:
+       ret = ring_buffer_read_page(iter->trace_buffer,
+                                   (struct buffer_data_read_page *)iter->spare,
+                                   cnt, iter->cpu, 0);
+       if (ret < 0) {
+               if (!ring_buffer_empty_cpu(iter->trace_buffer, iter->cpu))
+                       return 0;
+
+               ret = ring_buffer_wait(iter->trace_buffer, iter->cpu, 0, NULL,
+                                      NULL);
+               if (ret < 0)
+                       return ret;
+
+               goto again;
+       }
+
+       iter->copy_leftover = 0;
+
+read:
+       size = PAGE_SIZE - iter->copy_leftover;
+       if (size > cnt)
+               size = cnt;
+
+       ret = copy_to_user(ubuf, iter->spare + PAGE_SIZE - size, size);
+       if (ret == size)
+               return -EFAULT;
+
+       size -= ret;
+       *ppos += size;
+       iter->copy_leftover = ret;
+
+       return size;
+}
+
+static int hyp_trace_raw_open(struct inode *inode, struct file *file)
+{
+       int ret = hyp_trace_pipe_open(inode, file);
+       struct ht_iterator *iter;
+
+       if (ret)
+               return ret;
+
+       iter = file->private_data;
+       iter->spare = ring_buffer_alloc_read_page(iter->trace_buffer, 
iter->cpu);
+       if (IS_ERR(iter->spare)) {
+               ret = PTR_ERR(iter->spare);
+               iter->spare = NULL;
+               return ret;
+       }
+
+       return 0;
+}
+
+static int hyp_trace_raw_release(struct inode *inode, struct file *file)
+{
+       struct ht_iterator *iter = file->private_data;
+
+       ring_buffer_free_read_page(iter->trace_buffer, iter->cpu, iter->spare);
+
+       return hyp_trace_pipe_release(inode, file);
+}
+
+static const struct file_operations hyp_trace_raw_fops = {
+       .open           = hyp_trace_raw_open,
+       .read           = hyp_trace_raw_read,
+       .release        = hyp_trace_raw_release,
+};
+
 static int hyp_trace_clock_show(struct seq_file *m, void *v)
 {
        seq_puts(m, "[boot]\n");
@@ -803,6 +882,9 @@ int hyp_trace_init_tracefs(void)
 
                tracefs_create_file("trace_pipe", TRACEFS_MODE_READ, 
per_cpu_dir,
                                    (void *)cpu, &hyp_trace_pipe_fops);
+
+               tracefs_create_file("trace_pipe_raw", TRACEFS_MODE_READ, 
per_cpu_dir,
+                                   (void *)cpu, &hyp_trace_pipe_fops);
        }
 
        return 0;
-- 
2.47.1.613.gc27f4b7a9f-goog