[PATCH 1/3] powernv/memtrace: Allow mmaping trace buffers

[Jordan Niethe]

Let the memory removed from the linear mapping to be used for the trace
buffers be mmaped. This is a useful way of providing cache-inhibited
memory for the alignment_handler selftest.

Signed-off-by: Jordan Niethe <jniet...@gmail.com>
---
 arch/powerpc/platforms/powernv/memtrace.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/memtrace.c 
b/arch/powerpc/platforms/powernv/memtrace.c
index 5fc9408bb0b3..8a1df39305e9 100644
--- a/arch/powerpc/platforms/powernv/memtrace.c
+++ b/arch/powerpc/platforms/powernv/memtrace.c
@@ -45,10 +45,26 @@ static ssize_t memtrace_read(struct file *filp, char __user 
*ubuf,
        return simple_read_from_buffer(ubuf, count, ppos, ent->mem, ent->size);
 }
 
+int memtrace_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+       struct memtrace_entry *ent = filp->private_data;
+
+       if (ent->size < vma->vm_end - vma->vm_start)
+               return -EINVAL;
+
+       if (vma->vm_pgoff << PAGE_SHIFT >= ent->size)
+               return -EINVAL;
+
+       vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+       return remap_pfn_range(vma, vma->vm_start, PHYS_PFN(ent->start) + 
vma->vm_pgoff,
+                              vma->vm_end - vma->vm_start, vma->vm_page_prot);
+}
+
 static const struct file_operations memtrace_fops = {
        .llseek = default_llseek,
        .read   = memtrace_read,
        .open   = simple_open,
+       .mmap   = memtrace_mmap,
 };
 
 static void memtrace_clear_range(unsigned long start_pfn,
@@ -158,7 +174,7 @@ static int memtrace_init_debugfs(void)
                dir = debugfs_create_dir(ent->name, memtrace_debugfs_dir);
 
                ent->dir = dir;
-               debugfs_create_file("trace", 0400, dir, ent, &memtrace_fops);
+               debugfs_create_file_unsafe("trace", 0600, dir, ent, 
&memtrace_fops);
                debugfs_create_x64("start", 0400, dir, &ent->start);
                debugfs_create_x64("size", 0400, dir, &ent->size);
        }
-- 
2.25.1