On 01/05/2020 09:42, Chris Wilson wrote:
gdb uses ptrace() to peek and poke bytes of the target's address space.
The driver must implement an vm_ops->access() handler or else gdb will
be unable to inspect the pointer and report it as out-of-bounds.
Worse than useless as it causes immediate suspicion of the valid GTT
pointer, distracting the poor programmer trying to find his bug.
Testcase: igt/gem_mmap_gtt/ptrace
Testcase: igt/gem_mmap_offset/ptrace
Suggested-by: Kristian H. Kristensen <hoegsberg@xxxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Maciej Patelczyk <maciej.patelczyk@xxxxxxxxx>
Cc: Kristian H. Kristensen <hoegsberg@xxxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_mman.c | 31 +++++
.../drm/i915/gem/selftests/i915_gem_mman.c | 124 ++++++++++++++++++
2 files changed, 155 insertions(+)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index b39c24dae64e..aef917b7f168 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -396,6 +396,35 @@ static vm_fault_t vm_fault_gtt(struct vm_fault *vmf)
return i915_error_to_vmf_fault(ret);
}
+static int
+vm_access(struct vm_area_struct *area, unsigned long addr,
+ void *buf, int len, int write)
+{
+ struct i915_mmap_offset *mmo = area->vm_private_data;
+ struct drm_i915_gem_object *obj = mmo->obj;
+ void *vaddr;
+
What's the story with object_is_readonly and write=true here? Shouldn't
we reject, or what?
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
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