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 <[email protected]> Signed-off-by: Chris Wilson <[email protected]> Cc: Matthew Auld <[email protected]> Cc: Joonas Lahtinen <[email protected]> Cc: Maciej Patelczyk <[email protected]> Cc: Kristian H. Kristensen <[email protected]> --- drivers/gpu/drm/i915/gem/i915_gem_mman.c | 31 ++++++++++++++++++++++++ 1 file changed, 31 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; + + addr -= area->vm_start; + if (addr >= obj->base.size) + return -EINVAL; + + /* As this is primarily for debugging, let's focus on simplicity */ + vaddr = i915_gem_object_pin_map(obj, I915_MAP_FORCE_WC); + if (IS_ERR(vaddr)) + return PTR_ERR(vaddr); + + if (write) { + memcpy(vaddr + addr, buf, len); + __i915_gem_object_flush_map(obj, addr, len); + } else { + memcpy(buf, vaddr + addr, len); + } + + i915_gem_object_unpin_map(obj); + + return len; +} + void __i915_gem_object_release_mmap_gtt(struct drm_i915_gem_object *obj) { struct i915_vma *vma; @@ -745,12 +774,14 @@ static void vm_close(struct vm_area_struct *vma) static const struct vm_operations_struct vm_ops_gtt = { .fault = vm_fault_gtt, + .access = vm_access, .open = vm_open, .close = vm_close, }; static const struct vm_operations_struct vm_ops_cpu = { .fault = vm_fault_cpu, + .access = vm_access, .open = vm_open, .close = vm_close, }; -- 2.20.1 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
