Commit 9f909e21 authored by Chris Wilson's avatar Chris Wilson

drm/i915: Implement vm_ops->access for gdb access into mmaps

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.

v2: Write-protect readonly objects (Matthew).

Testcase: igt/gem_mmap_gtt/ptrace
Testcase: igt/gem_mmap_offset/ptrace
Suggested-by: default avatarKristian H. Kristensen <hoegsberg@google.com>
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Maciej Patelczyk <maciej.patelczyk@intel.com>
Cc: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200501145120.18830-1-chris@chris-wilson.co.uk
parent a211da9c
......@@ -396,6 +396,38 @@ 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;
if (i915_gem_object_is_readonly(obj) && write)
return -EACCES;
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 +777,14 @@ 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,
};
......
......@@ -952,6 +952,129 @@ static int igt_mmap(void *arg)
return 0;
}
static const char *repr_mmap_type(enum i915_mmap_type type)
{
switch (type) {
case I915_MMAP_TYPE_GTT: return "gtt";
case I915_MMAP_TYPE_WB: return "wb";
case I915_MMAP_TYPE_WC: return "wc";
case I915_MMAP_TYPE_UC: return "uc";
default: return "unknown";
}
}
static bool can_access(const struct drm_i915_gem_object *obj)
{
unsigned int flags =
I915_GEM_OBJECT_HAS_STRUCT_PAGE | I915_GEM_OBJECT_HAS_IOMEM;
return i915_gem_object_type_has(obj, flags);
}
static int __igt_mmap_access(struct drm_i915_private *i915,
struct drm_i915_gem_object *obj,
enum i915_mmap_type type)
{
struct i915_mmap_offset *mmo;
unsigned long __user *ptr;
unsigned long A, B;
unsigned long x, y;
unsigned long addr;
int err;
memset(&A, 0xAA, sizeof(A));
memset(&B, 0xBB, sizeof(B));
if (!can_mmap(obj, type) || !can_access(obj))
return 0;
mmo = mmap_offset_attach(obj, type, NULL);
if (IS_ERR(mmo))
return PTR_ERR(mmo);
addr = igt_mmap_node(i915, &mmo->vma_node, 0, PROT_WRITE, MAP_SHARED);
if (IS_ERR_VALUE(addr))
return addr;
ptr = (unsigned long __user *)addr;
err = __put_user(A, ptr);
if (err) {
pr_err("%s(%s): failed to write into user mmap\n",
obj->mm.region->name, repr_mmap_type(type));
goto out_unmap;
}
intel_gt_flush_ggtt_writes(&i915->gt);
err = access_process_vm(current, addr, &x, sizeof(x), 0);
if (err != sizeof(x)) {
pr_err("%s(%s): access_process_vm() read failed\n",
obj->mm.region->name, repr_mmap_type(type));
goto out_unmap;
}
err = access_process_vm(current, addr, &B, sizeof(B), FOLL_WRITE);
if (err != sizeof(B)) {
pr_err("%s(%s): access_process_vm() write failed\n",
obj->mm.region->name, repr_mmap_type(type));
goto out_unmap;
}
intel_gt_flush_ggtt_writes(&i915->gt);
err = __get_user(y, ptr);
if (err) {
pr_err("%s(%s): failed to read from user mmap\n",
obj->mm.region->name, repr_mmap_type(type));
goto out_unmap;
}
if (x != A || y != B) {
pr_err("%s(%s): failed to read/write values, found (%lx, %lx)\n",
obj->mm.region->name, repr_mmap_type(type),
x, y);
err = -EINVAL;
goto out_unmap;
}
out_unmap:
vm_munmap(addr, obj->base.size);
return err;
}
static int igt_mmap_access(void *arg)
{
struct drm_i915_private *i915 = arg;
struct intel_memory_region *mr;
enum intel_region_id id;
for_each_memory_region(mr, i915, id) {
struct drm_i915_gem_object *obj;
int err;
obj = i915_gem_object_create_region(mr, PAGE_SIZE, 0);
if (obj == ERR_PTR(-ENODEV))
continue;
if (IS_ERR(obj))
return PTR_ERR(obj);
err = __igt_mmap_access(i915, obj, I915_MMAP_TYPE_GTT);
if (err == 0)
err = __igt_mmap_access(i915, obj, I915_MMAP_TYPE_WB);
if (err == 0)
err = __igt_mmap_access(i915, obj, I915_MMAP_TYPE_WC);
if (err == 0)
err = __igt_mmap_access(i915, obj, I915_MMAP_TYPE_UC);
i915_gem_object_put(obj);
if (err)
return err;
}
return 0;
}
static int __igt_mmap_gpu(struct drm_i915_private *i915,
struct drm_i915_gem_object *obj,
enum i915_mmap_type type)
......@@ -1229,6 +1352,7 @@ int i915_gem_mman_live_selftests(struct drm_i915_private *i915)
SUBTEST(igt_smoke_tiling),
SUBTEST(igt_mmap_offset_exhaustion),
SUBTEST(igt_mmap),
SUBTEST(igt_mmap_access),
SUBTEST(igt_mmap_revoke),
SUBTEST(igt_mmap_gpu),
};
......
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