GCC really does not want to consider NULL (or near-NULL) addresses as
valid, so calculations based off of NULL end up getting range-tracked into
being an offset wthin a 0 byte array. It gets especially mad about this:
if (vbios_str == NULL)
vbios_str += sizeof(BIOS_ATOM_PREFIX) - 1;
...
if (vbios_str != NULL && *vbios_str == 0)
vbios_str++;
It sees this as being "sizeof(BIOS_ATOM_PREFIX) - 1" byte offset from
NULL, when building with -Warray-bounds (and the coming
-fdiagnostic-details flag):
In function 'atom_get_vbios_pn',
inlined from 'amdgpu_atom_parse' at
drivers/gpu/drm/amd/amdgpu/atom.c:1553:2:
drivers/gpu/drm/amd/amdgpu/atom.c:1447:34: error: array subscript 0 is outside
array bounds of 'unsigned char[0]' [-Werror=array-bounds=]
1447 | if (vbios_str != NULL && *vbios_str == 0)
| ^~~~~~~~~~
'amdgpu_atom_parse': events 1-2
1444 | if (vbios_str == NULL)
| ^
| |
| (1) when the condition is evaluated to true
......
1447 | if (vbios_str != NULL && *vbios_str == 0)
| ~~~~~~~~~~
| |
| (2) out of array bounds here
In function 'amdgpu_atom_parse':
cc1: note: source object is likely at address zero
As there isn't a sane way to convince it otherwise, hide vbios_str from
GCC's optimizer to avoid the warning so we can get closer to enabling
-Warray-bounds globally.
Signed-off-by: Kees Cook <[email protected]>
---
Cc: Alex Deucher <[email protected]>
Cc: "Christian König" <[email protected]>
Cc: Xinhui Pan <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Simona Vetter <[email protected]>
Cc: Jesse Zhang <[email protected]>
Cc: Tim Huang <[email protected]>
Cc: Srinivasan Shanmugam <[email protected]>
Cc: Alexander Richards <[email protected]>
Cc: Lijo Lazar <[email protected]>
Cc: Mario Limonciello <[email protected]>
Cc: "Gustavo A. R. Silva" <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
drivers/gpu/drm/amd/amdgpu/atom.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/atom.c
b/drivers/gpu/drm/amd/amdgpu/atom.c
index 81d195d366ce..427b073de2fc 100644
--- a/drivers/gpu/drm/amd/amdgpu/atom.c
+++ b/drivers/gpu/drm/amd/amdgpu/atom.c
@@ -1444,6 +1444,7 @@ static void atom_get_vbios_pn(struct atom_context *ctx)
if (vbios_str == NULL)
vbios_str += sizeof(BIOS_ATOM_PREFIX) - 1;
}
+ OPTIMIZER_HIDE_VAR(vbios_str);
if (vbios_str != NULL && *vbios_str == 0)
vbios_str++;
--
2.34.1
