drivers/gpu/drm/amd/amdgpu/atom.c | 1 + 1 file changed, 1 insertion(+)
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 <kees@kernel.org>
---
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Xinhui Pan <Xinhui.Pan@amd.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Jesse Zhang <jesse.zhang@amd.com>
Cc: Tim Huang <Tim.Huang@amd.com>
Cc: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Cc: Alexander Richards <electrodeyt@gmail.com>
Cc: Lijo Lazar <lijo.lazar@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
---
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
On Mon, Apr 21, 2025 at 5:59 PM Kees Cook <kees@kernel.org> wrote: > > 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 <kees@kernel.org> Acked-by: Alex Deucher <alexander.deucher@amd.com> Do you want me to pick this up, or do you want to take this through some other tree? Thanks, Alex > --- > Cc: Alex Deucher <alexander.deucher@amd.com> > Cc: "Christian König" <christian.koenig@amd.com> > Cc: Xinhui Pan <Xinhui.Pan@amd.com> > Cc: David Airlie <airlied@gmail.com> > Cc: Simona Vetter <simona@ffwll.ch> > Cc: Jesse Zhang <jesse.zhang@amd.com> > Cc: Tim Huang <Tim.Huang@amd.com> > Cc: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com> > Cc: Alexander Richards <electrodeyt@gmail.com> > Cc: Lijo Lazar <lijo.lazar@amd.com> > Cc: Mario Limonciello <mario.limonciello@amd.com> > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Cc: amd-gfx@lists.freedesktop.org > Cc: dri-devel@lists.freedesktop.org > --- > 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 >
On Tue, Apr 22, 2025 at 09:22:26AM -0400, Alex Deucher wrote: > On Mon, Apr 21, 2025 at 5:59 PM Kees Cook <kees@kernel.org> wrote: > > > > 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 <kees@kernel.org> > > Acked-by: Alex Deucher <alexander.deucher@amd.com> Thanks! > Do you want me to pick this up, or do you want to take this through > some other tree? Whatever is easier for you. I'm happy to carry it if you'd like. :) There's no rush on these -- it's been a long road to getting -Warray-bounds enabled. ;) -- Kees Cook
On Tue, Apr 22, 2025 at 10:56 AM Kees Cook <kees@kernel.org> wrote: > > On Tue, Apr 22, 2025 at 09:22:26AM -0400, Alex Deucher wrote: > > On Mon, Apr 21, 2025 at 5:59 PM Kees Cook <kees@kernel.org> wrote: > > > > > > 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 <kees@kernel.org> > > > > Acked-by: Alex Deucher <alexander.deucher@amd.com> > > Thanks! > > > Do you want me to pick this up, or do you want to take this through > > some other tree? > > Whatever is easier for you. I'm happy to carry it if you'd like. :) > There's no rush on these -- it's been a long road to getting > -Warray-bounds enabled. ;) I've picked it up. Thanks! Alex > > -- > Kees Cook
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