A struct file is a bit too large to put on the kernel stack in general
and triggers a warning for low settings of CONFIG_FRAME_WARN:
drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file':
drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free':
drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
It's also slightly dangerous to leave a reference to a stack object
in the drm_file structure after leaving the stack frame.
This changes the code to just allocate the object dynamically
and release it when we are done with it.
Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing")
Signed-off-by: Arnd Bergmann <[email protected]>
---
drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c
index 113dec05c7dc..18514065c93d 100644
--- a/drivers/gpu/drm/i915/selftests/mock_drm.c
+++ b/drivers/gpu/drm/i915/selftests/mock_drm.c
@@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915)
struct drm_file *mock_file(struct drm_i915_private *i915)
{
struct inode inode = fake_inode(i915);
- struct file filp = {};
+ struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL);
struct drm_file *file;
int err;
- err = drm_open(&inode, &filp);
+ err = drm_open(&inode, filp);
if (unlikely(err))
return ERR_PTR(err);
- file = filp.private_data;
+ file = filp->private_data;
file->authenticated = true;
return file;
}
@@ -48,7 +48,9 @@ struct drm_file *mock_file(struct drm_i915_private *i915)
void mock_file_free(struct drm_i915_private *i915, struct drm_file *file)
{
struct inode inode = fake_inode(i915);
- struct file filp = { .private_data = file };
+ struct file *filp = file->filp;
- drm_release(&inode, &filp);
+ drm_release(&inode, filp);
+
+ kfree(filp);
}
--
2.9.0
The varargs macro trick in _PIPE3/_PHY3/_PORT3 was meant as an optimization
to shrink the i915 kernel module by around 1000 bytes. However, the
downside is a size regression with CONFIG_KASAN, as I found from stack size
warnings with gcc-7.0.1:
before:
drivers/gpu/drm/i915/intel_dpll_mgr.c: In function 'bxt_ddi_pll_get_hw_state':
drivers/gpu/drm/i915/intel_dpll_mgr.c:1644:1: error: the frame size of 176 bytes is larger than 100 bytes [-Werror=frame-larger-than=]
drivers/gpu/drm/i915/intel_dpll_mgr.c: In function 'bxt_ddi_pll_enable':
drivers/gpu/drm/i915/intel_dpll_mgr.c:1548:1: error: the frame size of 224 bytes is larger than 100 bytes [-Werror=frame-larger-than=]
after:
drivers/gpu/drm/i915/intel_dpll_mgr.c: In function 'bxt_ddi_pll_get_hw_state':
drivers/gpu/drm/i915/intel_dpll_mgr.c:1644:1: error: the frame size of 1016 bytes is larger than 1000 bytes [-Werror=frame-larger-than=]
drivers/gpu/drm/i915/intel_dpll_mgr.c: In function 'bxt_ddi_pll_enable':
drivers/gpu/drm/i915/intel_dpll_mgr.c:1548:1: error: the frame size of 1960 bytes is larger than 1000 bytes [-Werror=frame-larger-than=]
I also checked the module sizes and got
before:
text data bss dec hex filename
2704592 412025 11104 3127721 2fb9a9 drivers/gpu/drm/i915/i915.o
after:
text data bss dec hex filename
2718538 412025 11104 3141667 2ff023 drivers/gpu/drm/i915/i915.o
showing a significant code size growth. This reverts the patch to avoid
the warning and get back to the better code with CONFIG_KASAN. If someone
has another idea to avoid the warning while keeping the more efficient
code for the non-KASAN case, that would obviously be better.
Fixes: ce64645d86ac ("drm/i915: use variadic macros and arrays to choose port/pipe based registers")
Signed-off-by: Arnd Bergmann <[email protected]>
---
drivers/gpu/drm/i915/i915_reg.h | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 04c8f69fcc62..aa732eccdeb5 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -48,8 +48,6 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
return !i915_mmio_reg_equal(reg, INVALID_MMIO_REG);
}
-#define _PICK(__index, ...) (((const u32 []){ __VA_ARGS__ })[__index])
-
#define _PIPE(pipe, a, b) ((a) + (pipe)*((b)-(a)))
#define _MMIO_PIPE(pipe, a, b) _MMIO(_PIPE(pipe, a, b))
#define _PLANE(plane, a, b) _PIPE(plane, a, b)
@@ -58,11 +56,14 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
#define _MMIO_TRANS(tran, a, b) _MMIO(_TRANS(tran, a, b))
#define _PORT(port, a, b) ((a) + (port)*((b)-(a)))
#define _MMIO_PORT(port, a, b) _MMIO(_PORT(port, a, b))
-#define _PIPE3(pipe, ...) _PICK(pipe, __VA_ARGS__)
+#define _PIPE3(pipe, a, b, c) ((pipe) == PIPE_A ? (a) : \
+ (pipe) == PIPE_B ? (b) : (c))
#define _MMIO_PIPE3(pipe, a, b, c) _MMIO(_PIPE3(pipe, a, b, c))
-#define _PORT3(port, ...) _PICK(port, __VA_ARGS__)
+#define _PORT3(port, a, b, c) ((port) == PORT_A ? (a) : \
+ (port) == PORT_B ? (b) : (c))
#define _MMIO_PORT3(pipe, a, b, c) _MMIO(_PORT3(pipe, a, b, c))
-#define _PHY3(phy, ...) _PICK(phy, __VA_ARGS__)
+#define _PHY3(phy, a, b, c) ((phy) == DPIO_PHY0 ? (a) : \
+ (phy) == DPIO_PHY1 ? (b) : (c))
#define _MMIO_PHY3(phy, a, b, c) _MMIO(_PHY3(phy, a, b, c))
#define _MASKED_FIELD(mask, value) ({ \
--
2.9.0
We get a warning with gcc-7 about a pointless comparison when
using a linear memmap:
drivers/gpu/drm/i915/selftests/scatterlist.c: In function 'alloc_table':
drivers/gpu/drm/i915/selftests/scatterlist.c:219:66: error: self-comparison always evaluates to false [-Werror=tautological-compare]
Splitting out the comparison into a separate function avoids the warning
and makes it slightly more obvious what happens.
Fixes: 935a2f776aa5 ("drm/i915: Add some selftests for sg_table manipulation")
Signed-off-by: Arnd Bergmann <[email protected]>
---
drivers/gpu/drm/i915/selftests/scatterlist.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/selftests/scatterlist.c b/drivers/gpu/drm/i915/selftests/scatterlist.c
index eb2cda8e2b9f..c072b0f9180b 100644
--- a/drivers/gpu/drm/i915/selftests/scatterlist.c
+++ b/drivers/gpu/drm/i915/selftests/scatterlist.c
@@ -189,6 +189,11 @@ static unsigned int random(unsigned long n,
return 1 + (prandom_u32_state(rnd) % 1024);
}
+static inline bool page_contiguous(struct page *first, struct page *last, unsigned long npages)
+{
+ return first + npages == last;
+}
+
static int alloc_table(struct pfn_table *pt,
unsigned long count, unsigned long max,
npages_fn_t npages_fn,
@@ -216,7 +221,8 @@ static int alloc_table(struct pfn_table *pt,
unsigned long npages = npages_fn(n, count, rnd);
/* Nobody expects the Sparse Memmap! */
- if (pfn_to_page(pfn + npages) != pfn_to_page(pfn) + npages) {
+ if (!page_contiguous(pfn_to_page(pfn),
+ pfn_to_page(pfn + npages), npages)) {
sg_free_table(&pt->st);
return -ENOSPC;
}
--
2.9.0
On Mon, Mar 20, 2017 at 10:40:27AM +0100, Arnd Bergmann wrote:
> A struct file is a bit too large to put on the kernel stack in general
> and triggers a warning for low settings of CONFIG_FRAME_WARN:
>
> drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file':
> drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
> drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free':
> drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
>
> It's also slightly dangerous to leave a reference to a stack object
> in the drm_file structure after leaving the stack frame.
> This changes the code to just allocate the object dynamically
> and release it when we are done with it.
>
> Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c
> index 113dec05c7dc..18514065c93d 100644
> --- a/drivers/gpu/drm/i915/selftests/mock_drm.c
> +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c
> @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915)
> struct drm_file *mock_file(struct drm_i915_private *i915)
> {
> struct inode inode = fake_inode(i915);
> - struct file filp = {};
> + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL);
> struct drm_file *file;
> int err;
>
> - err = drm_open(&inode, &filp);
> + err = drm_open(&inode, filp);
Aside: We should have a FIXME and/or merge David Herrmanns code to allow a
drm_file without a real struct file for kernel-internal use ...
-Daniel
> if (unlikely(err))
> return ERR_PTR(err);
>
> - file = filp.private_data;
> + file = filp->private_data;
> file->authenticated = true;
> return file;
> }
> @@ -48,7 +48,9 @@ struct drm_file *mock_file(struct drm_i915_private *i915)
> void mock_file_free(struct drm_i915_private *i915, struct drm_file *file)
> {
> struct inode inode = fake_inode(i915);
> - struct file filp = { .private_data = file };
> + struct file *filp = file->filp;
>
> - drm_release(&inode, &filp);
> + drm_release(&inode, filp);
> +
> + kfree(filp);
> }
> --
> 2.9.0
>
> _______________________________________________
> dri-devel mailing list
> [email protected]
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
On Mon, 20 Mar 2017, Arnd Bergmann <[email protected]> wrote:
> The varargs macro trick in _PIPE3/_PHY3/_PORT3 was meant as an optimization
> to shrink the i915 kernel module by around 1000 bytes.
To be clear, it was not at all intended to be an optimization, nothing
of the sort. The intention was to make it easier and less error prone to
add more parameters to said macros. The text size shring was just a
bonus.
> However, the
> downside is a size regression with CONFIG_KASAN, as I found from stack size
> warnings with gcc-7.0.1:
In his review of the original change, Chris provided this comparison
https://godbolt.org/g/YCK1od
How does CONFIG_KASAN change this? Would be nice to see how the
generated code blows up.
BR,
Jani.
>
> before:
> drivers/gpu/drm/i915/intel_dpll_mgr.c: In function 'bxt_ddi_pll_get_hw_state':
> drivers/gpu/drm/i915/intel_dpll_mgr.c:1644:1: error: the frame size of 176 bytes is larger than 100 bytes [-Werror=frame-larger-than=]
> drivers/gpu/drm/i915/intel_dpll_mgr.c: In function 'bxt_ddi_pll_enable':
> drivers/gpu/drm/i915/intel_dpll_mgr.c:1548:1: error: the frame size of 224 bytes is larger than 100 bytes [-Werror=frame-larger-than=]
>
> after:
> drivers/gpu/drm/i915/intel_dpll_mgr.c: In function 'bxt_ddi_pll_get_hw_state':
> drivers/gpu/drm/i915/intel_dpll_mgr.c:1644:1: error: the frame size of 1016 bytes is larger than 1000 bytes [-Werror=frame-larger-than=]
> drivers/gpu/drm/i915/intel_dpll_mgr.c: In function 'bxt_ddi_pll_enable':
> drivers/gpu/drm/i915/intel_dpll_mgr.c:1548:1: error: the frame size of 1960 bytes is larger than 1000 bytes [-Werror=frame-larger-than=]
>
> I also checked the module sizes and got
>
> before:
> text data bss dec hex filename
> 2704592 412025 11104 3127721 2fb9a9 drivers/gpu/drm/i915/i915.o
>
> after:
> text data bss dec hex filename
> 2718538 412025 11104 3141667 2ff023 drivers/gpu/drm/i915/i915.o
>
> showing a significant code size growth. This reverts the patch to avoid
> the warning and get back to the better code with CONFIG_KASAN. If someone
> has another idea to avoid the warning while keeping the more efficient
> code for the non-KASAN case, that would obviously be better.
>
> Fixes: ce64645d86ac ("drm/i915: use variadic macros and arrays to choose port/pipe based registers")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> drivers/gpu/drm/i915/i915_reg.h | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 04c8f69fcc62..aa732eccdeb5 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -48,8 +48,6 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
> return !i915_mmio_reg_equal(reg, INVALID_MMIO_REG);
> }
>
> -#define _PICK(__index, ...) (((const u32 []){ __VA_ARGS__ })[__index])
> -
> #define _PIPE(pipe, a, b) ((a) + (pipe)*((b)-(a)))
> #define _MMIO_PIPE(pipe, a, b) _MMIO(_PIPE(pipe, a, b))
> #define _PLANE(plane, a, b) _PIPE(plane, a, b)
> @@ -58,11 +56,14 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
> #define _MMIO_TRANS(tran, a, b) _MMIO(_TRANS(tran, a, b))
> #define _PORT(port, a, b) ((a) + (port)*((b)-(a)))
> #define _MMIO_PORT(port, a, b) _MMIO(_PORT(port, a, b))
> -#define _PIPE3(pipe, ...) _PICK(pipe, __VA_ARGS__)
> +#define _PIPE3(pipe, a, b, c) ((pipe) == PIPE_A ? (a) : \
> + (pipe) == PIPE_B ? (b) : (c))
> #define _MMIO_PIPE3(pipe, a, b, c) _MMIO(_PIPE3(pipe, a, b, c))
> -#define _PORT3(port, ...) _PICK(port, __VA_ARGS__)
> +#define _PORT3(port, a, b, c) ((port) == PORT_A ? (a) : \
> + (port) == PORT_B ? (b) : (c))
> #define _MMIO_PORT3(pipe, a, b, c) _MMIO(_PORT3(pipe, a, b, c))
> -#define _PHY3(phy, ...) _PICK(phy, __VA_ARGS__)
> +#define _PHY3(phy, a, b, c) ((phy) == DPIO_PHY0 ? (a) : \
> + (phy) == DPIO_PHY1 ? (b) : (c))
> #define _MMIO_PHY3(phy, a, b, c) _MMIO(_PHY3(phy, a, b, c))
>
> #define _MASKED_FIELD(mask, value) ({ \
--
Jani Nikula, Intel Open Source Technology Center
On Mon, Mar 20, 2017 at 11:08 AM, Jani Nikula
<[email protected]> wrote:
> On Mon, 20 Mar 2017, Arnd Bergmann <[email protected]> wrote:
>> The varargs macro trick in _PIPE3/_PHY3/_PORT3 was meant as an optimization
>> to shrink the i915 kernel module by around 1000 bytes.
>
> To be clear, it was not at all intended to be an optimization, nothing
> of the sort. The intention was to make it easier and less error prone to
> add more parameters to said macros. The text size shring was just a
> bonus.
>
>> However, the
>> downside is a size regression with CONFIG_KASAN, as I found from stack size
>> warnings with gcc-7.0.1:
>
> In his review of the original change, Chris provided this comparison
> https://godbolt.org/g/YCK1od
>
> How does CONFIG_KASAN change this? Would be nice to see how the
> generated code blows up.
>
I don't know how to generate a URL for it, but after adding this to the
command line for gcc-7,
-fsanitize=kernel-address -fasan-shadow-offset=0xdfff900000000000
--param asan-stack=1 --param asan-globals=1 --param
asan-instrumentation-with-call-threshold=10000
-fsanitize-address-use-after-scope
the code turned from really nice into the log series of checks below.
Without -fsanitize-address-use-after-scope (which didn't exist before gcc-7),
it's less bad but still exceeds the (arbitrary) 1536 byte limit.
Arnd
.LC0:
.string "2 32 4 1 i 96 24 9 <unknown> "
main:
.LASANPC0:
pushq %r12
pushq %rbp
movabsq $-2305966154516004864, %rdx
pushq %rbx
subq $160, %rsp
movq %rsp, %rbp
leaq 96(%rsp), %rbx
movq $1102416563, (%rsp)
shrq $3, %rbp
movq $.LC0, 8(%rsp)
movq $.LASANPC0, 16(%rsp)
leaq 0(%rbp,%rdx), %rax
movl $-235802127, (%rax)
movl $-218959356, 4(%rax)
movl $-218959118, 8(%rax)
movl $-234881024, 12(%rax)
movl $-202116109, 16(%rax)
movq %rbx, %rax
movl $1, 32(%rsp)
shrq $3, %rax
movzbl (%rax,%rdx), %eax
testb %al, %al
je .L2
cmpb $3, %al
jle .L53
.L2:
leaq 4(%rbx), %rdi
movabsq $-2305966154516004864, %rax
movl $0, 96(%rsp)
movq %rdi, %rdx
shrq $3, %rdx
movzbl (%rdx,%rax), %edx
movq %rdi, %rax
andl $7, %eax
addl $3, %eax
cmpb %dl, %al
jl .L3
testb %dl, %dl
jne .L54
.L3:
leaq 8(%rbx), %rdi
movabsq $-2305966154516004864, %rax
movl $1, 100(%rsp)
movq %rdi, %rdx
shrq $3, %rdx
movzbl (%rdx,%rax), %eax
testb %al, %al
je .L4
cmpb $3, %al
jle .L55
.L4:
leaq 12(%rbx), %rdi
movabsq $-2305966154516004864, %rax
movl $2, 104(%rsp)
movq %rdi, %rdx
shrq $3, %rdx
movzbl (%rdx,%rax), %edx
movq %rdi, %rax
andl $7, %eax
addl $3, %eax
cmpb %dl, %al
jl .L5
testb %dl, %dl
jne .L56
.L5:
leaq 16(%rbx), %rdi
movabsq $-2305966154516004864, %rax
movl $3, 108(%rsp)
movq %rdi, %rdx
shrq $3, %rdx
movzbl (%rdx,%rax), %eax
testb %al, %al
je .L6
cmpb $3, %al
jle .L57
.L6:
leaq 20(%rbx), %rdi
movabsq $-2305966154516004864, %rax
movl $4, 112(%rsp)
movq %rdi, %rdx
shrq $3, %rdx
movzbl (%rdx,%rax), %edx
movq %rdi, %rax
andl $7, %eax
addl $3, %eax
cmpb %dl, %al
jl .L7
testb %dl, %dl
jne .L58
.L7:
movslq 32(%rsp), %r12
movabsq $-2305966154516004864, %rax
movl $5, 116(%rsp)
leaq (%rbx,%r12,4), %rdi
movq %rdi, %rdx
shrq $3, %rdx
movzbl (%rdx,%rax), %edx
movq %rdi, %rax
andl $7, %eax
addl $3, %eax
cmpb %dl, %al
jl .L8
testb %dl, %dl
jne .L59
.L8:
pxor %xmm0, %xmm0
movabsq $-2305966154516004864, %rdx
movl 96(%rsp,%r12,4), %eax
movl $0, 16(%rdx,%rbp)
movups %xmm0, 0(%rbp,%rdx)
addq $160, %rsp
popq %rbx
popq %rbp
popq %r12
ret
.L59:
call __asan_report_load4_noabort
jmp .L8
.L58:
call __asan_report_store4_noabort
jmp .L7
.L57:
call __asan_report_store4_noabort
jmp .L6
.L56:
call __asan_report_store4_noabort
jmp .L5
.L55:
call __asan_report_store4_noabort
jmp .L4
.L54:
call __asan_report_store4_noabort
jmp .L3
.L53:
movq %rbx, %rdi
call __asan_report_store4_noabort
jmp .L2
On Mon, 20 Mar 2017, Arnd Bergmann <[email protected]> wrote:
> I don't know how to generate a URL for it, but after adding this to the
> command line for gcc-7,
>
> -fsanitize=kernel-address -fasan-shadow-offset=0xdfff900000000000
> --param asan-stack=1 --param asan-globals=1 --param
> asan-instrumentation-with-call-threshold=10000
> -fsanitize-address-use-after-scope
>
> the code turned from really nice into the log series of checks below.
> Without -fsanitize-address-use-after-scope (which didn't exist before gcc-7),
> it's less bad but still exceeds the (arbitrary) 1536 byte limit.
It seems to be the combination of --param asan-stack=1 and
-fsanitize-address-use-after-scope that really blows up the code [1]. I
filed a GCC bug on it, mostly to see what they say [2]. I don't know,
maybe they think it's expected. *shrug*.
BR,
Jani.
[1] https://godbolt.org/g/hgS817
[2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80114
--
Jani Nikula, Intel Open Source Technology Center
On Mon, Mar 20, 2017 at 1:02 PM, Arnd Bergmann <[email protected]> wrote:
> On Mon, Mar 20, 2017 at 1:00 PM, Joonas Lahtinen
> <[email protected]> wrote:
>> On ma, 2017-03-20 at 10:40 +0100, Arnd Bergmann wrote:
>
>>> diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c
>>> index 113dec05c7dc..18514065c93d 100644
>>> --- a/drivers/gpu/drm/i915/selftests/mock_drm.c
>>> +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c
>>> @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915)
>>> struct drm_file *mock_file(struct drm_i915_private *i915)
>>> {
>>> > struct inode inode = fake_inode(i915);
>>> > - struct file filp = {};
>>> > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL);
>>> > struct drm_file *file;
>>> > int err;
>>>
>>
>> filp = kzalloc(sizeof(*filp), GFP_KERNEL);
>> if (unlikely(!filp)) {
>> err = -ENOMEM;
>> goto err;
>> }
>>
>> And appropriate onion teardown in case drm_open fails, so that we don't
>> leak memory.
>
> Oops, of course you are right, sorry about that.
Actually it's even worse, as I had originally planned to also allocate the inode
dynamically, but for some reasons didn't do that in the patch I sent.
This version of the patch as I sent it is rather bogus, so please ignore it
(but not the other two patches I sent). If David's solution to this problem
can make it into 4.12, there is no problem at all. Another alternative
would be to use anon_inode_getfile(), again with proper error handling
and cleanup. This is a bit slower but gives us valid file and inode structures.
Arnd
On ma, 2017-03-20 at 10:40 +0100, Arnd Bergmann wrote:
> A struct file is a bit too large to put on the kernel stack in general
> and triggers a warning for low settings of CONFIG_FRAME_WARN:
>
> drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file':
> drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
> drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free':
> drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
>
> It's also slightly dangerous to leave a reference to a stack object
> in the drm_file structure after leaving the stack frame.
> This changes the code to just allocate the object dynamically
> and release it when we are done with it.
>
> Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing")
> Signed-off-by: Arnd Bergmann <[email protected]>
<SNIP>
> ---
> drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c
> index 113dec05c7dc..18514065c93d 100644
> --- a/drivers/gpu/drm/i915/selftests/mock_drm.c
> +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c
> @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915)
> struct drm_file *mock_file(struct drm_i915_private *i915)
> {
> > struct inode inode = fake_inode(i915);
> > - struct file filp = {};
> > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL);
> > struct drm_file *file;
> > int err;
>
filp = kzalloc(sizeof(*filp), GFP_KERNEL);
if (unlikely(!filp)) {
err = -ENOMEM;
goto err;
}
And appropriate onion teardown in case drm_open fails, so that we don't
leak memory.
Regards, Joonas
--
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
On Mon, Mar 20, 2017 at 1:00 PM, Joonas Lahtinen
<[email protected]> wrote:
> On ma, 2017-03-20 at 10:40 +0100, Arnd Bergmann wrote:
>> diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c
>> index 113dec05c7dc..18514065c93d 100644
>> --- a/drivers/gpu/drm/i915/selftests/mock_drm.c
>> +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c
>> @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915)
>> struct drm_file *mock_file(struct drm_i915_private *i915)
>> {
>> > struct inode inode = fake_inode(i915);
>> > - struct file filp = {};
>> > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL);
>> > struct drm_file *file;
>> > int err;
>>
>
> filp = kzalloc(sizeof(*filp), GFP_KERNEL);
> if (unlikely(!filp)) {
> err = -ENOMEM;
> goto err;
> }
>
> And appropriate onion teardown in case drm_open fails, so that we don't
> leak memory.
Oops, of course you are right, sorry about that.
Arnd
On Mon, Mar 20, 2017 at 10:40:28AM +0100, Arnd Bergmann wrote:
> We get a warning with gcc-7 about a pointless comparison when
> using a linear memmap:
>
> drivers/gpu/drm/i915/selftests/scatterlist.c: In function 'alloc_table':
> drivers/gpu/drm/i915/selftests/scatterlist.c:219:66: error: self-comparison always evaluates to false [-Werror=tautological-compare]
>
> Splitting out the comparison into a separate function avoids the warning
> and makes it slightly more obvious what happens.
I worried whether gcc will simply get smarter and apply its warning more
consistently, but I agree the helper is good documentation.
> Fixes: 935a2f776aa5 ("drm/i915: Add some selftests for sg_table manipulation")
> Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Chris Wilson <[email protected]>
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
On Mon, Mar 20, 2017 at 10:40:27AM +0100, Arnd Bergmann wrote:
> A struct file is a bit too large to put on the kernel stack in general
> and triggers a warning for low settings of CONFIG_FRAME_WARN:
>
> drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file':
> drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
> drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free':
> drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
>
> It's also slightly dangerous to leave a reference to a stack object
> in the drm_file structure after leaving the stack frame.
> This changes the code to just allocate the object dynamically
> and release it when we are done with it.
>
> Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c
> index 113dec05c7dc..18514065c93d 100644
> --- a/drivers/gpu/drm/i915/selftests/mock_drm.c
> +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c
> @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915)
> struct drm_file *mock_file(struct drm_i915_private *i915)
> {
> struct inode inode = fake_inode(i915);
> - struct file filp = {};
> + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL);
> struct drm_file *file;
> int err;
>
> - err = drm_open(&inode, &filp);
> + err = drm_open(&inode, filp);
> if (unlikely(err))
> return ERR_PTR(err);
>
> - file = filp.private_data;
> + file = filp->private_data;
What I don't like about this approach is that we leak the unwanted
inode/file. We only want the drm_file here and any access to above that
inside i915.ko is fubar.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
On Tue, Mar 21, 2017 at 09:56:52AM +0000, Chris Wilson wrote:
> On Mon, Mar 20, 2017 at 10:40:28AM +0100, Arnd Bergmann wrote:
> > We get a warning with gcc-7 about a pointless comparison when
> > using a linear memmap:
> >
> > drivers/gpu/drm/i915/selftests/scatterlist.c: In function 'alloc_table':
> > drivers/gpu/drm/i915/selftests/scatterlist.c:219:66: error: self-comparison always evaluates to false [-Werror=tautological-compare]
> >
> > Splitting out the comparison into a separate function avoids the warning
> > and makes it slightly more obvious what happens.
>
> I worried whether gcc will simply get smarter and apply its warning more
> consistently, but I agree the helper is good documentation.
>
> > Fixes: 935a2f776aa5 ("drm/i915: Add some selftests for sg_table manipulation")
> > Signed-off-by: Arnd Bergmann <[email protected]>
> Reviewed-by: Chris Wilson <[email protected]>
And applied.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre