Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
On Tue, 2021-03-23 at 14:04 +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann
>
> gcc warns about an sprintf() that uses the same buffer as source
> and destination, which is undefined behavior in C99:
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c: In function
> 'amdgpu_securedisplay_debugfs_write':
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:141:6: error: 'sprintf'
> argument 3 overlaps destination object 'i2c_output' [-Werror=restrict]
> 141 | sprintf(i2c_output, "%s 0x%X", i2c_output,
> | ^~
> 142 |
> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
> |
> ~
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:97:7: note: destination
> object referenced by 'restrict'-qualified argument 1 was declared here
> 97 | char i2c_output[256];
> | ^~
>
> Rewrite it to remember the current offset into the buffer instead.
>
> Signed-off-by: Arnd Bergmann
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> index 834440ab9ff7..69d7f6bff5d4 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> @@ -136,9 +136,10 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct
> file *f, const char __u
> ret = psp_securedisplay_invoke(psp,
> TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
> if (!ret) {
> if (securedisplay_cmd->status ==
> TA_SECUREDISPLAY_STATUS__SUCCESS) {
> + int pos = 0;
> memset(i2c_output, 0, sizeof(i2c_output));
> for (i = 0; i <
> TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
> - sprintf(i2c_output, "%s 0x%X",
> i2c_output,
> + pos += sprintf(i2c_output + pos, "
> 0x%X",
>
> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
> dev_info(adev->dev, "SECUREDISPLAY: I2C buffer
> out put is :%s\n", i2c_output);
Perhaps use a hex output like:
---
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c | 11 ---
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
index 9cf856c94f94..25bb34c72d20 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
@@ -97,13 +97,12 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct
file *f, const char __u
uint32_t op;
int i;
char str[64];
- char i2c_output[256];
int ret;
if (*pos || size > sizeof(str) - 1)
return -EINVAL;
- memset(str, 0, sizeof(str));
+ memset(str, 0, sizeof(str));
ret = copy_from_user(str, buf, size);
if (ret)
return -EFAULT;
@@ -139,11 +138,9 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct
file *f, const char __u
ret = psp_securedisplay_invoke(psp,
TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
if (!ret) {
if (securedisplay_cmd->status ==
TA_SECUREDISPLAY_STATUS__SUCCESS) {
- memset(i2c_output, 0, sizeof(i2c_output));
- for (i = 0; i <
TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
- sprintf(i2c_output, "%s 0x%X",
i2c_output,
-
securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
- dev_info(adev->dev, "SECUREDISPLAY: I2C buffer
out put is :%s\n", i2c_output);
+ dev_info(adev->dev, "SECUREDISPLAY: I2C buffer
output is: %*ph\n",
+(int)TA_SECUREDISPLAY_I2C_BUFFER_SIZE,
+
securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf);
} else {
psp_securedisplay_parse_resp_status(psp,
securedisplay_cmd->status);
}
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Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
On 24/03/2021 14.33, Arnd Bergmann wrote:
> On Tue, Mar 23, 2021 at 4:57 PM Rasmus Villemoes
> wrote:
>> On 23/03/2021 14.04, Arnd Bergmann wrote:
>>> if (securedisplay_cmd->status ==
>>> TA_SECUREDISPLAY_STATUS__SUCCESS) {
>>> + int pos = 0;
>>> memset(i2c_output, 0, sizeof(i2c_output));
>>> for (i = 0; i <
>>> TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
>>> - sprintf(i2c_output, "%s 0x%X",
>>> i2c_output,
>>> + pos += sprintf(i2c_output + pos, "
>>> 0x%X",
>>>
>>> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
>>> dev_info(adev->dev, "SECUREDISPLAY: I2C
>>> buffer out put is :%s\n", i2c_output);
>>
>> Eh, why not get rid of the 256 byte stack allocation and just replace
>> all of this by
>>
>> dev_info(adev->dev, ""SECUREDISPLAY: I2C buffer out put is: %*ph\n",
>> TA_SECUREDISPLAY_I2C_BUFFER_SIZE,
>> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf);
>>
>> That's much less code (both in #LOC and .text), and avoids adding yet
>> another place that will be audited over and over for "hm, yeah, that
>> sprintf() is actually not gonna overflow".
>>
>> Yeah, it'll lose the 0x prefixes for each byte and use lowercase hex chars.
>
> Ah, I didn't know the kernel's sprintf could do that, that's really nice.
If you're bored, you can "git grep -E -C4 '%[0.]2[xX]'" and find places
that are inside a small loop, many can trivially be converted to %ph,
though often with some small change in formatting. If you're lucky, you
even get to fix real bugs when people pass a "char" to %02x and "know"
that that will produce precisely two bytes of output, so they've sized
their stack buffer accordingly - boom when "char" happens to be signed
and one of the bytes have a value beyond ascii and %02x produces 0xffXX.
%ph has a hard-coded upper bound of 64 bytes, I think that's silly
because people instead do these inefficient and very verbose loops
instead, wasting stack, .text and runtime.
Rasmus
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Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
On Tue, Mar 23, 2021 at 4:57 PM Rasmus Villemoes
wrote:
> On 23/03/2021 14.04, Arnd Bergmann wrote:
> > if (securedisplay_cmd->status ==
> > TA_SECUREDISPLAY_STATUS__SUCCESS) {
> > + int pos = 0;
> > memset(i2c_output, 0, sizeof(i2c_output));
> > for (i = 0; i <
> > TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
> > - sprintf(i2c_output, "%s 0x%X",
> > i2c_output,
> > + pos += sprintf(i2c_output + pos, "
> > 0x%X",
> >
> > securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
> > dev_info(adev->dev, "SECUREDISPLAY: I2C
> > buffer out put is :%s\n", i2c_output);
>
> Eh, why not get rid of the 256 byte stack allocation and just replace
> all of this by
>
> dev_info(adev->dev, ""SECUREDISPLAY: I2C buffer out put is: %*ph\n",
> TA_SECUREDISPLAY_I2C_BUFFER_SIZE,
> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf);
>
> That's much less code (both in #LOC and .text), and avoids adding yet
> another place that will be audited over and over for "hm, yeah, that
> sprintf() is actually not gonna overflow".
>
> Yeah, it'll lose the 0x prefixes for each byte and use lowercase hex chars.
Ah, I didn't know the kernel's sprintf could do that, that's really nice.
I'll send a follow-up patch, as Alex has already applied the first one.
Alex, feel free to merge the two into one, or just keep as they are.
Arnd
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Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
On 23/03/2021 14.04, Arnd Bergmann wrote:
> From: Arnd Bergmann
>
> gcc warns about an sprintf() that uses the same buffer as source
> and destination, which is undefined behavior in C99:
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c: In function
> 'amdgpu_securedisplay_debugfs_write':
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:141:6: error: 'sprintf'
> argument 3 overlaps destination object 'i2c_output' [-Werror=restrict]
> 141 | sprintf(i2c_output, "%s 0x%X", i2c_output,
> | ^~
> 142 |
> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
> |
> ~
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:97:7: note: destination
> object referenced by 'restrict'-qualified argument 1 was declared here
>97 | char i2c_output[256];
> | ^~
>
> Rewrite it to remember the current offset into the buffer instead.
>
> Signed-off-by: Arnd Bergmann
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> index 834440ab9ff7..69d7f6bff5d4 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> @@ -136,9 +136,10 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct
> file *f, const char __u
> ret = psp_securedisplay_invoke(psp,
> TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
> if (!ret) {
> if (securedisplay_cmd->status ==
> TA_SECUREDISPLAY_STATUS__SUCCESS) {
> + int pos = 0;
> memset(i2c_output, 0, sizeof(i2c_output));
> for (i = 0; i <
> TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
> - sprintf(i2c_output, "%s 0x%X",
> i2c_output,
> + pos += sprintf(i2c_output + pos, "
> 0x%X",
>
> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
> dev_info(adev->dev, "SECUREDISPLAY: I2C buffer
> out put is :%s\n", i2c_output);
Eh, why not get rid of the 256 byte stack allocation and just replace
all of this by
dev_info(adev->dev, ""SECUREDISPLAY: I2C buffer out put is: %*ph\n",
TA_SECUREDISPLAY_I2C_BUFFER_SIZE,
securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf);
That's much less code (both in #LOC and .text), and avoids adding yet
another place that will be audited over and over for "hm, yeah, that
sprintf() is actually not gonna overflow".
Yeah, it'll lose the 0x prefixes for each byte and use lowercase hex chars.
Rasmus
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Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
Applied. Thanks!
Alex
On Tue, Mar 23, 2021 at 9:04 AM Arnd Bergmann wrote:
>
> From: Arnd Bergmann
>
> gcc warns about an sprintf() that uses the same buffer as source
> and destination, which is undefined behavior in C99:
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c: In function
> 'amdgpu_securedisplay_debugfs_write':
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:141:6: error: 'sprintf'
> argument 3 overlaps destination object 'i2c_output' [-Werror=restrict]
> 141 | sprintf(i2c_output, "%s 0x%X", i2c_output,
> | ^~
> 142 |
> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
> |
> ~
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:97:7: note: destination
> object referenced by 'restrict'-qualified argument 1 was declared here
>97 | char i2c_output[256];
> | ^~
>
> Rewrite it to remember the current offset into the buffer instead.
>
> Signed-off-by: Arnd Bergmann
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> index 834440ab9ff7..69d7f6bff5d4 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
> @@ -136,9 +136,10 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct
> file *f, const char __u
> ret = psp_securedisplay_invoke(psp,
> TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
> if (!ret) {
> if (securedisplay_cmd->status ==
> TA_SECUREDISPLAY_STATUS__SUCCESS) {
> + int pos = 0;
> memset(i2c_output, 0, sizeof(i2c_output));
> for (i = 0; i <
> TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
> - sprintf(i2c_output, "%s 0x%X",
> i2c_output,
> + pos += sprintf(i2c_output + pos, "
> 0x%X",
>
> securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
> dev_info(adev->dev, "SECUREDISPLAY: I2C
> buffer out put is :%s\n", i2c_output);
> } else {
> --
> 2.29.2
>
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[PATCH] amdgpu: fix gcc -Wrestrict warning
From: Arnd Bergmann
gcc warns about an sprintf() that uses the same buffer as source
and destination, which is undefined behavior in C99:
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c: In function
'amdgpu_securedisplay_debugfs_write':
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:141:6: error: 'sprintf'
argument 3 overlaps destination object 'i2c_output' [-Werror=restrict]
141 | sprintf(i2c_output, "%s 0x%X", i2c_output,
| ^~
142 |
securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
|
~
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:97:7: note: destination
object referenced by 'restrict'-qualified argument 1 was declared here
97 | char i2c_output[256];
| ^~
Rewrite it to remember the current offset into the buffer instead.
Signed-off-by: Arnd Bergmann
---
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
index 834440ab9ff7..69d7f6bff5d4 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
@@ -136,9 +136,10 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct
file *f, const char __u
ret = psp_securedisplay_invoke(psp,
TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
if (!ret) {
if (securedisplay_cmd->status ==
TA_SECUREDISPLAY_STATUS__SUCCESS) {
+ int pos = 0;
memset(i2c_output, 0, sizeof(i2c_output));
for (i = 0; i <
TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
- sprintf(i2c_output, "%s 0x%X",
i2c_output,
+ pos += sprintf(i2c_output + pos, "
0x%X",
securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
dev_info(adev->dev, "SECUREDISPLAY: I2C buffer
out put is :%s\n", i2c_output);
} else {
--
2.29.2
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