* Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
2021-03-23 13:04 [PATCH] amdgpu: fix gcc -Wrestrict warning Arnd Bergmann
@ 2021-03-23 15:33 ` Alex Deucher
2021-03-23 15:57 ` Rasmus Villemoes
2021-03-24 14:31 ` Joe Perches
2 siblings, 0 replies; 6+ messages in thread
From: Alex Deucher @ 2021-03-23 15:33 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Alex Deucher, Christian König, David Airlie, Daniel Vetter,
Jinzhou Su, Arnd Bergmann, LKML, Maling list - DRI developers,
Huang Rui, amd-gfx list
Applied. Thanks!
Alex
On Tue, Mar 23, 2021 at 9:04 AM Arnd Bergmann <arnd@kernel.org> wrote:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> 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 <arnd@arndb.de>
> ---
> 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
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
2021-03-23 13:04 [PATCH] amdgpu: fix gcc -Wrestrict warning Arnd Bergmann
2021-03-23 15:33 ` Alex Deucher
@ 2021-03-23 15:57 ` Rasmus Villemoes
2021-03-24 13:33 ` Arnd Bergmann
2021-03-24 14:31 ` Joe Perches
2 siblings, 1 reply; 6+ messages in thread
From: Rasmus Villemoes @ 2021-03-23 15:57 UTC (permalink / raw)
To: Arnd Bergmann, Alex Deucher, Christian König, David Airlie,
Daniel Vetter
Cc: Arnd Bergmann, Huang Rui, Jinzhou Su, amd-gfx, dri-devel, linux-kernel
On 23/03/2021 14.04, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> 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 <arnd@arndb.de>
> ---
> 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
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
2021-03-23 15:57 ` Rasmus Villemoes
@ 2021-03-24 13:33 ` Arnd Bergmann
2021-03-24 14:14 ` Rasmus Villemoes
0 siblings, 1 reply; 6+ messages in thread
From: Arnd Bergmann @ 2021-03-24 13:33 UTC (permalink / raw)
To: Rasmus Villemoes
Cc: Alex Deucher, Christian König, David Airlie, Daniel Vetter,
Huang Rui, Jinzhou Su, amd-gfx list, dri-devel,
Linux Kernel Mailing List
On Tue, Mar 23, 2021 at 4:57 PM Rasmus Villemoes
<linux@rasmusvillemoes.dk> 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
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
2021-03-24 13:33 ` Arnd Bergmann
@ 2021-03-24 14:14 ` Rasmus Villemoes
0 siblings, 0 replies; 6+ messages in thread
From: Rasmus Villemoes @ 2021-03-24 14:14 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Alex Deucher, Christian König, David Airlie, Daniel Vetter,
Huang Rui, Jinzhou Su, amd-gfx list, dri-devel,
Linux Kernel Mailing List
On 24/03/2021 14.33, Arnd Bergmann wrote:
> On Tue, Mar 23, 2021 at 4:57 PM Rasmus Villemoes
> <linux@rasmusvillemoes.dk> 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 0xffffffXX.
%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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] amdgpu: fix gcc -Wrestrict warning
2021-03-23 13:04 [PATCH] amdgpu: fix gcc -Wrestrict warning Arnd Bergmann
2021-03-23 15:33 ` Alex Deucher
2021-03-23 15:57 ` Rasmus Villemoes
@ 2021-03-24 14:31 ` Joe Perches
2 siblings, 0 replies; 6+ messages in thread
From: Joe Perches @ 2021-03-24 14:31 UTC (permalink / raw)
To: Arnd Bergmann, Alex Deucher, Christian König, David Airlie,
Daniel Vetter
Cc: Arnd Bergmann, Huang Rui, Jinzhou Su, amd-gfx, dri-devel, linux-kernel
On Tue, 2021-03-23 at 14:04 +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> 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 <arnd@arndb.de>
> ---
> 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);
}
^ permalink raw reply related [flat|nested] 6+ messages in thread