From: Rickard x Andersson <[email protected]>
In GCC version 12.1 a checksum field was added.
Signed-off-by: Rickard x Andersson <[email protected]>
---
kernel/gcov/gcc_4_7.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
index c699feda21ac..04880d8fba25 100644
--- a/kernel/gcov/gcc_4_7.c
+++ b/kernel/gcov/gcc_4_7.c
@@ -85,6 +85,7 @@ struct gcov_fn_info {
* @version: gcov version magic indicating the gcc version used for compilation
* @next: list head for a singly-linked list
* @stamp: uniquifying time stamp
+ * @checksum: unique object checksum
* @filename: name of the associated gcov data file
* @merge: merge functions (null for unused counter type)
* @n_functions: number of instrumented functions
@@ -97,6 +98,10 @@ struct gcov_info {
unsigned int version;
struct gcov_info *next;
unsigned int stamp;
+ /* Since GCC 12.1 a checksum field is added. */
+#if (__GNUC__ >= 12)
+ unsigned int checksum;
+#endif
const char *filename;
void (*merge[GCOV_COUNTERS])(gcov_type *, unsigned int);
unsigned int n_functions;
--
2.30.2
On 19.12.2022 16:06, Rickard Andersson wrote:
> From: Rickard x Andersson <[email protected]>
>
> In GCC version 12.1 a checksum field was added.
Thanks for the patch!
In another e-mail you mentioned that this patch fixes a kernel crash
during boot when using gcov-kernel with GCC 12. Please add this
information to the commit message and if possible the platform on which
this occurs.
Also this patch fixes a missing piece from a previous patch, so please add:
Fixes: 977ef30a7d88 ("gcov: support GCC 12.1 and newer compilers")
Cc: <[email protected]>
Finally I reviewed and tested the patch and it looks good to me, so
please add:
Reviewed-by: Peter Oberparleiter <[email protected]>
Tested-by: Peter Oberparleiter <[email protected]>
Please resend with these commit message changes. Thanks!
For the record: I wondered why my testing of the previous patch with GCC
12 didn't catch this. It turns out that this crash does not occur on
architectures with 8-byte pointer alignment such as s390x where I
performed my tests. Consider this pahole output on s390x without the patch:
struct gcov_info {
[...]
unsigned int stamp; /* 16 4 */
/* XXX 4 bytes hole, try to pack */
const char * filename; /* 24 8 */
[...]
}
And with the patch:
struct gcov_info {
[...]
unsigned int stamp; /* 16 4 */
unsigned int checksum; /* 20 4 */
const char * filename; /* 24 8 */
[...]
}
As can be seen, the offset of the filename and subsequent fields does
not change because the new field fills an alignment hole. It would
change (resulting in a crash during boot) if the alignment-requirement
of the const char *filename field would be different.
>
> Signed-off-by: Rickard x Andersson <[email protected]>
> ---
> kernel/gcov/gcc_4_7.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
> index c699feda21ac..04880d8fba25 100644
> --- a/kernel/gcov/gcc_4_7.c
> +++ b/kernel/gcov/gcc_4_7.c
> @@ -85,6 +85,7 @@ struct gcov_fn_info {
> * @version: gcov version magic indicating the gcc version used for compilation
> * @next: list head for a singly-linked list
> * @stamp: uniquifying time stamp
> + * @checksum: unique object checksum
> * @filename: name of the associated gcov data file
> * @merge: merge functions (null for unused counter type)
> * @n_functions: number of instrumented functions
> @@ -97,6 +98,10 @@ struct gcov_info {
> unsigned int version;
> struct gcov_info *next;
> unsigned int stamp;
> + /* Since GCC 12.1 a checksum field is added. */
> +#if (__GNUC__ >= 12)
> + unsigned int checksum;
> +#endif
> const char *filename;
> void (*merge[GCOV_COUNTERS])(gcov_type *, unsigned int);
> unsigned int n_functions;
--
Peter Oberparleiter
Linux on IBM Z Development - IBM Germany R&D
On 12/19/22 17:48, Peter Oberparleiter wrote:
> On 19.12.2022 16:06, Rickard Andersson wrote:
>> From: Rickard x Andersson <[email protected]>
>>
>> In GCC version 12.1 a checksum field was added.
>
> Thanks for the patch!
>
> In another e-mail you mentioned that this patch fixes a kernel crash
> during boot when using gcov-kernel with GCC 12. Please add this
> information to the commit message and if possible the platform on which
> this occurs.
>
> Also this patch fixes a missing piece from a previous patch, so please add:
>
> Fixes: 977ef30a7d88 ("gcov: support GCC 12.1 and newer compilers")
> Cc: <[email protected]>
>
> Finally I reviewed and tested the patch and it looks good to me, so
> please add:
>
> Reviewed-by: Peter Oberparleiter <[email protected]>
> Tested-by: Peter Oberparleiter <[email protected]>
>
> Please resend with these commit message changes. Thanks!
>
> For the record: I wondered why my testing of the previous patch with GCC
> 12 didn't catch this. It turns out that this crash does not occur on
> architectures with 8-byte pointer alignment such as s390x where I
> performed my tests. Consider this pahole output on s390x without the patch:
>
> struct gcov_info {
> [...]
> unsigned int stamp; /* 16 4 */
> /* XXX 4 bytes hole, try to pack */
> const char * filename; /* 24 8 */
> [...]
> }
>
> And with the patch:
>
> struct gcov_info {
> [...]
> unsigned int stamp; /* 16 4 */
> unsigned int checksum; /* 20 4 */
> const char * filename; /* 24 8 */
> [...]
> }
>
> As can be seen, the offset of the filename and subsequent fields does
> not change because the new field fills an alignment hole. It would
> change (resulting in a crash during boot) if the alignment-requirement
> of the const char *filename field would be different.
Hello.
Thank you Peter for the deep analysis and it finally explains why I didn't notice
while I was working on 977ef30a7d88.
Please add my review:
Reviewed-By: Martin Liska <[email protected]>
Thanks,
Martin
>
>>
>> Signed-off-by: Rickard x Andersson <[email protected]>
>> ---
>> kernel/gcov/gcc_4_7.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
>> index c699feda21ac..04880d8fba25 100644
>> --- a/kernel/gcov/gcc_4_7.c
>> +++ b/kernel/gcov/gcc_4_7.c
>> @@ -85,6 +85,7 @@ struct gcov_fn_info {
>> * @version: gcov version magic indicating the gcc version used for compilation
>> * @next: list head for a singly-linked list
>> * @stamp: uniquifying time stamp
>> + * @checksum: unique object checksum
>> * @filename: name of the associated gcov data file
>> * @merge: merge functions (null for unused counter type)
>> * @n_functions: number of instrumented functions
>> @@ -97,6 +98,10 @@ struct gcov_info {
>> unsigned int version;
>> struct gcov_info *next;
>> unsigned int stamp;
>> + /* Since GCC 12.1 a checksum field is added. */
>> +#if (__GNUC__ >= 12)
>> + unsigned int checksum;
>> +#endif
>> const char *filename;
>> void (*merge[GCOV_COUNTERS])(gcov_type *, unsigned int);
>> unsigned int n_functions;
>