[v2] nptl: Unconditionally use a 32-byte rseq area
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Commit Message
If the kernel headers provide a larger struct rseq, we used that
size as the argument to the rseq system call. As a result,
rseq registration would fail on older kernels which only accept
size 32.
Tested on x86_64-linux-gnu. Built with build-many-glibcs.py.
This needs to be backported all the way to glibc 2.35.
---
v2: Drop further struct rseq reference on ia64. Remove #include <sys/rseq.h>.
nptl/descr.h | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
base-commit: 3edc4ff2ceff4a59587ebecb94148d3bcfa1df62
Comments
On 7/20/23 07:46, Florian Weimer wrote:
> If the kernel headers provide a larger struct rseq, we used that
> size as the argument to the rseq system call. As a result,
> rseq registration would fail on older kernels which only accept
> size 32.
Yes, this change appears to be needed considering the way the upstream
kernel uapi has evolved.
Thanks,
Mathieu
>
> Tested on x86_64-linux-gnu. Built with build-many-glibcs.py.
> This needs to be backported all the way to glibc 2.35.
>
> ---
> v2: Drop further struct rseq reference on ia64. Remove #include <sys/rseq.h>.
> nptl/descr.h | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/nptl/descr.h b/nptl/descr.h
> index d06abd6ad9..0171576c23 100644
> --- a/nptl/descr.h
> +++ b/nptl/descr.h
> @@ -34,7 +34,6 @@
> #include <bits/types/res_state.h>
> #include <kernel-features.h>
> #include <tls-internal-struct.h>
> -#include <sys/rseq.h>
> #include <internal-sigset.h>
>
> #ifndef TCB_ALIGNMENT
> @@ -405,14 +404,25 @@ struct pthread
> /* Used on strsignal. */
> struct tls_internal_t tls_state;
>
> - /* rseq area registered with the kernel. */
> - struct rseq rseq_area;
> + /* rseq area registered with the kernel. Use a custom definition
> + here to isolate from kernel struct rseq changes. The
> + implementation of sched_getcpu needs acccess to the cpu_id field;
> + the other fields are unused and not included here. */
> + union
> + {
> + struct
> + {
> + uint32_t cpu_id_start;
> + uint32_t cpu_id;
> + };
> + char pad[32]; /* Original rseq area size. */
> + } rseq_area __attribute__ ((aligned (32)));
>
> /* Amount of end padding, if any, in this structure.
> This definition relies on rseq_area being last. */
> #define PTHREAD_STRUCT_END_PADDING \
> (sizeof (struct pthread) - offsetof (struct pthread, rseq_area) \
> - + sizeof (struct rseq))
> + + sizeof ((struct pthread) {}.rseq_area))
> } __attribute ((aligned (TCB_ALIGNMENT)));
>
> static inline bool
>
> base-commit: 3edc4ff2ceff4a59587ebecb94148d3bcfa1df62
>
* Mathieu Desnoyers:
> On 7/20/23 07:46, Florian Weimer wrote:
>> If the kernel headers provide a larger struct rseq, we used that
>> size as the argument to the rseq system call. As a result,
>> rseq registration would fail on older kernels which only accept
>> size 32.
>
> Yes, this change appears to be needed considering the way the upstream
> kernel uapi has evolved.
Andreas, is it okay to push this from an RM perspective?
Thanks,
Florian
>> Tested on x86_64-linux-gnu. Built with build-many-glibcs.py.
>> This needs to be backported all the way to glibc 2.35.
>> ---
>> v2: Drop further struct rseq reference on ia64. Remove #include <sys/rseq.h>.
>> nptl/descr.h | 18 ++++++++++++++----
>> 1 file changed, 14 insertions(+), 4 deletions(-)
>> diff --git a/nptl/descr.h b/nptl/descr.h
>> index d06abd6ad9..0171576c23 100644
>> --- a/nptl/descr.h
>> +++ b/nptl/descr.h
>> @@ -34,7 +34,6 @@
>> #include <bits/types/res_state.h>
>> #include <kernel-features.h>
>> #include <tls-internal-struct.h>
>> -#include <sys/rseq.h>
>> #include <internal-sigset.h>
>> #ifndef TCB_ALIGNMENT
>> @@ -405,14 +404,25 @@ struct pthread
>> /* Used on strsignal. */
>> struct tls_internal_t tls_state;
>> - /* rseq area registered with the kernel. */
>> - struct rseq rseq_area;
>> + /* rseq area registered with the kernel. Use a custom definition
>> + here to isolate from kernel struct rseq changes. The
>> + implementation of sched_getcpu needs acccess to the cpu_id field;
>> + the other fields are unused and not included here. */
>> + union
>> + {
>> + struct
>> + {
>> + uint32_t cpu_id_start;
>> + uint32_t cpu_id;
>> + };
>> + char pad[32]; /* Original rseq area size. */
>> + } rseq_area __attribute__ ((aligned (32)));
>> /* Amount of end padding, if any, in this structure.
>> This definition relies on rseq_area being last. */
>> #define PTHREAD_STRUCT_END_PADDING \
>> (sizeof (struct pthread) - offsetof (struct pthread, rseq_area) \
>> - + sizeof (struct rseq))
>> + + sizeof ((struct pthread) {}.rseq_area))
>> } __attribute ((aligned (TCB_ALIGNMENT)));
>> static inline bool
>> base-commit: 3edc4ff2ceff4a59587ebecb94148d3bcfa1df62
>>
Am Freitag, 21. Juli 2023, 16:01:51 CEST schrieb Florian Weimer:
> * Mathieu Desnoyers:
>
> > On 7/20/23 07:46, Florian Weimer wrote:
> >> If the kernel headers provide a larger struct rseq, we used that
> >> size as the argument to the rseq system call. As a result,
> >> rseq registration would fail on older kernels which only accept
> >> size 32.
> >
> > Yes, this change appears to be needed considering the way the upstream
> > kernel uapi has evolved.
>
> Andreas, is it okay to push this from an RM perspective?
Yes, please do it!
Best,
Andreas
@@ -34,7 +34,6 @@
#include <bits/types/res_state.h>
#include <kernel-features.h>
#include <tls-internal-struct.h>
-#include <sys/rseq.h>
#include <internal-sigset.h>
#ifndef TCB_ALIGNMENT
@@ -405,14 +404,25 @@ struct pthread
/* Used on strsignal. */
struct tls_internal_t tls_state;
- /* rseq area registered with the kernel. */
- struct rseq rseq_area;
+ /* rseq area registered with the kernel. Use a custom definition
+ here to isolate from kernel struct rseq changes. The
+ implementation of sched_getcpu needs acccess to the cpu_id field;
+ the other fields are unused and not included here. */
+ union
+ {
+ struct
+ {
+ uint32_t cpu_id_start;
+ uint32_t cpu_id;
+ };
+ char pad[32]; /* Original rseq area size. */
+ } rseq_area __attribute__ ((aligned (32)));
/* Amount of end padding, if any, in this structure.
This definition relies on rseq_area being last. */
#define PTHREAD_STRUCT_END_PADDING \
(sizeof (struct pthread) - offsetof (struct pthread, rseq_area) \
- + sizeof (struct rseq))
+ + sizeof ((struct pthread) {}.rseq_area))
} __attribute ((aligned (TCB_ALIGNMENT)));
static inline bool