This patch defines a prctl uAPI for switching the active memory consistency model of user-space processes. The implementation follows the way other prctl calls are implemented by disabling them unless arch-specific code provides the relevant macros. Signed-off-by: Christoph Müllner <christoph.muellner@xxxxxxxx> --- .../mm/dynamic-memory-consistency-model.rst | 27 +++++++++++++++++++ include/uapi/linux/prctl.h | 3 +++ kernel/sys.c | 12 +++++++++ 3 files changed, 42 insertions(+) diff --git a/Documentation/mm/dynamic-memory-consistency-model.rst b/Documentation/mm/dynamic-memory-consistency-model.rst index 3117c3d82b2b..1fce855a1fad 100644 --- a/Documentation/mm/dynamic-memory-consistency-model.rst +++ b/Documentation/mm/dynamic-memory-consistency-model.rst @@ -47,3 +47,30 @@ at run-time: * Only switching from a weaker to a stronger model is safe. * The stronger memory model affects all threads of a process, when running in user mode. * Forked processes derive their active memory model from their parents. + +User API via prctl +================== + +Two prctl calls are defined to get/set the active memory consistency model: + +* prctl(PR_GET_MEMORY_CONSISTENCY_MODEL) + + Returns the active memory consistency model for the calling process/thread. + If the architecture does not support dynamic memory consistency models, + then -1 is returned, and errno is set to EINVAL. + +* prctl(PR_SET_MEMORY_CONSISTENCY_MODEL, unsigned long new_model) + + Switches the memory consistency model for the calling process/thread + to the given model. If the architecture does not support dynamic + memory consistency models, or does not support the provided model, or + does not allow to switch to the proveided model then -1 is returned, + and errno is set to EINVAL. + +Supported memory consistency models +=================================== + +This section defines the memory consistency models which are supported +by the prctl interface. + +<none> diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 370ed14b1ae0..579662731eaa 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -306,4 +306,7 @@ struct prctl_mm_map { # define PR_RISCV_V_VSTATE_CTRL_NEXT_MASK 0xc # define PR_RISCV_V_VSTATE_CTRL_MASK 0x1f +#define PR_SET_MEMORY_CONSISTENCY_MODEL 71 +#define PR_GET_MEMORY_CONSISTENCY_MODEL 72 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index e219fcfa112d..a1b92a38f889 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -146,6 +146,12 @@ #ifndef RISCV_V_GET_CONTROL # define RISCV_V_GET_CONTROL() (-EINVAL) #endif +#ifndef SET_MEMORY_CONSISTENCY_MODEL +# define SET_MEMORY_CONSISTENCY_MODEL(a) (-EINVAL) +#endif +#ifndef GET_MEMORY_CONSISTENCY_MODEL +# define GET_MEMORY_CONSISTENCY_MODEL() (-EINVAL) +#endif /* * this is where the system-wide overflow UID and GID are defined, for @@ -2743,6 +2749,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_RISCV_V_GET_CONTROL: error = RISCV_V_GET_CONTROL(); break; + case PR_SET_MEMORY_CONSISTENCY_MODEL: + error = SET_MEMORY_CONSISTENCY_MODEL(arg2); + break; + case PR_GET_MEMORY_CONSISTENCY_MODEL: + error = GET_MEMORY_CONSISTENCY_MODEL(); + break; default: error = -EINVAL; break; -- 2.43.0