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Commit 2743a5b0 authored by Paul Mackerras's avatar Paul Mackerras
Browse files

perfcounters: provide expansion room in the ABI 



Impact: ABI change

This expands several fields in the perf_counter_hw_event struct and adds
a "flags" argument to the perf_counter_open system call, in order that
features can be added in future without ABI changes.

In particular the record_type field is expanded to 64 bits, and the
space for flag bits has been expanded from 32 to 64 bits.

This also adds some new fields:

* read_format (64 bits) is intended to provide a way to specify what
  userspace wants to get back when it does a read() on a simple
  (non-interrupting) counter;

* exclude_idle (1 bit) provides a way for userspace to ask that events
  that occur when the cpu is idle be excluded;

* extra_config_len will provide a way for userspace to supply an
  arbitrary amount of extra machine-specific PMU configuration data
  immediately following the perf_counter_hw_event struct, to allow
  sophisticated users to program things such as instruction matching
  CAMs and address range registers;

* __reserved_3 and __reserved_4 provide space for future expansion.

Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent a1ef58f4

include/linux/perf_counter.h

+9 −3
Original line number Diff line number Diff line
@@ -69,9 +69,10 @@ struct perf_counter_hw_event { 
	__s64			type;



	__u64			irq_period;

	__u32			record_type;

	__u64			record_type;

	__u64			read_format;



	__u32			disabled       :  1, /* off by default        */

	__u64			disabled       :  1, /* off by default        */

				nmi	       :  1, /* NMI sampling          */

				raw	       :  1, /* raw event type        */

				inherit	       :  1, /* children inherit it   */
@@ -80,10 +81,15 @@ struct perf_counter_hw_event { 
				exclude_user   :  1, /* don't count user      */

				exclude_kernel :  1, /* ditto kernel          */

				exclude_hv     :  1, /* ditto hypervisor      */

				exclude_idle   :  1, /* don't count when idle */



				__reserved_1 : 23;

				__reserved_1 : 55;



	__u32			extra_config_len;

	__u32			__reserved_4;



	__u64			__reserved_2;

	__u64			__reserved_3;

};



/*

include/linux/syscalls.h

+1 −1
Original line number Diff line number Diff line
@@ -698,5 +698,5 @@ int kernel_execve(const char *filename, char *const argv[], char *const envp[]); 


asmlinkage long sys_perf_counter_open(

		const struct perf_counter_hw_event __user *hw_event_uptr,

		pid_t pid, int cpu, int group_fd);

		pid_t pid, int cpu, int group_fd, unsigned long flags);

#endif

kernel/perf_counter.c

+7 −3
Original line number Diff line number Diff line
@@ -1683,16 +1683,16 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event, 
}



/**

 * sys_perf_task_open - open a performance counter, associate it to a task/cpu

 * sys_perf_counter_open - open a performance counter, associate it to a task/cpu

 *

 * @hw_event_uptr:	event type attributes for monitoring/sampling

 * @pid:		target pid

 * @cpu:		target cpu

 * @group_fd:		group leader counter fd

 */

SYSCALL_DEFINE4(perf_counter_open,

SYSCALL_DEFINE5(perf_counter_open,

		const struct perf_counter_hw_event __user *, hw_event_uptr,

		pid_t, pid, int, cpu, int, group_fd)

		pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)

{

	struct perf_counter *counter, *group_leader;

	struct perf_counter_hw_event hw_event;
@@ -1703,6 +1703,10 @@ SYSCALL_DEFINE4(perf_counter_open, 
	int fput_needed2 = 0;

	int ret;



	/* for future expandability... */

	if (flags)

		return -EINVAL;



	if (copy_from_user(&hw_event, hw_event_uptr, sizeof(hw_event)) != 0)

		return -EFAULT;