Commit 974802ea authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: Add forward/backward attribute ABI compatibility 



Provide for means of extending the perf_counter_attr in a 'natural' way.

We allow growing the structure by appending fields at the end by specifying
the full structure size inside it.

When a new kernel sees a smaller (old) structure, it will 0 pad the tail.
When an old kernel sees a larger (new) structure, it will verify the tail
consists of 0s, otherwise fail.

If we fail due to a size-mismatch, we return -E2BIG and write the kernel's
native attribe size back into the provided structure.

Furthermore, add some attribute verification, so that we'll fail counter
creation when unknown bits are present (PERF_SAMPLE, PERF_FORMAT, or in
the __reserved fields).

(This ABI detail is introduced while keeping the existing syscall ABI.)

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent bbd36e5e

include/linux/perf_counter.h

+15 −4
Original line number Diff line number Diff line
@@ -120,6 +120,8 @@ enum perf_counter_sample_format { 
	PERF_SAMPLE_ID				= 1U << 6,

	PERF_SAMPLE_CPU				= 1U << 7,

	PERF_SAMPLE_PERIOD			= 1U << 8,



	PERF_SAMPLE_MAX = 1U << 9,		/* non-ABI */

};



/*
@@ -131,17 +133,26 @@ enum perf_counter_read_format { 
	PERF_FORMAT_TOTAL_TIME_ENABLED		= 1U << 0,

	PERF_FORMAT_TOTAL_TIME_RUNNING		= 1U << 1,

	PERF_FORMAT_ID				= 1U << 2,



	PERF_FORMAT_MAX = 1U << 3, 		/* non-ABI */

};



#define PERF_ATTR_SIZE_VER0	64	/* sizeof first published struct */



/*

 * Hardware event to monitor via a performance monitoring counter:

 */

struct perf_counter_attr {



	/*

	 * Major type: hardware/software/tracepoint/etc.

	 */

	__u32			type;

	__u32			__reserved_1;



	/*

	 * Size of the attr structure, for fwd/bwd compat.

	 */

	__u32			size;



	/*

	 * Type specific configuration information.
@@ -168,12 +179,12 @@ struct perf_counter_attr { 
				comm	       :  1, /* include comm data     */

				freq           :  1, /* use freq, not period  */



				__reserved_2   : 53;

				__reserved_1   : 53;



	__u32			wakeup_events;	/* wakeup every n events */

	__u32			__reserved_3;

	__u32			__reserved_2;



	__u64			__reserved_4;

	__u64			__reserved_3;

};



/*

include/linux/syscalls.h

+1 −1
Original line number Diff line number Diff line
@@ -758,6 +758,6 @@ int kernel_execve(const char *filename, char *const argv[], char *const envp[]); 




asmlinkage long sys_perf_counter_open(

		const struct perf_counter_attr __user *attr_uptr,

		struct perf_counter_attr __user *attr_uptr,

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

#endif

kernel/perf_counter.c

+86 −3
Original line number Diff line number Diff line
@@ -3584,6 +3584,9 @@ perf_counter_alloc(struct perf_counter_attr *attr, 
	case PERF_TYPE_TRACEPOINT:

		pmu = tp_perf_counter_init(counter);

		break;



	default:

		break;

	}

done:

	err = 0;
@@ -3610,6 +3613,85 @@ done: 
	return counter;

}



static int perf_copy_attr(struct perf_counter_attr __user *uattr,

			  struct perf_counter_attr *attr)

{

	int ret;

	u32 size;



	if (!access_ok(VERIFY_WRITE, uattr, PERF_ATTR_SIZE_VER0))

		return -EFAULT;



	/*

	 * zero the full structure, so that a short copy will be nice.

	 */

	memset(attr, 0, sizeof(*attr));



	ret = get_user(size, &uattr->size);

	if (ret)

		return ret;



	if (size > PAGE_SIZE)	/* silly large */

		goto err_size;



	if (!size)		/* abi compat */

		size = PERF_ATTR_SIZE_VER0;



	if (size < PERF_ATTR_SIZE_VER0)

		goto err_size;



	/*

	 * If we're handed a bigger struct than we know of,

	 * ensure all the unknown bits are 0.

	 */

	if (size > sizeof(*attr)) {

		unsigned long val;

		unsigned long __user *addr;

		unsigned long __user *end;



		addr = PTR_ALIGN((void __user *)uattr + sizeof(*attr),

				sizeof(unsigned long));

		end  = PTR_ALIGN((void __user *)uattr + size,

				sizeof(unsigned long));



		for (; addr < end; addr += sizeof(unsigned long)) {

			ret = get_user(val, addr);

			if (ret)

				return ret;

			if (val)

				goto err_size;

		}

	}



	ret = copy_from_user(attr, uattr, size);

	if (ret)

		return -EFAULT;



	/*

	 * If the type exists, the corresponding creation will verify

	 * the attr->config.

	 */

	if (attr->type >= PERF_TYPE_MAX)

		return -EINVAL;



	if (attr->__reserved_1 || attr->__reserved_2 || attr->__reserved_3)

		return -EINVAL;



	if (attr->sample_type & ~(PERF_SAMPLE_MAX-1))

		return -EINVAL;



	if (attr->read_format & ~(PERF_FORMAT_MAX-1))

		return -EINVAL;



out:

	return ret;



err_size:

	put_user(sizeof(*attr), &uattr->size);

	ret = -E2BIG;

	goto out;

}



/**

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

 *
@@ -3619,7 +3701,7 @@ done: 
 * @group_fd:		group leader counter fd

 */

SYSCALL_DEFINE5(perf_counter_open,

		const struct perf_counter_attr __user *, attr_uptr,

		struct perf_counter_attr __user *, attr_uptr,

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

{

	struct perf_counter *counter, *group_leader;
@@ -3635,8 +3717,9 @@ SYSCALL_DEFINE5(perf_counter_open, 
	if (flags)

		return -EINVAL;



	if (copy_from_user(&attr, attr_uptr, sizeof(attr)) != 0)

		return -EFAULT;

	ret = perf_copy_attr(attr_uptr, &attr);

	if (ret)

		return ret;



	if (!attr.exclude_kernel) {

		if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))

tools/perf/perf.h

+3 −2
Original line number Diff line number Diff line
@@ -53,11 +53,12 @@ static inline unsigned long long rdclock(void) 
	_min1 < _min2 ? _min1 : _min2; })



static inline int

sys_perf_counter_open(struct perf_counter_attr *attr_uptr,

sys_perf_counter_open(struct perf_counter_attr *attr,

		      pid_t pid, int cpu, int group_fd,

		      unsigned long flags)

{

	return syscall(__NR_perf_counter_open, attr_uptr, pid, cpu,

	attr->size = sizeof(*attr);

	return syscall(__NR_perf_counter_open, attr, pid, cpu,

		       group_fd, flags);

}

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