Merge branch 'devel-stable' into for-next

Kernel-provided User Helpers

============================

These are segment of kernel provided user code reachable from user space

at a fixed address in kernel memory.  This is used to provide user space

with some operations which require kernel help because of unimplemented

native feature and/or instructions in many ARM CPUs. The idea is for this

code to be executed directly in user mode for best efficiency but which is

too intimate with the kernel counter part to be left to user libraries.

In fact this code might even differ from one CPU to another depending on

the available instruction set, or whether it is a SMP systems. In other

words, the kernel reserves the right to change this code as needed without

warning. Only the entry points and their results as documented here are

guaranteed to be stable.

This is different from (but doesn't preclude) a full blown VDSO

implementation, however a VDSO would prevent some assembly tricks with

constants that allows for efficient branching to those code segments. And

since those code segments only use a few cycles before returning to user

code, the overhead of a VDSO indirect far call would add a measurable

overhead to such minimalistic operations.

User space is expected to bypass those helpers and implement those things

inline (either in the code emitted directly by the compiler, or part of

the implementation of a library call) when optimizing for a recent enough

processor that has the necessary native support, but only if resulting

binaries are already to be incompatible with earlier ARM processors due to

useage of similar native instructions for other things.  In other words

don't make binaries unable to run on earlier processors just for the sake

of not using these kernel helpers if your compiled code is not going to

use new instructions for other purpose.

New helpers may be added over time, so an older kernel may be missing some

helpers present in a newer kernel.  For this reason, programs must check

the value of __kuser_helper_version (see below) before assuming that it is

safe to call any particular helper.  This check should ideally be

performed only once at process startup time, and execution aborted early

if the required helpers are not provided by the kernel version that

process is running on.

kuser_helper_version

--------------------

Location:	0xffff0ffc

Reference declaration:

  extern int32_t __kuser_helper_version;

Definition:

  This field contains the number of helpers being implemented by the

  running kernel.  User space may read this to determine the availability

  of a particular helper.

Usage example:

#define __kuser_helper_version (*(int32_t *)0xffff0ffc)

void check_kuser_version(void)

{

	if (__kuser_helper_version < 2) {

		fprintf(stderr, "can't do atomic operations, kernel too old\n");

		abort();

	}

}

Notes:

  User space may assume that the value of this field never changes

  during the lifetime of any single process.  This means that this

  field can be read once during the initialisation of a library or

  startup phase of a program.

kuser_get_tls

-------------

Location:	0xffff0fe0

Reference prototype:

  void * __kuser_get_tls(void);

Input:

  lr = return address

Output:

  r0 = TLS value

Clobbered registers:

  none

Definition:

  Get the TLS value as previously set via the __ARM_NR_set_tls syscall.

Usage example:

typedef void * (__kuser_get_tls_t)(void);

#define __kuser_get_tls (*(__kuser_get_tls_t *)0xffff0fe0)

void foo()

{

	void *tls = __kuser_get_tls();

	printf("TLS = %p\n", tls);

}

Notes:

  - Valid only if __kuser_helper_version >= 1 (from kernel version 2.6.12).

kuser_cmpxchg

-------------

Location:	0xffff0fc0

Reference prototype:

  int __kuser_cmpxchg(int32_t oldval, int32_t newval, volatile int32_t *ptr);

Input:

  r0 = oldval

  r1 = newval

  r2 = ptr

  lr = return address

Output:

  r0 = success code (zero or non-zero)

  C flag = set if r0 == 0, clear if r0 != 0

Clobbered registers:

  r3, ip, flags

Definition:

  Atomically store newval in *ptr only if *ptr is equal to oldval.

  Return zero if *ptr was changed or non-zero if no exchange happened.

  The C flag is also set if *ptr was changed to allow for assembly

  optimization in the calling code.

Usage example:

typedef int (__kuser_cmpxchg_t)(int oldval, int newval, volatile int *ptr);

#define __kuser_cmpxchg (*(__kuser_cmpxchg_t *)0xffff0fc0)

int atomic_add(volatile int *ptr, int val)

{

	int old, new;

	do {

		old = *ptr;

		new = old + val;

	} while(__kuser_cmpxchg(old, new, ptr));

	return new;

}

Notes:

  - This routine already includes memory barriers as needed.

  - Valid only if __kuser_helper_version >= 2 (from kernel version 2.6.12).

kuser_memory_barrier

--------------------

Location:	0xffff0fa0

Reference prototype:

  void __kuser_memory_barrier(void);

Input:

  lr = return address

Output:

  none

Clobbered registers:

  none

Definition:

  Apply any needed memory barrier to preserve consistency with data modified

  manually and __kuser_cmpxchg usage.

Usage example:

typedef void (__kuser_dmb_t)(void);

#define __kuser_dmb (*(__kuser_dmb_t *)0xffff0fa0)

Notes:

  - Valid only if __kuser_helper_version >= 3 (from kernel version 2.6.15).

kuser_cmpxchg64

---------------

Location:	0xffff0f60

Reference prototype:

  int __kuser_cmpxchg64(const int64_t *oldval,

                        const int64_t *newval,

                        volatile int64_t *ptr);

Input:

  r0 = pointer to oldval

  r1 = pointer to newval

  r2 = pointer to target value

  lr = return address

Output:

  r0 = success code (zero or non-zero)

  C flag = set if r0 == 0, clear if r0 != 0

Clobbered registers:

  r3, lr, flags

Definition:

  Atomically store the 64-bit value pointed by *newval in *ptr only if *ptr

  is equal to the 64-bit value pointed by *oldval.  Return zero if *ptr was

  changed or non-zero if no exchange happened.

  The C flag is also set if *ptr was changed to allow for assembly

  optimization in the calling code.

Usage example:

typedef int (__kuser_cmpxchg64_t)(const int64_t *oldval,

                                  const int64_t *newval,

                                  volatile int64_t *ptr);

#define __kuser_cmpxchg64 (*(__kuser_cmpxchg64_t *)0xffff0f60)

int64_t atomic_add64(volatile int64_t *ptr, int64_t val)

{

	int64_t old, new;

	do {

		old = *ptr;

		new = old + val;

	} while(__kuser_cmpxchg64(&old, &new, ptr));

	return new;

}

Notes:

  - This routine already includes memory barriers as needed.

  - Due to the length of this sequence, this spans 2 conventional kuser

    "slots", therefore 0xffff0f80 is not used as a valid entry point.

  - Valid only if __kuser_helper_version >= 5 (from kernel version 3.1).

	select GENERIC_ATOMIC64 if (CPU_V6 || !CPU_32v6K || !AEABI)

	select HAVE_OPROFILE if (HAVE_PERF_EVENTS)

	select HAVE_ARCH_KGDB

	select HAVE_KPROBES if (!XIP_KERNEL && !THUMB2_KERNEL)

	select HAVE_KPROBES if !XIP_KERNEL

	select HAVE_KRETPROBES if (HAVE_KPROBES)

	select HAVE_FUNCTION_TRACER if (!XIP_KERNEL)

	select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL)

	.macro	ldrusr, reg, ptr, inc, cond=al, rept=1, abort=9001f

	usracc	ldr, \reg, \ptr, \inc, \cond, \rept, \abort

	.endm

/* Utility macro for declaring string literals */

	.macro	string name:req, string

	.type \name , #object

\name:

	.asciz "\string"

	.size \name , . - \name

	.endm

#endif /* __ASM_ASSEMBLER_H__ */

#ifndef __ASM_ARM_DMA_H

#define __ASM_ARM_DMA_H

#include <asm/memory.h>

/*

 * This is the maximum virtual address which can be DMA'd from.

 */

#ifndef ARM_DMA_ZONE_SIZE

#define MAX_DMA_ADDRESS	0xffffffff

#ifndef CONFIG_ZONE_DMA

#define MAX_DMA_ADDRESS	0xffffffffUL

#else

#define MAX_DMA_ADDRESS	(PAGE_OFFSET + ARM_DMA_ZONE_SIZE)

#define MAX_DMA_ADDRESS	({ \

	extern unsigned long arm_dma_zone_size; \

	arm_dma_zone_size ? \

		(PAGE_OFFSET + arm_dma_zone_size) : 0xffffffffUL; })

#endif

#ifdef CONFIG_ISA_DMA_API

/*

 * HWCAP flags - for elf_hwcap (in kernel) and AT_HWCAP

 */

#define HWCAP_SWP	1

#define HWCAP_HALF	2

#define HWCAP_THUMB	4

#define HWCAP_26BIT	8	/* Play it safe */

#define HWCAP_FAST_MULT	16

#define HWCAP_FPA	32

#define HWCAP_VFP	64

#define HWCAP_EDSP	128

#define HWCAP_JAVA	256

#define HWCAP_IWMMXT	512

#define HWCAP_CRUNCH	1024

#define HWCAP_THUMBEE	2048

#define HWCAP_NEON	4096

#define HWCAP_VFPv3	8192

#define HWCAP_VFPv3D16	16384

#define HWCAP_TLS	32768

#define HWCAP_SWP	(1 << 0)

#define HWCAP_HALF	(1 << 1)

#define HWCAP_THUMB	(1 << 2)

#define HWCAP_26BIT	(1 << 3)	/* Play it safe */

#define HWCAP_FAST_MULT	(1 << 4)

#define HWCAP_FPA	(1 << 5)

#define HWCAP_VFP	(1 << 6)

#define HWCAP_EDSP	(1 << 7)

#define HWCAP_JAVA	(1 << 8)

#define HWCAP_IWMMXT	(1 << 9)

#define HWCAP_CRUNCH	(1 << 10)

#define HWCAP_THUMBEE	(1 << 11)

#define HWCAP_NEON	(1 << 12)

#define HWCAP_VFPv3	(1 << 13)

#define HWCAP_VFPv3D16	(1 << 14)

#define HWCAP_TLS	(1 << 15)

#define HWCAP_VFPv4	(1 << 16)

#define HWCAP_IDIVA	(1 << 17)

#define HWCAP_IDIVT	(1 << 18)

#define HWCAP_IDIV	(HWCAP_IDIVA | HWCAP_IDIVT)

#if defined(__KERNEL__) && !defined(__ASSEMBLY__)

/*