---

yaml
---
r: 258406
b: refs/heads/master
c: 07f1c29
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: fb89fcfb151698776be6c900aec8161b01990e92
+refs/heads/master: 07f1c295de593ec0b0dca3092299c048c03374da

trunk/CREDITS

@@ -518,7 +518,7 @@ N: Zach Brown
 E: zab@zabbo.net
 D: maestro pci sound
 
-M: David Brownell
+N: David Brownell
 D: Kernel engineer, mentor, and friend.  Maintained USB EHCI and
 D: gadget layers, SPI subsystem, GPIO subsystem, and more than a few
 D: device drivers.  His encouragement also helped many engineers get

trunk/Documentation/Changes

@@ -2,13 +2,7 @@ Intro
 =====
 
 This document is designed to provide a list of the minimum levels of
-software necessary to run the 2.6 kernels, as well as provide brief
-instructions regarding any other "Gotchas" users may encounter when
-trying life on the Bleeding Edge.  If upgrading from a pre-2.4.x
-kernel, please consult the Changes file included with 2.4.x kernels for
-additional information; most of that information will not be repeated
-here.  Basically, this document assumes that your system is already
-functional and running at least 2.4.x kernels.
+software necessary to run the 3.0 kernels.
 
 This document is originally based on my "Changes" file for 2.0.x kernels
 and therefore owes credit to the same people as that file (Jared Mauch,
@@ -22,11 +16,10 @@ Upgrade to at *least* these software revisions before thinking you've
 encountered a bug!  If you're unsure what version you're currently
 running, the suggested command should tell you.
 
-Again, keep in mind that this list assumes you are already
-functionally running a Linux 2.4 kernel.  Also, not all tools are
-necessary on all systems; obviously, if you don't have any ISDN
-hardware, for example, you probably needn't concern yourself with
-isdn4k-utils.
+Again, keep in mind that this list assumes you are already functionally
+running a Linux kernel.  Also, not all tools are necessary on all
+systems; obviously, if you don't have any ISDN hardware, for example,
+you probably needn't concern yourself with isdn4k-utils.
 
 o  Gnu C                  3.2                     # gcc --version
 o  Gnu make               3.80                    # make --version
@@ -114,12 +107,12 @@ Ksymoops
 
 If the unthinkable happens and your kernel oopses, you may need the
 ksymoops tool to decode it, but in most cases you don't.
-In the 2.6 kernel it is generally preferred to build the kernel with
-CONFIG_KALLSYMS so that it produces readable dumps that can be used as-is
-(this also produces better output than ksymoops).
-If for some reason your kernel is not build with CONFIG_KALLSYMS and
-you have no way to rebuild and reproduce the Oops with that option, then
-you can still decode that Oops with ksymoops.
+It is generally preferred to build the kernel with CONFIG_KALLSYMS so
+that it produces readable dumps that can be used as-is (this also
+produces better output than ksymoops).  If for some reason your kernel
+is not build with CONFIG_KALLSYMS and you have no way to rebuild and
+reproduce the Oops with that option, then you can still decode that Oops
+with ksymoops.
 
 Module-Init-Tools
 -----------------
@@ -261,8 +254,8 @@ needs to be recompiled or (preferably) upgraded.
 NFS-utils
 ---------
 
-In 2.4 and earlier kernels, the nfs server needed to know about any
-client that expected to be able to access files via NFS.  This
+In ancient (2.4 and earlier) kernels, the nfs server needed to know
+about any client that expected to be able to access files via NFS.  This
 information would be given to the kernel by "mountd" when the client
 mounted the filesystem, or by "exportfs" at system startup.  exportfs
 would take information about active clients from /var/lib/nfs/rmtab.
@@ -272,11 +265,11 @@ which is not always easy, particularly when trying to implement
 fail-over.  Even when the system is working well, rmtab suffers from
 getting lots of old entries that never get removed.
 
-With 2.6 we have the option of having the kernel tell mountd when it
-gets a request from an unknown host, and mountd can give appropriate
-export information to the kernel.  This removes the dependency on
-rmtab and means that the kernel only needs to know about currently
-active clients.
+With modern kernels we have the option of having the kernel tell mountd
+when it gets a request from an unknown host, and mountd can give
+appropriate export information to the kernel.  This removes the
+dependency on rmtab and means that the kernel only needs to know about
+currently active clients.
 
 To enable this new functionality, you need to:
 

trunk/Documentation/CodingStyle

@@ -680,8 +680,8 @@ ones already enabled by DEBUG.
 		Chapter 14: Allocating memory
 
 The kernel provides the following general purpose memory allocators:
-kmalloc(), kzalloc(), kcalloc(), and vmalloc().  Please refer to the API
-documentation for further information about them.
+kmalloc(), kzalloc(), kcalloc(), vmalloc(), and vzalloc().  Please refer to
+the API documentation for further information about them.
 
 The preferred form for passing a size of a struct is the following:
 

trunk/Documentation/arm/kernel_user_helpers.txt

@@ -0,0 +1,267 @@
+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).