diff --git a/Documentation/asm-annotations.rst b/Documentation/asm-annotations.rst
new file mode 100644
index 000000000000..29ccd6e61fe5
--- /dev/null
+++ b/Documentation/asm-annotations.rst
@@ -0,0 +1,216 @@
+Assembler Annotations
+=====================
+
+Copyright (c) 2017-2019 Jiri Slaby
+
+This document describes the new macros for annotation of data and code in
+assembly. In particular, it contains information about ``SYM_FUNC_START``,
+``SYM_FUNC_END``, ``SYM_CODE_START``, and similar.
+
+Rationale
+---------
+Some code like entries, trampolines, or boot code needs to be written in
+assembly. The same as in C, such code is grouped into functions and
+accompanied with data. Standard assemblers do not force users into precisely
+marking these pieces as code, data, or even specifying their length.
+Nevertheless, assemblers provide developers with such annotations to aid
+debuggers throughout assembly. On top of that, developers also want to mark
+some functions as *global* in order to be visible outside of their translation
+units.
+
+Over time, the Linux kernel has adopted macros from various projects (like
+``binutils``) to facilitate such annotations. So for historic reasons,
+developers have been using ``ENTRY``, ``END``, ``ENDPROC``, and other
+annotations in assembly. Due to the lack of their documentation, the macros
+are used in rather wrong contexts at some locations. Clearly, ``ENTRY`` was
+intended to denote the beginning of global symbols (be it data or code).
+``END`` used to mark the end of data or end of special functions with
+*non-standard* calling convention. In contrast, ``ENDPROC`` should annotate
+only ends of *standard* functions.
+
+When these macros are used correctly, they help assemblers generate a nice
+object with both sizes and types set correctly. For example, the result of
+``arch/x86/lib/putuser.S``::
+
+ Num: Value Size Type Bind Vis Ndx Name
+ 25: 0000000000000000 33 FUNC GLOBAL DEFAULT 1 __put_user_1
+ 29: 0000000000000030 37 FUNC GLOBAL DEFAULT 1 __put_user_2
+ 32: 0000000000000060 36 FUNC GLOBAL DEFAULT 1 __put_user_4
+ 35: 0000000000000090 37 FUNC GLOBAL DEFAULT 1 __put_user_8
+
+This is not only important for debugging purposes. When there are properly
+annotated objects like this, tools can be run on them to generate more useful
+information. In particular, on properly annotated objects, ``objtool`` can be
+run to check and fix the object if needed. Currently, ``objtool`` can report
+missing frame pointer setup/destruction in functions. It can also
+automatically generate annotations for :doc:`ORC unwinder <x86/orc-unwinder>`
+for most code. Both of these are especially important to support reliable
+stack traces which are in turn necessary for :doc:`Kernel live patching
+<livepatch/livepatch>`.
+
+Caveat and Discussion
+---------------------
+As one might realize, there were only three macros previously. That is indeed
+insufficient to cover all the combinations of cases:
+
+* standard/non-standard function
+* code/data
+* global/local symbol
+
+There was a discussion_ and instead of extending the current ``ENTRY/END*``
+macros, it was decided that brand new macros should be introduced instead::
+
+ So how about using macro names that actually show the purpose, instead
+ of importing all the crappy, historic, essentially randomly chosen
+ debug symbol macro names from the binutils and older kernels?
+
+.. _discussion: https://lkml.kernel.org/r/20170217104757.28588-1-jslaby@suse.cz
+
+Macros Description
+------------------
+
+The new macros are prefixed with the ``SYM_`` prefix and can be divided into
+three main groups:
+
+1. ``SYM_FUNC_*`` -- to annotate C-like functions. This means functions with
+ standard C calling conventions, i.e. the stack contains a return address at
+ the predefined place and a return from the function can happen in a
+ standard way. When frame pointers are enabled, save/restore of frame
+ pointer shall happen at the start/end of a function, respectively, too.
+
+ Checking tools like ``objtool`` should ensure such marked functions conform
+ to these rules. The tools can also easily annotate these functions with
+ debugging information (like *ORC data*) automatically.
+
+2. ``SYM_CODE_*`` -- special functions called with special stack. Be it
+ interrupt handlers with special stack content, trampolines, or startup
+ functions.
+
+ Checking tools mostly ignore checking of these functions. But some debug
+ information still can be generated automatically. For correct debug data,
+ this code needs hints like ``UNWIND_HINT_REGS`` provided by developers.
+
+3. ``SYM_DATA*`` -- obviously data belonging to ``.data`` sections and not to
+ ``.text``. Data do not contain instructions, so they have to be treated
+ specially by the tools: they should not treat the bytes as instructions,
+ nor assign any debug information to them.
+
+Instruction Macros
+~~~~~~~~~~~~~~~~~~
+This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated above.
+
+* ``SYM_FUNC_START`` and ``SYM_FUNC_START_LOCAL`` are supposed to be **the
+ most frequent markings**. They are used for functions with standard calling
+ conventions -- global and local. Like in C, they both align the functions to
+ architecture specific ``__ALIGN`` bytes. There are also ``_NOALIGN`` variants
+ for special cases where developers do not want this implicit alignment.
+
+ ``SYM_FUNC_START_WEAK`` and ``SYM_FUNC_START_WEAK_NOALIGN`` markings are
+ also offered as an assembler counterpart to the *weak* attribute known from
+ C.
+
+ All of these **shall** be coupled with ``SYM_FUNC_END``. First, it marks
+ the sequence of instructions as a function and computes its size to the
+ generated object file. Second, it also eases checking and processing such
+ object files as the tools can trivially find exact function boundaries.
+
+ So in most cases, developers should write something like in the following
+ example, having some asm instructions in between the macros, of course::
+
+ SYM_FUNC_START(function_hook)
+ ... asm insns ...
+ SYM_FUNC_END(function_hook)
+
+ In fact, this kind of annotation corresponds to the now deprecated ``ENTRY``
+ and ``ENDPROC`` macros.
+
+* ``SYM_FUNC_START_ALIAS`` and ``SYM_FUNC_START_LOCAL_ALIAS`` serve for those
+ who decided to have two or more names for one function. The typical use is::
+
+ SYM_FUNC_START_ALIAS(__memset)
+ SYM_FUNC_START(memset)
+ ... asm insns ...
+ SYM_FUNC_END(memset)
+ SYM_FUNC_END_ALIAS(__memset)
+
+ In this example, one can call ``__memset`` or ``memset`` with the same
+ result, except the debug information for the instructions is generated to
+ the object file only once -- for the non-``ALIAS`` case.
+
+* ``SYM_CODE_START`` and ``SYM_CODE_START_LOCAL`` should be used only in
+ special cases -- if you know what you are doing. This is used exclusively
+ for interrupt handlers and similar where the calling convention is not the C
+ one. ``_NOALIGN`` variants exist too. The use is the same as for the ``FUNC``
+ category above::
+
+ SYM_CODE_START_LOCAL(bad_put_user)
+ ... asm insns ...
+ SYM_CODE_END(bad_put_user)
+
+ Again, every ``SYM_CODE_START*`` **shall** be coupled by ``SYM_CODE_END``.
+
+ To some extent, this category corresponds to deprecated ``ENTRY`` and
+ ``END``. Except ``END`` had several other meanings too.
+
+* ``SYM_INNER_LABEL*`` is used to denote a label inside some
+ ``SYM_{CODE,FUNC}_START`` and ``SYM_{CODE,FUNC}_END``. They are very similar
+ to C labels, except they can be made global. An example of use::
+
+ SYM_CODE_START(ftrace_caller)
+ /* save_mcount_regs fills in first two parameters */
+ ...
+
+ SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL)
+ /* Load the ftrace_ops into the 3rd parameter */
+ ...
+
+ SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
+ call ftrace_stub
+ ...
+ retq
+ SYM_CODE_END(ftrace_caller)
+
+Data Macros
+~~~~~~~~~~~
+Similar to instructions, there is a couple of macros to describe data in the
+assembly.
+
+* ``SYM_DATA_START`` and ``SYM_DATA_START_LOCAL`` mark the start of some data
+ and shall be used in conjunction with either ``SYM_DATA_END``, or
+ ``SYM_DATA_END_LABEL``. The latter adds also a label to the end, so that
+ people can use ``lstack`` and (local) ``lstack_end`` in the following
+ example::
+
+ SYM_DATA_START_LOCAL(lstack)
+ .skip 4096
+ SYM_DATA_END_LABEL(lstack, SYM_L_LOCAL, lstack_end)
+
+* ``SYM_DATA`` and ``SYM_DATA_LOCAL`` are variants for simple, mostly one-line
+ data::
+
+ SYM_DATA(HEAP, .long rm_heap)
+ SYM_DATA(heap_end, .long rm_stack)
+
+ In the end, they expand to ``SYM_DATA_START`` with ``SYM_DATA_END``
+ internally.
+
+Support Macros
+~~~~~~~~~~~~~~
+All the above reduce themselves to some invocation of ``SYM_START``,
+``SYM_END``, or ``SYM_ENTRY`` at last. Normally, developers should avoid using
+these.
+
+Further, in the above examples, one could see ``SYM_L_LOCAL``. There are also
+``SYM_L_GLOBAL`` and ``SYM_L_WEAK``. All are intended to denote linkage of a
+symbol marked by them. They are used either in ``_LABEL`` variants of the
+earlier macros, or in ``SYM_START``.
+
+
+Overriding Macros
+~~~~~~~~~~~~~~~~~
+Architecture can also override any of the macros in their own
+``asm/linkage.h``, including macros specifying the type of a symbol
+(``SYM_T_FUNC``, ``SYM_T_OBJECT``, and ``SYM_T_NONE``). As every macro
+described in this file is surrounded by ``#ifdef`` + ``#endif``, it is enough
+to define the macros differently in the aforementioned architecture-dependent
+header.
diff --git a/Documentation/index.rst b/Documentation/index.rst
index b843e313d2f2..2ceab197246f 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -135,6 +135,14 @@ needed).
mic/index
scheduler/index
+Architecture-agnostic documentation
+-----------------------------------
+
+.. toctree::
+ :maxdepth: 2
+
+ asm-annotations
+
Architecture-specific documentation
-----------------------------------
diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index 14caa9d9fb7f..e07188e8d763 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -13,9 +13,13 @@
#ifdef __ASSEMBLY__
-#define GLOBAL(name) \
- .globl name; \
- name:
+/*
+ * GLOBAL is DEPRECATED
+ *
+ * use SYM_DATA_START, SYM_FUNC_START, SYM_INNER_LABEL, SYM_CODE_START, or
+ * similar
+ */
+#define GLOBAL(name) SYM_ENTRY(name, SYM_L_GLOBAL, SYM_A_NONE)
#if defined(CONFIG_X86_64) || defined(CONFIG_X86_ALIGNMENT_16)
#define __ALIGN .p2align 4, 0x90
diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index 7e020782ade2..f3ae8f3dea2c 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -75,32 +75,58 @@
#ifdef __ASSEMBLY__
+/* SYM_T_FUNC -- type used by assembler to mark functions */
+#ifndef SYM_T_FUNC
+#define SYM_T_FUNC STT_FUNC
+#endif
+
+/* SYM_T_OBJECT -- type used by assembler to mark data */
+#ifndef SYM_T_OBJECT
+#define SYM_T_OBJECT STT_OBJECT
+#endif
+
+/* SYM_T_NONE -- type used by assembler to mark entries of unknown type */
+#ifndef SYM_T_NONE
+#define SYM_T_NONE STT_NOTYPE
+#endif
+
+/* SYM_A_* -- align the symbol? */
+#define SYM_A_ALIGN ALIGN
+#define SYM_A_NONE /* nothing */
+
+/* SYM_L_* -- linkage of symbols */
+#define SYM_L_GLOBAL(name) .globl name
+#define SYM_L_WEAK(name) .weak name
+#define SYM_L_LOCAL(name) /* nothing */
+
#ifndef LINKER_SCRIPT
#define ALIGN __ALIGN
#define ALIGN_STR __ALIGN_STR
+/* === DEPRECATED annotations === */
+
#ifndef GLOBAL
+/* deprecated, use SYM_DATA*, SYM_ENTRY, or similar */
#define GLOBAL(name) \
.globl name ASM_NL \
name:
#endif
#ifndef ENTRY
+/* deprecated, use SYM_FUNC_START */
#define ENTRY(name) \
- .globl name ASM_NL \
- ALIGN ASM_NL \
- name:
+ SYM_FUNC_START(name)
#endif
#endif /* LINKER_SCRIPT */
#ifndef WEAK
+/* deprecated, use SYM_FUNC_START_WEAK* */
#define WEAK(name) \
- .weak name ASM_NL \
- ALIGN ASM_NL \
- name:
+ SYM_FUNC_START_WEAK(name)
#endif
#ifndef END
+/* deprecated, use SYM_FUNC_END, SYM_DATA_END, or SYM_END */
#define END(name) \
.size name, .-name
#endif
@@ -110,11 +136,214 @@
* static analysis tools such as stack depth analyzer.
*/
#ifndef ENDPROC
+/* deprecated, use SYM_FUNC_END */
#define ENDPROC(name) \
- .type name, @function ASM_NL \
- END(name)
+ SYM_FUNC_END(name)
#endif
+/* === generic annotations === */
+
+/* SYM_ENTRY -- use only if you have to for non-paired symbols */
+#ifndef SYM_ENTRY
+#define SYM_ENTRY(name, linkage, align...) \
+ linkage(name) ASM_NL \
+ align ASM_NL \
+ name:
#endif
+/* SYM_START -- use only if you have to */
+#ifndef SYM_START
+#define SYM_START(name, linkage, align...) \
+ SYM_ENTRY(name, linkage, align)
#endif
+
+/* SYM_END -- use only if you have to */
+#ifndef SYM_END
+#define SYM_END(name, sym_type) \
+ .type name sym_type ASM_NL \
+ .size name, .-name
+#endif
+
+/* === code annotations === */
+
+/*
+ * FUNC -- C-like functions (proper stack frame etc.)
+ * CODE -- non-C code (e.g. irq handlers with different, special stack etc.)
+ *
+ * Objtool validates stack for FUNC, but not for CODE.
+ * Objtool generates debug info for both FUNC & CODE, but needs special
+ * annotations for each CODE's start (to describe the actual stack frame).
+ *
+ * ALIAS -- does not generate debug info -- the aliased function will
+ */
+
+/* SYM_INNER_LABEL_ALIGN -- only for labels in the middle of code */
+#ifndef SYM_INNER_LABEL_ALIGN
+#define SYM_INNER_LABEL_ALIGN(name, linkage) \
+ .type name SYM_T_NONE ASM_NL \
+ SYM_ENTRY(name, linkage, SYM_A_ALIGN)
+#endif
+
+/* SYM_INNER_LABEL -- only for labels in the middle of code */
+#ifndef SYM_INNER_LABEL
+#define SYM_INNER_LABEL(name, linkage) \
+ .type name SYM_T_NONE ASM_NL \
+ SYM_ENTRY(name, linkage, SYM_A_NONE)
+#endif
+
+/*
+ * SYM_FUNC_START_LOCAL_ALIAS -- use where there are two local names for one
+ * function
+ */
+#ifndef SYM_FUNC_START_LOCAL_ALIAS
+#define SYM_FUNC_START_LOCAL_ALIAS(name) \
+ SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)
+#endif
+
+/*
+ * SYM_FUNC_START_ALIAS -- use where there are two global names for one
+ * function
+ */
+#ifndef SYM_FUNC_START_ALIAS
+#define SYM_FUNC_START_ALIAS(name) \
+ SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_START -- use for global functions */
+#ifndef SYM_FUNC_START
+/*
+ * The same as SYM_FUNC_START_ALIAS, but we will need to distinguish these two
+ * later.
+ */
+#define SYM_FUNC_START(name) \
+ SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment */
+#ifndef SYM_FUNC_START_NOALIGN
+#define SYM_FUNC_START_NOALIGN(name) \
+ SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)
+#endif
+
+/* SYM_FUNC_START_LOCAL -- use for local functions */
+#ifndef SYM_FUNC_START_LOCAL
+/* the same as SYM_FUNC_START_LOCAL_ALIAS, see comment near SYM_FUNC_START */
+#define SYM_FUNC_START_LOCAL(name) \
+ SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o alignment */
+#ifndef SYM_FUNC_START_LOCAL_NOALIGN
+#define SYM_FUNC_START_LOCAL_NOALIGN(name) \
+ SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)
+#endif
+
+/* SYM_FUNC_START_WEAK -- use for weak functions */
+#ifndef SYM_FUNC_START_WEAK
+#define SYM_FUNC_START_WEAK(name) \
+ SYM_START(name, SYM_L_WEAK, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment */
+#ifndef SYM_FUNC_START_WEAK_NOALIGN
+#define SYM_FUNC_START_WEAK_NOALIGN(name) \
+ SYM_START(name, SYM_L_WEAK, SYM_A_NONE)
+#endif
+
+/* SYM_FUNC_END_ALIAS -- the end of LOCAL_ALIASed or ALIASed function */
+#ifndef SYM_FUNC_END_ALIAS
+#define SYM_FUNC_END_ALIAS(name) \
+ SYM_END(name, SYM_T_FUNC)
+#endif
+
+/*
+ * SYM_FUNC_END -- the end of SYM_FUNC_START_LOCAL, SYM_FUNC_START,
+ * SYM_FUNC_START_WEAK, ...
+ */
+#ifndef SYM_FUNC_END
+/* the same as SYM_FUNC_END_ALIAS, see comment near SYM_FUNC_START */
+#define SYM_FUNC_END(name) \
+ SYM_END(name, SYM_T_FUNC)
+#endif
+
+/* SYM_CODE_START -- use for non-C (special) functions */
+#ifndef SYM_CODE_START
+#define SYM_CODE_START(name) \
+ SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)
+#endif
+
+/* SYM_CODE_START_NOALIGN -- use for non-C (special) functions, w/o alignment */
+#ifndef SYM_CODE_START_NOALIGN
+#define SYM_CODE_START_NOALIGN(name) \
+ SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)
+#endif
+
+/* SYM_CODE_START_LOCAL -- use for local non-C (special) functions */
+#ifndef SYM_CODE_START_LOCAL
+#define SYM_CODE_START_LOCAL(name) \
+ SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)
+#endif
+
+/*
+ * SYM_CODE_START_LOCAL_NOALIGN -- use for local non-C (special) functions,
+ * w/o alignment
+ */
+#ifndef SYM_CODE_START_LOCAL_NOALIGN
+#define SYM_CODE_START_LOCAL_NOALIGN(name) \
+ SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)
+#endif
+
+/* SYM_CODE_END -- the end of SYM_CODE_START_LOCAL, SYM_CODE_START, ... */
+#ifndef SYM_CODE_END
+#define SYM_CODE_END(name) \
+ SYM_END(name, SYM_T_NONE)
+#endif
+
+/* === data annotations === */
+
+/* SYM_DATA_START -- global data symbol */
+#ifndef SYM_DATA_START
+#define SYM_DATA_START(name) \
+ SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)
+#endif
+
+/* SYM_DATA_START -- local data symbol */
+#ifndef SYM_DATA_START_LOCAL
+#define SYM_DATA_START_LOCAL(name) \
+ SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)
+#endif
+
+/* SYM_DATA_END -- the end of SYM_DATA_START symbol */
+#ifndef SYM_DATA_END
+#define SYM_DATA_END(name) \
+ SYM_END(name, SYM_T_OBJECT)
+#endif
+
+/* SYM_DATA_END_LABEL -- the labeled end of SYM_DATA_START symbol */
+#ifndef SYM_DATA_END_LABEL
+#define SYM_DATA_END_LABEL(name, linkage, label) \
+ linkage(label) ASM_NL \
+ .type label SYM_T_OBJECT ASM_NL \
+ label: \
+ SYM_END(name, SYM_T_OBJECT)
+#endif
+
+/* SYM_DATA -- start+end wrapper around simple global data */
+#ifndef SYM_DATA
+#define SYM_DATA(name, data...) \
+ SYM_DATA_START(name) ASM_NL \
+ data ASM_NL \
+ SYM_DATA_END(name)
+#endif
+
+/* SYM_DATA_LOCAL -- start+end wrapper around simple local data */
+#ifndef SYM_DATA_LOCAL
+#define SYM_DATA_LOCAL(name, data...) \
+ SYM_DATA_START_LOCAL(name) ASM_NL \
+ data ASM_NL \
+ SYM_DATA_END(name)
+#endif
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _LINUX_LINKAGE_H */