From 74a3c2aefe04f381ca14d0e589c62edd4af94b4c Mon Sep 17 00:00:00 2001 From: Eric Lin Date: Thu, 11 Aug 2022 17:15:16 +0800 Subject: Documentation: irqdomain: Fix typo of "at least once" Signed-off-by: Eric Lin Link: https://lore.kernel.org/r/20220811091516.2107908-1-dslin1010@gmail.com Signed-off-by: Jonathan Corbet --- Documentation/core-api/irq/irq-domain.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'Documentation/core-api') diff --git a/Documentation/core-api/irq/irq-domain.rst b/Documentation/core-api/irq/irq-domain.rst index d30b4d0a9769..f88a6ee67a35 100644 --- a/Documentation/core-api/irq/irq-domain.rst +++ b/Documentation/core-api/irq/irq-domain.rst @@ -71,7 +71,7 @@ variety of methods: Note that irq domain lookups must happen in contexts that are compatible with a RCU read-side critical section. -The irq_create_mapping() function must be called *atleast once* +The irq_create_mapping() function must be called *at least once* before any call to irq_find_mapping(), lest the descriptor will not be allocated. -- cgit v1.2.3 From d2bef8e1037cc69695c6b146bb05ce053450e0de Mon Sep 17 00:00:00 2001 From: Akhil Raj Date: Sat, 27 Aug 2022 20:23:59 +0530 Subject: Remove duplicate words inside documentation I have removed repeated `the` inside the documentation Signed-off-by: Akhil Raj Link: https://lore.kernel.org/r/20220827145359.32599-1-lf32.dev@gmail.com Signed-off-by: Jonathan Corbet --- Documentation/admin-guide/kdump/vmcoreinfo.rst | 2 +- Documentation/bpf/map_cgroup_storage.rst | 4 ++-- Documentation/core-api/cpu_hotplug.rst | 2 +- Documentation/driver-api/isa.rst | 2 +- Documentation/filesystems/caching/backend-api.rst | 2 +- Documentation/locking/seqlock.rst | 2 +- 6 files changed, 7 insertions(+), 7 deletions(-) (limited to 'Documentation/core-api') diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst index 8419019b6a88..6726f439958c 100644 --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst @@ -200,7 +200,7 @@ prb A pointer to the printk ringbuffer (struct printk_ringbuffer). This may be pointing to the static boot ringbuffer or the dynamically -allocated ringbuffer, depending on when the the core dump occurred. +allocated ringbuffer, depending on when the core dump occurred. Used by user-space tools to read the active kernel log buffer. printk_rb_static diff --git a/Documentation/bpf/map_cgroup_storage.rst b/Documentation/bpf/map_cgroup_storage.rst index cab9543017bf..8e5fe532c07e 100644 --- a/Documentation/bpf/map_cgroup_storage.rst +++ b/Documentation/bpf/map_cgroup_storage.rst @@ -31,7 +31,7 @@ The map uses key of type of either ``__u64 cgroup_inode_id`` or }; ``cgroup_inode_id`` is the inode id of the cgroup directory. -``attach_type`` is the the program's attach type. +``attach_type`` is the program's attach type. Linux 5.9 added support for type ``__u64 cgroup_inode_id`` as the key type. When this key type is used, then all attach types of the particular cgroup and @@ -155,7 +155,7 @@ However, the BPF program can still only associate with one map of each type ``BPF_MAP_TYPE_CGROUP_STORAGE`` or more than one ``BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE``. -In all versions, userspace may use the the attach parameters of cgroup and +In all versions, userspace may use the attach parameters of cgroup and attach type pair in ``struct bpf_cgroup_storage_key`` as the key to the BPF map APIs to read or update the storage for a given attachment. For Linux 5.9 attach type shared storages, only the first value in the struct, cgroup inode diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst index c6f4ba2fb32d..f75778d37488 100644 --- a/Documentation/core-api/cpu_hotplug.rst +++ b/Documentation/core-api/cpu_hotplug.rst @@ -560,7 +560,7 @@ available: * cpuhp_state_remove_instance(state, node) * cpuhp_state_remove_instance_nocalls(state, node) -The arguments are the same as for the the cpuhp_state_add_instance*() +The arguments are the same as for the cpuhp_state_add_instance*() variants above. The functions differ in the way how the installed callbacks are treated: diff --git a/Documentation/driver-api/isa.rst b/Documentation/driver-api/isa.rst index def4a7b690b5..3df1b1696524 100644 --- a/Documentation/driver-api/isa.rst +++ b/Documentation/driver-api/isa.rst @@ -100,7 +100,7 @@ I believe platform_data is available for this, but if rather not, moving the isa_driver pointer to the private struct isa_dev is ofcourse fine as well. -Then, if the the driver did not provide a .match, it matches. If it did, +Then, if the driver did not provide a .match, it matches. If it did, the driver match() method is called to determine a match. If it did **not** match, dev->platform_data is reset to indicate this to diff --git a/Documentation/filesystems/caching/backend-api.rst b/Documentation/filesystems/caching/backend-api.rst index d7507becf674..3a199fc50828 100644 --- a/Documentation/filesystems/caching/backend-api.rst +++ b/Documentation/filesystems/caching/backend-api.rst @@ -122,7 +122,7 @@ volumes, calling:: to tell fscache that a volume has been withdrawn. This waits for all outstanding accesses on the volume to complete before returning. -When the the cache is completely withdrawn, fscache should be notified by +When the cache is completely withdrawn, fscache should be notified by calling:: void fscache_relinquish_cache(struct fscache_cache *cache); diff --git a/Documentation/locking/seqlock.rst b/Documentation/locking/seqlock.rst index 64405e5da63e..bfda1a5fecad 100644 --- a/Documentation/locking/seqlock.rst +++ b/Documentation/locking/seqlock.rst @@ -39,7 +39,7 @@ as the writer can invalidate a pointer that the reader is following. Sequence counters (``seqcount_t``) ================================== -This is the the raw counting mechanism, which does not protect against +This is the raw counting mechanism, which does not protect against multiple writers. Write side critical sections must thus be serialized by an external lock. -- cgit v1.2.3 From 787983da77185d355564b0436f7b4eaa40b8904b Mon Sep 17 00:00:00 2001 From: Gary Guo Date: Sat, 3 Jul 2021 17:38:57 +0200 Subject: vsprintf: add new `%pA` format specifier This patch adds a format specifier `%pA` to `vsprintf` which formats a pointer as `core::fmt::Arguments`. Doing so allows us to directly format to the internal buffer of `printf`, so we do not have to use a temporary buffer on the stack to pre-assemble the message on the Rust side. This specifier is intended only to be used from Rust and not for C, so `checkpatch.pl` is intentionally unchanged to catch any misuse. Reviewed-by: Kees Cook Acked-by: Petr Mladek Reviewed-by: Greg Kroah-Hartman Co-developed-by: Alex Gaynor Signed-off-by: Alex Gaynor Co-developed-by: Wedson Almeida Filho Signed-off-by: Wedson Almeida Filho Signed-off-by: Gary Guo Co-developed-by: Miguel Ojeda Signed-off-by: Miguel Ojeda --- Documentation/core-api/printk-formats.rst | 10 ++++++++++ lib/vsprintf.c | 13 +++++++++++++ 2 files changed, 23 insertions(+) (limited to 'Documentation/core-api') diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 5e89497ba314..dbe1aacc79d0 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -625,6 +625,16 @@ Examples:: %p4cc Y10 little-endian (0x20303159) %p4cc NV12 big-endian (0xb231564e) +Rust +---- + +:: + + %pA + +Only intended to be used from Rust code to format ``core::fmt::Arguments``. +Do *not* use it from C. + Thanks ====== diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 3c1853a9d1c0..c414a8d9f1ea 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2246,6 +2246,9 @@ int __init no_hash_pointers_enable(char *str) } early_param("no_hash_pointers", no_hash_pointers_enable); +/* Used for Rust formatting ('%pA'). */ +char *rust_fmt_argument(char *buf, char *end, void *ptr); + /* * Show a '%p' thing. A kernel extension is that the '%p' is followed * by an extra set of alphanumeric characters that are extended format @@ -2372,6 +2375,10 @@ early_param("no_hash_pointers", no_hash_pointers_enable); * * Note: The default behaviour (unadorned %p) is to hash the address, * rendering it useful as a unique identifier. + * + * There is also a '%pA' format specifier, but it is only intended to be used + * from Rust code to format core::fmt::Arguments. Do *not* use it from C. + * See rust/kernel/print.rs for details. */ static noinline_for_stack char *pointer(const char *fmt, char *buf, char *end, void *ptr, @@ -2444,6 +2451,12 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, return device_node_string(buf, end, ptr, spec, fmt + 1); case 'f': return fwnode_string(buf, end, ptr, spec, fmt + 1); + case 'A': + if (!IS_ENABLED(CONFIG_RUST)) { + WARN_ONCE(1, "Please remove %%pA from non-Rust code\n"); + return error_string(buf, end, "(%pA?)", spec); + } + return rust_fmt_argument(buf, end, ptr); case 'x': return pointer_string(buf, end, ptr, spec); case 'e': -- cgit v1.2.3 From f4bf1cd4ac9c8c4610b687e49a1ba691ab286235 Mon Sep 17 00:00:00 2001 From: Jonathan Corbet Date: Tue, 27 Sep 2022 10:05:57 -0600 Subject: docs: move asm-annotations.rst into core-api This one file should not really be in the top-level documentation directory. core-api/ may not be a perfect fit but seems to be best, so move it there. Adjust a couple of internal document references to make them location-independent, and point checkpatch.pl at the new location. Cc: Jiri Slaby Cc: Joe Perches Reviewed-by: David Vernet Acked-by: Jani Nikula Signed-off-by: Jonathan Corbet Acked-by: Randy Dunlap Link: https://lore.kernel.org/r/20220927160559.97154-6-corbet@lwn.net Signed-off-by: Jonathan Corbet --- Documentation/asm-annotations.rst | 221 ---------------------------- Documentation/core-api/asm-annotations.rst | 222 +++++++++++++++++++++++++++++ Documentation/core-api/index.rst | 1 + Documentation/index.rst | 8 -- scripts/checkpatch.pl | 2 +- 5 files changed, 224 insertions(+), 230 deletions(-) delete mode 100644 Documentation/asm-annotations.rst create mode 100644 Documentation/core-api/asm-annotations.rst (limited to 'Documentation/core-api') diff --git a/Documentation/asm-annotations.rst b/Documentation/asm-annotations.rst deleted file mode 100644 index a64f2ca469d4..000000000000 --- a/Documentation/asm-annotations.rst +++ /dev/null @@ -1,221 +0,0 @@ -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 ` -for most code. Both of these are especially important to support reliable -stack traces which are in turn necessary for :doc:`Kernel live patching -`. - -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://lore.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. For example, on x86, this means that 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. - -``objtool`` requires that all code must be contained in an ELF symbol. Symbol -names that have a ``.L`` prefix do not emit symbol table entries. ``.L`` -prefixed symbols can be used within a code region, but should be avoided for -denoting a range of code via ``SYM_*_START/END`` annotations. - -* ``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(memset) - ... asm insns ... - SYM_FUNC_END(memset) - - In fact, this kind of annotation corresponds to the now deprecated ``ENTRY`` - and ``ENDPROC`` macros. - -* ``SYM_FUNC_ALIAS``, ``SYM_FUNC_ALIAS_LOCAL``, and ``SYM_FUNC_ALIAS_WEAK`` can - be used to define multiple names for a function. The typical use is:: - - SYM_FUNC_START(__memset) - ... asm insns ... - SYN_FUNC_END(__memset) - SYM_FUNC_ALIAS(memset, __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/core-api/asm-annotations.rst b/Documentation/core-api/asm-annotations.rst new file mode 100644 index 000000000000..bc514ed59887 --- /dev/null +++ b/Documentation/core-api/asm-annotations.rst @@ -0,0 +1,222 @@ +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 the ORC unwinder +(Documentation/x86/orc-unwinder.rst) +for most code. Both of these are especially important to support reliable +stack traces which are in turn necessary for kernel live patching +(Documentation/livepatch/livepatch.rst). + +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://lore.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. For example, on x86, this means that 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. + +``objtool`` requires that all code must be contained in an ELF symbol. Symbol +names that have a ``.L`` prefix do not emit symbol table entries. ``.L`` +prefixed symbols can be used within a code region, but should be avoided for +denoting a range of code via ``SYM_*_START/END`` annotations. + +* ``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(memset) + ... asm insns ... + SYM_FUNC_END(memset) + + In fact, this kind of annotation corresponds to the now deprecated ``ENTRY`` + and ``ENDPROC`` macros. + +* ``SYM_FUNC_ALIAS``, ``SYM_FUNC_ALIAS_LOCAL``, and ``SYM_FUNC_ALIAS_WEAK`` can + be used to define multiple names for a function. The typical use is:: + + SYM_FUNC_START(__memset) + ... asm insns ... + SYN_FUNC_END(__memset) + SYM_FUNC_ALIAS(memset, __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/core-api/index.rst b/Documentation/core-api/index.rst index dc95df462eea..f5d8e3779fe8 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -23,6 +23,7 @@ it. printk-formats printk-index symbol-namespaces + asm-annotations Data structures and low-level utilities ======================================= diff --git a/Documentation/index.rst b/Documentation/index.rst index da80c584133c..5a700548ae82 100644 --- a/Documentation/index.rst +++ b/Documentation/index.rst @@ -89,14 +89,6 @@ platform firmwares. devicetree/index -Architecture-agnostic documentation ------------------------------------ - -.. toctree:: - :maxdepth: 1 - - asm-annotations - Architecture-specific documentation ----------------------------------- diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 79e759aac543..812af52f97d2 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -3751,7 +3751,7 @@ sub process { if ($realfile =~ /\.S$/ && $line =~ /^\+\s*(?:[A-Z]+_)?SYM_[A-Z]+_(?:START|END)(?:_[A-Z_]+)?\s*\(\s*\.L/) { WARN("AVOID_L_PREFIX", - "Avoid using '.L' prefixed local symbol names for denoting a range of code via 'SYM_*_START/END' annotations; see Documentation/asm-annotations.rst\n" . $herecurr); + "Avoid using '.L' prefixed local symbol names for denoting a range of code via 'SYM_*_START/END' annotations; see Documentation/core-api/asm-annotations.rst\n" . $herecurr); } # check we are in a valid source file C or perl if not then ignore this hunk -- cgit v1.2.3 From e40573a43d163a5c9fe14c647bc4c5201d782893 Mon Sep 17 00:00:00 2001 From: Jonathan Corbet Date: Tue, 27 Sep 2022 10:05:58 -0600 Subject: docs: put atomic*.txt and memory-barriers.txt into the core-api book These files describe part of the core API, but have never been converted to RST due to ... let's say local oppposition. So, create a set of special-purpose wrappers to ..include these files into a separate page so that they can be a part of the htmldocs build. Then link them into the core-api manual and remove them from the "staging" dumping ground. Acked-by: Jani Nikula Signed-off-by: Jonathan Corbet Reviewed-by: David Vernet Acked-by: Randy Dunlap Link: https://lore.kernel.org/r/20220927160559.97154-7-corbet@lwn.net Signed-off-by: Jonathan Corbet --- Documentation/core-api/index.rst | 3 ++ Documentation/core-api/wrappers/atomic_bitops.rst | 18 ++++++++++ Documentation/core-api/wrappers/atomic_t.rst | 19 ++++++++++ .../core-api/wrappers/memory-barriers.rst | 18 ++++++++++ Documentation/staging/index.rst | 42 ---------------------- 5 files changed, 58 insertions(+), 42 deletions(-) create mode 100644 Documentation/core-api/wrappers/atomic_bitops.rst create mode 100644 Documentation/core-api/wrappers/atomic_t.rst create mode 100644 Documentation/core-api/wrappers/memory-barriers.rst (limited to 'Documentation/core-api') diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index f5d8e3779fe8..b0e7b4771fff 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -45,6 +45,8 @@ Library functionality that is used throughout the kernel. this_cpu_ops timekeeping errseq + wrappers/atomic_t + wrappers/atomic_bitops Low level entry and exit ======================== @@ -68,6 +70,7 @@ Documentation/locking/index.rst for more related documentation. local_ops padata ../RCU/index + wrappers/memory-barriers.rst Low-level hardware management ============================= diff --git a/Documentation/core-api/wrappers/atomic_bitops.rst b/Documentation/core-api/wrappers/atomic_bitops.rst new file mode 100644 index 000000000000..bf24e4081a8f --- /dev/null +++ b/Documentation/core-api/wrappers/atomic_bitops.rst @@ -0,0 +1,18 @@ +.. SPDX-License-Identifier: GPL-2.0 + This is a simple wrapper to bring atomic_bitops.txt into the RST world + until such a time as that file can be converted directly. + +============= +Atomic bitops +============= + +.. raw:: latex + + \footnotesize + +.. include:: ../../atomic_bitops.txt + :literal: + +.. raw:: latex + + \normalsize diff --git a/Documentation/core-api/wrappers/atomic_t.rst b/Documentation/core-api/wrappers/atomic_t.rst new file mode 100644 index 000000000000..ed109a964c77 --- /dev/null +++ b/Documentation/core-api/wrappers/atomic_t.rst @@ -0,0 +1,19 @@ +.. SPDX-License-Identifier: GPL-2.0 + This is a simple wrapper to bring atomic_t.txt into the RST world + until such a time as that file can be converted directly. + +============ +Atomic types +============ + +.. raw:: latex + + \footnotesize + +.. include:: ../../atomic_t.txt + :literal: + +.. raw:: latex + + \normalsize + diff --git a/Documentation/core-api/wrappers/memory-barriers.rst b/Documentation/core-api/wrappers/memory-barriers.rst new file mode 100644 index 000000000000..532460b5e3eb --- /dev/null +++ b/Documentation/core-api/wrappers/memory-barriers.rst @@ -0,0 +1,18 @@ +.. SPDX-License-Identifier: GPL-2.0 + This is a simple wrapper to bring memory-barriers.txt into the RST world + until such a time as that file can be converted directly. + +============================ +Linux kernel memory barriers +============================ + +.. raw:: latex + + \footnotesize + +.. include:: ../../memory-barriers.txt + :literal: + +.. raw:: latex + + \normalsize diff --git a/Documentation/staging/index.rst b/Documentation/staging/index.rst index abd0d18254d2..ded8254bc0d7 100644 --- a/Documentation/staging/index.rst +++ b/Documentation/staging/index.rst @@ -14,45 +14,3 @@ Unsorted Documentation static-keys tee xz - -Atomic Types -============ - -.. raw:: latex - - \footnotesize - -.. include:: ../atomic_t.txt - :literal: - -.. raw:: latex - - \normalsize - -Atomic bitops -============= - -.. raw:: latex - - \footnotesize - -.. include:: ../atomic_bitops.txt - :literal: - -.. raw:: latex - - \normalsize - -Memory Barriers -=============== - -.. raw:: latex - - \footnotesize - -.. include:: ../memory-barriers.txt - :literal: - -.. raw:: latex - - \normalsize -- cgit v1.2.3