From f3c8d4c7a7280cdc6622adb4f8e39d51b3786d68 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Tue, 4 Jun 2019 19:13:55 +0900 Subject: kbuild: remove headers_{install,check}_all headers_install_all does not make much sense any more because different architectures export different set of uapi/linux/ headers. As you see in include/uapi/linux/Kbuild, the installation of a.out.h, kvm.h, and kvm_para.h is arch-dependent. So, headers_install_all repeats the installation/removal of them. If somebody really thinks it is useful to do headers_install for all architectures, it would be possible by small shell-scripting, but the top Makefile does not have to provide entry targets just for that purpose. Signed-off-by: Masahiro Yamada Acked-by: Sam Ravnborg --- Documentation/kbuild/headers_install.txt | 7 ------- Documentation/kbuild/makefiles.txt | 6 +----- 2 files changed, 1 insertion(+), 12 deletions(-) (limited to 'Documentation') diff --git a/Documentation/kbuild/headers_install.txt b/Documentation/kbuild/headers_install.txt index f0153adb95e2..f07e34eab70b 100644 --- a/Documentation/kbuild/headers_install.txt +++ b/Documentation/kbuild/headers_install.txt @@ -39,12 +39,5 @@ INSTALL_HDR_PATH indicates where to install the headers. It defaults to An 'include' directory is automatically created inside INSTALL_HDR_PATH and headers are installed in 'INSTALL_HDR_PATH/include'. -The command "make headers_install_all" exports headers for all architectures -simultaneously. (This is mostly of interest to distribution maintainers, -who create an architecture-independent tarball from the resulting include -directory.) You also can use HDR_ARCH_LIST to specify list of architectures. -Remember to provide the appropriate linux/asm directory via "mv" or "ln -s" -before building a C library with headers exported this way. - The kernel header export infrastructure is maintained by David Woodhouse . diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index d65ad5746f94..bac301a73a86 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -897,11 +897,7 @@ When kbuild executes, the following steps are followed (roughly): --- 6.2 Add prerequisites to archheaders: The archheaders: rule is used to generate header files that - may be installed into user space by "make header_install" or - "make headers_install_all". In order to support - "make headers_install_all", this target has to be able to run - on an unconfigured tree, or a tree configured for another - architecture. + may be installed into user space by "make header_install". It is run before "make archprepare" when run on the architecture itself. -- cgit v1.2.3 From e846f0dc57f441e5e93194d39bc9b8ac2ab5e0a4 Mon Sep 17 00:00:00 2001 From: Jani Nikula Date: Tue, 4 Jun 2019 15:42:48 +0300 Subject: kbuild: add support for ensuring headers are self-contained Sometimes it's useful to be able to explicitly ensure certain headers remain self-contained, i.e. that they are compilable as standalone units, by including and/or forward declaring everything they depend on. Add special target header-test-y where individual Makefiles can add headers to be tested if CONFIG_HEADER_TEST is enabled. This will generate a dummy C file per header that gets built as part of extra-y. Signed-off-by: Jani Nikula Reviewed-by: Sam Ravnborg Signed-off-by: Masahiro Yamada --- Documentation/dontdiff | 1 + Documentation/kbuild/makefiles.txt | 7 +++++++ 2 files changed, 8 insertions(+) (limited to 'Documentation') diff --git a/Documentation/dontdiff b/Documentation/dontdiff index 5eba889ea84d..554dfe4883d2 100644 --- a/Documentation/dontdiff +++ b/Documentation/dontdiff @@ -19,6 +19,7 @@ *.grep *.grp *.gz +*.hdrtest.c *.html *.i *.jpeg diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index bac301a73a86..ca4b24ec0399 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -1018,6 +1018,13 @@ When kbuild executes, the following steps are followed (roughly): In this example, extra-y is used to list object files that shall be built, but shall not be linked as part of built-in.a. + header-test-y + + header-test-y specifies headers (*.h) in the current directory that + should be compile tested to ensure they are self-contained, + i.e. compilable as standalone units. If CONFIG_HEADER_TEST is enabled, + this autogenerates dummy sources to include the headers, and builds them + as part of extra-y. --- 6.7 Commands useful for building a boot image -- cgit v1.2.3 From c93a0368aaa2962e6c89da20f79b8789b42e3387 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 1 Jul 2019 09:58:41 +0900 Subject: kbuild: do not create wrappers for header-test-y header-test-y does not work with headers in sub-directories. For example, you may want to write a Makefile, like this: include/linux/Kbuild: header-test-y += mtd/nand.h This entry will create a wrapper include/linux/mtd/nand.hdrtest.c with the following content: #include "mtd/nand.h" To make this work, we need to add $(srctree)/include/linux to the header search path. It would be tedious to add ccflags-y. Instead, we could change the *.hdrtest.c rule to wrap: #include "nand.h" This works for in-tree build since #include "..." searches in the relative path from the header with this directive. For O=... build, we need to add $(srctree)/include/linux/mtd to the header search path, which will be even more tedious. After all, I thought it would be handier to compile headers directly without creating wrappers. I added a new build rule to compile %.h into %.h.s The target is %.h.s instead of %.h.o because it is slightly faster. Also, as for GCC, an empty assembly is smaller than an empty object. I wrote the build rule: $(CC) $(c_flags) -S -o $@ -x c /dev/null -include $< instead of: $(CC) $(c_flags) -S -o $@ -x c $< Both work fine with GCC, but the latter is bad for Clang. This comes down to the difference in the -Wunused-function policy. GCC does not warn about unused 'static inline' functions at all. Clang does not warn about the ones in included headers, but does about the ones in the source. So, we should handle headers as headers, not as source files. In fact, this has been hidden since commit abb2ea7dfd82 ("compiler, clang: suppress warning for unused static inline functions"), but we should not rely on that. Signed-off-by: Masahiro Yamada Acked-by: Jani Nikula Tested-by: Jani Nikula --- Documentation/dontdiff | 1 - Documentation/kbuild/makefiles.txt | 3 +-- 2 files changed, 1 insertion(+), 3 deletions(-) (limited to 'Documentation') diff --git a/Documentation/dontdiff b/Documentation/dontdiff index 554dfe4883d2..5eba889ea84d 100644 --- a/Documentation/dontdiff +++ b/Documentation/dontdiff @@ -19,7 +19,6 @@ *.grep *.grp *.gz -*.hdrtest.c *.html *.i *.jpeg diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index ca4b24ec0399..5080fec34609 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -1023,8 +1023,7 @@ When kbuild executes, the following steps are followed (roughly): header-test-y specifies headers (*.h) in the current directory that should be compile tested to ensure they are self-contained, i.e. compilable as standalone units. If CONFIG_HEADER_TEST is enabled, - this autogenerates dummy sources to include the headers, and builds them - as part of extra-y. + this builds them as part of extra-y. --- 6.7 Commands useful for building a boot image -- cgit v1.2.3 From 1e21cbfada87f697a2a7c450542a7d28925abee6 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 1 Jul 2019 09:58:42 +0900 Subject: kbuild: support header-test-pattern-y In my view, most of headers can be self-contained. So, it would be tedious to add every header to header-test-y explicitly. We usually end up with "all headers with some exceptions". There are two types in exceptions: [1] headers that are never compiled as standalone units For examples, include/linux/compiler-gcc.h is not intended for direct inclusion. We should always exclude such ones. [2] headers that are conditionally compiled as standalone units Some headers can be compiled only for particular architectures. For example, include/linux/arm-cci.h can be compiled only for arm/arm64 because it requires to exist. Clang can compile include/soc/nps/mtm.h only for arc because it contains an arch-specific register in inline assembler. So, you can write Makefile like this: header-test- += linux/compiler-gcc.h header-test-$(CONFIG_ARM) += linux/arm-cci.h header-test-$(CONFIG_ARM64) += linux/arm-cci.h header-test-$(CONFIG_ARC) += soc/nps/mtm.h The new syntax header-test-pattern-y will be useful to specify "the rest". The typical usage is like this: header-test-pattern-y += */*.h This will add all the headers in sub-directories to the test coverage, excluding $(header-test-). In this regards, header-test-pattern-y behaves like a weaker variant of header-test-y. Caveat: The patterns in header-test-pattern-y are prefixed with $(srctree)/$(src)/ but not $(objtree)/$(obj)/. Stale generated headers are often left over when you traverse the git history without cleaning. Wildcard patterns for $(objtree) may match to stale headers, which could fail to compile. One pitfall is $(srctree)/$(src)/ and $(objtree)/$(obj)/ point to the same directory for in-tree building. So, header-test-pattern-y should be used with care since it can potentially match to stale headers. Caveat2: You could use wildcard for header-test-. For example, header-test- += asm-generic/% ... will exclude headers in asm-generic directory. Unfortunately, the wildcard character is '%' instead of '*' here because this is evaluated by $(filter-out ...) whereas header-test-pattern-y is evaluated by $(wildcard ...). This is a kludge, but seems useful in some places... Signed-off-by: Masahiro Yamada Tested-by: Jani Nikula --- Documentation/kbuild/makefiles.txt | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'Documentation') diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 5080fec34609..b817e6cefb77 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -1025,6 +1025,16 @@ When kbuild executes, the following steps are followed (roughly): i.e. compilable as standalone units. If CONFIG_HEADER_TEST is enabled, this builds them as part of extra-y. + header-test-pattern-y + + This works as a weaker version of header-test-y, and accepts wildcard + patterns. The typical usage is: + + header-test-pattern-y += *.h + + This specifies all the files that matches to '*.h' in the current + directory, but the files in 'header-test-' are excluded. + --- 6.7 Commands useful for building a boot image Kbuild provides a few macros that are useful when building a -- cgit v1.2.3 From 95fd3f87bfbe8edaa5e955e0f858a0a573c09ab6 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sat, 6 Jul 2019 12:07:13 +0900 Subject: kbuild: add a flag to force absolute path for srctree In old days, Kbuild always used an absolute path for $(srctree). Since commit 890676c65d69 ("kbuild: Use relative path when building in the source tree"), $(srctree) is '.' when O= was not passed from the command line. Yet, using absolute paths is useful in some cases even without O=, for instance, to create a cscope file with absolute path tags. 'O=.' was known to work as a workaround to force Kbuild to use absolute paths even when you are building in the source tree. Since commit 25b146c5b8ce ("kbuild: allow Kbuild to start from any directory"), Kbuild is too clever to be tricked. Even if you pass 'O=.' Kbuild notices you are building in the source tree, then use '.' for $(srctree). So, 'make O=. cscope' is no help to create absolute path tags. We cannot force one or the other according to commit e93bc1a0cab3 ("Revert "kbuild: specify absolute paths for cscope""). Both of relative path and absolute path have pros and cons. This commit adds a new flag KBUILD_ABS_SRCTREE to allow users to choose the absolute path for $(srctree). 'make KBUILD_ABS_SRCTREE=1 cscope' will work as a replacement of 'make O=. cscope'. Reported-by: Pawan Gupta Signed-off-by: Masahiro Yamada --- Documentation/kbuild/kbuild.txt | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'Documentation') diff --git a/Documentation/kbuild/kbuild.txt b/Documentation/kbuild/kbuild.txt index 9c230ea71963..dcfeb32e3360 100644 --- a/Documentation/kbuild/kbuild.txt +++ b/Documentation/kbuild/kbuild.txt @@ -183,6 +183,15 @@ The output directory is often set using "O=..." on the commandline. The value can be overridden in which case the default value is ignored. +KBUILD_ABS_SRCTREE +-------------------------------------------------- +Kbuild uses a relative path to point to the tree when possible. For instance, +when building in the source tree, the source tree path is '.' + +Setting this flag requests Kbuild to use absolute path to the source tree. +There are some useful cases to do so, like when generating tag files with +absolute path entries etc. + KBUILD_SIGN_PIN -------------------------------------------------- This variable allows a passphrase or PIN to be passed to the sign-file -- cgit v1.2.3