diff options
Diffstat (limited to 'Documentation/kbuild')
| -rw-r--r-- | Documentation/kbuild/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/kbuild/headers_install.txt | 47 | ||||
| -rw-r--r-- | Documentation/kbuild/makefiles.txt | 39 |
3 files changed, 57 insertions, 31 deletions
diff --git a/Documentation/kbuild/00-INDEX b/Documentation/kbuild/00-INDEX index e8d2b6d..8c5e6aa 100644 --- a/Documentation/kbuild/00-INDEX +++ b/Documentation/kbuild/00-INDEX @@ -1,5 +1,7 @@ 00-INDEX - this file: info on the kernel build process +headers_install.txt + - how to export Linux headers for use by userspace kbuild.txt - developer information on kbuild kconfig.txt diff --git a/Documentation/kbuild/headers_install.txt b/Documentation/kbuild/headers_install.txt new file mode 100644 index 0000000..951eb9f --- /dev/null +++ b/Documentation/kbuild/headers_install.txt @@ -0,0 +1,47 @@ +Exporting kernel headers for use by userspace +============================================= + +The "make headers_install" command exports the kernel's header files in a +form suitable for use by userspace programs. + +The linux kernel's exported header files describe the API for user space +programs attempting to use kernel services. These kernel header files are +used by the system's C library (such as glibc or uClibc) to define available +system calls, as well as constants and structures to be used with these +system calls. The C library's header files include the kernel header files +from the "linux" subdirectory. The system's libc headers are usually +installed at the default location /usr/include and the kernel headers in +subdirectories under that (most notably /usr/include/linux and +/usr/include/asm). + +Kernel headers are backwards compatible, but not forwards compatible. This +means that a program built against a C library using older kernel headers +should run on a newer kernel (although it may not have access to new +features), but a program built against newer kernel headers may not work on an +older kernel. + +The "make headers_install" command can be run in the top level directory of the +kernel source code (or using a standard out-of-tree build). It takes two +optional arguments: + + make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr/include + +ARCH indicates which architecture to produce headers for, and defaults to the +current architecture. The linux/asm directory of the exported kernel headers +is platform-specific, to see a complete list of supported architectures use +the command: + + ls -d include/asm-* | sed 's/.*-//' + +INSTALL_HDR_PATH indicates where to install the headers. It defaults to +"./usr/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 +<dwmw2@infradead.org>. diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index c600e2f..764f599 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -23,11 +23,10 @@ This document describes the Linux kernel Makefiles. === 4 Host Program support --- 4.1 Simple Host Program --- 4.2 Composite Host Programs - --- 4.3 Defining shared libraries - --- 4.4 Using C++ for host programs - --- 4.5 Controlling compiler options for host programs - --- 4.6 When host programs are actually built - --- 4.7 Using hostprogs-$(CONFIG_FOO) + --- 4.3 Using C++ for host programs + --- 4.4 Controlling compiler options for host programs + --- 4.5 When host programs are actually built + --- 4.6 Using hostprogs-$(CONFIG_FOO) === 5 Kbuild clean infrastructure @@ -643,29 +642,7 @@ Both possibilities are described in the following. Finally, the two .o files are linked to the executable, lxdialog. Note: The syntax <executable>-y is not permitted for host-programs. ---- 4.3 Defining shared libraries - - Objects with extension .so are considered shared libraries, and - will be compiled as position independent objects. - Kbuild provides support for shared libraries, but the usage - shall be restricted. - In the following example the libkconfig.so shared library is used - to link the executable conf. - - Example: - #scripts/kconfig/Makefile - hostprogs-y := conf - conf-objs := conf.o libkconfig.so - libkconfig-objs := expr.o type.o - - Shared libraries always require a corresponding -objs line, and - in the example above the shared library libkconfig is composed by - the two objects expr.o and type.o. - expr.o and type.o will be built as position independent code and - linked as a shared library libkconfig.so. C++ is not supported for - shared libraries. - ---- 4.4 Using C++ for host programs +--- 4.3 Using C++ for host programs kbuild offers support for host programs written in C++. This was introduced solely to support kconfig, and is not recommended @@ -688,7 +665,7 @@ Both possibilities are described in the following. qconf-cxxobjs := qconf.o qconf-objs := check.o ---- 4.5 Controlling compiler options for host programs +--- 4.4 Controlling compiler options for host programs When compiling host programs, it is possible to set specific flags. The programs will always be compiled utilising $(HOSTCC) passed @@ -716,7 +693,7 @@ Both possibilities are described in the following. When linking qconf, it will be passed the extra option "-L$(QTDIR)/lib". ---- 4.6 When host programs are actually built +--- 4.5 When host programs are actually built Kbuild will only build host-programs when they are referenced as a prerequisite. @@ -747,7 +724,7 @@ Both possibilities are described in the following. This will tell kbuild to build lxdialog even if not referenced in any rule. ---- 4.7 Using hostprogs-$(CONFIG_FOO) +--- 4.6 Using hostprogs-$(CONFIG_FOO) A typical pattern in a Kbuild file looks like this: |