Merge tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy...

[linux-2.6-microblaze.git] / Documentation / kbuild / makefiles.rst

diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
index 5ea1e72..6b7368d 100644 (file)
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -341,19 +341,7 @@ more details, with real examples.
 
        Examples are:
 
-       1) head objects
-
-           Some objects must be placed at the head of vmlinux. They are
-           directly linked to vmlinux without going through built-in.a
-           A typical use-case is an object that contains the entry point.
-
-           arch/$(SRCARCH)/Makefile should specify such objects as head-y.
-
-           Discussion:
-             Given that we can control the section order in the linker script,
-             why do we need head-y?
-
-       2) vmlinux linker script
+       1) vmlinux linker script
 
            The linker script for vmlinux is located at
            arch/$(SRCARCH)/kernel/vmlinux.lds
@@ -361,10 +349,6 @@ more details, with real examples.
        Example::
 
                # arch/x86/kernel/Makefile
-               extra-y := head_$(BITS).o
-               extra-y += head$(BITS).o
-               extra-y += ebda.o
-               extra-y += platform-quirks.o
                extra-y += vmlinux.lds
 
        $(extra-y) should only contain targets needed for vmlinux.
@@ -683,22 +667,27 @@ more details, with real examples.
        In the above example, -Wno-unused-but-set-variable will be added to
        KBUILD_CFLAGS only if gcc really accepts it.
 
-    cc-ifversion
-       cc-ifversion tests the version of $(CC) and equals the fourth parameter
-       if version expression is true, or the fifth (if given) if the version
-       expression is false.
+    gcc-min-version
+       gcc-min-version tests if the value of $(CONFIG_GCC_VERSION) is greater than
+       or equal to the provided value and evaluates to y if so.
+
+       Example::
+
+               cflags-$(call gcc-min-version, 70100) := -foo
+
+       In this example, cflags-y will be assigned the value -foo if $(CC) is gcc and
+       $(CONFIG_GCC_VERSION) is >= 7.1.
+
+    clang-min-version
+       clang-min-version tests if the value of $(CONFIG_CLANG_VERSION) is greater
+       than or equal to the provided value and evaluates to y if so.
 
        Example::
 
-               #fs/reiserfs/Makefile
-               ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
+               cflags-$(call clang-min-version, 110000) := -foo
 
-       In this example, ccflags-y will be assigned the value -O1 if the
-       $(CC) version is less than 4.2.
-       cc-ifversion takes all the shell operators:
-       -eq, -ne, -lt, -le, -gt, and -ge
-       The third parameter may be a text as in this example, but it may also
-       be an expanded variable or a macro.
+       In this example, cflags-y will be assigned the value -foo if $(CC) is clang
+       and $(CONFIG_CLANG_VERSION) is >= 11.0.0.
 
     cc-cross-prefix
        cc-cross-prefix is used to check if there exists a $(CC) in path with
@@ -1099,8 +1088,7 @@ When kbuild executes, the following steps are followed (roughly):
    - The values of the above variables are expanded in arch/$(SRCARCH)/Makefile.
 5) All object files are then linked and the resulting file vmlinux is
    located at the root of the obj tree.
-   The very first objects linked are listed in head-y, assigned by
-   arch/$(SRCARCH)/Makefile.
+   The very first objects linked are listed in scripts/head-object-list.txt.
 6) Finally, the architecture-specific part does any required post processing
    and builds the final bootimage.
    - This includes building boot records
@@ -1272,6 +1260,9 @@ When kbuild executes, the following steps are followed (roughly):
        All object files for vmlinux. They are linked to vmlinux in the same
        order as listed in KBUILD_VMLINUX_OBJS.
 
+       The objects listed in scripts/head-object-list.txt are exceptions;
+       they are placed before the other objects.
+
     KBUILD_VMLINUX_LIBS
 
        All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and
@@ -1315,8 +1306,7 @@ When kbuild executes, the following steps are followed (roughly):
        machinery is all architecture-independent.
 
 
-       head-y, core-y, libs-y, drivers-y
-           $(head-y) lists objects to be linked first in vmlinux.
+       core-y, libs-y, drivers-y
 
            $(libs-y) lists directories where a lib.a archive can be located.