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kbuild: add a flag to force absolute path for srctree

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In old days, Kbuild always used an absolute path for $(srctree).

Since commit 890676c65d ("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 25b146c5b8 ("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 e93bc1a0ca
("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 <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit is contained in:
Masahiro Yamada 2019-07-06 12:07:13 +09:00
parent 051f278e9d
commit 95fd3f87bf
3 changed files with 14 additions and 2 deletions
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9
Documentation/kbuild/kbuild.txt
View File

@ -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

4
Makefile
View File

@ -244,6 +244,10 @@ else
building_out_of_srctree := 1
endif
ifneq ($(KBUILD_ABS_SRCTREE),)
srctree := $(abs_srctree)
endif
objtree := .
VPATH := $(srctree)

3
scripts/tags.sh
View File

@ -17,8 +17,7 @@ ignore="$(echo "$RCS_FIND_IGNORE" | sed 's|\\||g' )"
# tags and cscope files should also ignore MODVERSION *.mod.c files
ignore="$ignore ( -name *.mod.c ) -prune -o"
# Do not use full path if we do not use O=.. builds
# Use make O=. {tags|cscope}
# Use make KBUILD_ABS_SRCTREE=1 {tags|cscope}
# to force full paths for a non-O= build
if [ "${srctree}" = "." -o -z "${srctree}" ]; then
tree=