Hi Nishanth,
2017-03-28 6:44 GMT+09:00 Nishanth Menon nm@ti.com:
Hi,
we've kind of run into an interesting situation recently, but might be of interest for various folks trying to reduce the image sizes.
our AM335x device has a limited amount of sram.. and the SPL tries to fit into it (a bit tricky given the restricted space we have on it on certain class of devices).
arch/arm/mach-omap2/am33xx/u-boot-spl.lds is a bit custom tailored around this.
Key in this is: . = ALIGN(4); .rodata : { *(SORT_BY_ALIGNMENT(.rodata*)) } >.sram
. = ALIGN(4); .data : { *(SORT_BY_ALIGNMENT(.data*)) } >.sram
Now, our jenkins build system happens to use a varied build path and uses O= path. to simplify the details: mkdir /tmp/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/cccccccccccccccccccccccccccccccccccccccccccccccccc mkdir /tmp/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/cccccccccccccccccccccccccccccccccccccccccccccccccc/b
git clone u-boot cd u-boot
git clean -fdx make CROSS_COMPILE=arm-linux-gnueabihf- O=../b am335x_evm_defconfig make CROSS_COMPILE=arm-linux-gnueabihf- O=../b all
depending on depth of the path, this would fail.. a little bit of headscratching later.. when using O= build system uses absolute paths, which translates to __FILE__ being absolute paths as well..
in u-boot, any printf("%s", __FILE__) makes u-boot allocate this file path in rodata.
So, depending on how deep the path is rodata size varies and ends up pushing .data out of sram max range.
we dont really care to put a print of complete absolute path anyways, and I am not really sure of a clean way to resolve this: a) override __FILE__ with something.. -Wbuiltin-macro-redefined kicks in b) replace usage of __FILE__ with something like __FILENAME__ as recommended by [1]
What is the suggestion we do?
[1] http://stackoverflow.com/questions/8487986/file-macro-shows-full-path
When O= is given, the build system runs in the object tree, not in the source tree. (This is the same as Linux.)
If you see the top Makefile:
ifeq ($(KBUILD_SRC),) # building in the source tree srctree := . else ifeq ($(KBUILD_SRC)/,$(dir $(CURDIR))) # building in a subdirectory of the source tree srctree := .. else srctree := $(KBUILD_SRC) endif endif
If O= points to a sub-directory of the source tree, the relative path "srctree := .." is used.
Otherwise, the absolute path srctree := $(KBUILD_SRC) is used. In your case, "O=../b" means the source tree and the obj tree are siblings. So, absolute path.
If you want to see a short relative path for __FILE__, I'd recommend to use a sub-directory for O=.
For example, your source tree is located at ~/aaaaaaaaa/bbbbbbb/cccccccc/u-boot, create a directory ~/aaaaaaaaa/bbbbbbb/cccccccc/u-boot/foo, then give O=foo
Masahiro