Hi Heinrich,
On Tue, Sep 12, 2017 at 8:50 AM, Heinrich Schuchardt xypron.glpk@gmx.de wrote:
On 09/12/2017 01:19 AM, Dr. Philipp Tomsich wrote:
On 12 Sep 2017, at 00:40, Heinrich Schuchardt xypron.glpk@gmx.de wrote:
For qemu-x86_64_defconfig on Debian Stretch ld 2.28 creates a .got and a .got.plt section in u-boot-spl.
If we do not ignore these sections objcopy generates an u-boot-spl-nodtb.bin file of 4 GiB which leads to subsequent failure of the build process.
According to https://sourceware.org/bugzilla/show_bug.cgi?id=22120#c2 objcopy can not generate files with holes.
With the patch we can run qemu with the generated u-boot.rom.
Signed-off-by: Heinrich Schuchardt xypron.glpk@gmx.de
I ran the Travis CI tests with no error reported: https://travis-ci.org/xypron2/u-boot/builds/274042004
It is unclear to me why on Debian Stretch the .got and .got.plt sections are generated. The problem does not exist on Debian Jessie which uses binutils 2.25.
I found this comment in the BFD code which describes under which circumstances the .got.plt section is not generated:
https://sourceware.org/viewvc/src/bfd/elf64-x86-64.c?view=markup#l2921
Don't allocate .got.plt section if there are no GOT nor PLT entries and there is no reference to _GLOBAL_OFFSET_TABLE_.
Can we have some binutils guys to look at this? Why does the behavior get changes between versions?
scripts/Makefile.spl | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl index dd8065d87d..3b2d79d562 100644 --- a/scripts/Makefile.spl +++ b/scripts/Makefile.spl @@ -286,7 +286,8 @@ quiet_cmd_objcopy = OBJCOPY $@ cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@
OBJCOPYFLAGS_$(SPL_BIN)-nodtb.bin = $(SPL_OBJCFLAGS) -O binary \
$(if $(CONFIG_SPL_X86_16BIT_INIT),-R .start16 -R .resetvec)
$(if $(CONFIG_SPL_X86_16BIT_INIT), \-R .start16 -R .resetvec -R .got -R .got.plt)
Simon, would you take a look at this?
If there is a non-empty .got, it can not be safely removed. The remaining code can (and will) reference data within the .got. Did you check the contents of the .got and where these are referenced from?
This is from spl/u-boot-spl.map:
.text 0x00000000fffd0000 0xa032 *(.text*) .text 0x00000000fffd0000 0xcc arch/x86/cpu/start.o 0x00000000fffd0000 _x86boot_start 0x00000000fffd0020 _start
.got 0x0000000000120000 0x4 .got 0x0000000000120000 0x4 arch/x86/cpu/start.o
.got.plt 0x0000000000120004 0xc .got.plt 0x0000000000120004 0xc arch/x86/cpu/start.o 0x0000000000120004 _GLOBAL_OFFSET_TABLE_
So in .got there is just the reference to the BIOS start address. And .got.plt contains additionally a pointer to .got.
Did you check the contents of the .got and where these are referenced from?
It is unclear to me what additional information is needed and how it can be extracted.
Regards, Bin