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Re: [XEN][PATCH v2] coverage: extend coverage on .init and lib code
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
- Date: Sat, 6 Dec 2025 11:10:48 +0200
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- Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Jason Andryuk <jason.andryuk@xxxxxxx>, Victor Lira <victorm.lira@xxxxxxx>
- Delivery-date: Sat, 06 Dec 2025 09:11:20 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 05.12.25 22:00, Andrew Cooper wrote:
On 05/12/2025 7:34 pm, Grygorii Strashko wrote:
From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
Extend coverage support on .init and lib code.
Add two hidden Kconfig options:
- RELAX_INIT_CHECK "Relax strict check for .init sections only in %.init.o
files"
- DO_NOT_FREE_INIT_MEMORY "Prevent freeing of .init sections at the end of
Xen boot."
Both selected selected when COVERAGE=y, as getting coverage report for
".init" code is required:
- to bypass strict check for .init sections only in %.init.o files;
- the .init code stay in memory after Xen boot.
RELAX_INIT_CHECK/DO_NOT_FREE_INIT_MEMORY could be used by other debug
features in the future.
Signed-off-by: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
---
changes in v2:
- add RELAX_INIT_CHECK and DO_NOT_FREE_INIT_MEMORY, those are two different
things,
both potentially reusable
- enable coverage for libfdt/libelf always
- enable colverage for .init always
This is a lot nicer (i.e. more simple).
But, I still don't know why we need to avoid freeing init memory to make
this work. What explodes if we dont?
It will just crash when coverage data is collected.
First I made changes in make file to get .init covered
then I hit a crash
then I checked %.init.o
conclusion was obvious.
For example:
objdump -x bzimage.init.o | grep gcov
0000000000000010 l O .bss 0000000000000028 __gcov0.bzimage_check
0000000000000040 l O .bss 0000000000000040 __gcov0.bzimage_headroom
0000000000000000 l O .bss 0000000000000008 __gcov0.output_length
0000000000000080 l O .bss 0000000000000060 __gcov0.bzimage_parse
0000000000000098 l O .init.data.rel.local 0000000000000028
__gcov_.bzimage_parse
0000000000000070 l O .init.data.rel.local 0000000000000028
__gcov_.bzimage_headroom
0000000000000048 l O .init.data.rel.local 0000000000000028
__gcov_.bzimage_check
0000000000000020 l O .init.data.rel.local 0000000000000028
__gcov_.output_length
0000000000000000 *UND* 0000000000000000 __gcov_init
0000000000000000 *UND* 0000000000000000 __gcov_exit
0000000000000000 *UND* 0000000000000000 __gcov_merge_add
0000000000000008 R_X86_64_PLT32 __gcov_init-0x0000000000000004
0000000000000012 R_X86_64_PLT32 __gcov_exit-0x0000000000000004
0000000000000020 R_X86_64_64 __gcov_merge_add
--
Best regards,
-grygorii
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