Hi Andrew,
On 06.12.25 16:21, Andrew Cooper wrote:
On 06/12/2025 2:15 pm, Andrew Cooper wrote:
On 06/12/2025 9:10 am, Grygorii Strashko wrote:
On 05.12.25 22:00, Andrew Cooper wrote:
On 05/12/2025 7:34 pm, Grygorii Strashko wrote:
From: Grygorii Strashko <[email protected]>
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 <[email protected]>
---
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
Aah, we should exclude the OJBCOPY too. That's what's moving
.data.rel.local amongst other sections we target with attributes directly.
we can't target.
I've come up with below diff - seems it's working without
DO_NOT_FREE_INIT_MEMORY.
Is this what you have in mind?
diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug
index 8fc201d12c2c..16b1a82db46e 100644
--- a/xen/Kconfig.debug
+++ b/xen/Kconfig.debug
@@ -40,7 +40,6 @@ config COVERAGE
depends on SYSCTL && !LIVEPATCH
select SUPPRESS_DUPLICATE_SYMBOL_WARNINGS if !ENFORCE_UNIQUE_SYMBOLS
select RELAX_INIT_CHECK
- select DO_NOT_FREE_INIT_MEMORY
help
Enable code coverage support.
diff --git a/xen/Rules.mk b/xen/Rules.mk
index 8c4861a427e6..47fdcc1d23b5 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -33,11 +33,15 @@ cov-cflags-y :=
nocov-y :=
noubsan-y :=
+# when coverage is enabled the gcc internal section should stay in memory
+# after Xen boot
+ifneq ($(CONFIG_COVERAGE),y)
SPECIAL_DATA_SECTIONS := rodata $(foreach a,1 2 4 8 16, \
$(foreach w,1 2 4, \
rodata.str$(w).$(a)) \
rodata.cst$(a)) \
$(foreach r,rel rel.ro,data.$(r).local)
+endif
# The filename build.mk has precedence over Makefile
include $(firstword $(wildcard $(srcdir)/build.mk) $(srcdir)/Makefile)
diff --git a/xen/common/libelf/Makefile b/xen/common/libelf/Makefile
index 60b3ae40728f..8180c78f1510 100644
--- a/xen/common/libelf/Makefile
+++ b/xen/common/libelf/Makefile
@@ -1,8 +1,10 @@
obj-bin-y := libelf.o
libelf-objs := libelf-tools.o libelf-loader.o libelf-dominfo.o
+ifneq ($(CONFIG_COVERAGE),y)
SECTIONS := text data $(SPECIAL_DATA_SECTIONS)
OBJCOPYFLAGS := $(foreach s,$(SECTIONS),--rename-section .$(s)=.init.$(s))
+endif
CFLAGS-y += -Wno-pointer-sign
diff --git a/xen/common/libfdt/Makefile b/xen/common/libfdt/Makefile
index ae0f69c01373..fb26e5bff0fd 100644
--- a/xen/common/libfdt/Makefile
+++ b/xen/common/libfdt/Makefile
@@ -4,7 +4,9 @@ SECTIONS := text data $(SPECIAL_DATA_SECTIONS)
# For CONFIG_OVERLAY_DTB, libfdt functionalities will be needed during runtime.
ifneq ($(CONFIG_OVERLAY_DTB),y)
-OBJCOPYFLAGS := $(foreach s,$(SECTIONS),--rename-section .$(s)=.init.$(s))
+ ifneq ($(CONFIG_COVERAGE),y)
+ OBJCOPYFLAGS := $(foreach s,$(SECTIONS),--rename-section
.$(s)=.init.$(s))
+ endif
endif
obj-y += libfdt.o
--
Best regards,
-grygorii
