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Subject[tip: x86/kdump] x86/purgatory: Disable various profiling and sanitizing options
The following commit has been merged into the x86/kdump branch of tip:

Commit-ID: e2ac07c06058ae2d58b45bbf2a2a352771d76fcb
Gitweb: https://git.kernel.org/tip/e2ac07c06058ae2d58b45bbf2a2a352771d76fcb
Author: Hans de Goede <hdegoede@redhat.com>
AuthorDate: Tue, 17 Mar 2020 14:08:40 +01:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Tue, 17 Mar 2020 15:57:19 +01:00

x86/purgatory: Disable various profiling and sanitizing options

Since the purgatory is a special stand-alone binary, various profiling
and sanitizing options must be disabled. Having these options enabled
typically will cause dependencies on various special symbols exported by
special libs / stubs used by these frameworks. Since the purgatory is
special, it is not linked against these stubs causing missing symbols in
the purgatory if these options are not disabled.

Sync the set of disabled profiling and sanitizing options with that from
drivers/firmware/efi/libstub/Makefile, adding
-DDISABLE_BRANCH_PROFILING to the CFLAGS and setting:

GCOV_PROFILE := n
UBSAN_SANITIZE := n

This fixes broken references to ftrace_likely_update() when
CONFIG_TRACE_BRANCH_PROFILING is enabled and to __gcov_init() and
__gcov_exit() when CONFIG_GCOV_KERNEL is enabled.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200317130841.290418-1-hdegoede@redhat.com
---
arch/x86/purgatory/Makefile | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index fb4ee54..9733d1c 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -17,7 +17,10 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS
LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
targets += purgatory.ro

+# Sanitizer, etc. runtimes are unavailable and cannot be linked here.
+GCOV_PROFILE := n
KASAN_SANITIZE := n
+UBSAN_SANITIZE := n
KCOV_INSTRUMENT := n

# These are adjustments to the compiler flags used for objects that
@@ -25,7 +28,7 @@ KCOV_INSTRUMENT := n

PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss
-PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN)
+PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING

# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
# in turn leaves some undefined symbols like __fentry__ in purgatory and not
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