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Subject[tip: x86/kdump] x86/purgatory: Fail the build if purgatory.ro has missing symbols
The following commit has been merged into the x86/kdump branch of tip:

Commit-ID: e4160b2e4b02377c67f8ecd05786811598f39acd
Gitweb: https://git.kernel.org/tip/e4160b2e4b02377c67f8ecd05786811598f39acd
Author: Hans de Goede <hdegoede@redhat.com>
AuthorDate: Tue, 17 Mar 2020 14:08:41 +01:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Tue, 17 Mar 2020 15:59:12 +01:00

x86/purgatory: Fail the build if purgatory.ro has missing symbols

Linking purgatory.ro with -r enables "incremental linking"; this means
no checks for unresolved symbols are done while linking purgatory.ro.

A change to the sha256 code has caused the purgatory in 5.4-rc1 to have
a missing symbol on memzero_explicit(), yet things still happily build.

Add an extra check for unresolved symbols by calling ld without -r
before running bin2c to generate kexec-purgatory.c.

This causes a build of 5.4-rc1 with this patch added to fail as it should:

CHK arch/x86/purgatory/purgatory.ro
ld: arch/x86/purgatory/purgatory.ro: in function `sha256_transform':
sha256.c:(.text+0x1c0c): undefined reference to `memzero_explicit'
make[2]: *** [arch/x86/purgatory/Makefile:72:
arch/x86/purgatory/kexec-purgatory.c] Error 1
make[1]: *** [scripts/Makefile.build:509: arch/x86/purgatory] Error 2
make: *** [Makefile:1650: arch/x86] Error 2

Also remove --no-undefined from LDFLAGS_purgatory.ro as that has no
effect.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200317130841.290418-2-hdegoede@redhat.com
---
arch/x86/purgatory/.gitignore | 1 +
arch/x86/purgatory/Makefile | 13 ++++++++++---
2 files changed, 11 insertions(+), 3 deletions(-)
create mode 100644 arch/x86/purgatory/.gitignore

diff --git a/arch/x86/purgatory/.gitignore b/arch/x86/purgatory/.gitignore
new file mode 100644
index 0000000..d2be150
--- /dev/null
+++ b/arch/x86/purgatory/.gitignore
@@ -0,0 +1 @@
+purgatory.chk
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 9733d1c..54aadbb 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -14,8 +14,12 @@ $(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE

CFLAGS_sha256.o := -D__DISABLE_EXPORTS

-LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
-targets += purgatory.ro
+# When linking purgatory.ro with -r unresolved symbols are not checked,
+# also link a purgatory.chk binary without -r to check for unresolved symbols.
+PURGATORY_LDFLAGS := -e purgatory_start -nostdlib -z nodefaultlib
+LDFLAGS_purgatory.ro := -r $(PURGATORY_LDFLAGS)
+LDFLAGS_purgatory.chk := $(PURGATORY_LDFLAGS)
+targets += purgatory.ro purgatory.chk

# Sanitizer, etc. runtimes are unavailable and cannot be linked here.
GCOV_PROFILE := n
@@ -61,12 +65,15 @@ CFLAGS_string.o += $(PURGATORY_CFLAGS)
$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
$(call if_changed,ld)

+$(obj)/purgatory.chk: $(obj)/purgatory.ro FORCE
+ $(call if_changed,ld)
+
targets += kexec-purgatory.c

quiet_cmd_bin2c = BIN2C $@
cmd_bin2c = $(objtree)/scripts/bin2c kexec_purgatory < $< > $@

-$(obj)/kexec-purgatory.c: $(obj)/purgatory.ro FORCE
+$(obj)/kexec-purgatory.c: $(obj)/purgatory.ro $(obj)/purgatory.chk FORCE
$(call if_changed,bin2c)

obj-$(CONFIG_KEXEC_FILE) += kexec-purgatory.o
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