linux-kernel - Re: [PATCH v4 2/2] x86/purgatory: Make sure we fail the build if purgatory.ro has missing symbols

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Message-ID: <20200312001006.GA170175@rani.riverdale.lan>
Date:   Wed, 11 Mar 2020 20:10:08 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] x86/purgatory: Make sure we fail the build if
 purgatory.ro has missing symbols

On Wed, Mar 11, 2020 at 10:46:01PM +0100, Hans de Goede wrote:
> Since we link purgatory.ro with -r aka we enable "incremental linking"
> no checks for unresolved symbols is done while linking purgatory.ro.
> 

Do we actually need to link purgatory with -r? We could use
--emit-relocs to get the relocation sections generated the way the main
x86 kernel does, no?

Eg like the below? This would avoid the double-link creating
purgatory.chk.

diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index fb4ee5444379..5332f95ca1d3 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -14,8 +14,8 @@ $(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
+LDFLAGS_purgatory := -e purgatory_start --emit-relocs -nostdlib -z nodefaultlib
+targets += purgatory
 
 KASAN_SANITIZE	:= n
 KCOV_INSTRUMENT := n
@@ -55,7 +55,7 @@ CFLAGS_sha256.o			+= $(PURGATORY_CFLAGS)
 CFLAGS_REMOVE_string.o		+= $(PURGATORY_CFLAGS_REMOVE)
 CFLAGS_string.o			+= $(PURGATORY_CFLAGS)
 
-$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
+$(obj)/purgatory: $(PURGATORY_OBJS) FORCE
 		$(call if_changed,ld)
 
 targets += kexec-purgatory.c
@@ -63,7 +63,7 @@ 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 FORCE
 	$(call if_changed,bin2c)
 
 obj-$(CONFIG_KEXEC_FILE)	+= kexec-purgatory.o