linux-kernel - [PATCH v5 2/2] x86/purgatory: Add linker script

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Message-Id: <20230321-kexec_clang16-v5-2-5563bf7c4173@chromium.org>
Date:   Thu, 30 Mar 2023 11:44:48 +0200
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Eric Biederman <ebiederm@...ssion.com>
Cc:     Baoquan He <bhe@...hat.com>, Philipp Rudo <prudo@...hat.com>,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Ross Zwisler <zwisler@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Simon Horman <horms@...nel.org>,
        Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v5 2/2] x86/purgatory: Add linker script

Make sure that the .text section is not divided in multiple overlapping
sections. This is not supported by kexec_file.

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 arch/x86/purgatory/.gitignore        |  2 ++
 arch/x86/purgatory/Makefile          | 20 +++++++++----
 arch/x86/purgatory/kexec-purgatory.S |  2 +-
 arch/x86/purgatory/purgatory.lds.S   | 57 ++++++++++++++++++++++++++++++++++++
 4 files changed, 74 insertions(+), 7 deletions(-)

diff --git a/arch/x86/purgatory/.gitignore b/arch/x86/purgatory/.gitignore
index d2be1500671d..1fe71fe5945d 100644
--- a/arch/x86/purgatory/.gitignore
+++ b/arch/x86/purgatory/.gitignore
@@ -1 +1,3 @@
 purgatory.chk
+purgatory.lds
+purgatory
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 17f09dc26381..4dc96d409bec 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -16,10 +16,11 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS
 
 # 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 -z nodefaultlib
-LDFLAGS_purgatory.ro := -r $(PURGATORY_LDFLAGS)
-LDFLAGS_purgatory.chk := $(PURGATORY_LDFLAGS)
-targets += purgatory.ro purgatory.chk
+PURGATORY_LDFLAGS := -nostdlib -z nodefaultlib
+LDFLAGS_purgatory := -r $(PURGATORY_LDFLAGS) -T
+LDFLAGS_purgatory.chk := -e purgatory_start $(PURGATORY_LDFLAGS)
+
+targets += purgatory.lds purgatory.ro purgatory.chk
 
 # Sanitizer, etc. runtimes are unavailable and cannot be linked here.
 GCOV_PROFILE	:= n
@@ -72,10 +73,17 @@ CFLAGS_string.o			+= $(PURGATORY_CFLAGS)
 AFLAGS_REMOVE_setup-x86_$(BITS).o	+= -Wa,-gdwarf-2
 AFLAGS_REMOVE_entry64.o			+= -Wa,-gdwarf-2
 
-$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
+OBJCOPYFLAGS_purgatory.ro := -O elf64-x86-64
+OBJCOPYFLAGS_purgatory.ro += --remove-section='*debug*'
+OBJCOPYFLAGS_purgatory.ro += --remove-section='.comment'
+OBJCOPYFLAGS_purgatory.ro += --remove-section='.note.*'
+$(obj)/purgatory.ro: $(obj)/purgatory FORCE
+		$(call if_changed,objcopy)
+
+$(obj)/purgatory.chk: $(obj)/purgatory FORCE
 		$(call if_changed,ld)
 
-$(obj)/purgatory.chk: $(obj)/purgatory.ro FORCE
+$(obj)/purgatory: $(obj)/purgatory.lds $(PURGATORY_OBJS) FORCE
 		$(call if_changed,ld)
 
 $(obj)/kexec-purgatory.o: $(obj)/purgatory.ro $(obj)/purgatory.chk
diff --git a/arch/x86/purgatory/kexec-purgatory.S b/arch/x86/purgatory/kexec-purgatory.S
index 8530fe93b718..54b0d0b4dc42 100644
--- a/arch/x86/purgatory/kexec-purgatory.S
+++ b/arch/x86/purgatory/kexec-purgatory.S
@@ -5,7 +5,7 @@
 	.align	8
 kexec_purgatory:
 	.globl	kexec_purgatory
-	.incbin	"arch/x86/purgatory/purgatory.ro"
+	.incbin	"arch/x86/purgatory/purgatory"
 .Lkexec_purgatory_end:
 
 	.align	8
diff --git a/arch/x86/purgatory/purgatory.lds.S b/arch/x86/purgatory/purgatory.lds.S
new file mode 100644
index 000000000000..610da88aafa0
--- /dev/null
+++ b/arch/x86/purgatory/purgatory.lds.S
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <asm-generic/vmlinux.lds.h>
+
+OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT)
+
+#undef i386
+
+#include <asm/cache.h>
+#include <asm/page_types.h>
+
+ENTRY(purgatory_start)
+
+SECTIONS
+{
+	. = 0;
+	.head.text : {
+		_head = . ;
+		HEAD_TEXT
+		_ehead = . ;
+	}
+	.rodata : {
+		_rodata = . ;
+		*(.rodata)	 /* read-only data */
+		*(.rodata.*)
+		_erodata = . ;
+	}
+	.text :	{
+		_text = .; 	/* Text */
+		*(.text)
+		*(.text.*)
+		*(.noinstr.text)
+		_etext = . ;
+	}
+	.data :	{
+		_data = . ;
+		*(.data)
+		*(.data.*)
+		*(.bss.efistub)
+		_edata = . ;
+	}
+	. = ALIGN(L1_CACHE_BYTES);
+	.bss : {
+		_bss = . ;
+		*(.bss)
+		*(.bss.*)
+		*(COMMON)
+		. = ALIGN(8);	/* For convenience during zeroing */
+		_ebss = .;
+	}
+
+	/* Sections to be discarded */
+	/DISCARD/ : {
+		*(.eh_frame)
+		*(*__ksymtab*)
+		*(___kcrctab*)
+	}
+}

-- 
2.40.0.348.gf938b09366-goog