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From: Kees Cook <keescook@chromium.org>
To: Thomas Gleixner <tglx@linutronix.de>, Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	linux-efi@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Ard Biesheuvel <ardb@kernel.org>,
	linux-arch@vger.kernel.org, Fangrui Song <maskray@google.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	x86@kernel.org, Russell King <linux@armlinux.org.uk>,
	clang-built-linux@googlegroups.com,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@suse.de>,
	Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
	Sedat Dilek <sedat.dilek@gmail.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Peter Collingbourne <pcc@google.com>,
	linux-arm-kernel@lists.infradead.org,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org, James Morse <james.morse@arm.com>
Subject: [PATCH v5 06/36] x86/boot: Remove run-time relocations from head_{32, 64}.S
Date: Fri, 31 Jul 2020 16:07:50 -0700
Message-ID: <20200731230820.1742553-7-keescook@chromium.org> (raw)
In-Reply-To: <20200731230820.1742553-1-keescook@chromium.org>

From: Arvind Sankar <nivedita@alum.mit.edu>

The BFD linker generates run-time relocations for z_input_len and
z_output_len, even though they are absolute symbols.

This is fixed for binutils-2.35 [1]. Work around this for earlier
versions by defining two variables input_len and output_len in addition
to the symbols, and use them via position-independent references.

This eliminates the last two run-time relocations in the head code and
allows us to drop the -z noreloc-overflow flag to the linker.

Move the -pie and --no-dynamic-linker LDFLAGS to LDFLAGS_vmlinux instead
of KBUILD_LDFLAGS. There shouldn't be anything else getting linked, but
this is the more logical location for these flags, and modversions might
call the linker if an EXPORT_SYMBOL is left over accidentally in one of
the decompressors.

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=25754

Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/boot/compressed/Makefile  | 12 ++----------
 arch/x86/boot/compressed/head_32.S | 17 ++++++++---------
 arch/x86/boot/compressed/head_64.S |  4 ++--
 arch/x86/boot/compressed/mkpiggy.c |  6 ++++++
 4 files changed, 18 insertions(+), 21 deletions(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 489fea16bcfb..7db0102a573d 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -51,16 +51,8 @@ UBSAN_SANITIZE :=n
 KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)
 # Compressed kernel should be built as PIE since it may be loaded at any
 # address by the bootloader.
-ifeq ($(CONFIG_X86_32),y)
-KBUILD_LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
-else
-# To build 64-bit compressed kernel as PIE, we disable relocation
-# overflow check to avoid relocation overflow error with a new linker
-# command-line option, -z noreloc-overflow.
-KBUILD_LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "\-z noreloc-overflow" \
-	&& echo "-z noreloc-overflow -pie --no-dynamic-linker")
-endif
-LDFLAGS_vmlinux := -T
+LDFLAGS_vmlinux := $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
+LDFLAGS_vmlinux += -T
 
 hostprogs	:= mkpiggy
 HOST_EXTRACFLAGS += -I$(srctree)/tools/include
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 8c1a4f5610f5..659fad53ca82 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -178,18 +178,17 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 /*
  * Do the extraction, and jump to the new kernel..
  */
-				/* push arguments for extract_kernel: */
-	pushl	$z_output_len	/* decompressed length, end of relocs */
+	/* push arguments for extract_kernel: */
 
-	pushl	%ebp		/* output address */
-
-	pushl	$z_input_len	/* input_len */
+	pushl	output_len@GOTOFF(%ebx)	/* decompressed length, end of relocs */
+	pushl	%ebp			/* output address */
+	pushl	input_len@GOTOFF(%ebx)	/* input_len */
 	leal	input_data@GOTOFF(%ebx), %eax
-	pushl	%eax		/* input_data */
+	pushl	%eax			/* input_data */
 	leal	boot_heap@GOTOFF(%ebx), %eax
-	pushl	%eax		/* heap area */
-	pushl	%esi		/* real mode pointer */
-	call	extract_kernel	/* returns kernel location in %eax */
+	pushl	%eax			/* heap area */
+	pushl	%esi			/* real mode pointer */
+	call	extract_kernel		/* returns kernel location in %eax */
 	addl	$24, %esp
 
 /*
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 11429092c224..9e46729cf162 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -534,9 +534,9 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 	movq	%rsi, %rdi		/* real mode address */
 	leaq	boot_heap(%rip), %rsi	/* malloc area for uncompression */
 	leaq	input_data(%rip), %rdx  /* input_data */
-	movl	$z_input_len, %ecx	/* input_len */
+	movl	input_len(%rip), %ecx	/* input_len */
 	movq	%rbp, %r8		/* output target address */
-	movl	$z_output_len, %r9d	/* decompressed length, end of relocs */
+	movl	output_len(%rip), %r9d	/* decompressed length, end of relocs */
 	call	extract_kernel		/* returns kernel location in %rax */
 	popq	%rsi
 
diff --git a/arch/x86/boot/compressed/mkpiggy.c b/arch/x86/boot/compressed/mkpiggy.c
index 7e01248765b2..52aa56cdbacc 100644
--- a/arch/x86/boot/compressed/mkpiggy.c
+++ b/arch/x86/boot/compressed/mkpiggy.c
@@ -60,6 +60,12 @@ int main(int argc, char *argv[])
 	printf(".incbin \"%s\"\n", argv[1]);
 	printf("input_data_end:\n");
 
+	printf(".section \".rodata\",\"a\",@progbits\n");
+	printf(".globl input_len\n");
+	printf("input_len:\n\t.long %lu\n", ilen);
+	printf(".globl output_len\n");
+	printf("output_len:\n\t.long %lu\n", (unsigned long)olen);
+
 	retval = 0;
 bail:
 	if (f)
-- 
2.25.1


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  parent reply index

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31 23:07 [PATCH v5 00/36] Warn on orphan section placement Kees Cook
2020-07-31 23:07 ` [PATCH v5 01/36] x86/boot/compressed: Move .got.plt entries out of the .got section Kees Cook
2020-07-31 23:07 ` [PATCH v5 02/36] x86/boot/compressed: Force hidden visibility for all symbol references Kees Cook
2020-07-31 23:07 ` [PATCH v5 03/36] x86/boot/compressed: Get rid of GOT fixup code Kees Cook
2020-07-31 23:07 ` [PATCH v5 04/36] x86/boot: Add .text.* to setup.ld Kees Cook
2020-07-31 23:07 ` [PATCH v5 05/36] x86/boot: Remove run-time relocations from .head.text code Kees Cook
2020-07-31 23:42   ` Nick Desaulniers
2020-07-31 23:07 ` Kees Cook [this message]
2020-08-07 18:12   ` [PATCH v5 06/36] x86/boot: Remove run-time relocations from head_{32, 64}.S Nick Desaulniers
2020-08-07 20:20     ` [PATCH v5 06/36] x86/boot: Remove run-time relocations from head_{32,64}.S Arvind Sankar
2020-07-31 23:07 ` [PATCH v5 07/36] x86/boot: Check that there are no run-time relocations Kees Cook
2020-07-31 23:07 ` [PATCH v5 08/36] vmlinux.lds.h: Create COMMON_DISCARDS Kees Cook
2020-07-31 23:07 ` [PATCH v5 09/36] vmlinux.lds.h: Add .gnu.version* to COMMON_DISCARDS Kees Cook
2020-07-31 23:07 ` [PATCH v5 10/36] vmlinux.lds.h: Avoid KASAN and KCSAN's unwanted sections Kees Cook
2020-07-31 23:07 ` [PATCH v5 11/36] vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG Kees Cook
2020-07-31 23:07 ` [PATCH v5 12/36] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to ELF_DETAILS Kees Cook
2020-07-31 23:07 ` [PATCH v5 13/36] vmlinux.lds.h: add PGO and AutoFDO input sections Kees Cook
2020-08-01  3:51   ` Arvind Sankar
2020-08-01  6:18     ` Kees Cook
2020-08-01 17:27       ` Arvind Sankar
2020-08-03 19:05     ` Andi Kleen
2020-08-03 20:15       ` Arvind Sankar
2020-08-04  1:19         ` Fāng-ruì Sòng
2020-08-04  4:45         ` Andi Kleen
2020-08-04  5:32           ` Fāng-ruì Sòng
2020-08-04 16:06           ` Arvind Sankar
2020-08-21 19:18             ` Kees Cook
2020-07-31 23:07 ` [PATCH v5 14/36] efi/libstub: Disable -mbranch-protection Kees Cook
2020-07-31 23:07 ` [PATCH v5 15/36] arm64/mm: Remove needless section quotes Kees Cook
2020-07-31 23:08 ` [PATCH v5 16/36] arm64/kernel: Remove needless Call Frame Information annotations Kees Cook
2020-07-31 23:08 ` [PATCH v5 17/36] arm64/build: Remove .eh_frame* sections due to unwind tables Kees Cook
2020-07-31 23:08 ` [PATCH v5 18/36] arm64/build: Use common DISCARDS in linker script Kees Cook
2020-07-31 23:08 ` [PATCH v5 19/36] arm64/build: Add missing DWARF sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 20/36] arm64/build: Assert for unwanted sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 21/36] arm64/build: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 22/36] arm/build: Refactor linker script headers Kees Cook
2020-07-31 23:08 ` [PATCH v5 23/36] arm/build: Explicitly keep .ARM.attributes sections Kees Cook
2020-08-03 19:02   ` Nick Desaulniers
2020-08-17 22:06     ` Fangrui Song
2020-07-31 23:08 ` [PATCH v5 24/36] arm/build: Add missing sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 25/36] arm/build: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 26/36] arm/boot: Handle all sections explicitly Kees Cook
2020-07-31 23:08 ` [PATCH v5 27/36] arm/boot: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 28/36] x86/asm: Avoid generating unused kprobe sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 29/36] x86/build: Enforce an empty .got.plt section Kees Cook
2020-08-01  2:12   ` Arvind Sankar
2020-08-01  5:32     ` Kees Cook
2020-08-21 17:49     ` Kees Cook
2020-07-31 23:08 ` [PATCH v5 30/36] x86/build: Assert for unwanted sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 31/36] x86/build: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 32/36] x86/boot/compressed: Reorganize zero-size section asserts Kees Cook
2020-08-01  1:47   ` Arvind Sankar
2020-08-01  2:53     ` Arvind Sankar
2020-08-01  5:36       ` Kees Cook
2020-08-01 17:12         ` Arvind Sankar
2020-08-21 18:24           ` Kees Cook
2020-08-01  5:35     ` Kees Cook
2020-08-01 17:00       ` Arvind Sankar
2020-08-21 18:19     ` Kees Cook
2020-07-31 23:08 ` [PATCH v5 33/36] x86/boot/compressed: Remove, discard, or assert for unwanted sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 34/36] x86/boot/compressed: Add missing debugging sections to output Kees Cook
2020-07-31 23:08 ` [PATCH v5 35/36] x86/boot/compressed: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 36/36] arm/build: Assert for unwanted sections Kees Cook

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