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Groups > linux.kernel > #1379345
| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v5 04/21] x86, boot: Move compressed kernel to end of decompression buffer |
| Date | 2016-04-15 00:40 +0200 |
| Message-ID | <rnY5B-14p-29@gated-at.bofh.it> (permalink) |
| References | <rnXVT-YO-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
From: Yinghai Lu <yinghai@kernel.org>
This change makes later calculations about where the kernel is located
easier to reason about. To better understand this change, we must first
clarify what VO and ZO are. They were introduced in commits by hpa:
77d1a49 x86, boot: make symbols from the main vmlinux available
37ba7ab x86, boot: make kernel_alignment adjustable; new bzImage fields
Specifically:
VO:
- uncompressed kernel image
- size: VO__end - VO__text ("VO_INIT_SIZE" define)
ZO:
- bootable compressed kernel image (boot/compressed/vmlinux)
- head text + compressed kernel (VO and relocs table) + decompressor code
- size: ZO__end - ZO_startup_32 ("ZO_INIT_SIZE" define, though see below)
The INIT_SIZE definition is used to find the larger of the two image sizes:
#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset)
#define VO_INIT_SIZE (VO__end - VO__text)
#if ZO_INIT_SIZE > VO_INIT_SIZE
#define INIT_SIZE ZO_INIT_SIZE
#else
#define INIT_SIZE VO_INIT_SIZE
#endif
The current code uses extract_offset to decide where to position the
copied ZO (i.e. ZO starts at extract_offset). (This is why ZO_INIT_SIZE
currently includes the extract_offset.)
When INIT_SIZE is bigger than VO_INIT_SIZE (uncommon but possible),
the copied ZO occupies the memory from extract_offset to the end of
decompression buffer. It overlaps with the soon-to-be-uncompressed kernel
like this:
|-----compressed kernel image------|
V V
0 extract_offset +INIT_SIZE
|-----------|---------------|-------------------------|--------|
| | | |
VO__text startup_32 of ZO VO__end ZO__end
^ ^
|-------uncompressed kernel image---------|
When INIT_SIZE is equal to VO_INIT_SIZE (likely) there's still space
left from end of ZO to the end of decompressing buffer, like below.
|-compressed kernel image-|
V V
0 extract_offset +INIT_SIZE
|-----------|---------------|-------------------------|--------|
| | | |
VO__text startup_32 of ZO ZO__end VO__end
^ ^
|------------uncompressed kernel image-------------|
To simplify calculations and avoid special cases, it is cleaner to
always place the compressed kernel image in memory so that ZO__end
is at the end of the decompression buffer, instead of placing that
start extract_offset as is currently done.
This patch adds BP_init_size (which is the INIT_SIZE as passed in from
the boot_params) into asm-offsets.c to make it visible to the assembly
code. Then when moving the ZO, it calculates the starting position of
the copied ZO (via BP_init_size and the ZO run size) so that the VO__end
will be at the end of the decompression buffer. To make the position
calculation safe, the end of ZO is page aligned (and a comment is added
to the existing VO alignment for good measure).
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
[kees: rewrote changelog]
Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/boot/compressed/head_32.S | 11 +++++++++--
arch/x86/boot/compressed/head_64.S | 8 ++++++--
arch/x86/boot/compressed/mkpiggy.c | 3 ---
arch/x86/boot/compressed/vmlinux.lds.S | 1 +
arch/x86/kernel/asm-offsets.c | 1 +
arch/x86/kernel/vmlinux.lds.S | 2 +-
6 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 8ef964ddc18e..0c140f99c602 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -148,7 +148,9 @@ preferred_addr:
1:
/* Target address to relocate to for decompression */
- addl $z_extract_offset, %ebx
+ movl BP_init_size(%esi), %eax
+ subl $_end, %eax
+ addl %eax, %ebx
/* Set up the stack */
leal boot_stack_end(%ebx), %esp
@@ -210,8 +212,13 @@ relocated:
/* push arguments for decompress_kernel: */
pushl $z_run_size /* size of kernel with .bss and .brk */
pushl $z_output_len /* decompressed length, end of relocs */
- leal z_extract_offset_negative(%ebx), %ebp
+
+ movl BP_init_size(%esi), %eax
+ subl $_end, %eax
+ movl %ebx, %ebp
+ subl %eax, %ebp
pushl %ebp /* output address */
+
pushl $z_input_len /* input_len */
leal input_data(%ebx), %eax
pushl %eax /* input_data */
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index b0c0d16ef58d..67dd8d300c61 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -102,7 +102,9 @@ ENTRY(startup_32)
1:
/* Target address to relocate to for decompression */
- addl $z_extract_offset, %ebx
+ movl BP_init_size(%esi), %eax
+ subl $_end, %eax
+ addl %eax, %ebx
/*
* Prepare for entering 64 bit mode
@@ -330,7 +332,9 @@ preferred_addr:
1:
/* Target address to relocate to for decompression */
- leaq z_extract_offset(%rbp), %rbx
+ movl BP_init_size(%rsi), %ebx
+ subl $_end, %ebx
+ addq %rbp, %rbx
/* Set up the stack */
leaq boot_stack_end(%rbx), %rsp
diff --git a/arch/x86/boot/compressed/mkpiggy.c b/arch/x86/boot/compressed/mkpiggy.c
index d8222f213182..b980046c3329 100644
--- a/arch/x86/boot/compressed/mkpiggy.c
+++ b/arch/x86/boot/compressed/mkpiggy.c
@@ -85,9 +85,6 @@ int main(int argc, char *argv[])
printf("z_output_len = %lu\n", (unsigned long)olen);
printf(".globl z_extract_offset\n");
printf("z_extract_offset = 0x%lx\n", offs);
- /* z_extract_offset_negative allows simplification of head_32.S */
- printf(".globl z_extract_offset_negative\n");
- printf("z_extract_offset_negative = -0x%lx\n", offs);
printf(".globl z_run_size\n");
printf("z_run_size = %lu\n", run_size);
diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
index 34d047c98284..e24e0a0c90c9 100644
--- a/arch/x86/boot/compressed/vmlinux.lds.S
+++ b/arch/x86/boot/compressed/vmlinux.lds.S
@@ -70,5 +70,6 @@ SECTIONS
_epgtable = . ;
}
#endif
+ . = ALIGN(PAGE_SIZE); /* keep ZO size page aligned */
_end = .;
}
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 5c042466f274..674134e9f5e5 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -80,6 +80,7 @@ void common(void) {
OFFSET(BP_hardware_subarch, boot_params, hdr.hardware_subarch);
OFFSET(BP_version, boot_params, hdr.version);
OFFSET(BP_kernel_alignment, boot_params, hdr.kernel_alignment);
+ OFFSET(BP_init_size, boot_params, hdr.init_size);
OFFSET(BP_pref_address, boot_params, hdr.pref_address);
OFFSET(BP_code32_start, boot_params, hdr.code32_start);
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 4c941f88d405..9297a002d8e5 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -334,7 +334,7 @@ SECTIONS
__brk_limit = .;
}
- . = ALIGN(PAGE_SIZE);
+ . = ALIGN(PAGE_SIZE); /* keep VO_INIT_SIZE page aligned */
_end = .;
STABS_DEBUG
--
2.6.3
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH v5 00/21] x86, boot: KASLR cleanup and 64-bit improvements Kees Cook <keescook@chromium.org> - 2016-04-15 00:30 +0200
[PATCH v5 05/21] x86, boot: Calculate decompression size during boot not build Kees Cook <keescook@chromium.org> - 2016-04-15 00:30 +0200
Re: [PATCH v5 05/21] x86, boot: Calculate decompression size during boot not build Ingo Molnar <mingo@kernel.org> - 2016-04-15 10:20 +0200
[PATCH v5 21/21] x86, KASLR: Allow randomization below load address Kees Cook <keescook@chromium.org> - 2016-04-15 00:30 +0200
[PATCH v5 09/21] x86, KASLR: Correctly bounds-check relocations Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 20/21] x86, KASLR: Remove unused slot tracking code Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 01/21] x86, KASLR: Remove unneeded boot_params argument Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
Re: [PATCH v5 01/21] x86, KASLR: Remove unneeded boot_params argument Ingo Molnar <mingo@kernel.org> - 2016-04-15 09:30 +0200
[PATCH v5 19/21] x86, KASLR: Add physical address randomization >4G Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 13/21] x86, boot: Report overlap failures in memcpy Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
Re: [PATCH v5 13/21] x86, boot: Report overlap failures in memcpy Lasse Collin <lasse.collin@tukaani.org> - 2016-04-15 17:00 +0200
[PATCH v5 02/21] x86, KASLR: Handle kernel relocation above 2G Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
Re: [PATCH v5 02/21] x86, KASLR: Handle kernel relocation above 2G Ingo Molnar <mingo@kernel.org> - 2016-04-15 09:50 +0200
[PATCH v5 16/21] x86, KASLR: Add virtual address choosing function Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 15/21] x86, KASLR: Add slot_area support functions Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 04/21] x86, boot: Move compressed kernel to end of decompression buffer Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
Re: [PATCH v5 04/21] x86, boot: Move compressed kernel to end of decompression buffer Ingo Molnar <mingo@kernel.org> - 2016-04-15 10:20 +0200
Re: [PATCH v5 04/21] x86, boot: Move compressed kernel to end of decompression buffer Ingo Molnar <mingo@kernel.org> - 2016-04-15 11:10 +0200
[PATCH v5 12/21] x86, 64bit: Set ident_mapping for KASLR Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 08/21] x86, KASLR: Clean up unused code from old run_size Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 14/21] x86, KASLR: Add slot_area to manage random slots Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 17/21] x86, KASLR: Clarify purpose of each get_random_long Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 11/21] x86, boot: Split out kernel_ident_mapping_init Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 10/21] x86, KASLR: Consolidate mem_avoid entries Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
[PATCH v5 03/21] x86, KASLR: Drop CONFIG_RANDOMIZE_BASE_MAX_OFFSET Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
Re: [PATCH v5 03/21] x86, KASLR: Drop CONFIG_RANDOMIZE_BASE_MAX_OFFSET Ingo Molnar <mingo@kernel.org> - 2016-04-15 10:10 +0200
[PATCH v5 06/21] x86, KASLR: Update description for decompressor worst case size Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
Re: [PATCH v5 06/21] x86, KASLR: Update description for decompressor worst case size Lasse Collin <lasse.collin@tukaani.org> - 2016-04-15 18:20 +0200
[PATCH v5 07/21] x86, boot: Fix run_size calculation Kees Cook <keescook@chromium.org> - 2016-04-15 00:40 +0200
Re: [PATCH v5 07/21] x86, boot: Fix run_size calculation Ingo Molnar <mingo@kernel.org> - 2016-04-15 10:40 +0200
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