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| Started by | Baoquan He <bhe@redhat.com> |
|---|---|
| First post | 2016-03-22 08:40 +0100 |
| Last post | 2016-03-22 22:00 +0100 |
| Articles | 2 — 2 participants |
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[PATCH v4 06/20] x86, boot: Fix run_size calculation Baoquan He <bhe@redhat.com> - 2016-03-22 08:40 +0100
Re: [PATCH v4 06/20] x86, boot: Fix run_size calculation Kees Cook <keescook@chromium.org> - 2016-03-22 22:00 +0100
| From | Baoquan He <bhe@redhat.com> |
|---|---|
| Date | 2016-03-22 08:40 +0100 |
| Subject | [PATCH v4 06/20] x86, boot: Fix run_size calculation |
| Message-ID | <rfp51-1bB-43@gated-at.bofh.it> |
From: Yinghai Lu <yinghai@kernel.org>
Firstly, current run_size is calculated via shell script
arch/x86/tools/calc_run_size.sh. It gets file offset and mem size of section
.bss and .brk in vmlinux, then add them as follows:
run_size=$(( $offsetA + $sizeA + $sizeB ))
However this is completely wrong. The offset is the starting address of
section or segment in elf file. Below is a vmlinux I compiled:
[bhe@x1 linux]$ objdump -h vmlinux
vmlinux: file format elf64-x86-64
Sections:
Idx Name Size VMA LMA File off Algn
27 .bss 00170000 ffffffff81ec8000 0000000001ec8000 012c8000 2**12
ALLOC
28 .brk 00027000 ffffffff82038000 0000000002038000 012c8000 2**0
ALLOC
Here we can get run_size is 0x145f000.
0x012c8000 + 0x00170000 + 0x00027000 = 0x145f000
[bhe@x1 linux]$ readelf -l vmlinux
Elf file type is EXEC (Executable file)
Entry point 0x1000000
There are 5 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000200000 0xffffffff81000000 0x0000000001000000
0x0000000000b5e000 0x0000000000b5e000 R E 200000
LOAD 0x0000000000e00000 0xffffffff81c00000 0x0000000001c00000
0x0000000000145000 0x0000000000145000 RW 200000
LOAD 0x0000000001000000 0x0000000000000000 0x0000000001d45000
0x0000000000018158 0x0000000000018158 RW 200000
LOAD 0x000000000115e000 0xffffffff81d5e000 0x0000000001d5e000
0x000000000016a000 0x0000000000301000 RWE 200000
NOTE 0x000000000099bcac 0xffffffff8179bcac 0x000000000179bcac
0x00000000000001bc 0x00000000000001bc 4
Section to Segment mapping:
Segment Sections...
00 .text .notes __ex_table .rodata __bug_table .pci_fixup .tracedata __ksymtab __ksymtab_gpl __ksymtab_strings __init_rodata __param __modver
01 .data .vvar
02 .data..percpu
03 .init.text .init.data .x86_cpu_dev.init .parainstructions .altinstructions .altinstr_replacement .iommu_table .apicdrivers .exit.text .smp_locks .bss .brk
04 .notes
Here we can get the same value as current run_size if we add p_offset
and p_memsz.
0x000000000115e000 + 0x0000000000301000 = 0x145f000
But is it right? Obviously not. We should calculate it using the last LOAD
program segment like this:
run_size = phdr->p_paddr + phdr->p_memsz - physical load addr of kernel
run_size = 0x0000000001d5e000 + 0x0000000000301000 - 0x0000000001000000 = 0x105f000
It's equal to VO_end-VO_text and certainly it's simpler to do.
_end: 0xffffffff8205f000
_text:0xffffffff81000000
run_size = 0xffffffff8205f000 - 0xffffffff81000000 = 0x105f000
Secondly run_size is a simple constant, we don't need to pass it around
and we already have voffset.h for that. We can share voffset.h between
misc.c and header.S instead of getting run_size in other ways. Hence in
this patch, we move voffset.h creation code to boot/compressed/Makefile.
Dependence was:
boot/header.S ==> boot/voffset.h ==> vmlinux
boot/header.S ==> compressed/vmlinux ==> compressed/misc.c
Now become:
boot/header.S ==> compressed/vmlinux ==> compressed/misc.c ==> boot/voffset.h ==> vmlinux
Use macro in misc.c to replace passed run_size.
Fixes: e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd")
Cc: Junjie Mao <eternal.n08@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Baoquan He <bhe@redhat.com>
---
v2->v3:
Adjust the patch log.
v3->v4:
Correct calculation errors in patch log that Kees pointed out.
arch/x86/boot/Makefile | 11 +----------
arch/x86/boot/compressed/Makefile | 12 ++++++++++++
arch/x86/boot/compressed/misc.c | 3 +++
3 files changed, 16 insertions(+), 10 deletions(-)
diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index bd021e5..40f0ae2 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -78,15 +78,6 @@ $(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
-sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|_end\)$$/\#define VO_\2 0x\1/p'
-
-quiet_cmd_voffset = VOFFSET $@
- cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@
-
-targets += voffset.h
-$(obj)/voffset.h: vmlinux FORCE
- $(call if_changed,voffset)
-
sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(startup_32\|startup_64\|efi32_stub_entry\|efi64_stub_entry\|efi_pe_entry\|input_data\|_end\|_ehead\|_text\|z_.*\)$$/\#define ZO_\2 0x\1/p'
quiet_cmd_zoffset = ZOFFSET $@
@@ -98,7 +89,7 @@ $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE
AFLAGS_header.o += -I$(obj)
-$(obj)/header.o: $(obj)/voffset.h $(obj)/zoffset.h
+$(obj)/header.o: $(obj)/zoffset.h
LDFLAGS_setup.elf := -T
$(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index f9ce75d..d9dedd9 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -41,6 +41,18 @@ LDFLAGS_vmlinux := -T
hostprogs-y := mkpiggy
HOST_EXTRACFLAGS += -I$(srctree)/tools/include
+sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p'
+
+quiet_cmd_voffset = VOFFSET $@
+ cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@
+
+targets += ../voffset.h
+
+$(obj)/../voffset.h: vmlinux FORCE
+ $(call if_changed,voffset)
+
+$(obj)/misc.o: $(obj)/../voffset.h
+
vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
$(obj)/string.o $(obj)/cmdline.o \
$(obj)/piggy.o $(obj)/cpuflags.o
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index e7c6fdf..4d317b7 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -11,6 +11,7 @@
#include "misc.h"
#include "../string.h"
+#include "../voffset.h"
/* WARNING!!
* This code is compiled with -fPIC and it is relocated dynamically
@@ -415,6 +416,8 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
lines = real_mode->screen_info.orig_video_lines;
cols = real_mode->screen_info.orig_video_cols;
+ run_size = VO__end - VO__text;
+
console_init();
debug_putstr("early console in decompress_kernel\n");
--
2.5.0
[toc] | [next] | [standalone]
| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Date | 2016-03-22 22:00 +0100 |
| Message-ID | <rfBzc-1rA-15@gated-at.bofh.it> |
| In reply to | #1362380 |
On Tue, Mar 22, 2016 at 12:32 AM, Baoquan He <bhe@redhat.com> wrote:
> From: Yinghai Lu <yinghai@kernel.org>
>
> Firstly, current run_size is calculated via shell script
> arch/x86/tools/calc_run_size.sh. It gets file offset and mem size of section
> .bss and .brk in vmlinux, then add them as follows:
>
> run_size=$(( $offsetA + $sizeA + $sizeB ))
>
> However this is completely wrong. The offset is the starting address of
> section or segment in elf file. Below is a vmlinux I compiled:
>
> [bhe@x1 linux]$ objdump -h vmlinux
>
> vmlinux: file format elf64-x86-64
>
> Sections:
> Idx Name Size VMA LMA File off Algn
> 27 .bss 00170000 ffffffff81ec8000 0000000001ec8000 012c8000 2**12
> ALLOC
> 28 .brk 00027000 ffffffff82038000 0000000002038000 012c8000 2**0
> ALLOC
>
> Here we can get run_size is 0x145f000.
> 0x012c8000 + 0x00170000 + 0x00027000 = 0x145f000
>
> [bhe@x1 linux]$ readelf -l vmlinux
>
> Elf file type is EXEC (Executable file)
> Entry point 0x1000000
> There are 5 program headers, starting at offset 64
>
> Program Headers:
> Type Offset VirtAddr PhysAddr
> FileSiz MemSiz Flags Align
> LOAD 0x0000000000200000 0xffffffff81000000 0x0000000001000000
> 0x0000000000b5e000 0x0000000000b5e000 R E 200000
> LOAD 0x0000000000e00000 0xffffffff81c00000 0x0000000001c00000
> 0x0000000000145000 0x0000000000145000 RW 200000
> LOAD 0x0000000001000000 0x0000000000000000 0x0000000001d45000
> 0x0000000000018158 0x0000000000018158 RW 200000
> LOAD 0x000000000115e000 0xffffffff81d5e000 0x0000000001d5e000
> 0x000000000016a000 0x0000000000301000 RWE 200000
> NOTE 0x000000000099bcac 0xffffffff8179bcac 0x000000000179bcac
> 0x00000000000001bc 0x00000000000001bc 4
>
> Section to Segment mapping:
> Segment Sections...
> 00 .text .notes __ex_table .rodata __bug_table .pci_fixup .tracedata __ksymtab __ksymtab_gpl __ksymtab_strings __init_rodata __param __modver
> 01 .data .vvar
> 02 .data..percpu
> 03 .init.text .init.data .x86_cpu_dev.init .parainstructions .altinstructions .altinstr_replacement .iommu_table .apicdrivers .exit.text .smp_locks .bss .brk
> 04 .notes
>
> Here we can get the same value as current run_size if we add p_offset
> and p_memsz.
> 0x000000000115e000 + 0x0000000000301000 = 0x145f000
>
> But is it right? Obviously not. We should calculate it using the last LOAD
> program segment like this:
> run_size = phdr->p_paddr + phdr->p_memsz - physical load addr of kernel
> run_size = 0x0000000001d5e000 + 0x0000000000301000 - 0x0000000001000000 = 0x105f000
>
> It's equal to VO_end-VO_text and certainly it's simpler to do.
> _end: 0xffffffff8205f000
> _text:0xffffffff81000000
> run_size = 0xffffffff8205f000 - 0xffffffff81000000 = 0x105f000
>
> Secondly run_size is a simple constant, we don't need to pass it around
> and we already have voffset.h for that. We can share voffset.h between
> misc.c and header.S instead of getting run_size in other ways. Hence in
> this patch, we move voffset.h creation code to boot/compressed/Makefile.
>
> Dependence was:
> boot/header.S ==> boot/voffset.h ==> vmlinux
> boot/header.S ==> compressed/vmlinux ==> compressed/misc.c
> Now become:
> boot/header.S ==> compressed/vmlinux ==> compressed/misc.c ==> boot/voffset.h ==> vmlinux
>
> Use macro in misc.c to replace passed run_size.
>
> Fixes: e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd")
> Cc: Junjie Mao <eternal.n08@gmail.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> Signed-off-by: Baoquan He <bhe@redhat.com>
Thanks for spending the time to convince me on this. :)
Acked-by: Kees Cook <keescook@chromium.org>
-Kees
> ---
> v2->v3:
> Adjust the patch log.
> v3->v4:
> Correct calculation errors in patch log that Kees pointed out.
>
> arch/x86/boot/Makefile | 11 +----------
> arch/x86/boot/compressed/Makefile | 12 ++++++++++++
> arch/x86/boot/compressed/misc.c | 3 +++
> 3 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
> index bd021e5..40f0ae2 100644
> --- a/arch/x86/boot/Makefile
> +++ b/arch/x86/boot/Makefile
> @@ -78,15 +78,6 @@ $(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
>
> SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
>
> -sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|_end\)$$/\#define VO_\2 0x\1/p'
> -
> -quiet_cmd_voffset = VOFFSET $@
> - cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@
> -
> -targets += voffset.h
> -$(obj)/voffset.h: vmlinux FORCE
> - $(call if_changed,voffset)
> -
> sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(startup_32\|startup_64\|efi32_stub_entry\|efi64_stub_entry\|efi_pe_entry\|input_data\|_end\|_ehead\|_text\|z_.*\)$$/\#define ZO_\2 0x\1/p'
>
> quiet_cmd_zoffset = ZOFFSET $@
> @@ -98,7 +89,7 @@ $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE
>
>
> AFLAGS_header.o += -I$(obj)
> -$(obj)/header.o: $(obj)/voffset.h $(obj)/zoffset.h
> +$(obj)/header.o: $(obj)/zoffset.h
>
> LDFLAGS_setup.elf := -T
> $(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index f9ce75d..d9dedd9 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -41,6 +41,18 @@ LDFLAGS_vmlinux := -T
> hostprogs-y := mkpiggy
> HOST_EXTRACFLAGS += -I$(srctree)/tools/include
>
> +sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p'
> +
> +quiet_cmd_voffset = VOFFSET $@
> + cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@
> +
> +targets += ../voffset.h
> +
> +$(obj)/../voffset.h: vmlinux FORCE
> + $(call if_changed,voffset)
> +
> +$(obj)/misc.o: $(obj)/../voffset.h
> +
> vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
> $(obj)/string.o $(obj)/cmdline.o \
> $(obj)/piggy.o $(obj)/cpuflags.o
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index e7c6fdf..4d317b7 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -11,6 +11,7 @@
>
> #include "misc.h"
> #include "../string.h"
> +#include "../voffset.h"
>
> /* WARNING!!
> * This code is compiled with -fPIC and it is relocated dynamically
> @@ -415,6 +416,8 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
> lines = real_mode->screen_info.orig_video_lines;
> cols = real_mode->screen_info.orig_video_cols;
>
> + run_size = VO__end - VO__text;
> +
> console_init();
> debug_putstr("early console in decompress_kernel\n");
>
> --
> 2.5.0
>
--
Kees Cook
Chrome OS & Brillo Security
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