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purgatory: core purgatory functionality

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Create a stand alone relocatable object purgatory which runs between two
kernels.  This name, concept and some code has been taken from
kexec-tools.  Idea is that this code runs after a crash and it runs in
minimal environment.  So keep it separate from rest of the kernel and in
long term we will have to practically do no maintenance of this code.

This code also has the logic to do verify sha256 hashes of various
segments which have been loaded into memory.  So first we verify that the
kernel we are jumping to is fine and has not been corrupted and make
progress only if checsums are verified.

This code also takes care of copying some memory contents to backup region.

[sfr@canb.auug.org.au: run host built programs from objtree]
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: WANG Chao <chaowang@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vivek Goyal 2014-08-08 14:26:02 -07:00 committed by Linus Torvalds
parent daeba0641a
commit 8fc5b4d412
8 changed files with 305 additions and 0 deletions
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4
arch/x86/Kbuild
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@ -16,3 +16,7 @@ obj-$(CONFIG_IA32_EMULATION) += ia32/
obj-y += platform/
obj-y += net/
ifeq ($(CONFIG_X86_64),y)
obj-$(CONFIG_KEXEC) += purgatory/
endif

8
arch/x86/Makefile
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@ -183,6 +183,14 @@ archscripts: scripts_basic
archheaders:
$(Q)$(MAKE) $(build)=arch/x86/syscalls all
archprepare:
ifeq ($(CONFIG_KEXEC),y)
# Build only for 64bit. No loaders for 32bit yet.
ifeq ($(CONFIG_X86_64),y)
$(Q)$(MAKE) $(build)=arch/x86/purgatory arch/x86/purgatory/kexec-purgatory.c
endif
endif
###
# Kernel objects

30
arch/x86/purgatory/Makefile Normal file
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@ -0,0 +1,30 @@
purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string.o
targets += $(purgatory-y)
PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
targets += purgatory.ro
# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
# in turn leaves some undefined symbols like __fentry__ in purgatory and not
# sure how to relocate those. Like kexec-tools, use custom flags.
KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -MD -Os -mcmodel=large
$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
$(call if_changed,ld)
targets += kexec-purgatory.c
quiet_cmd_bin2c = BIN2C $@
cmd_bin2c = cat $(obj)/purgatory.ro | $(objtree)/scripts/basic/bin2c kexec_purgatory > $(obj)/kexec-purgatory.c
$(obj)/kexec-purgatory.c: $(obj)/purgatory.ro FORCE
$(call if_changed,bin2c)
# No loaders for 32bits yet.
ifeq ($(CONFIG_X86_64),y)
obj-$(CONFIG_KEXEC) += kexec-purgatory.o
endif

101
arch/x86/purgatory/entry64.S Normal file
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@ -0,0 +1,101 @@
/*
* Copyright (C) 2003,2004 Eric Biederman (ebiederm@xmission.com)
* Copyright (C) 2014 Red Hat Inc.
* Author(s): Vivek Goyal <vgoyal@redhat.com>
*
* This code has been taken from kexec-tools.
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/
.text
.balign 16
.code64
.globl entry64, entry64_regs
entry64:
/* Setup a gdt that should be preserved */
lgdt gdt(%rip)
/* load the data segments */
movl $0x18, %eax /* data segment */
movl %eax, %ds
movl %eax, %es
movl %eax, %ss
movl %eax, %fs
movl %eax, %gs
/* Setup new stack */
leaq stack_init(%rip), %rsp
pushq $0x10 /* CS */
leaq new_cs_exit(%rip), %rax
pushq %rax
lretq
new_cs_exit:
/* Load the registers */
movq rax(%rip), %rax
movq rbx(%rip), %rbx
movq rcx(%rip), %rcx
movq rdx(%rip), %rdx
movq rsi(%rip), %rsi
movq rdi(%rip), %rdi
movq rsp(%rip), %rsp
movq rbp(%rip), %rbp
movq r8(%rip), %r8
movq r9(%rip), %r9
movq r10(%rip), %r10
movq r11(%rip), %r11
movq r12(%rip), %r12
movq r13(%rip), %r13
movq r14(%rip), %r14
movq r15(%rip), %r15
/* Jump to the new code... */
jmpq *rip(%rip)
.section ".rodata"
.balign 4
entry64_regs:
rax: .quad 0x0
rbx: .quad 0x0
rcx: .quad 0x0
rdx: .quad 0x0
rsi: .quad 0x0
rdi: .quad 0x0
rsp: .quad 0x0
rbp: .quad 0x0
r8: .quad 0x0
r9: .quad 0x0
r10: .quad 0x0
r11: .quad 0x0
r12: .quad 0x0
r13: .quad 0x0
r14: .quad 0x0
r15: .quad 0x0
rip: .quad 0x0
.size entry64_regs, . - entry64_regs
/* GDT */
.section ".rodata"
.balign 16
gdt:
/* 0x00 unusable segment
* 0x08 unused
* so use them as gdt ptr
*/
.word gdt_end - gdt - 1
.quad gdt
.word 0, 0, 0
/* 0x10 4GB flat code segment */
.word 0xFFFF, 0x0000, 0x9A00, 0x00AF
/* 0x18 4GB flat data segment */
.word 0xFFFF, 0x0000, 0x9200, 0x00CF
gdt_end:
stack: .quad 0, 0
stack_init:

72
arch/x86/purgatory/purgatory.c Normal file
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@ -0,0 +1,72 @@
/*
* purgatory: Runs between two kernels
*
* Copyright (C) 2014 Red Hat Inc.
*
* Author:
* Vivek Goyal <vgoyal@redhat.com>
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/
#include "sha256.h"
#include "../boot/string.h"
struct sha_region {
unsigned long start;
unsigned long len;
};
unsigned long backup_dest = 0;
unsigned long backup_src = 0;
unsigned long backup_sz = 0;
u8 sha256_digest[SHA256_DIGEST_SIZE] = { 0 };
struct sha_region sha_regions[16] = {};
/*
* On x86, second kernel requries first 640K of memory to boot. Copy
* first 640K to a backup region in reserved memory range so that second
* kernel can use first 640K.
*/
static int copy_backup_region(void)
{
if (backup_dest)
memcpy((void *)backup_dest, (void *)backup_src, backup_sz);
return 0;
}
int verify_sha256_digest(void)
{
struct sha_region *ptr, *end;
u8 digest[SHA256_DIGEST_SIZE];
struct sha256_state sctx;
sha256_init(&sctx);
end = &sha_regions[sizeof(sha_regions)/sizeof(sha_regions[0])];
for (ptr = sha_regions; ptr < end; ptr++)
sha256_update(&sctx, (uint8_t *)(ptr->start), ptr->len);
sha256_final(&sctx, digest);
if (memcmp(digest, sha256_digest, sizeof(digest)))
return 1;
return 0;
}
void purgatory(void)
{
int ret;
ret = verify_sha256_digest();
if (ret) {
/* loop forever */
for (;;)
;
}
copy_backup_region();
}

58
arch/x86/purgatory/setup-x86_64.S Normal file
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@ -0,0 +1,58 @@
/*
* purgatory: setup code
*
* Copyright (C) 2003,2004 Eric Biederman (ebiederm@xmission.com)
* Copyright (C) 2014 Red Hat Inc.
*
* This code has been taken from kexec-tools.
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/
.text
.globl purgatory_start
.balign 16
purgatory_start:
.code64
/* Load a gdt so I know what the segment registers are */
lgdt gdt(%rip)
/* load the data segments */
movl $0x18, %eax /* data segment */
movl %eax, %ds
movl %eax, %es
movl %eax, %ss
movl %eax, %fs
movl %eax, %gs
/* Setup a stack */
leaq lstack_end(%rip), %rsp
/* Call the C code */
call purgatory
jmp entry64
.section ".rodata"
.balign 16
gdt: /* 0x00 unusable segment
* 0x08 unused
* so use them as the gdt ptr
*/
.word gdt_end - gdt - 1
.quad gdt
.word 0, 0, 0
/* 0x10 4GB flat code segment */
.word 0xFFFF, 0x0000, 0x9A00, 0x00AF
/* 0x18 4GB flat data segment */
.word 0xFFFF, 0x0000, 0x9200, 0x00CF
gdt_end:
.bss
.balign 4096
lstack:
.skip 4096
lstack_end:

19
arch/x86/purgatory/stack.S Normal file
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@ -0,0 +1,19 @@
/*
* purgatory: stack
*
* Copyright (C) 2014 Red Hat Inc.
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/
/* A stack for the loaded kernel.
* Seperate and in the data section so it can be prepopulated.
*/
.data
.balign 4096
.globl stack, stack_end
stack:
.skip 4096
stack_end:

13
arch/x86/purgatory/string.c Normal file
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@ -0,0 +1,13 @@
/*
* Simple string functions.
*
* Copyright (C) 2014 Red Hat Inc.
*
* Author:
* Vivek Goyal <vgoyal@redhat.com>
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/
#include "../boot/string.c"