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Merge branch 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 relocation changes from Ingo Molnar:
 "This tree contains a single change, ELF relocation handling in C - one
  of the kernel randomization patches that makes sense even without
  randomization present upstream"

* 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, relocs: Move ELF relocation handling to C
This commit is contained in:
Linus Torvalds 2013-09-04 09:38:10 -07:00
parent 6832d9652f a021506107
commit aafcd5d757
8 changed files with 97 additions and 40 deletions
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8
arch/x86/Kconfig
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@ -1716,9 +1716,10 @@ config X86_NEED_RELOCS
depends on X86_32 && RELOCATABLE
config PHYSICAL_ALIGN
hex "Alignment value to which kernel should be aligned" if X86_32
hex "Alignment value to which kernel should be aligned"
default "0x1000000"
range 0x2000 0x1000000
range 0x2000 0x1000000 if X86_32
range 0x200000 0x1000000 if X86_64
---help---
This value puts the alignment restrictions on physical address
where kernel is loaded and run from. Kernel is compiled for an
@ -1736,6 +1737,9 @@ config PHYSICAL_ALIGN
end result is that kernel runs from a physical address meeting
above alignment restrictions.
On 32-bit this value must be a multiple of 0x2000. On 64-bit
this value must be a multiple of 0x200000.
Don't change this unless you know what you are doing.
config HOTPLUG_CPU

8
arch/x86/Makefile
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@ -16,6 +16,10 @@ endif
# e.g.: obj-y += foo_$(BITS).o
export BITS
ifdef CONFIG_X86_NEED_RELOCS
LDFLAGS_vmlinux := --emit-relocs
endif
ifeq ($(CONFIG_X86_32),y)
BITS := 32
UTS_MACHINE := i386
@ -25,10 +29,6 @@ ifeq ($(CONFIG_X86_32),y)
KBUILD_AFLAGS += $(biarch)
KBUILD_CFLAGS += $(biarch)
ifdef CONFIG_RELOCATABLE
LDFLAGS_vmlinux := --emit-relocs
endif
KBUILD_CFLAGS += -msoft-float -mregparm=3 -freg-struct-return
# Never want PIC in a 32-bit kernel, prevent breakage with GCC built

31
arch/x86/boot/compressed/head_32.S
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@ -181,8 +181,9 @@ relocated:
/*
* Do the decompression, and jump to the new kernel..
*/
leal z_extract_offset_negative(%ebx), %ebp
/* push arguments for decompress_kernel: */
pushl $z_output_len /* decompressed length */
leal z_extract_offset_negative(%ebx), %ebp
pushl %ebp /* output address */
pushl $z_input_len /* input_len */
leal input_data(%ebx), %eax
@ -191,33 +192,7 @@ relocated:
pushl %eax /* heap area */
pushl %esi /* real mode pointer */
call decompress_kernel
addl $20, %esp
#if CONFIG_RELOCATABLE
/*
* Find the address of the relocations.
*/
leal z_output_len(%ebp), %edi
/*
* Calculate the delta between where vmlinux was compiled to run
* and where it was actually loaded.
*/
movl %ebp, %ebx
subl $LOAD_PHYSICAL_ADDR, %ebx
jz 2f /* Nothing to be done if loaded at compiled addr. */
/*
* Process relocations.
*/
1: subl $4, %edi
movl (%edi), %ecx
testl %ecx, %ecx
jz 2f
addl %ebx, -__PAGE_OFFSET(%ebx, %ecx)
jmp 1b
2:
#endif
addl $24, %esp
/*
* Jump to the decompressed kernel.

1
arch/x86/boot/compressed/head_64.S
View File

@ -338,6 +338,7 @@ relocated:
leaq input_data(%rip), %rdx /* input_data */
movl $z_input_len, %ecx /* input_len */
movq %rbp, %r8 /* output target address */
movq $z_output_len, %r9 /* decompressed length */
call decompress_kernel
popq %rsi

77
arch/x86/boot/compressed/misc.c
View File

@ -271,6 +271,79 @@ static void error(char *x)
asm("hlt");
}
#if CONFIG_X86_NEED_RELOCS
static void handle_relocations(void *output, unsigned long output_len)
{
int *reloc;
unsigned long delta, map, ptr;
unsigned long min_addr = (unsigned long)output;
unsigned long max_addr = min_addr + output_len;
/*
* Calculate the delta between where vmlinux was linked to load
* and where it was actually loaded.
*/
delta = min_addr - LOAD_PHYSICAL_ADDR;
if (!delta) {
debug_putstr("No relocation needed... ");
return;
}
debug_putstr("Performing relocations... ");
/*
* The kernel contains a table of relocation addresses. Those
* addresses have the final load address of the kernel in virtual
* memory. We are currently working in the self map. So we need to
* create an adjustment for kernel memory addresses to the self map.
* This will involve subtracting out the base address of the kernel.
*/
map = delta - __START_KERNEL_map;
/*
* Process relocations: 32 bit relocations first then 64 bit after.
* Two sets of binary relocations are added to the end of the kernel
* before compression. Each relocation table entry is the kernel
* address of the location which needs to be updated stored as a
* 32-bit value which is sign extended to 64 bits.
*
* Format is:
*
* kernel bits...
* 0 - zero terminator for 64 bit relocations
* 64 bit relocation repeated
* 0 - zero terminator for 32 bit relocations
* 32 bit relocation repeated
*
* So we work backwards from the end of the decompressed image.
*/
for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
int extended = *reloc;
extended += map;
ptr = (unsigned long)extended;
if (ptr < min_addr || ptr > max_addr)
error("32-bit relocation outside of kernel!\n");
*(uint32_t *)ptr += delta;
}
#ifdef CONFIG_X86_64
for (reloc--; *reloc; reloc--) {
long extended = *reloc;
extended += map;
ptr = (unsigned long)extended;
if (ptr < min_addr || ptr > max_addr)
error("64-bit relocation outside of kernel!\n");
*(uint64_t *)ptr += delta;
}
#endif
}
#else
static inline void handle_relocations(void *output, unsigned long output_len)
{ }
#endif
static void parse_elf(void *output)
{
#ifdef CONFIG_X86_64
@ -325,7 +398,8 @@ static void parse_elf(void *output)
asmlinkage void decompress_kernel(void *rmode, memptr heap,
unsigned char *input_data,
unsigned long input_len,
unsigned char *output)
unsigned char *output,
unsigned long output_len)
{
real_mode = rmode;
@ -365,6 +439,7 @@ asmlinkage void decompress_kernel(void *rmode, memptr heap,
debug_putstr("\nDecompressing Linux... ");
decompress(input_data, input_len, NULL, NULL, output, NULL, error);
parse_elf(output);
handle_relocations(output, output_len);
debug_putstr("done.\nBooting the kernel.\n");
return;
}

2
arch/x86/include/asm/page_32_types.h
View File

@ -15,6 +15,8 @@
*/
#define __PAGE_OFFSET _AC(CONFIG_PAGE_OFFSET, UL)
#define __START_KERNEL_map __PAGE_OFFSET
#define THREAD_SIZE_ORDER 1
#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)

5
arch/x86/include/asm/page_64_types.h
View File

@ -32,11 +32,6 @@
*/
#define __PAGE_OFFSET _AC(0xffff880000000000, UL)
#define __PHYSICAL_START ((CONFIG_PHYSICAL_START + \
(CONFIG_PHYSICAL_ALIGN - 1)) & \
~(CONFIG_PHYSICAL_ALIGN - 1))
#define __START_KERNEL (__START_KERNEL_map + __PHYSICAL_START)
#define __START_KERNEL_map _AC(0xffffffff80000000, UL)
/* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */

5
arch/x86/include/asm/page_types.h
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@ -33,6 +33,11 @@
(((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0 ) | \
VM_READ | VM_WRITE | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
#define __PHYSICAL_START ALIGN(CONFIG_PHYSICAL_START, \
CONFIG_PHYSICAL_ALIGN)
#define __START_KERNEL (__START_KERNEL_map + __PHYSICAL_START)
#ifdef CONFIG_X86_64
#include <asm/page_64_types.h>
#else