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Commit aafcd5d7 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 6832d965 a0215061

arch/x86/Kconfig

+6 −2
Original line number Diff line number Diff line
@@ -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

arch/x86/Makefile

+4 −4
Original line number Diff line number Diff line
@@ -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

arch/x86/boot/compressed/head_32.S

+3 −28
Original line number Diff line number Diff line
@@ -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.

arch/x86/boot/compressed/head_64.S

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/boot/compressed/misc.c

+76 −1
Original line number Diff line number Diff line
@@ -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;

}