Commit c9f2a9a6 authored by Matt Fleming's avatar Matt Fleming Committed by Ingo Molnar
Browse files

x86/efi: Hoist page table switching code into efi_call_virt() 



This change is a prerequisite for pending patches that switch to
a dedicated EFI page table, instead of using 'trampoline_pgd'
which shares PGD entries with 'swapper_pg_dir'. The pending
patches make it impossible to dereference the runtime service
function pointer without first switching %cr3.

It's true that we now have duplicated switching code in
efi_call_virt() and efi_call_phys_{prolog,epilog}() but we are
sacrificing code duplication for a little more clarity and the
ease of writing the page table switching code in C instead of
asm.

Signed-off-by: default avatarMatt Fleming <matt@codeblueprint.co.uk>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarBorislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1448658575-17029-5-git-send-email-matt@codeblueprint.co.uk


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b61a76f8

arch/x86/include/asm/efi.h

+25 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 


#include <asm/fpu/api.h>

#include <asm/pgtable.h>

#include <asm/tlb.h>



/*

 * We map the EFI regions needed for runtime services non-contiguously,
@@ -64,6 +65,17 @@ extern u64 asmlinkage efi_call(void *fp, ...); 


#define efi_call_phys(f, args...)		efi_call((f), args)



/*

 * Scratch space used for switching the pagetable in the EFI stub

 */

struct efi_scratch {

	u64	r15;

	u64	prev_cr3;

	pgd_t	*efi_pgt;

	bool	use_pgd;

	u64	phys_stack;

} __packed;



#define efi_call_virt(f, ...)						\

({									\

	efi_status_t __s;						\
@@ -71,7 +83,20 @@ extern u64 asmlinkage efi_call(void *fp, ...); 
	efi_sync_low_kernel_mappings();					\

	preempt_disable();						\

	__kernel_fpu_begin();						\

									\

	if (efi_scratch.use_pgd) {					\

		efi_scratch.prev_cr3 = read_cr3();			\

		write_cr3((unsigned long)efi_scratch.efi_pgt);		\

		__flush_tlb_all();					\

	}								\

									\

	__s = efi_call((void *)efi.systab->runtime->f, __VA_ARGS__);	\

									\

	if (efi_scratch.use_pgd) {					\

		write_cr3(efi_scratch.prev_cr3);			\

		__flush_tlb_all();					\

	}								\

									\

	__kernel_fpu_end();						\

	preempt_enable();						\

	__s;								\

arch/x86/platform/efi/efi_64.c

+11 −13
Original line number Diff line number Diff line
@@ -47,16 +47,7 @@ 
 */

static u64 efi_va = EFI_VA_START;



/*

 * Scratch space used for switching the pagetable in the EFI stub

 */

struct efi_scratch {

	u64 r15;

	u64 prev_cr3;

	pgd_t *efi_pgt;

	bool use_pgd;

	u64 phys_stack;

} __packed;

struct efi_scratch efi_scratch;



static void __init early_code_mapping_set_exec(int executable)

{
@@ -83,8 +74,11 @@ pgd_t * __init efi_call_phys_prolog(void) 
	int pgd;

	int n_pgds;



	if (!efi_enabled(EFI_OLD_MEMMAP))

		return NULL;

	if (!efi_enabled(EFI_OLD_MEMMAP)) {

		save_pgd = (pgd_t *)read_cr3();

		write_cr3((unsigned long)efi_scratch.efi_pgt);

		goto out;

	}



	early_code_mapping_set_exec(1);
@@ -96,6 +90,7 @@ pgd_t * __init efi_call_phys_prolog(void) 
		vaddress = (unsigned long)__va(pgd * PGDIR_SIZE);

		set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), *pgd_offset_k(vaddress));

	}

out:

	__flush_tlb_all();



	return save_pgd;
@@ -109,8 +104,11 @@ void __init efi_call_phys_epilog(pgd_t *save_pgd) 
	int pgd_idx;

	int nr_pgds;



	if (!save_pgd)

	if (!efi_enabled(EFI_OLD_MEMMAP)) {

		write_cr3((unsigned long)save_pgd);

		__flush_tlb_all();

		return;

	}



	nr_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT) , PGDIR_SIZE);

arch/x86/platform/efi/efi_stub_64.S

+0 −43
Original line number Diff line number Diff line
@@ -38,41 +38,6 @@ 
	mov %rsi, %cr0;			\

	mov (%rsp), %rsp



	/* stolen from gcc */

	.macro FLUSH_TLB_ALL

	movq %r15, efi_scratch(%rip)

	movq %r14, efi_scratch+8(%rip)

	movq %cr4, %r15

	movq %r15, %r14

	andb $0x7f, %r14b

	movq %r14, %cr4

	movq %r15, %cr4

	movq efi_scratch+8(%rip), %r14

	movq efi_scratch(%rip), %r15

	.endm



	.macro SWITCH_PGT

	cmpb $0, efi_scratch+24(%rip)

	je 1f

	movq %r15, efi_scratch(%rip)		# r15

	# save previous CR3

	movq %cr3, %r15

	movq %r15, efi_scratch+8(%rip)		# prev_cr3

	movq efi_scratch+16(%rip), %r15		# EFI pgt

	movq %r15, %cr3

	1:

	.endm



	.macro RESTORE_PGT

	cmpb $0, efi_scratch+24(%rip)

	je 2f

	movq efi_scratch+8(%rip), %r15

	movq %r15, %cr3

	movq efi_scratch(%rip), %r15

	FLUSH_TLB_ALL

	2:

	.endm



ENTRY(efi_call)

	SAVE_XMM

	mov (%rsp), %rax
@@ -83,16 +48,8 @@ ENTRY(efi_call) 
	mov %r8, %r9

	mov %rcx, %r8

	mov %rsi, %rcx

	SWITCH_PGT

	call *%rdi

	RESTORE_PGT

	addq $48, %rsp

	RESTORE_XMM

	ret

ENDPROC(efi_call)
 


	.data

ENTRY(efi_scratch)

	.fill 3,8,0

	.byte 0

	.quad 0

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