Commit 3b6f99a9 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Ingo Molnar
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x86/boot: Disable UBSAN in early boot code 



The early boot code runs from a 1:1 mapping of memory, and may execute
before the kernel virtual mapping is even up. This means absolute symbol
references cannot be permitted in this code.

UBSAN injects references to global data structures into the code, and
without -fPIC, those references are emitted as absolute references to
kernel virtual addresses. Accessing those will fault before the kernel
virtual mapping is up, so UBSAN needs to be disabled in early boot code.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20241205112804.3416920-13-ardb+git@google.com
parent 0d9b9a32

arch/x86/coco/sev/shared.c

+4 −3
Original line number Diff line number Diff line
@@ -498,7 +498,7 @@ static const struct snp_cpuid_table *snp_cpuid_get_table(void) 
 *

 * Return: XSAVE area size on success, 0 otherwise.

 */

static u32 snp_cpuid_calc_xsave_size(u64 xfeatures_en, bool compacted)

static u32 __head snp_cpuid_calc_xsave_size(u64 xfeatures_en, bool compacted)

{

	const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table();

	u64 xfeatures_found = 0;
@@ -576,7 +576,8 @@ static void snp_cpuid_hv(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpui 
		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_CPUID_HV);

}



static int snp_cpuid_postprocess(struct ghcb *ghcb, struct es_em_ctxt *ctxt,

static int __head

snp_cpuid_postprocess(struct ghcb *ghcb, struct es_em_ctxt *ctxt,

		      struct cpuid_leaf *leaf)

{

	struct cpuid_leaf leaf_hv = *leaf;

arch/x86/include/asm/init.h

+1 −1
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ 
#ifndef _ASM_X86_INIT_H

#define _ASM_X86_INIT_H



#define __head	__section(".head.text")

#define __head	__section(".head.text") __no_sanitize_undefined



struct x86_mapping_info {

	void *(*alloc_pgt_page)(void *); /* allocate buf for page table */