Commit 533568e0 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Ingo Molnar
Browse files

x86/boot/64: Use RIP_REL_REF() to access early_top_pgt[] 



early_top_pgt[] is assigned from code that executes from a 1:1 mapping
so it cannot use a plain access from C. Replace the use of
fixup_pointer() with RIP_REL_REF(), which is better and simpler.

For legibility and to align with the code that populates the lower page
table levels, statically initialize the root level page table with an
entry pointing to level3_kernel_pgt[], and overwrite it when needed to
enable 5-level paging.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240221113506.2565718-24-ardb+git@google.com
parent eb54c2ae

arch/x86/kernel/head64.c

+9 −12
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ static struct desc_struct startup_gdt[GDT_ENTRIES] __initdata = { 
	[GDT_ENTRY_KERNEL_DS]           = GDT_ENTRY_INIT(DESC_DATA64, 0, 0xfffff),

};



#ifdef CONFIG_X86_5LEVEL

static void __head *fixup_pointer(void *ptr, unsigned long physaddr)

{

	return ptr - (void *)_text + (void *)physaddr;
@@ -87,7 +88,6 @@ static unsigned long __head *fixup_long(void *ptr, unsigned long physaddr) 
	return fixup_pointer(ptr, physaddr);

}



#ifdef CONFIG_X86_5LEVEL

static unsigned int __head *fixup_int(void *ptr, unsigned long physaddr)

{

	return fixup_pointer(ptr, physaddr);
@@ -165,14 +165,14 @@ static unsigned long __head sme_postprocess_startup(struct boot_params *bp, pmdv 
 * doesn't have to generate PC-relative relocations when accessing globals from

 * that function. Clang actually does not generate them, which leads to

 * boot-time crashes. To work around this problem, every global pointer must

 * be adjusted using fixup_pointer().

 * be accessed using RIP_REL_REF().

 */

unsigned long __head __startup_64(unsigned long physaddr,

				  struct boot_params *bp)

{

	pmd_t (*early_pgts)[PTRS_PER_PMD] = RIP_REL_REF(early_dynamic_pgts);

	unsigned long load_delta, *p;

	unsigned long pgtable_flags;

	unsigned long load_delta;

	pgdval_t *pgd;

	p4dval_t *p4d;

	pudval_t *pud;
@@ -202,17 +202,14 @@ unsigned long __head __startup_64(unsigned long physaddr, 


	/* Fixup the physical addresses in the page table */



	pgd = fixup_pointer(early_top_pgt, physaddr);

	p = pgd + pgd_index(__START_KERNEL_map);

	if (la57)

		*p = (unsigned long)level4_kernel_pgt;

	else

		*p = (unsigned long)level3_kernel_pgt;

	*p += _PAGE_TABLE_NOENC - __START_KERNEL_map + load_delta;

	pgd = &RIP_REL_REF(early_top_pgt)->pgd;

	pgd[pgd_index(__START_KERNEL_map)] += load_delta;



	if (la57) {

		p4d = fixup_pointer(level4_kernel_pgt, physaddr);

		p4d[511] += load_delta;

		p4d = (p4dval_t *)&RIP_REL_REF(level4_kernel_pgt);

		p4d[MAX_PTRS_PER_P4D - 1] += load_delta;



		pgd[pgd_index(__START_KERNEL_map)] = (pgdval_t)p4d | _PAGE_TABLE_NOENC;

	}



	RIP_REL_REF(level3_kernel_pgt)[PTRS_PER_PUD - 2].pud += load_delta;

arch/x86/kernel/head_64.S

+2 −1
Original line number Diff line number Diff line
@@ -624,7 +624,8 @@ SYM_CODE_END(vc_no_ghcb) 
	.balign 4



SYM_DATA_START_PTI_ALIGNED(early_top_pgt)

	.fill	512,8,0

	.fill	511,8,0

	.quad	level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC

	.fill	PTI_USER_PGD_FILL,8,0

SYM_DATA_END(early_top_pgt)