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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: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240221113506.2565718-24-ardb+git@google.com
This commit is contained in:
Ard Biesheuvel 2024-02-21 12:35:13 +01:00 committed by Ingo Molnar
parent eb54c2ae4a
commit 533568e06b
2 changed files with 11 additions and 13 deletions
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21
arch/x86/kernel/head64.c
View File

@ -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;

3
arch/x86/kernel/head_64.S
View File

@ -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)