From 533568e06b157b175912a960efe5ebce8710b4f9 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Wed, 21 Feb 2024 12:35:13 +0100 Subject: [PATCH] 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 Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20240221113506.2565718-24-ardb+git@google.com --- arch/x86/kernel/head64.c | 21 +++++++++------------ arch/x86/kernel/head_64.S | 3 ++- 2 files changed, 11 insertions(+), 13 deletions(-) diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 7e2c9b581d58..72351c3121a6 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -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; diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index e09cf0b09141..d295bf68bf94 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -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)