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Date: Wed, 21 Feb 2024 12:35:10 +0100
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Subject: [PATCH v5 03/16] x86/startup_64: Use RIP_REL_REF() to access early_dynamic_pgts[]
From: Ard Biesheuvel <ardb+git@google.com>
To: linux-kernel@vger.kernel.org
Cc: Ard Biesheuvel <ardb@kernel.org>, Kevin Loughlin <kevinloughlin@google.com>, 
	Tom Lendacky <thomas.lendacky@amd.com>, Dionna Glaze <dionnaglaze@google.com>, 
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, 
	Dave Hansen <dave.hansen@linux.intel.com>, Andy Lutomirski <luto@kernel.org>, 
	Arnd Bergmann <arnd@arndb.de>, Nathan Chancellor <nathan@kernel.org>, 
	Nick Desaulniers <ndesaulniers@google.com>, Justin Stitt <justinstitt@google.com>, 
	Kees Cook <keescook@chromium.org>, Brian Gerst <brgerst@gmail.com>, linux-arch@vger.kernel.org, 
	llvm@lists.linux.dev
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From: Ard Biesheuvel <ardb@kernel.org>

early_dynamic_pgts[] and next_early_pgt are accessed 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.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/kernel/head64.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index f98f5b6a06b5..2ac904110f6a 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -170,6 +170,7 @@ static unsigned long __head sme_postprocess_startup(struct boot_params *bp, pmdv
 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;
 	pgdval_t *pgd;
@@ -179,7 +180,6 @@ unsigned long __head __startup_64(unsigned long physaddr,
 	pteval_t *mask_ptr;
 	bool la57;
 	int i;
-	unsigned int *next_pgt_ptr;
 
 	la57 = check_la57_support(physaddr);
 
@@ -231,15 +231,14 @@ unsigned long __head __startup_64(unsigned long physaddr,
 	 * it avoids problems around wraparound.
 	 */
 
-	next_pgt_ptr = fixup_pointer(&next_early_pgt, physaddr);
-	pud = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++], physaddr);
-	pmd = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++], physaddr);
+	pud = &early_pgts[0]->pmd;
+	pmd = &early_pgts[1]->pmd;
+	RIP_REL_REF(next_early_pgt) = 2;
 
 	pgtable_flags = _KERNPG_TABLE_NOENC + sme_get_me_mask();
 
 	if (la57) {
-		p4d = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++],
-				    physaddr);
+		p4d = &early_pgts[RIP_REL_REF(next_early_pgt)++]->pmd;
 
 		i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
 		pgd[i + 0] = (pgdval_t)p4d + pgtable_flags;
-- 
2.44.0.rc0.258.g7320e95886-goog