[tip: x86/boot] x86/boot/64: Use RIP_REL_REF() to access early page tables

tip-bot2 for Ard Biesheuvel
2024-02-26T12:12:46Z

The following commit has been merged into the x86/boot branch of tip:

Commit-ID: eb54c2ae4a4825c42a6a2b4022926bda7448f735
Gitweb: https://git.kernel.org/tip/eb54c2ae4a4825c42a6a2b4022926bda7448f735
Author: Ard Biesheuvel <ardb@kernel.org>
AuthorDate: Wed, 21 Feb 2024 12:35:12 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 26 Feb 2024 12:58:35 +01:00

x86/boot/64: Use RIP_REL_REF() to access early page tables

The early statically allocated page tables are populated from code that
executes from a 1:1 mapping so it cannot use plain accesses 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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240221113506.2565718-23-ardb+git@google.com
---
arch/x86/kernel/head64.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index e2573dd..7e2c9b5 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -215,13 +215,11 @@ unsigned long __head __startup_64(unsigned long physaddr,
p4d[511] += load_delta;
}

- pud = fixup_pointer(level3_kernel_pgt, physaddr);
- pud[510] += load_delta;
- pud[511] += load_delta;
+ RIP_REL_REF(level3_kernel_pgt)[PTRS_PER_PUD - 2].pud += load_delta;
+ RIP_REL_REF(level3_kernel_pgt)[PTRS_PER_PUD - 1].pud += load_delta;

- pmd = fixup_pointer(level2_fixmap_pgt, physaddr);
for (i = FIXMAP_PMD_TOP; i > FIXMAP_PMD_TOP - FIXMAP_PMD_NUM; i--)
- pmd[i] += load_delta;
+ RIP_REL_REF(level2_fixmap_pgt)[i].pmd += load_delta;

/*
* Set up the identity mapping for the switchover. These
@@ -284,7 +282,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
* error, causing the BIOS to halt the system.
*/

- pmd = fixup_pointer(level2_kernel_pgt, physaddr);
+ pmd = &RIP_REL_REF(level2_kernel_pgt)->pmd;

/* invalidate pages before the kernel image */
for (i = 0; i < pmd_index((unsigned long)_text); i++)