[PATCH v5 05/16] x86/startup_64: Use RIP_REL_REF() to access early page tables

Ard Biesheuvel
2024-02-21T11:35:48Z

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>
---
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 e2573ddae32f..7e2c9b581d58 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++)
--
2.44.0.rc0.258.g7320e95886-goog