[PATCH v3 27/60] arm64: head: Run feature override detection before mapping the kernel

Ard Biesheuvel
2023-03-07T14:11:19Z

To permit the feature overrides to be taken into account before the
KASLR init code runs and the kernel mapping is created, move the
detection code to an earlier stage in the boot.

In a subsequent patch, this will be taken advantage of by merging the
preliminary and permanent mappings of the kernel text and data into a
single one that gets created and relocated before start_kernel() is
called.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/kernel/head.S | 17 +++++++++--------
arch/arm64/kernel/vmlinux.lds.S | 4 +---
2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index ade0cb99c8a83a3d..0a345898a12939af 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -375,9 +375,9 @@ SYM_FUNC_START_LOCAL(create_idmap)

map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14, EXTRA_SHIFT

- /* Remap BSS and the kernel page tables r/w in the ID map */
+ /* Remap [.init].data, BSS and the kernel page tables r/w in the ID map */
adrp x1, _text
- adrp x2, __bss_start
+ adrp x2, __initdata_begin
adrp x3, _end
bic x4, x2, #SWAPPER_BLOCK_SIZE - 1
mov x5, SWAPPER_RW_MMUFLAGS
@@ -491,9 +491,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
bl kasan_early_init
#endif
- mov x0, x20 // pass the full boot status
- mov x1, x22 // pass the low FDT mapping
- bl __pi_init_feature_override // Parse cpu feature overrides
#ifdef CONFIG_UNWIND_PATCH_PAC_INTO_SCS
bl scs_patch_vmlinux
#endif
@@ -770,12 +767,16 @@ SYM_FUNC_START_LOCAL(__primary_switch)
bl __pi_memset
dsb ishst // Make zero page visible to PTW

-#ifdef CONFIG_RELOCATABLE
- adrp x23, KERNEL_START
- and x23, x23, MIN_KIMG_ALIGN - 1
adrp x1, early_init_stack
mov sp, x1
mov x29, xzr
+ mov x0, x20 // pass the full boot status
+ mov x1, x22 // pass the low FDT mapping
+ bl __pi_init_feature_override // Parse cpu feature overrides
+
+#ifdef CONFIG_RELOCATABLE
+ adrp x23, KERNEL_START
+ and x23, x23, MIN_KIMG_ALIGN - 1
#ifdef CONFIG_RANDOMIZE_BASE
mov x0, x22
bl __pi_kaslr_early_init
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index ec24b1e70d606ec8..6c79ad2945749260 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -318,10 +318,8 @@ SECTIONS
init_pg_dir = .;
. += INIT_DIR_SIZE;
init_pg_end = .;
-#ifdef CONFIG_RELOCATABLE
- . += SZ_4K; /* stack for the early relocation code */
+ . += SZ_4K; /* stack for the early C runtime */
early_init_stack = .;
-#endif

. = ALIGN(SEGMENT_ALIGN);
__pecoff_data_size = ABSOLUTE(. - __initdata_begin);
--
2.39.2