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arm64: head: move memstart_offset_seed handling to C code

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Now that we can set BSS variables from the early code running from the
ID map, we can set memstart_offset_seed directly from the C code that
derives the value instead of passing it back and forth between C and asm
code.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240214122845.2033971-60-ardb+git@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Ard Biesheuvel 2024-02-14 13:29:01 +01:00 committed by Catalin Marinas
parent 8d47b8e5c7
commit aa6a52b247
3 changed files with 5 additions and 7 deletions
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7
arch/arm64/kernel/head.S
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@ -82,7 +82,6 @@
* x21 primary_entry() .. start_kernel() FDT pointer passed at boot in x0
* x22 create_idmap() .. start_kernel() ID map VA of the DT blob
* x23 __primary_switch() physical misalignment/KASLR offset
* x24 __primary_switch() linear map KASLR seed
* x25 primary_entry() .. start_kernel() supported VA size
* x28 create_idmap() callee preserved temp register
*/
@ -483,11 +482,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
str x25, [x8] // ... observes the correct value
dc civac, x8 // Make visible to booting secondaries
#endif
#ifdef CONFIG_RANDOMIZE_BASE
adrp x5, memstart_offset_seed // Save KASLR linear map seed
strh w24, [x5, :lo12:memstart_offset_seed]
#endif
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
bl kasan_early_init
#endif
@ -779,7 +773,6 @@ SYM_FUNC_START_LOCAL(__primary_switch)
#ifdef CONFIG_RANDOMIZE_BASE
mov x0, x22
bl __pi_kaslr_early_init
and x24, x0, #SZ_2M - 1 // capture memstart offset seed
bic x0, x0, #SZ_2M - 1
orr x23, x23, x0 // record kernel offset
#endif

1
arch/arm64/kernel/image-vars.h
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@ -46,6 +46,7 @@ PROVIDE(__pi_id_aa64smfr0_override = id_aa64smfr0_override);
PROVIDE(__pi_id_aa64zfr0_override = id_aa64zfr0_override);
PROVIDE(__pi_arm64_sw_feature_override = arm64_sw_feature_override);
PROVIDE(__pi__ctype = _ctype);
PROVIDE(__pi_memstart_offset_seed = memstart_offset_seed);
#ifdef CONFIG_KVM

4
arch/arm64/kernel/pi/kaslr_early.c
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@ -16,6 +16,8 @@
#include <asm/memory.h>
#include <asm/pgtable.h>
extern u16 memstart_offset_seed;
static u64 __init get_kaslr_seed(void *fdt)
{
static char const chosen_str[] __initconst = "chosen";
@ -51,6 +53,8 @@ asmlinkage u64 __init kaslr_early_init(void *fdt)
return 0;
}
memstart_offset_seed = seed & U16_MAX;
/*
* OK, so we are proceeding with KASLR enabled. Calculate a suitable
* kernel image offset from the seed. Let's place the kernel in the