Commit aa6a52b2 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Catalin Marinas
Browse files

arm64: head: move memstart_offset_seed handling to C code 



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: default avatarArd Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240214122845.2033971-60-ardb+git@google.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 8d47b8e5

arch/arm64/kernel/head.S

+0 −7
Original line number Diff line number Diff line
@@ -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

arch/arm64/kernel/image-vars.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/arm64/kernel/pi/kaslr_early.c

+4 −0
Original line number Diff line number Diff line
@@ -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