linux-hardening - [PATCH v4 09/26] arm64: head: pass ID map root table address to __enable

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Message-Id: <20220613144550.3760857-10-ardb@kernel.org>
Date:   Mon, 13 Jun 2022 16:45:33 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-hardening@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Brown <broonie@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: [PATCH v4 09/26] arm64: head: pass ID map root table address to __enable_mmu()

We will be adding an initial ID map that covers the entire kernel image,
so we will pass the actual ID map root table to use to __enable_mmu(),
rather than hard code it.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/arm64/kernel/head.S  | 14 ++++++++------
 arch/arm64/kernel/sleep.S |  1 +
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 1cbc52097bf9..70c462bbd6bf 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -595,6 +595,7 @@ SYM_FUNC_START_LOCAL(secondary_startup)
 	bl	__cpu_secondary_check52bitva
 	bl	__cpu_setup			// initialise processor
 	adrp	x1, swapper_pg_dir
+	adrp	x2, idmap_pg_dir
 	bl	__enable_mmu
 	ldr	x8, =__secondary_switched
 	br	x8
@@ -648,6 +649,7 @@ SYM_FUNC_END(__secondary_too_slow)
  *
  *  x0  = SCTLR_EL1 value for turning on the MMU.
  *  x1  = TTBR1_EL1 value
+ *  x2  = ID map root table address
  *
  * Returns to the caller via x30/lr. This requires the caller to be covered
  * by the .idmap.text section.
@@ -656,14 +658,13 @@ SYM_FUNC_END(__secondary_too_slow)
  * If it isn't, park the CPU
  */
 SYM_FUNC_START(__enable_mmu)
-	mrs	x2, ID_AA64MMFR0_EL1
-	ubfx	x2, x2, #ID_AA64MMFR0_TGRAN_SHIFT, 4
-	cmp     x2, #ID_AA64MMFR0_TGRAN_SUPPORTED_MIN
+	mrs	x3, ID_AA64MMFR0_EL1
+	ubfx	x3, x3, #ID_AA64MMFR0_TGRAN_SHIFT, 4
+	cmp     x3, #ID_AA64MMFR0_TGRAN_SUPPORTED_MIN
 	b.lt    __no_granule_support
-	cmp     x2, #ID_AA64MMFR0_TGRAN_SUPPORTED_MAX
+	cmp     x3, #ID_AA64MMFR0_TGRAN_SUPPORTED_MAX
 	b.gt    __no_granule_support
-	update_early_cpu_boot_status 0, x2, x3
-	adrp	x2, idmap_pg_dir
+	update_early_cpu_boot_status 0, x3, x4
 	phys_to_ttbr x1, x1
 	phys_to_ttbr x2, x2
 	msr	ttbr0_el1, x2			// load TTBR0
@@ -819,6 +820,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 #endif
 
 	adrp	x1, init_pg_dir
+	adrp	x2, idmap_pg_dir
 	bl	__enable_mmu
 #ifdef CONFIG_RELOCATABLE
 #ifdef CONFIG_RELR
diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index 4ea9392f86e0..e36b09d942f7 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -104,6 +104,7 @@ SYM_CODE_START(cpu_resume)
 	bl	__cpu_setup
 	/* enable the MMU early - so we can access sleep_save_stash by va */
 	adrp	x1, swapper_pg_dir
+	adrp	x2, idmap_pg_dir
 	bl	__enable_mmu
 	ldr	x8, =_cpu_resume
 	br	x8
-- 
2.30.2