[PATCH v15 11/15] arm64: kexec: install a copy of the linear-map

From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: pasha.tatashin@soleen.com, jmorris@namei.org, sashal@kernel.org,
	ebiederm@xmission.com, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org, corbet@lwn.net,
	catalin.marinas@arm.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org, maz@kernel.org,
	james.morse@arm.com, vladimir.murzin@arm.com,
	matthias.bgg@gmail.com, linux-mm@kvack.org, mark.rutland@arm.com,
	steve.capper@arm.com, rfontana@redhat.com, tglx@linutronix.de,
	selindag@gmail.com, tyhicks@linux.microsoft.com,
	kernelfans@gmail.com, akpm@linux-foundation.org,
	madvenka@linux.microsoft.com
Subject: [PATCH v15 11/15] arm64: kexec: install a copy of the linear-map
Date: Tue,  8 Jun 2021 20:44:15 -0400	[thread overview]
Message-ID: <20210609004419.936873-12-pasha.tatashin@soleen.com> (raw)
In-Reply-To: <20210609004419.936873-1-pasha.tatashin@soleen.com>

To perform the kexec relocation with the MMU enabled, we need a copy
of the linear map.

Create one, and install it from the relocation code. This has to be done
from the assembly code as it will be idmapped with TTBR0. The kernel
runs in TTRB1, so can't use the break-before-make sequence on the mapping
it is executing from.

The makes no difference yet as the relocation code runs with the MMU
disabled.

Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
---
 arch/arm64/include/asm/assembler.h  | 19 +++++++++++++++++++
 arch/arm64/include/asm/kexec.h      |  2 ++
 arch/arm64/kernel/asm-offsets.c     |  2 ++
 arch/arm64/kernel/hibernate-asm.S   | 20 --------------------
 arch/arm64/kernel/machine_kexec.c   | 16 ++++++++++++++--
 arch/arm64/kernel/relocate_kernel.S |  3 +++
 6 files changed, 40 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index f1367863d995..7f268bfa98c6 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -447,6 +447,25 @@ USER(\label, ic	ivau, \tmp2)			// invalidate I line PoU
 	isb
 	.endm
 
+/*
+ * To prevent the possibility of old and new partial table walks being visible
+ * in the tlb, switch the ttbr to a zero page when we invalidate the old
+ * records. D4.7.1 'General TLB maintenance requirements' in ARM DDI 0487A.i
+ * Even switching to our copied tables will cause a changed output address at
+ * each stage of the walk.
+ */
+	.macro break_before_make_ttbr_switch zero_page, page_table, tmp, tmp2
+	phys_to_ttbr \tmp, \zero_page
+	msr	ttbr1_el1, \tmp
+	isb
+	tlbi	vmalle1
+	dsb	nsh
+	phys_to_ttbr \tmp, \page_table
+	offset_ttbr1 \tmp, \tmp2
+	msr	ttbr1_el1, \tmp
+	isb
+	.endm
+
 /*
  * reset_pmuserenr_el0 - reset PMUSERENR_EL0 if PMUv3 present
  */
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 753a1c398898..d678f0ceb7ee 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -97,6 +97,8 @@ struct kimage_arch {
 	phys_addr_t dtb_mem;
 	phys_addr_t kern_reloc;
 	phys_addr_t el2_vectors;
+	phys_addr_t ttbr1;
+	phys_addr_t zero_page;
 };
 
 #ifdef CONFIG_KEXEC_FILE
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index ee37d0e0fb6d..f9794cd95eef 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -160,6 +160,8 @@ int main(void)
 #ifdef CONFIG_KEXEC_CORE
   DEFINE(KIMAGE_ARCH_DTB_MEM,		offsetof(struct kimage, arch.dtb_mem));
   DEFINE(KIMAGE_ARCH_EL2_VECTORS,	offsetof(struct kimage, arch.el2_vectors));
+  DEFINE(KIMAGE_ARCH_ZERO_PAGE,		offsetof(struct kimage, arch.zero_page));
+  DEFINE(KIMAGE_ARCH_TTBR1,		offsetof(struct kimage, arch.ttbr1));
   DEFINE(KIMAGE_HEAD,			offsetof(struct kimage, head));
   DEFINE(KIMAGE_START,			offsetof(struct kimage, start));
   BLANK();
diff --git a/arch/arm64/kernel/hibernate-asm.S b/arch/arm64/kernel/hibernate-asm.S
index e4b0de990dec..f349b3adecc7 100644
--- a/arch/arm64/kernel/hibernate-asm.S
+++ b/arch/arm64/kernel/hibernate-asm.S
@@ -15,26 +15,6 @@
 #include <asm/page.h>
 #include <asm/virt.h>
 
-/*
- * To prevent the possibility of old and new partial table walks being visible
- * in the tlb, switch the ttbr to a zero page when we invalidate the old
- * records. D4.7.1 'General TLB maintenance requirements' in ARM DDI 0487A.i
- * Even switching to our copied tables will cause a changed output address at
- * each stage of the walk.
- */
-.macro break_before_make_ttbr_switch zero_page, page_table, tmp, tmp2
-	phys_to_ttbr \tmp, \zero_page
-	msr	ttbr1_el1, \tmp
-	isb
-	tlbi	vmalle1
-	dsb	nsh
-	phys_to_ttbr \tmp, \page_table
-	offset_ttbr1 \tmp, \tmp2
-	msr	ttbr1_el1, \tmp
-	isb
-.endm
-
-
 /*
  * Resume from hibernate
  *
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index f6b8ed04455b..4e796e46baa3 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -153,6 +153,8 @@ static void *kexec_page_alloc(void *arg)
 
 int machine_kexec_post_load(struct kimage *kimage)
 {
+	int rc;
+	pgd_t *trans_pgd;
 	void *reloc_code = page_to_virt(kimage->control_code_page);
 	long reloc_size;
 	struct trans_pgd_info info = {
@@ -169,12 +171,22 @@ int machine_kexec_post_load(struct kimage *kimage)
 
 	kimage->arch.el2_vectors = 0;
 	if (is_hyp_nvhe()) {
-		int rc = trans_pgd_copy_el2_vectors(&info,
-						    &kimage->arch.el2_vectors);
+		rc = trans_pgd_copy_el2_vectors(&info,
+						&kimage->arch.el2_vectors);
 		if (rc)
 			return rc;
 	}
 
+	/* Create a copy of the linear map */
+	trans_pgd = kexec_page_alloc(kimage);
+	if (!trans_pgd)
+		return -ENOMEM;
+	rc = trans_pgd_create_copy(&info, &trans_pgd, PAGE_OFFSET, PAGE_END);
+	if (rc)
+		return rc;
+	kimage->arch.ttbr1 = __pa(trans_pgd);
+	kimage->arch.zero_page = __pa(empty_zero_page);
+
 	reloc_size = __relocate_new_kernel_end - __relocate_new_kernel_start;
 	memcpy(reloc_code, __relocate_new_kernel_start, reloc_size);
 	kimage->arch.kern_reloc = __pa(reloc_code);
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index 7a600ba33ae1..e83b6380907d 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -29,10 +29,13 @@
  */
 SYM_CODE_START(arm64_relocate_new_kernel)
 	/* Setup the list loop variables. */
+	ldr	x18, [x0, #KIMAGE_ARCH_ZERO_PAGE] /* x18 = zero page for BBM */
+	ldr	x17, [x0, #KIMAGE_ARCH_TTBR1]	/* x17 = linear map copy */
 	ldr	x16, [x0, #KIMAGE_HEAD]		/* x16 = kimage_head */
 	mov	x14, xzr			/* x14 = entry ptr */
 	mov	x13, xzr			/* x13 = copy dest */
 	raw_dcache_line_size x15, x1		/* x15 = dcache line size */
+	break_before_make_ttbr_switch	x18, x17, x1, x2 /* set linear map */
 .Lloop:
 	and	x12, x16, PAGE_MASK		/* x12 = addr */
 
-- 
2.25.1

