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Date: Thu, 31 May 2018 18:31:06 +0800
From: Jun Yao <yaojun8558363@...il.com>
To: linux-arm-kernel@...ts.infradead.org
Cc: catalin.marinas@....com,
will.deacon@....com,
ard.biesheuvel@...aro.org,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH v2 1/2] arm64/mm: split tramp_pg_dir off from the data segment
In order to make tramp_pg_dir read-only, split it off from the data
segment and create a dedicated pgdir segment for it.
Signed-off-by: Jun Yao <yaojun8558363@...il.com>
---
arch/arm64/include/asm/sections.h | 1 +
arch/arm64/kernel/vmlinux.lds.S | 3 +++
arch/arm64/mm/mmu.c | 13 +++++++++++++
3 files changed, 17 insertions(+)
diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h
index caab039d6305..46a6646e886b 100644
--- a/arch/arm64/include/asm/sections.h
+++ b/arch/arm64/include/asm/sections.h
@@ -29,5 +29,6 @@ extern char __inittext_begin[], __inittext_end[];
extern char __irqentry_text_start[], __irqentry_text_end[];
extern char __mmuoff_data_start[], __mmuoff_data_end[];
extern char __entry_tramp_text_start[], __entry_tramp_text_end[];
+extern char __tramp_pgdir_segment_start[], __tramp_pgdir_segment_end[];
#endif /* __ASM_SECTIONS_H */
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 605d1b60469c..c3368782171d 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -220,8 +220,11 @@ SECTIONS
. += IDMAP_DIR_SIZE;
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+ . = ALIGN(SEGMENT_ALIGN);
+ __tramp_pgdir_segment_start = .;
tramp_pg_dir = .;
. += PAGE_SIZE;
+ __tramp_pgdir_segment_end = .;
#endif
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2dbb2c9f1ec1..a675fb88914e 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -573,6 +573,9 @@ static void __init map_kernel(pgd_t *pgdp)
{
static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_inittext,
vmlinux_initdata, vmlinux_data;
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+ static struct vm_struct vmlinux_tramp_pgdir, vmlinux_data_end;
+#endif
/*
* External debuggers may need to write directly to the text
@@ -593,7 +596,17 @@ static void __init map_kernel(pgd_t *pgdp)
&vmlinux_inittext, 0, VM_NO_GUARD);
map_kernel_segment(pgdp, __initdata_begin, __initdata_end, PAGE_KERNEL,
&vmlinux_initdata, 0, VM_NO_GUARD);
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+ map_kernel_segment(pgdp, _data, __tramp_pgdir_segment_start,
+ PAGE_KERNEL, &vmlinux_data, 0, VM_NO_GUARD);
+ map_kernel_segment(pgdp, __tramp_pgdir_segment_start,
+ __tramp_pgdir_segment_end, PAGE_KERNEL,
+ &vmlinux_tramp_pgdir, NO_CONT_MAPPINGS, VM_NO_GUARD);
+ map_kernel_segment(pgdp, __tramp_pgdir_segment_end, _end, PAGE_KERNEL,
+ &vmlinux_data_end, 0, 0);
+#else
map_kernel_segment(pgdp, _data, _end, PAGE_KERNEL, &vmlinux_data, 0, 0);
+#endif
if (!READ_ONCE(pgd_val(*pgd_offset_raw(pgdp, FIXADDR_START)))) {
/*
--
2.17.0
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