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[v4,5/6] arm64: mmu: apply strict permissions to .init.text and .init.data

Message ID 1488637848-13588-6-git-send-email-ard.biesheuvel@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Ard Biesheuvel March 4, 2017, 2:30 p.m. UTC 
To avoid having mappings that are writable and executable at the same
time, split the init region into a .init.text region that is mapped
read-only, and a .init.data region that is mapped non-executable.

This is possible now that the alternative patching occurs via the linear
mapping, and the linear alias of the init region is always mapped writable
(but never executable).

Since the alternatives descriptions themselves are read-only data, move
those into the .init.text region.

Reviewed-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm64/include/asm/sections.h |  3 ++-
 arch/arm64/kernel/vmlinux.lds.S   | 25 +++++++++++++-------
 arch/arm64/mm/mmu.c               | 12 ++++++----
 3 files changed, 26 insertions(+), 14 deletions(-)

Comments

Mark Rutland March 7, 2017, 2:21 p.m. UTC | #1 
On Sat, Mar 04, 2017 at 02:30:47PM +0000, Ard Biesheuvel wrote:
> diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h
> index 4e7e7067afdb..22582819b2e5 100644
> --- a/arch/arm64/include/asm/sections.h
> +++ b/arch/arm64/include/asm/sections.h
> @@ -24,7 +24,8 @@ extern char __hibernate_exit_text_start[], __hibernate_exit_text_end[];
>  extern char __hyp_idmap_text_start[], __hyp_idmap_text_end[];
>  extern char __hyp_text_start[], __hyp_text_end[];
>  extern char __idmap_text_start[], __idmap_text_end[];
> +extern char __initdata_begin[], __initdata_end[];
> +extern char __inittext_begin[], __inittext_end[];
>  extern char __irqentry_text_start[], __irqentry_text_end[];
>  extern char __mmuoff_data_start[], __mmuoff_data_end[];
> -
>  #endif /* __ASM_SECTIONS_H */

Unintended whitespace change?

Please restore the line above the endif. 

> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index b8deffa9e1bf..2c93d259046c 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -143,12 +143,27 @@ SECTIONS
>  
>  	. = ALIGN(SEGMENT_ALIGN);
>  	__init_begin = .;
> +	__inittext_begin = .;
>  
>  	INIT_TEXT_SECTION(8)
>  	.exit.text : {
>  		ARM_EXIT_KEEP(EXIT_TEXT)
>  	}
>  
> +	. = ALIGN(4);
> +	.altinstructions : {
> +		__alt_instructions = .;
> +		*(.altinstructions)
> +		__alt_instructions_end = .;
> +	}
> +	.altinstr_replacement : {
> +		*(.altinstr_replacement)
> +	}
> +
> +	. = ALIGN(PAGE_SIZE);

Arguably this should be SEGMENT_ALIGN for consitency, but given this is
just .init* this should be fine.

> +	__inittext_end = .;
> +	__initdata_begin = .;
> +
>  	.init.data : {
>  		INIT_DATA
>  		INIT_SETUP(16)

[...]

> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index edd982f88714..0612573ef869 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -459,14 +459,18 @@ early_param("rodata", parse_rodata);
>   */
>  static void __init map_kernel(pgd_t *pgd)
>  {
> -	static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_init, vmlinux_data;
> +	static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_inittext,
> +				vmlinux_initdata, vmlinux_data;
>  
>  	pgprot_t text_prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
>  
>  	map_kernel_segment(pgd, _text, _etext, text_prot, &vmlinux_text);
> -	map_kernel_segment(pgd, __start_rodata, __init_begin, PAGE_KERNEL, &vmlinux_rodata);
> -	map_kernel_segment(pgd, __init_begin, __init_end, PAGE_KERNEL_EXEC,
> -			   &vmlinux_init);
> +	map_kernel_segment(pgd, __start_rodata, __inittext_begin, PAGE_KERNEL,
> +			   &vmlinux_rodata);
> +	map_kernel_segment(pgd, __inittext_begin, __inittext_end, text_prot,
> +			   &vmlinux_inittext);
> +	map_kernel_segment(pgd, __initdata_begin, __initdata_end, PAGE_KERNEL,
> +			   &vmlinux_initdata);
>  	map_kernel_segment(pgd, _data, _end, PAGE_KERNEL, &vmlinux_data);


This all look fine, given text_prot is used for the init text.

With the whitespace restored:

Reviewed-by: Mark Rutland <mark.rutland@arm.com>

Mark.
diff mbox

Patch

diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h
index 4e7e7067afdb..22582819b2e5 100644
--- a/arch/arm64/include/asm/sections.h
+++ b/arch/arm64/include/asm/sections.h
@@ -24,7 +24,8 @@  extern char __hibernate_exit_text_start[], __hibernate_exit_text_end[];
 extern char __hyp_idmap_text_start[], __hyp_idmap_text_end[];
 extern char __hyp_text_start[], __hyp_text_end[];
 extern char __idmap_text_start[], __idmap_text_end[];
+extern char __initdata_begin[], __initdata_end[];
+extern char __inittext_begin[], __inittext_end[];
 extern char __irqentry_text_start[], __irqentry_text_end[];
 extern char __mmuoff_data_start[], __mmuoff_data_end[];
-
 #endif /* __ASM_SECTIONS_H */
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index b8deffa9e1bf..2c93d259046c 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -143,12 +143,27 @@  SECTIONS
 
 	. = ALIGN(SEGMENT_ALIGN);
 	__init_begin = .;
+	__inittext_begin = .;
 
 	INIT_TEXT_SECTION(8)
 	.exit.text : {
 		ARM_EXIT_KEEP(EXIT_TEXT)
 	}
 
+	. = ALIGN(4);
+	.altinstructions : {
+		__alt_instructions = .;
+		*(.altinstructions)
+		__alt_instructions_end = .;
+	}
+	.altinstr_replacement : {
+		*(.altinstr_replacement)
+	}
+
+	. = ALIGN(PAGE_SIZE);
+	__inittext_end = .;
+	__initdata_begin = .;
+
 	.init.data : {
 		INIT_DATA
 		INIT_SETUP(16)
@@ -164,15 +179,6 @@  SECTIONS
 
 	PERCPU_SECTION(L1_CACHE_BYTES)
 
-	. = ALIGN(4);
-	.altinstructions : {
-		__alt_instructions = .;
-		*(.altinstructions)
-		__alt_instructions_end = .;
-	}
-	.altinstr_replacement : {
-		*(.altinstr_replacement)
-	}
 	.rela : ALIGN(8) {
 		*(.rela .rela*)
 	}
@@ -181,6 +187,7 @@  SECTIONS
 	__rela_size	= SIZEOF(.rela);
 
 	. = ALIGN(SEGMENT_ALIGN);
+	__initdata_end = .;
 	__init_end = .;
 
 	_data = .;
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index edd982f88714..0612573ef869 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -459,14 +459,18 @@  early_param("rodata", parse_rodata);
  */
 static void __init map_kernel(pgd_t *pgd)
 {
-	static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_init, vmlinux_data;
+	static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_inittext,
+				vmlinux_initdata, vmlinux_data;
 
 	pgprot_t text_prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
 
 	map_kernel_segment(pgd, _text, _etext, text_prot, &vmlinux_text);
-	map_kernel_segment(pgd, __start_rodata, __init_begin, PAGE_KERNEL, &vmlinux_rodata);
-	map_kernel_segment(pgd, __init_begin, __init_end, PAGE_KERNEL_EXEC,
-			   &vmlinux_init);
+	map_kernel_segment(pgd, __start_rodata, __inittext_begin, PAGE_KERNEL,
+			   &vmlinux_rodata);
+	map_kernel_segment(pgd, __inittext_begin, __inittext_end, text_prot,
+			   &vmlinux_inittext);
+	map_kernel_segment(pgd, __initdata_begin, __initdata_end, PAGE_KERNEL,
+			   &vmlinux_initdata);
 	map_kernel_segment(pgd, _data, _end, PAGE_KERNEL, &vmlinux_data);
 
 	if (!pgd_val(*pgd_offset_raw(pgd, FIXADDR_START))) {