diff mbox series

[02/16] x86/build: Remove RWX sections and align on 4KB

Message ID aac3ce7c5aa706269d468fbe16129ee383deac2e.1662459668.git.baskov@ispras.ru
State Superseded
Headers show
Series x86_64: Improvements at compressed kernel stage | expand

Commit Message

Evgeniy Baskov Sept. 6, 2022, 10:41 a.m. UTC 
Avoid creating sections with maximal privileges to prepare for W^X
implementation. Align sections on page size (4KB) to allow protecting
them in page table.

Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
---
 arch/x86/kernel/vmlinux.lds.S | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

Comments

Ard Biesheuvel Oct. 19, 2022, 7:04 a.m. UTC | #1 
On Tue, 6 Sept 2022 at 12:41, Evgeniy Baskov <baskov@ispras.ru> wrote:
>
> Avoid creating sections with maximal privileges to prepare for W^X

privileges

> implementation. Align sections on page size (4KB) to allow protecting
> them in page table.
>

in the page tables.

> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
> ---
>  arch/x86/kernel/vmlinux.lds.S | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> index 15f29053cec4..6587e0201b50 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -102,12 +102,11 @@ jiffies = jiffies_64;
>  PHDRS {
>         text PT_LOAD FLAGS(5);          /* R_E */
>         data PT_LOAD FLAGS(6);          /* RW_ */
> -#ifdef CONFIG_X86_64
> -#ifdef CONFIG_SMP
> +#if defined(CONFIG_X86_64) && defined(CONFIG_SMP)
>         percpu PT_LOAD FLAGS(6);        /* RW_ */
>  #endif
> -       init PT_LOAD FLAGS(7);          /* RWE */
> -#endif
> +       inittext PT_LOAD FLAGS(5);      /* R_E */
> +       init PT_LOAD FLAGS(6);          /* RW_ */

Please explain in the commit log how this change affects X86_32

>         note PT_NOTE FLAGS(0);          /* ___ */
>  }
>
> @@ -226,9 +225,10 @@ SECTIONS
>  #endif
>
>         INIT_TEXT_SECTION(PAGE_SIZE)
> -#ifdef CONFIG_X86_64
> -       :init
> -#endif
> +       :inittext
> +
> +       . = ALIGN(PAGE_SIZE);
> +
>
>         /*
>          * Section for code used exclusively before alternatives are run. All
> @@ -240,6 +240,7 @@ SECTIONS
>         .altinstr_aux : AT(ADDR(.altinstr_aux) - LOAD_OFFSET) {
>                 *(.altinstr_aux)
>         }
> +       :init
>
>         INIT_DATA_SECTION(16)
>
> --
> 2.35.1
>
Evgeniy Baskov Oct. 20, 2022, 11:15 a.m. UTC | #2 
On 2022-10-19 10:04, Ard Biesheuvel wrote:
> On Tue, 6 Sept 2022 at 12:41, Evgeniy Baskov <baskov@ispras.ru> wrote:
>> 
>> Avoid creating sections with maximal privileges to prepare for W^X
> 
> privileges
> 
>> implementation. Align sections on page size (4KB) to allow protecting
>> them in page table.
>> 
> 
> in the page tables.
> 
>> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
>> ---
>>  arch/x86/kernel/vmlinux.lds.S | 15 ++++++++-------
>>  1 file changed, 8 insertions(+), 7 deletions(-)
>> 
>> diff --git a/arch/x86/kernel/vmlinux.lds.S 
>> b/arch/x86/kernel/vmlinux.lds.S
>> index 15f29053cec4..6587e0201b50 100644
>> --- a/arch/x86/kernel/vmlinux.lds.S
>> +++ b/arch/x86/kernel/vmlinux.lds.S
>> @@ -102,12 +102,11 @@ jiffies = jiffies_64;
>>  PHDRS {
>>         text PT_LOAD FLAGS(5);          /* R_E */
>>         data PT_LOAD FLAGS(6);          /* RW_ */
>> -#ifdef CONFIG_X86_64
>> -#ifdef CONFIG_SMP
>> +#if defined(CONFIG_X86_64) && defined(CONFIG_SMP)
>>         percpu PT_LOAD FLAGS(6);        /* RW_ */
>>  #endif
>> -       init PT_LOAD FLAGS(7);          /* RWE */
>> -#endif
>> +       inittext PT_LOAD FLAGS(5);      /* R_E */
>> +       init PT_LOAD FLAGS(6);          /* RW_ */
> 
> Please explain in the commit log how this change affects X86_32
> 
>>         note PT_NOTE FLAGS(0);          /* ___ */
>>  }
>> 
>> @@ -226,9 +225,10 @@ SECTIONS
>>  #endif
>> 
>>         INIT_TEXT_SECTION(PAGE_SIZE)
>> -#ifdef CONFIG_X86_64
>> -       :init
>> -#endif
>> +       :inittext
>> +
>> +       . = ALIGN(PAGE_SIZE);
>> +
>> 
>>         /*
>>          * Section for code used exclusively before alternatives are 
>> run. All
>> @@ -240,6 +240,7 @@ SECTIONS
>>         .altinstr_aux : AT(ADDR(.altinstr_aux) - LOAD_OFFSET) {
>>                 *(.altinstr_aux)
>>         }
>> +       :init
>> 
>>         INIT_DATA_SECTION(16)
>> 
>> --
>> 2.35.1
>> 

Thanks for pointing you, I'll fix all mentioned nitpicks before sending
this again.
diff mbox series

Patch

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 15f29053cec4..6587e0201b50 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -102,12 +102,11 @@  jiffies = jiffies_64;
 PHDRS {
 	text PT_LOAD FLAGS(5);          /* R_E */
 	data PT_LOAD FLAGS(6);          /* RW_ */
-#ifdef CONFIG_X86_64
-#ifdef CONFIG_SMP
+#if defined(CONFIG_X86_64) && defined(CONFIG_SMP)
 	percpu PT_LOAD FLAGS(6);        /* RW_ */
 #endif
-	init PT_LOAD FLAGS(7);          /* RWE */
-#endif
+	inittext PT_LOAD FLAGS(5);      /* R_E */
+	init PT_LOAD FLAGS(6);          /* RW_ */
 	note PT_NOTE FLAGS(0);          /* ___ */
 }
 
@@ -226,9 +225,10 @@  SECTIONS
 #endif
 
 	INIT_TEXT_SECTION(PAGE_SIZE)
-#ifdef CONFIG_X86_64
-	:init
-#endif
+	:inittext
+
+	. = ALIGN(PAGE_SIZE);
+
 
 	/*
 	 * Section for code used exclusively before alternatives are run. All
@@ -240,6 +240,7 @@  SECTIONS
 	.altinstr_aux : AT(ADDR(.altinstr_aux) - LOAD_OFFSET) {
 		*(.altinstr_aux)
 	}
+	:init
 
 	INIT_DATA_SECTION(16)