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

From: Evgeniy Baskov
Date: Thu Oct 20 2022 - 07:15:46 EST


On 2022-10-19 10:04, Ard Biesheuvel wrote:
On Tue, 6 Sept 2022 at 12:41, Evgeniy Baskov <baskov@xxxxxxxxx> 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@xxxxxxxxx>
---
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.