From 2225a8dda263edc35a0e8b858fe2945cf6240fde Mon Sep 17 00:00:00 2001
From: Ariel Marcovitch <arielmarcovitch@gmail.com>
Date: Sat, 2 Jan 2021 22:11:56 +0200
Subject: [PATCH] powerpc: Fix alignment bug within the init sections
References: bsc#1065729
Patch-mainline: v5.11-rc4
Git-commit: 2225a8dda263edc35a0e8b858fe2945cf6240fde
This is a bug that causes early crashes in builds with an .exit.text
section smaller than a page and an .init.text section that ends in the
beginning of a physical page (this is kinda random, which might
explain why this wasn't really encountered before).
The init sections are ordered like this:
.init.text
.exit.text
.init.data
Currently, these sections aren't page aligned.
Because the init code might become read-only at runtime and because
the .init.text section can potentially reside on the same physical
page as .init.data, the beginning of .init.data might be mapped
read-only along with .init.text.
Then when the kernel tries to modify a variable in .init.data (like
kthreadd_done, used in kernel_init()) the kernel panics.
To avoid this, make _einittext page aligned and also align .exit.text
to make sure .init.data is always seperated from the text segments.
Fixes: 060ef9d89d18 ("powerpc32: PAGE_EXEC required for inittext")
Signed-off-by: Ariel Marcovitch <ariel.marcovitch@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210102201156.10805-1-ariel.marcovitch@gmail.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kernel/vmlinux.lds.S | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -185,6 +185,12 @@ SECTIONS
__init_begin = .;
INIT_TEXT_SECTION(PAGE_SIZE) :kernel
+ /*
+ *.init.text might be RO so we must ensure this section ends on
+ * a page boundary.
+ */
+ . = ALIGN(PAGE_SIZE);
+
/* .exit.text is discarded at runtime, not link time,
* to deal with references from __bug_table
*/
@@ -192,6 +198,8 @@ SECTIONS
EXIT_TEXT
}
+ . = ALIGN(PAGE_SIZE);
+
.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) {
INIT_DATA
__vtop_table_begin = .;