The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 2225a8dda263edc35a0e8b858fe2945cf6240fde Mon Sep 17 00:00:00 2001
From: Ariel Marcovitch <arielmarcovitch@xxxxxxxxx>
Date: Sat, 2 Jan 2021 22:11:56 +0200
Subject: [PATCH] powerpc: Fix alignment bug within the init sections
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@xxxxxxxxx>
Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210102201156.10805-1-ariel.marcovitch@xxxxxxxxx
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 8e0b1298bf19..4ab426b8b0e0 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -187,6 +187,12 @@ SECTIONS
.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
_sinittext = .;
INIT_TEXT
+
+ /*
+ *.init.text might be RO so we must ensure this section ends on
+ * a page boundary.
+ */
+ . = ALIGN(PAGE_SIZE);
_einittext = .;
#ifdef CONFIG_PPC64
*(.tramp.ftrace.init);
@@ -200,6 +206,8 @@ SECTIONS
EXIT_TEXT
}
+ . = ALIGN(PAGE_SIZE);
+
INIT_DATA_SECTION(16)
. = ALIGN(8);
