FAILED: patch "[PATCH] powerpc: Fix alignment bug within the init sections" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-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 <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2225a8dda263edc35a0e8b858fe2945cf6240fde Mon Sep 17 00:00:00 2001
From: Ariel Marcovitch <[email protected]>
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.

index 8e0b1298bf19..4ab426b8b0e0 100644
@@ -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);