linux-kernel - [PATCH 2/2] ARM: module: fix handling of unwind init sections

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Message-ID: <20200506152533.31286-2-vincent.whitchurch@axis.com>
Date:   Wed, 6 May 2020 17:25:33 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     <linux@...linux.org.uk>, <jeyu@...nel.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kernel@...s.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>
Subject: [PATCH 2/2] ARM: module: fix handling of unwind init sections

Unwind information for init sections is placed in .ARM.exidx.init.text
and .ARM.extab.init.text.  The module core doesn't know that these are
init sections so they are allocated along with the core sections, and if
the core and init sections get allocated in different memory regions
(which is possible with CONFIG_ARM_MODULE_PLTS=y) and they can't reach
each other, relocation fails:

  final section addresses:
  	...
  	0x7f800000 .init.text
	..
  	0xcbb54078 .ARM.exidx.init.text
	..

 section 16 reloc 0 sym '': relocation 42 out of range (0xcbb54078 ->
 0x7f800000)

Fix this by informing the module core that these sections are init
sections, and by removing the init unwind tables before the module core
frees the init sections.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
 arch/arm/kernel/module.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index deef17f34bd2..af0a8500a24e 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -55,6 +55,13 @@ void *module_alloc(unsigned long size)
 }
 #endif
 
+bool module_init_section(const char *name)
+{
+	return strstarts(name, ".init") ||
+		strstarts(name, ".ARM.extab.init") ||
+		strstarts(name, ".ARM.exidx.init");
+}
+
 bool module_exit_section(const char *name)
 {
 	return strstarts(name, ".exit") ||
@@ -409,8 +416,17 @@ module_arch_cleanup(struct module *mod)
 #ifdef CONFIG_ARM_UNWIND
 	int i;
 
-	for (i = 0; i < ARM_SEC_MAX; i++)
-		if (mod->arch.unwind[i])
-			unwind_table_del(mod->arch.unwind[i]);
+	for (i = 0; i < ARM_SEC_MAX; i++) {
+		unwind_table_del(mod->arch.unwind[i]);
+		mod->arch.unwind[i] = NULL;
+	}
+#endif
+}
+
+void __weak module_arch_freeing_init(struct module *mod)
+{
+#ifdef CONFIG_ARM_UNWIND
+	unwind_table_del(mod->arch.unwind[ARM_SEC_INIT]);
+	mod->arch.unwind[ARM_SEC_INIT] = NULL;
 #endif
 }
-- 
2.25.1