linux-kernel - [PATCH v2 1/2] module: allow arch overrides for .init section names

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Date:   Mon, 11 May 2020 13:48:02 +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 v2 1/2] module: allow arch overrides for .init section names

ARM stores unwind information for .init.text in sections named
.ARM.extab.init.text and .ARM.exidx.init.text.  Since those aren't
currently recognized as init sections, they're allocated along with the
core section, and relocation fails if the core and the init section are
allocated from different regions and can't reach other.

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

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

Allow architectures to override the section name so that ARM can fix
this.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
v2: Add comment and move module_init_section() next to module_exit_section().

 include/linux/moduleloader.h | 5 +++++
 kernel/module.c              | 9 +++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index ca92aea8a6bd..4fa67a8b2265 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -29,6 +29,11 @@ void *module_alloc(unsigned long size);
 /* Free memory returned from module_alloc. */
 void module_memfree(void *module_region);
 
+/* Determines if the section name is an init section (that is only used during
+ * module loading).
+ */
+bool module_init_section(const char *name);
+
 /* Determines if the section name is an exit section (that is only used during
  * module unloading)
  */
diff --git a/kernel/module.c b/kernel/module.c
index 33569a01d6e1..84d0c455fb44 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2400,7 +2400,7 @@ static void layout_sections(struct module *mod, struct load_info *info)
 			if ((s->sh_flags & masks[m][0]) != masks[m][0]
 			    || (s->sh_flags & masks[m][1])
 			    || s->sh_entsize != ~0UL
-			    || strstarts(sname, ".init"))
+			    || module_init_section(sname))
 				continue;
 			s->sh_entsize = get_offset(mod, &mod->core_layout.size, s, i);
 			pr_debug("\t%s\n", sname);
@@ -2433,7 +2433,7 @@ static void layout_sections(struct module *mod, struct load_info *info)
 			if ((s->sh_flags & masks[m][0]) != masks[m][0]
 			    || (s->sh_flags & masks[m][1])
 			    || s->sh_entsize != ~0UL
-			    || !strstarts(sname, ".init"))
+			    || !module_init_section(sname))
 				continue;
 			s->sh_entsize = (get_offset(mod, &mod->init_layout.size, s, i)
 					 | INIT_OFFSET_MASK);
@@ -2768,6 +2768,11 @@ void * __weak module_alloc(unsigned long size)
 	return vmalloc_exec(size);
 }
 
+bool __weak module_init_section(const char *name)
+{
+	return strstarts(name, ".init");
+}
+
 bool __weak module_exit_section(const char *name)
 {
 	return strstarts(name, ".exit");
-- 
2.25.1