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

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Date:   Wed, 6 May 2020 17:25:32 +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 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>
---
 include/linux/moduleloader.h | 2 ++
 kernel/module.c              | 9 +++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index ca92aea8a6bd..07d079085f11 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -29,6 +29,8 @@ void *module_alloc(unsigned long size);
 /* Free memory returned from module_alloc. */
 void module_memfree(void *module_region);
 
+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..a5f2b4e1ef53 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2370,6 +2370,11 @@ static long get_offset(struct module *mod, unsigned int *size,
 	return ret;
 }
 
+bool __weak module_init_section(const char *name)
+{
+	return strstarts(name, ".init");
+}
+
 /* Lay out the SHF_ALLOC sections in a way not dissimilar to how ld
    might -- code, read-only data, read-write data, small data.  Tally
    sizes, and place the offsets into sh_entsize fields: high bit means it
@@ -2400,7 +2405,7 @@ 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 +2438,7 @@ 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);
-- 
2.25.1