linux-kernel - [tip:x86/asmlinkage] lto: Handle LTO common symbols in module loader

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Date:	Thu, 13 Feb 2014 20:30:59 -0800
From:	tip-bot for Joe Mario <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	rusty@...tcorp.com.au, jmario@...hat.com, ak@...ux.intel.com,
	tglx@...utronix.de, hpa@...ux.intel.com
Subject: [tip:x86/asmlinkage] lto:
  Handle LTO common symbols in module loader

Commit-ID:  80375980f1608f43b47abc2671456b23ec68c434
Gitweb:     http://git.kernel.org/tip/80375980f1608f43b47abc2671456b23ec68c434
Author:     Joe Mario <jmario@...hat.com>
AuthorDate: Sat, 8 Feb 2014 09:01:09 +0100
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Thu, 13 Feb 2014 20:24:50 -0800

lto: Handle LTO common symbols in module loader

Here is the workaround I made for having the kernel not reject modules
built with -flto.  The clean solution would be to get the compiler to not
emit the symbol.  Or if it has to emit the symbol, then emit it as
initialized data but put it into a comdat/linkonce section.

Minor tweaks by AK over Joe's patch.

Cc: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Link: http://lkml.kernel.org/r/1391846481-31491-5-git-send-email-ak@linux.intel.com
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
---
 kernel/module.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index d24fcf2..b99e801 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1948,6 +1948,10 @@ static int simplify_symbols(struct module *mod, const struct load_info *info)
 
 		switch (sym[i].st_shndx) {
 		case SHN_COMMON:
+			/* Ignore common symbols */
+			if (!strncmp(name, "__gnu_lto", 9))
+				break;
+
 			/* We compiled with -fno-common.  These are not
 			   supposed to happen.  */
 			pr_debug("Common symbol: %s\n", name);
--
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