linux-kernel - Re: mmotm 2018-05-10-16-34 uploaded (objtool)

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Message-ID: <20180511154519.w6bbhptv67fvsgnr@treble>
Date:   Fri, 11 May 2018 10:45:19 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     akpm@...ux-foundation.org, broonie@...nel.org, mhocko@...e.cz,
        sfr@...b.auug.org.au, linux-next@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, mm-commits@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: mmotm 2018-05-10-16-34 uploaded (objtool)

On Thu, May 10, 2018 at 06:06:38PM -0700, Randy Dunlap wrote:
> >> Hi Josh, Peter:
> >>
> >> Is this something that you already have fixes for?
> >>
> >>
> >> on x86_64:
> >>
> >> drivers/video/fbdev/omap2/omapfb/dss/dispc.o: warning: objtool: dispc_runtime_suspend()+0xbb8: sibling call from callable instruction with modified stack frame
> >> drivers/video/fbdev/omap2/omapfb/dss/dispc.o: warning: objtool: dispc_runtime_resume()+0xcc5: sibling call from callable instruction with modified stack frame
> > 
> > I don't recall seeing that one.  Can you share the .config and/or .o
> > file?
> > 
> 
> Sure.  Both are attached.

Here's a fix (applies on top of the GCC 8 patches I posted this week):

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 9bb04fddd3c8..a358489a1560 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -961,11 +961,15 @@ static struct rela *find_switch_table(struct objtool_file *file,
 		if (find_symbol_containing(file->rodata, text_rela->addend))
 			continue;
 
+		/* mov [rodata addr], %reg */
 		rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend);
-		if (!rodata_rela)
-			continue;
+		if (rodata_rela)
+			return rodata_rela;
 
-		return rodata_rela;
+		/* mov [rodata_addr](%rip), %reg */
+		rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend + 4);
+		if (rodata_rela)
+			return rodata_rela;
 	}
 
 	return NULL;