linux-kernel - Re: objtool crashes with some clang produced .o files

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Message-ID: <20201211163748.b37gashl6an6misu@treble>
Date:   Fri, 11 Dec 2020 10:37:48 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: objtool crashes with some clang produced .o files

On Fri, Dec 11, 2020 at 10:32:05AM +0100, Peter Zijlstra wrote:
> Looking at elf.c, it seems we're missing an STT_SECTION symbol for
> .text.
> 
> And indeed, when I add -fno-asynchronous-unwind-tables to clang-11, that
> goes missing from the readelf .symtab listing. Help ?!

I had a similar problem with ORC relocations:

  e81e07244325 ("objtool: Support Clang non-section symbols in ORC generation")

If Clang strips the section symbol then we have to find the function
symbol instead.

Does this fix it?

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index c6ab44543c92..9bc18864154f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -472,8 +472,25 @@ static int create_static_call_sections(struct objtool_file *file)
 			return -1;
 		}
 		memset(reloc, 0, sizeof(*reloc));
-		reloc->sym = insn->sec->sym;
-		reloc->addend = insn->offset;
+
+		if (insn->sec->sym) {
+			reloc->sym = insn->sec->sym;
+			reloc->addend = insn->offset;
+		} else {
+			reloc->sym = find_symbol_containing(insn->sec, insn->offset);
+			if (!reloc->sym) {
+				WARN_FUNC("can't create static call: missing containing symbol",
+					  insn->sec, insn->offset);
+				return -1;
+			}
+
+			reloc->addend = insn->offset - reloc->sym->offset;
+		}
+
 		reloc->type = R_X86_64_PC32;
 		reloc->offset = idx * sizeof(struct static_call_site);
 		reloc->sec = reloc_sec;