linux-kernel - Re: linux-next: Tree for Jul 6 (arch/riscv/)

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Date:   Thu, 06 Jul 2023 14:46:50 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     rdunlap@...radead.org
CC:     Stephen Rothwell <sfr@...b.auug.org.au>,
        linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, Conor Dooley <conor@...nel.org>
Subject:     Re: linux-next: Tree for Jul 6 (arch/riscv/)

On Thu, 06 Jul 2023 14:36:05 PDT (-0700), rdunlap@...radead.org wrote:
>
>
> On 7/6/23 14:32, Palmer Dabbelt wrote:
>> On Thu, 06 Jul 2023 14:27:53 PDT (-0700), rdunlap@...radead.org wrote:
>>>
>>>
>>> On 7/5/23 18:57, Stephen Rothwell wrote:
>>>> Hi all,
>>>>
>>>> Please do *not* add any v6.6 related stuff to your linux-next included
>>>> branches until after v6.5-rc1 has been released.
>>>>
>>>> Changes since 20230705:
>>>>
>>>
>>> on riscv64:
>>>
>>> WARNING: modpost: vmlinux: section mismatch in reference: $xrv64i2p1_m2p0_a2p1_zicsr2p0_zifencei2p0_zihintpause2p0_zmmul1p0+0x14 (section: .text.unlikely.set_bit.constprop.0) -> numa_nodes_parsed (section: .init.data)
>>>
>>>
>>> Full randconfig file is attached.
>>
>> Thanks, I'm giving it a look.  Do you happen to also have your toolchain version easily availiable?  The mapping symbols are new and we've seen some odd stuff happen, something is likely broken somewhere...
>
> I'm using gcc-13.1.0 from  https://mirrors.edge.kernel.org/pub/tools/crosstool/

Cool, those are pretty easy to run.  I've yet to actually reproduce the
failures, but I'd guess we just want to ignore the mapping symbols with
something like

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index b29b29707f10..2f801469301d 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -614,6 +614,18 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname)
 		/* Expoline thunks are linked on all kernel modules during final link of .ko */
 		if (strstarts(symname, "__s390_indirect_jump_r"))
 			return 1;
+
+	/*
+	 * RISC-V defines various special symbols that start with "$".  The
+	 * mapping symbols, which exist to differentiate between incompatible
+	 * instruction encodings when disassembling, show up all over the place
+	 * and are generally not meant to be treated like other symbols.  So
+	 * just ignore any of the special symbols.
+	 */
+	if (info->hdr->e_machine == EM_RISCV)
+		if (symname[0] == '$')
+			return 1;
+
 	/* Do not ignore this symbol */
 	return 0;
 }

I haven't even built that, though...

These also trip up backtraces, so we probably need something over there as
well.