linux-kernel - Re: [PATCH v2 2/3] riscv/purgatory: do not link with string.o and its dependencies

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Date:   Thu, 03 Aug 2023 08:13:48 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Conor Dooley <conor@...nel.org>
CC:     petrtesarik@...weicloud.com,
        Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, Conor Dooley <conor.dooley@...rochip.com>,
        lihuafei1@...wei.com, liaochang1@...wei.com, masahiroy@...nel.org,
        keescook@...omium.org, akpm@...ux-foundation.org, heiko@...ech.de,
        ribalda@...omium.org, hi@...ssa.is, lizhengyu3@...wei.com,
        linux-riscv@...ts.infradead.org, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, duwe@...e.de,
        roberto.sassu@...weicloud.com, petr@...arici.cz
Subject:     Re: [PATCH v2 2/3] riscv/purgatory: do not link with string.o and its dependencies

On Wed, 26 Jul 2023 09:33:49 PDT (-0700), Conor Dooley wrote:
> On Wed, Jul 26, 2023 at 11:54:00AM +0200, Petr Tesarik wrote:
>> From: Petr Tesarik <petr.tesarik.ext@...wei.com>
>> 
>> Linking with this object file makes kexec_file_load(2) fail because of
>> multiple unknown relocation types:
>> 
>> - R_RISCV_ADD16, R_RISCV_SUB16: used by alternatives in strcmp()
>> - R_RISCV_GOT_HI20: used to resolve _ctype in strcasecmp()
>> 
>> All this hassle is needed for one single call to memcmp() from
>> verify_sha256_digest() to compare 32 bytes of SHA256 checksum.
>> 
>> Simply replace this memcmp() call with an explicit loop over those 32 bytes
>> and remove the need to link with string.o and all the other object files
>> that provide undefined symbols from that object file.
>> 
>> Fixes: 838b3e28488f ("RISC-V: Load purgatory in kexec_file")
>> Signed-off-by: Petr Tesarik <petr.tesarik.ext@...wei.com>
>
> This version keeps the automation happy,
> Acked-by: Conor Dooley <conor.dooley@...rochip.com>

Oddly enough, this breaks my builds.  I tried fixing the first one with
something like

    From 41c5a952f77e53bf4201296abff0132725aa19e6 Mon Sep 17 00:00:00 2001
    From: Palmer Dabbelt <palmer@...osinc.com>
    Date: Wed, 2 Aug 2023 20:22:33 -0700
    Subject: [PATCH] RISC-V: Include io from timex
    
    Without this I get some implicit declarations.
    
      CC      arch/riscv/kernel/asm-offsets.s
    In file included from linux/include/linux/timex.h:67,
                     from linux/include/linux/time32.h:13,
                     from linux/include/linux/time.h:60,
                     from linux/include/linux/ktime.h:24,
                     from linux/include/linux/timer.h:6,
                     from linux/include/linux/workqueue.h:9,
                     from linux/include/linux/mm_types.h:19,
                     from linux/include/linux/mmzone.h:22,
                     from linux/include/linux/gfp.h:7,
                     from linux/include/linux/mm.h:7,
                     from linux/arch/riscv/kernel/asm-offsets.c:10:
    linux/arch/riscv/include/asm/timex.h: In function 'get_cycles':
    linux/arch/riscv/include/asm/timex.h:25:16: error: implicit declaration of function 'readl_relaxed' [-Werror=implicit-function-declaration]
       25 |         return readl_relaxed(((u32 *)clint_time_val));
          |
    
    Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
    ---
     arch/riscv/include/asm/timex.h | 1 +
     1 file changed, 1 insertion(+)
    
    diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
    index a06697846e69..1a4d181193e0 100644
    --- a/arch/riscv/include/asm/timex.h
    +++ b/arch/riscv/include/asm/timex.h
    @@ -7,6 +7,7 @@
     #define _ASM_RISCV_TIMEX_H
     
     #include <asm/csr.h>
    +#include <asm/io.h>
     
     typedef unsigned long cycles_t;
 
    -- 
    2.41.0

The other two look fine and are somewhat independent, so I've picked those up
for fixes.

Thanks!

>
> Thanks,
> Conor.