linux-kernel - Re: [PATCH] LoongArch: Fix lockdep static memory detection

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Date:   Fri, 15 Sep 2023 17:23:16 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Helge Deller <deller@....de>
Cc:     WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev,
        Guenter Roeck <linux@...ck-us.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: Fix lockdep static memory detection

On Fri, Sep 15, 2023 at 4:16 PM Helge Deller <deller@....de> wrote:
>
> On 9/15/23 05:22, Huacai Chen wrote:
> > Hi Helge,
> >
> > On Wed, Sep 13, 2023 at 3:18 AM Helge Deller <deller@....de> wrote:
> >>
> >> Since commit 0a6b58c5cd0d ("lockdep: fix static memory detection even
> >> more") the lockdep code uses is_kernel_core_data(), is_kernel_rodata()
> >> and init_section_contains() to verify if a lock is located inside a
> >> kernel static data section.
> >>
> >> This change triggers a failure on LoongArch, for which the vmlinux.lds.S
> >> script misses to put the locks (as part of in the .data.rel symbols)
> >> into the Linux data section.
> >> This patch fixes the lockdep problem by moving *(.data.rel*) symbols
> >> into the kernel data section (from _sdata to _edata).
> >>
> >> Additionally, move other wrongly assigned symbols too:
> >> - altinstructions into the _initdata section,
>
> > I think altinstructions cannot  be put into _initdata because it will
> > be used by modules.
>
> No.
> arch/loongarch/kernel/vmlinux.lds.S is used for the static parts of the kernel
> and altinstructions are replaced before modules are loaded.
> For altinstructions in modules the linker script scripts/module.lds.S is used.
OK, then what about .got/.plt? It seems arm64 also doesn't put them in
the data section.

Huacai

>
> Helge
>
>
> >> - PLT symbols behind the read-only section, and
> >> - *(.la_abs) into the data section.
> >>
> >> Signed-off-by: Helge Deller <deller@....de>
> >> Reported-by: Guenter Roeck <linux@...ck-us.net>
> >> Fixes: 0a6b58c5cd0d ("lockdep: fix static memory detection even more")
> >> Cc: stable <stable@...nel.org> # v6.4+
> >>
> >> diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
> >> index b1686afcf876..bb2ec86f37a8 100644
> >> --- a/arch/loongarch/kernel/vmlinux.lds.S
> >> +++ b/arch/loongarch/kernel/vmlinux.lds.S
> >> @@ -53,33 +53,6 @@ SECTIONS
> >>          . = ALIGN(PECOFF_SEGMENT_ALIGN);
> >>          _etext = .;
> >>
> >> -       /*
> >> -        * struct alt_inst entries. From the header (alternative.h):
> >> -        * "Alternative instructions for different CPU types or capabilities"
> >> -        * Think locking instructions on spinlocks.
> >> -        */
> >> -       . = ALIGN(4);
> >> -       .altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
> >> -               __alt_instructions = .;
> >> -               *(.altinstructions)
> >> -               __alt_instructions_end = .;
> >> -       }
> >> -
> >> -#ifdef CONFIG_RELOCATABLE
> >> -       . = ALIGN(8);
> >> -       .la_abs : AT(ADDR(.la_abs) - LOAD_OFFSET) {
> >> -               __la_abs_begin = .;
> >> -               *(.la_abs)
> >> -               __la_abs_end = .;
> >> -       }
> >> -#endif
> >> -
> >> -       .got : ALIGN(16) { *(.got) }
> >> -       .plt : ALIGN(16) { *(.plt) }
> >> -       .got.plt : ALIGN(16) { *(.got.plt) }
> >> -
> >> -       .data.rel : { *(.data.rel*) }
> >> -
> >>          . = ALIGN(PECOFF_SEGMENT_ALIGN);
> >>          __init_begin = .;
> >>          __inittext_begin = .;
> >> @@ -94,6 +67,18 @@ SECTIONS
> >>
> >>          __initdata_begin = .;
> >>
> >> +       /*
> >> +        * struct alt_inst entries. From the header (alternative.h):
> >> +        * "Alternative instructions for different CPU types or capabilities"
> >> +        * Think locking instructions on spinlocks.
> >> +        */
> >> +       . = ALIGN(4);
> >> +       .altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
> >> +               __alt_instructions = .;
> >> +               *(.altinstructions)
> >> +               __alt_instructions_end = .;
> >> +       }
> >> +
> >>          INIT_DATA_SECTION(16)
> >>          .exit.data : {
> >>                  EXIT_DATA
> >> @@ -113,6 +98,11 @@ SECTIONS
> >>
> >>          _sdata = .;
> >>          RO_DATA(4096)
> >> +
> >> +       .got : ALIGN(16) { *(.got) }
> >> +       .plt : ALIGN(16) { *(.plt) }
> >> +       .got.plt : ALIGN(16) { *(.got.plt) }
> >> +
> >>          RW_DATA(1 << CONFIG_L1_CACHE_SHIFT, PAGE_SIZE, THREAD_SIZE)
> >>
> >>          .rela.dyn : ALIGN(8) {
> >> @@ -121,6 +111,17 @@ SECTIONS
> >>                  __rela_dyn_end = .;
> >>          }
> >>
> >> +       .data.rel : { *(.data.rel*) }
> >> +
> >> +#ifdef CONFIG_RELOCATABLE
> >> +       . = ALIGN(8);
> >> +       .la_abs : AT(ADDR(.la_abs) - LOAD_OFFSET) {
> >> +               __la_abs_begin = .;
> >> +               *(.la_abs)
> >> +               __la_abs_end = .;
> >> +       }
> >> +#endif
> >> +
> >>          .sdata : {
> >>                  *(.sdata)
> >>          }
>