From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Nick Desaulniers <ndesaulniers@google.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Joe Lawrence <joe.lawrence@redhat.com>,
Christophe Leroy <christophe.leroy@c-s.fr>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com,
Kees Cook <keescook@chromium.org>,
Fangrui Song <maskray@google.com>
Subject: Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker
Date: Wed, 2 Sep 2020 06:46:45 +0000 [thread overview]
Message-ID: <b2066ccd-2b81-6032-08e3-41105b400f75@csgroup.eu> (raw)
In-Reply-To: <20200901222523.1941988-3-ndesaulniers@google.com>
On 09/01/2020 10:25 PM, Nick Desaulniers wrote:
> Rather than invoke the compiler as the driver, use the linker. That way
> we can check --orphan-handling=warn support correctly, as cc-ldoption
> was removed in
> commit 055efab3120b ("kbuild: drop support for cc-ldoption").
>
> Requires dropping the .got section. I couldn't find how it was used in
> the vdso32.
ld crashes:
LD arch/powerpc/kernel/vdso32/vdso32.so.dbg
/bin/sh: line 1: 23780 Segmentation fault (core dumped)
ppc-linux-ld -EB -m elf32ppc -shared -soname linux-vdso32.so.1
--eh-frame-hdr --orphan-handling=warn -T
arch/powerpc/kernel/vdso32/vdso32.lds
arch/powerpc/kernel/vdso32/sigtramp.o
arch/powerpc/kernel/vdso32/gettimeofday.o
arch/powerpc/kernel/vdso32/datapage.o
arch/powerpc/kernel/vdso32/cacheflush.o
arch/powerpc/kernel/vdso32/note.o arch/powerpc/kernel/vdso32/getcpu.o -o
arch/powerpc/kernel/vdso32/vdso32.so.dbg
make[4]: *** [arch/powerpc/kernel/vdso32/vdso32.so.dbg] Error 139
[root@localhost linux-powerpc]# ppc-linux-ld --version
GNU ld (GNU Binutils) 2.26.20160125
Christophe
>
> Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
> Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> Not sure removing .got is a good idea or not. Otherwise I observe the
> following link error:
> powerpc-linux-gnu-ld: warning: orphan section `.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.got'
> powerpc-linux-gnu-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
> powerpc-linux-gnu-ld: final link failed: bad value
>
> sigtramp.c doesn't mention anything from the GOT AFAICT, and doesn't
> look like it contains relocations that do, so I'm not sure where
> references to _GLOBAL_OFFSET_TABLE_ are coming from.
>
> arch/powerpc/kernel/vdso32/Makefile | 7 +++++--
> arch/powerpc/kernel/vdso32/vdso32.lds.S | 3 ++-
> 2 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
> index 87ab1152d5ce..611a5951945a 100644
> --- a/arch/powerpc/kernel/vdso32/Makefile
> +++ b/arch/powerpc/kernel/vdso32/Makefile
> @@ -27,6 +27,9 @@ UBSAN_SANITIZE := n
> ccflags-y := -shared -fno-common -fno-builtin -nostdlib \
> -Wl,-soname=linux-vdso32.so.1 -Wl,--hash-style=both
> asflags-y := -D__VDSO32__ -s
> +ldflags-y := -shared -soname linux-vdso32.so.1 \
> + $(call ld-option, --eh-frame-hdr) \
> + $(call ld-option, --orphan-handling=warn) -T
>
> obj-y += vdso32_wrapper.o
> extra-y += vdso32.lds
> @@ -49,8 +52,8 @@ $(obj-vdso32): %.o: %.S FORCE
> $(call if_changed_dep,vdso32as)
>
> # actual build commands
> -quiet_cmd_vdso32ld = VDSO32L $@
> - cmd_vdso32ld = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ $(call cc-ldoption, -Wl$(comma)--orphan-handling=warn) -Wl,-T$(filter %.lds,$^) $(filter %.o,$^)
> +quiet_cmd_vdso32ld = LD $@
> + cmd_vdso32ld = $(cmd_ld)
> quiet_cmd_vdso32as = VDSO32A $@
> cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) -c -o $@ $<
>
> diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
> index 4c985467a668..0ccdebad18b8 100644
> --- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
> +++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
> @@ -61,7 +61,6 @@ SECTIONS
> .fixup : { *(.fixup) }
>
> .dynamic : { *(.dynamic) } :text :dynamic
> - .got : { *(.got) } :text
> .plt : { *(.plt) }
>
> _end = .;
> @@ -108,7 +107,9 @@ SECTIONS
> .debug_varnames 0 : { *(.debug_varnames) }
>
> /DISCARD/ : {
> + *(.got)
> *(.note.GNU-stack)
> + *(.branch_lt)
> *(.data .data.* .gnu.linkonce.d.* .sdata*)
> *(.bss .sbss .dynbss .dynsbss)
> *(.glink .iplt .plt .rela*)
>
next prev parent reply other threads:[~2020-09-02 6:47 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 22:25 [PATCH 0/2] link vdso with linker Nick Desaulniers
2020-09-01 22:25 ` [PATCH 1/2] powerpc/vdso64: link vdso64 " Nick Desaulniers
2020-09-02 12:14 ` Michael Ellerman
2020-09-02 17:41 ` Nick Desaulniers
2020-09-02 18:02 ` Christophe Leroy
2021-04-22 22:44 ` Nick Desaulniers
2021-04-23 7:40 ` Christophe Leroy
2021-04-23 17:18 ` Christophe Leroy
2022-03-02 16:48 ` Christophe Leroy
2020-09-01 22:25 ` [PATCH 2/2] powerpc/vdso32: " Nick Desaulniers
2020-09-02 2:58 ` Kees Cook
2020-09-02 6:46 ` Christophe Leroy [this message]
2020-09-02 14:14 ` Segher Boessenkool
2020-09-02 15:43 ` Christophe Leroy
2020-09-02 16:57 ` Segher Boessenkool
2020-09-02 7:56 ` Christophe Leroy
2020-09-02 10:16 ` Christophe Leroy
2020-09-02 5:21 ` [PATCH 0/2] link vdso " Nathan Chancellor
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