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    SubjectRe: [PATCH v4 14/17] arm/build: Warn on orphan section placement
    On Sun, Jun 28, 2020 at 11:18 PM Kees Cook <keescook@chromium.org> wrote:
    >
    > We don't want to depend on the linker's orphan section placement
    > heuristics as these can vary between linkers, and may change between
    > versions. All sections need to be explicitly named in the linker
    > script.
    >
    > Specifically, this would have made a recently fixed bug very obvious:
    >
    > ld: warning: orphan section `.fixup' from `arch/arm/lib/copy_from_user.o' being placed in section `.fixup'
    >
    > Discard unneeded sections .iplt, .rel.iplt, .igot.plt, and .modinfo.
    >
    > Add missing text stub sections .vfp11_veneer and .v4_bx.
    >
    > Add debug sections explicitly.
    >
    > Finally enable orphan section warning.
    >
    > Signed-off-by: Kees Cook <keescook@chromium.org>

    Thanks for following up on the previous suggestion regarding .glu_7 /
    .glu_7t ordering. LGTM
    Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

    > ---
    > arch/arm/include/asm/vmlinux.lds.h | 6 +++++-
    > arch/arm/kernel/vmlinux-xip.lds.S | 1 +
    > arch/arm/kernel/vmlinux.lds.S | 1 +
    > 3 files changed, 7 insertions(+), 1 deletion(-)
    >
    > diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h
    > index c66b16cd8837..d44fae722e7a 100644
    > --- a/arch/arm/include/asm/vmlinux.lds.h
    > +++ b/arch/arm/include/asm/vmlinux.lds.h
    > @@ -39,6 +39,8 @@
    > __idmap_text_end = .; \
    >
    > #define ARM_COMMON_DISCARD \
    > + *(.iplt) *(.rel.iplt) *(.igot.plt) \
    > + *(.modinfo) \
    > *(.discard) \
    > *(.discard.*)
    >
    > @@ -63,7 +65,9 @@
    > #define ARM_STUBS_TEXT \
    > *(.gnu.warning) \
    > *(.glue_7) \
    > - *(.glue_7t)
    > + *(.glue_7t) \
    > + *(.vfp11_veneer) \
    > + *(.v4_bx)
    >
    > #define ARM_TEXT \
    > IDMAP_TEXT \
    > diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
    > index 57fcbf55f913..11ffa79751da 100644
    > --- a/arch/arm/kernel/vmlinux-xip.lds.S
    > +++ b/arch/arm/kernel/vmlinux-xip.lds.S
    > @@ -150,6 +150,7 @@ SECTIONS
    > _end = .;
    >
    > STABS_DEBUG
    > + DWARF_DEBUG
    > ARM_DETAILS
    > }
    >
    > diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
    > index 1d3d3b599635..dc672fe35de3 100644
    > --- a/arch/arm/kernel/vmlinux.lds.S
    > +++ b/arch/arm/kernel/vmlinux.lds.S
    > @@ -149,6 +149,7 @@ SECTIONS
    > _end = .;
    >
    > STABS_DEBUG
    > + DWARF_DEBUG
    > ARM_DETAILS
    > }
    >
    > --
    > 2.25.1
    >
    > --
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    --
    Thanks,
    ~Nick Desaulniers

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