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    SubjectRe: [PATCH v2 08/18] arm64: don't disable ADR_PREL_PG_HI21* with ARM64_ERRATUM_843419
    On Wed, Nov 15, 2017 at 10:29:12PM +0000, Ard Biesheuvel wrote:
    > On 15 November 2017 at 21:34, Sami Tolvanen <samitolvanen@google.com> wrote:
    > > CONFIG_LTO_CLANG depends on GNU gold, which can generate ADR_PREL_PG_HI21*
    > > relocations even with --fix-cortex-a53-843419.
    > >
    > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
    > > ---
    > > arch/arm64/kernel/module.c | 2 --
    > > 1 file changed, 2 deletions(-)
    > >
    > > diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
    > > index f469e0435903..fec9a578f122 100644
    > > --- a/arch/arm64/kernel/module.c
    > > +++ b/arch/arm64/kernel/module.c
    > > @@ -336,14 +336,12 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
    > > ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
    > > AARCH64_INSN_IMM_ADR);
    > > break;
    > > -#ifndef CONFIG_ARM64_ERRATUM_843419
    > > case R_AARCH64_ADR_PREL_PG_HI21_NC:
    > > overflow_check = false;
    > > case R_AARCH64_ADR_PREL_PG_HI21:
    > > ovf = reloc_insn_imm(RELOC_OP_PAGE, loc, val, 12, 21,
    > > AARCH64_INSN_IMM_ADR);
    > > break;
    > > -#endif
    > > case R_AARCH64_ADD_ABS_LO12_NC:
    > > case R_AARCH64_LDST8_ABS_LO12_NC:
    > > overflow_check = false;
    > > --
    > > 2.15.0.448.gf294e3d99a-goog
    > >
    >
    > I think this change is reasonable in itself, but i do wonder how we
    > can ensure that the adrp instructions that GNU gold does generate are
    > not affected by the erratum, given that modules are partially linked
    > object files, not shared libraries.

    Right, and this would also mean that we silently load vulnerable modules
    that are linked with either LD that doesn't support --fix-cortex-a53-843419
    or simply wasn't passed.

    Will
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