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Fri, 25 Oct 2019 08:28:17 -0700 (PDT) MIME-Version: 1.0 References: <20191024124833.4158-1-ard.biesheuvel@linaro.org> <20191024124833.4158-43-ard.biesheuvel@linaro.org> <20191025152534.GF31224@sasha-vm> In-Reply-To: <20191025152534.GF31224@sasha-vm> From: Ard Biesheuvel Date: Fri, 25 Oct 2019 17:28:06 +0200 Message-ID: Subject: Re: [PATCH for-stable-4.14 42/48] arm64: Always enable spectre-v2 vulnerability detection To: Sasha Levin Cc: Alexandru Elisei , stable , Will Deacon , Catalin Marinas , Marc Zyngier , Mark Rutland , Suzuki K Poulose , Jeremy Linton , Andre Przywara , Stefan Wahren , Will Deacon Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, 25 Oct 2019 at 17:25, Sasha Levin wrote: > > On Thu, Oct 24, 2019 at 04:37:12PM +0200, Ard Biesheuvel wrote: > >On Thu, 24 Oct 2019 at 16:34, Alexandru Elisei wrote: > >> > >> Hi, > >> > >> On 10/24/19 1:48 PM, Ard Biesheuvel wrote: > >> > From: Jeremy Linton > >> > > >> > [ Upstream commit 8c1e3d2bb44cbb998cb28ff9a18f105fee7f1eb3 ] > >> > > >> > Ensure we are always able to detect whether or not the CPU is affect= ed > >> > by Spectre-v2, so that we can later advertise this to userspace. > >> > > >> > Signed-off-by: Jeremy Linton > >> > Reviewed-by: Andre Przywara > >> > Reviewed-by: Catalin Marinas > >> > Tested-by: Stefan Wahren > >> > Signed-off-by: Will Deacon > >> > Signed-off-by: Ard Biesheuvel > >> > --- > >> > arch/arm64/kernel/cpu_errata.c | 15 ++++++++------- > >> > 1 file changed, 8 insertions(+), 7 deletions(-) > >> > > >> > diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_= errata.c > >> > index bf6d8aa9b45a..647c533cfd90 100644 > >> > --- a/arch/arm64/kernel/cpu_errata.c > >> > +++ b/arch/arm64/kernel/cpu_errata.c > >> > @@ -76,7 +76,6 @@ cpu_enable_trap_ctr_access(const struct arm64_cpu_= capabilities *__unused) > >> > config_sctlr_el1(SCTLR_EL1_UCT, 0); > >> > } > >> > > >> > -#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR > >> > #include > >> > #include > >> > > >> > @@ -217,11 +216,11 @@ static int detect_harden_bp_fw(void) > >> > ((midr & MIDR_CPU_MODEL_MASK) =3D=3D MIDR_QCOM_FALKOR_V1)) > >> > cb =3D qcom_link_stack_sanitization; > >> > > >> > - install_bp_hardening_cb(cb, smccc_start, smccc_end); > >> > + if (IS_ENABLED(CONFIG_HARDEN_BRANCH_PREDICTOR)) > >> > + install_bp_hardening_cb(cb, smccc_start, smccc_end); > >> > > >> > return 1; > >> > } > >> > -#endif /* CONFIG_HARDEN_BRANCH_PREDICTOR */ > >> > > >> > DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required); > >> > > >> > @@ -457,7 +456,6 @@ static bool has_ssbd_mitigation(const struct arm= 64_cpu_capabilities *entry, > >> > .type =3D ARM64_CPUCAP_LOCAL_CPU_ERRATUM, \ > >> > CAP_MIDR_RANGE_LIST(midr_list) > >> > > >> > -#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR > >> > /* > >> > * List of CPUs that do not need any Spectre-v2 mitigation at all. > >> > */ > >> > @@ -489,6 +487,12 @@ check_branch_predictor(const struct arm64_cpu_c= apabilities *entry, int scope) > >> > if (!need_wa) > >> > return false; > >> > > >> > + if (!IS_ENABLED(CONFIG_HARDEN_BRANCH_PREDICTOR)) { > >> > + pr_warn_once("spectrev2 mitigation disabled by kernel = configuration\n"); > >> > + __hardenbp_enab =3D false; > >> > >> This breaks when building, because __hardenbp_enab is declared in the = next patch: > >> > >> $ make -j32 defconfig && make -j32 > >> > >> [..] > >> arch/arm64/kernel/cpu_errata.c: In function =E2=80=98check_branch_pred= ictor=E2=80=99: > >> arch/arm64/kernel/cpu_errata.c:492:3: error: =E2=80=98__hardenbp_enab= =E2=80=99 undeclared (first > >> use in this function) > >> __hardenbp_enab =3D false; > >> ^~~~~~~~~~~~~~~ > >> arch/arm64/kernel/cpu_errata.c:492:3: note: each undeclared identifier= is reported > >> only once for each function it appears in > >> make[1]: *** [scripts/Makefile.build:326: arch/arm64/kernel/cpu_errata= .o] Error 1 > >> make[1]: *** Waiting for unfinished jobs.... > >> > > > >Indeed, but as discussed, this matches the state of both mainline and > >v4.19, which carry these patches in the same [wrong] order as well. > > > >Greg should confirm, but as I understand it, it is preferred to be > >bug-compatible with mainline rather than fixing problems when spotting > >them while doing the backport. > > Is it just patch ordering? If so I'd rather fix it, there's no reason to > carry this issue into the stable trees. > > We reserve "bug compatibility" for functional issues that are not yet > fixed upstream, it doesn't seem to be the case here. > The patches don't apply cleanly in the opposite order.