| Message ID | 20181113152906.55802-1-agraf@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] arm64: Make kpti command line options x86 compatible | expand |
On Tue, Nov 13, 2018 at 04:29:06PM +0100, Alexander Graf wrote: > I've already stumbled over 2 cases where people got confused about how to > disable kpti on AArch64. In both cases, they used existing x86_64 options > and just applied that to an AArch64 system, expecting it to work. > > I think it makes a lot of sense to have compatible kernel command line > parameters whenever we can have them be compatible. > > So this patch adds the pti= and no_pti kernel command line options, mapping > them into the existing kpti= command line framework. It preserves the old > syntax to maintain compatibility with older command lines. > > While at it, the patch also marks the respective options as dual-arch. > > Reported-by: Richard Brown <rbrown@suse.de> > Signed-off-by: Alexander Graf <agraf@suse.de> > > --- > > v1 -> v2: > > - Actually make it compile. Sorry for the sloppy v1. > --- > Documentation/admin-guide/kernel-parameters.txt | 6 +++--- > arch/arm64/kernel/cpufeature.c | 20 +++++++++++++++++++- > 2 files changed, 22 insertions(+), 4 deletions(-) This patch doesn't help though, right, because kpti= has already been included with backports etc so the ship has sailed? Yeah, it's not ideal, but we went over this before: http://lists.infradead.org/pipermail/linux-arm-kernel/2018-August/598395.html The thing we really need is the sysfs interface hooking up so you can easily check the state of the mitigation. Still waiting for a follow-up on that ;) http://lists.infradead.org/pipermail/linux-arm-kernel/2018-September/603412.html Will
> Am 15.11.2018 um 16:47 schrieb Will Deacon <will.deacon@arm.com>: > >> On Tue, Nov 13, 2018 at 04:29:06PM +0100, Alexander Graf wrote: >> I've already stumbled over 2 cases where people got confused about how to >> disable kpti on AArch64. In both cases, they used existing x86_64 options >> and just applied that to an AArch64 system, expecting it to work. >> >> I think it makes a lot of sense to have compatible kernel command line >> parameters whenever we can have them be compatible. >> >> So this patch adds the pti= and no_pti kernel command line options, mapping >> them into the existing kpti= command line framework. It preserves the old >> syntax to maintain compatibility with older command lines. >> >> While at it, the patch also marks the respective options as dual-arch. >> >> Reported-by: Richard Brown <rbrown@suse.de> >> Signed-off-by: Alexander Graf <agraf@suse.de> >> >> --- >> >> v1 -> v2: >> >> - Actually make it compile. Sorry for the sloppy v1. >> --- >> Documentation/admin-guide/kernel-parameters.txt | 6 +++--- >> arch/arm64/kernel/cpufeature.c | 20 +++++++++++++++++++- >> 2 files changed, 22 insertions(+), 4 deletions(-) > > This patch doesn't help though, right, because kpti= has already been > included with backports etc so the ship has sailed? Not necessarily. We can always mark this as stable and have distros pull it in. Consistency is definitely useful for everyone. > Yeah, it's not ideal, > but we went over this before: > > http://lists.infradead.org/pipermail/linux-arm-kernel/2018-August/598395.html Ah, I mist havd missed that. But if you already have 2 people sending very similar patches, there is probably something to it :). > > The thing we really need is the sysfs interface hooking up so you can easily > check the state of the mitigation. Still waiting for a follow-up on that ;) > > http://lists.infradead.org/pipermail/linux-arm-kernel/2018-September/603412.html That one is very much needed as well, yes. Alex > > Will
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 81d1d5a74728..4a1c6bcfcdb5 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3522,8 +3522,8 @@ pt. [PARIDE] See Documentation/blockdev/paride.txt. - pti= [X86_64] Control Page Table Isolation of user and - kernel address spaces. Disabling this feature + pti= [X86_64,ARM64] Control Page Table Isolation of user + and kernel address spaces. Disabling this feature removes hardening, but improves performance of system calls and interrupts. @@ -3534,7 +3534,7 @@ Not specifying this option is equivalent to pti=auto. - nopti [X86_64] + nopti [X86_64,ARM64] Equivalent to pti=off pty.legacy_count= diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index af50064dea51..a67b4b563a7c 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -978,13 +978,31 @@ static int __init parse_kpti(char *str) bool enabled; int ret = strtobool(str, &enabled); - if (ret) + if (ret) { + if (!strncmp(str, "auto", 4)) { + __kpti_forced = 0; + return 0; + } return ret; + } __kpti_forced = enabled ? 1 : -1; return 0; } early_param("kpti", parse_kpti); + +static int __init parse_pti(char *str) +{ + return parse_kpti(str); +} +early_param("pti", parse_pti); + +static int __init parse_no_pti(char *p) +{ + __kpti_forced = -1; + return 0; +} +early_param("nopti", parse_no_pti); #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ #ifdef CONFIG_ARM64_HW_AFDBM
I've already stumbled over 2 cases where people got confused about how to disable kpti on AArch64. In both cases, they used existing x86_64 options and just applied that to an AArch64 system, expecting it to work. I think it makes a lot of sense to have compatible kernel command line parameters whenever we can have them be compatible. So this patch adds the pti= and no_pti kernel command line options, mapping them into the existing kpti= command line framework. It preserves the old syntax to maintain compatibility with older command lines. While at it, the patch also marks the respective options as dual-arch. Reported-by: Richard Brown <rbrown@suse.de> Signed-off-by: Alexander Graf <agraf@suse.de> --- v1 -> v2: - Actually make it compile. Sorry for the sloppy v1. --- Documentation/admin-guide/kernel-parameters.txt | 6 +++--- arch/arm64/kernel/cpufeature.c | 20 +++++++++++++++++++- 2 files changed, 22 insertions(+), 4 deletions(-)