From: Amit Kachhap <amit.kachhap@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Kees Cook <keescook@chromium.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Richard Henderson <richard.henderson@linaro.org>,
Kristina Martsenko <kristina.martsenko@arm.com>,
James Morse <james.morse@arm.com>,
Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
Mark Brown <Mark.Brown@arm.com>,
Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
Will Deacon <will@kernel.org>, Dave Martin <Dave.Martin@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 06/16] arm64: enable ptrauth earlier
Date: Fri, 17 Jan 2020 16:13:06 +0530 [thread overview]
Message-ID: <2d14a778-5fdf-7735-6fb1-57de3aa3e275@arm.com> (raw)
In-Reply-To: <20200116162414.GF10277@arrakis.emea.arm.com>
On 1/16/20 9:54 PM, Catalin Marinas wrote:
> On Mon, Dec 16, 2019 at 02:17:08PM +0530, Amit Daniel Kachhap wrote:
>> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
>> index 5aaf1bb..c59c28f 100644
>> --- a/arch/arm64/kernel/head.S
>> +++ b/arch/arm64/kernel/head.S
>> @@ -13,6 +13,7 @@
>> #include <linux/init.h>
>> #include <linux/irqchip/arm-gic-v3.h>
>>
>> +#include <asm/alternative.h>
>> #include <asm/assembler.h>
>> #include <asm/boot.h>
>> #include <asm/ptrace.h>
>> @@ -713,6 +714,7 @@ secondary_startup:
>> * Common entry point for secondary CPUs.
>> */
>> bl __cpu_secondary_check52bitva
>> + bl __cpu_secondary_checkptrauth
>> mov x0, #ARM64_CPU_BOOT_LATE
>> bl __cpu_setup // initialise processor
>> adrp x1, swapper_pg_dir
>> @@ -831,6 +833,24 @@ __no_granule_support:
>> early_park_cpu CPU_STUCK_REASON_NO_GRAN
>> ENDPROC(__no_granule_support)
>>
>> +ENTRY(__cpu_secondary_checkptrauth)
>> +#ifdef CONFIG_ARM64_PTR_AUTH
>> + /* Check if the CPU supports ptrauth */
>> + mrs x2, id_aa64isar1_el1
>> + ubfx x2, x2, #ID_AA64ISAR1_APA_SHIFT, #8
>> + cbnz x2, 1f
>> +alternative_if ARM64_HAS_ADDRESS_AUTH
>> + mov x3, 1
>> +alternative_else
>> + mov x3, 0
>> +alternative_endif
>> + cbz x3, 1f
>> + /* Park the mismatched secondary CPU */
>> + early_park_cpu CPU_STUCK_REASON_NO_PTRAUTH
>> +#endif
>> +1: ret
>> +ENDPROC(__cpu_secondary_checkptrauth)
>
> Do we actually need to park secondary CPUs early? Let's say a secondary
> CPU doesn't have PAC, __cpu_setup won't set the corresponding SCTLR_EL1
> bits and the instructions are NOPs. Wouldn't the cpufeature framework
> park it later anyway?
In the current cpufeature framework, such missing cpufeature in
secondary cpu will lead to kernel panic (inside check_early_cpufeatures)
and not cpu offline. However Kristina in her RFC V2 [1] added such
feature to park it.
Later for moving the enabling ptrauth to assembly this work got dropped.
Suzuki provided the template code for doing that [2].
Later James suggested to do this like existing
__cpu_secondary_check52bitva which parks the secondary cpu very early
and also to save wasted cpu cycles [3].
So your question is still valid that it can be done in cpufeature. Let
me know your opinion that which one is better.
[1]:
https://lore.kernel.org/linux-arm-kernel/20190529190332.29753-4-kristina.martsenko@arm.com/
[2]:
https://lore.kernel.org/linux-arm-kernel/9886324a-5a12-5dd8-b84c-3f32098e3d35@arm.com/
[3]: https://www.spinics.net/lists/arm-kernel/msg763622.html
>
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next prev parent reply other threads:[~2020-01-17 10:43 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-16 8:47 [PATCH v3 00/16] arm64: return address signing Amit Daniel Kachhap
2019-12-16 8:47 ` [PATCH v3 01/16] arm64: cpufeature: add pointer auth meta-capabilities Amit Daniel Kachhap
2020-01-15 12:26 ` Catalin Marinas
2020-01-15 13:52 ` Suzuki Kuruppassery Poulose
2020-01-15 16:01 ` Catalin Marinas
2020-01-16 12:35 ` Amit Kachhap
2019-12-16 8:47 ` [PATCH v3 02/16] arm64: rename ptrauth key structures to be user-specific Amit Daniel Kachhap
2020-01-15 16:42 ` Catalin Marinas
2019-12-16 8:47 ` [PATCH v3 03/16] arm64: install user ptrauth keys at kernel exit time Amit Daniel Kachhap
2020-01-15 17:02 ` Catalin Marinas
2020-01-16 12:39 ` Amit Kachhap
2019-12-16 8:47 ` [PATCH v3 04/16] arm64: create macro to park cpu in an infinite loop Amit Daniel Kachhap
2020-01-07 11:13 ` Suzuki Kuruppassery Poulose
2020-01-15 17:03 ` Catalin Marinas
2019-12-16 8:47 ` [PATCH v3 05/16] arm64: ptrauth: Add bootup/runtime flags for __cpu_setup Amit Daniel Kachhap
2020-01-07 11:18 ` Suzuki Kuruppassery Poulose
2020-01-09 8:33 ` Amit Kachhap
2020-01-15 17:30 ` Catalin Marinas
2020-01-16 12:40 ` Amit Kachhap
2019-12-16 8:47 ` [PATCH v3 06/16] arm64: enable ptrauth earlier Amit Daniel Kachhap
2020-01-07 11:35 ` Suzuki Kuruppassery Poulose
2020-01-09 8:29 ` Amit Kachhap
2020-01-10 10:18 ` Suzuki Kuruppassery Poulose
2020-01-16 16:24 ` Catalin Marinas
2020-01-17 10:43 ` Amit Kachhap [this message]
2020-01-17 12:00 ` Catalin Marinas
2020-01-20 14:27 ` Amit Kachhap
2019-12-16 8:47 ` [PATCH v3 07/16] arm64: initialize and switch ptrauth kernel keys Amit Daniel Kachhap
2020-01-16 18:00 ` Catalin Marinas
2019-12-16 8:47 ` [PATCH v3 08/16] arm64: initialize ptrauth keys for kernel booting task Amit Daniel Kachhap
2020-01-16 17:59 ` Catalin Marinas
2020-01-20 10:50 ` Amit Kachhap
2019-12-16 8:47 ` [PATCH v3 09/16] arm64: mask PAC bits of __builtin_return_address Amit Daniel Kachhap
2020-01-17 10:14 ` Catalin Marinas
2020-01-20 14:20 ` Amit Kachhap
2020-01-21 16:52 ` Catalin Marinas
2019-12-16 8:47 ` [PATCH v3 10/16] arm64: unwind: strip PAC from kernel addresses Amit Daniel Kachhap
2020-01-17 10:22 ` Catalin Marinas
2019-12-16 8:47 ` [PATCH v3 11/16] arm64: __show_regs: strip PAC from lr in printk Amit Daniel Kachhap
2020-01-17 10:25 ` Catalin Marinas
2019-12-16 8:47 ` [PATCH v3 12/16] arm64: suspend: restore the kernel ptrauth keys Amit Daniel Kachhap
2020-01-17 10:31 ` Catalin Marinas
2019-12-16 8:47 ` [PATCH v3 13/16] arm64: kprobe: disable probe of ptrauth instruction Amit Daniel Kachhap
2020-01-17 11:16 ` Catalin Marinas
2020-01-20 14:24 ` Amit Kachhap
2019-12-16 8:47 ` [PATCH v3 14/16] kconfig: Add support for 'as-option' Amit Daniel Kachhap
2019-12-17 11:43 ` Masahiro Yamada
2020-01-17 11:33 ` Catalin Marinas
2020-01-17 17:51 ` Masahiro Yamada
2020-01-20 10:26 ` Vincenzo Frascino
2019-12-16 8:47 ` [PATCH v3 15/16] arm64: compile the kernel with ptrauth return address signing Amit Daniel Kachhap
2020-01-17 11:49 ` Catalin Marinas
2020-01-21 14:37 ` Amit Kachhap
2020-01-21 14:46 ` Vincenzo Frascino
2020-01-21 16:50 ` Catalin Marinas
2019-12-16 8:47 ` [PATCH v3 16/16] lkdtm: arm64: test kernel pointer authentication Amit Daniel Kachhap
2020-01-17 11:53 ` Catalin Marinas
2019-12-16 9:35 ` [RESEND PATCH v3 00/16] arm64: return address signing Amit Daniel Kachhap
2019-12-30 19:09 ` [PATCH " Kees Cook
2020-01-07 11:07 ` Amit Kachhap
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