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Message-ID: <87zhi2tfea.fsf@mpe.ellerman.id.au>
Date: Tue, 15 Oct 2019 22:30:21 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Nayna Jain <nayna@...ux.ibm.com>, linuxppc-dev@...abs.org,
linux-efi@...r.kernel.org, linux-integrity@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Jeremy Kerr <jk@...abs.org>,
Matthew Garret <matthew.garret@...ula.com>,
Mimi Zohar <zohar@...ux.ibm.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Claudio Carvalho <cclaudio@...ux.ibm.com>,
George Wilson <gcwilson@...ux.ibm.com>,
Elaine Palmer <erpalmer@...ibm.com>,
Eric Ricther <erichte@...ux.ibm.com>,
Oliver O'Halloran <oohall@...il.com>,
Nayna Jain <nayna@...ux.ibm.com>
Subject: Re: [PATCH v7 1/8] powerpc: detect the secure boot mode of the system
Hi Nayna,
Just a few comments.
Nayna Jain <nayna@...ux.ibm.com> writes:
> Secure boot on PowerNV defines different IMA policies based on the secure
> boot state of the system.
This description has got out of sync with what the patch does I think.
There's no IMA in here. I think you can just drop that sentence.
> This patch defines a function to detect the secure boot state of the
> system.
That's what the patch really does ^ - just make it clear that it's only
on powernv.
>
> The PPC_SECURE_BOOT config represents the base enablement of secureboot
> on POWER.
s/POWER/powerpc/.
>
> Signed-off-by: Nayna Jain <nayna@...ux.ibm.com>
> ---
> arch/powerpc/Kconfig | 10 ++++++
> arch/powerpc/include/asm/secure_boot.h | 29 ++++++++++++++++++
> arch/powerpc/kernel/Makefile | 2 ++
> arch/powerpc/kernel/secure_boot.c | 42 ++++++++++++++++++++++++++
> 4 files changed, 83 insertions(+)
> create mode 100644 arch/powerpc/include/asm/secure_boot.h
> create mode 100644 arch/powerpc/kernel/secure_boot.c
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 3e56c9c2f16e..b4a221886fcf 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -934,6 +934,16 @@ config PPC_MEM_KEYS
>
> If unsure, say y.
>
> +config PPC_SECURE_BOOT
> + prompt "Enable secure boot support"
> + bool
> + depends on PPC_POWERNV
> + help
> + Systems with firmware secure boot enabled needs to define security
^
need
> + policies to extend secure boot to the OS. This config allows user
^
a
> + to enable OS secure boot on systems that have firmware support for
> + it. If in doubt say N.
> +
> endmenu
>
> config ISA_DMA_API
> diff --git a/arch/powerpc/include/asm/secure_boot.h b/arch/powerpc/include/asm/secure_boot.h
> new file mode 100644
> index 000000000000..23d2ef2f1f7b
> --- /dev/null
> +++ b/arch/powerpc/include/asm/secure_boot.h
> @@ -0,0 +1,29 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Secure boot definitions
> + *
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain
> + */
> +#ifndef _ASM_POWER_SECURE_BOOT_H
> +#define _ASM_POWER_SECURE_BOOT_H
> +
> +#ifdef CONFIG_PPC_SECURE_BOOT
> +
> +bool is_powerpc_os_secureboot_enabled(void);
> +struct device_node *get_powerpc_os_sb_node(void);
This function is never used outside arch/powerpc/kernel/secure_boot.c
and so doesn't need to be public.
> +#else
> +
> +static inline bool is_powerpc_os_secureboot_enabled(void)
> +{
I know there's a distinction between firmware secureboot and OS
secureboot, but I don't think we need that baked into the name. So just
is_ppc_secureboot_enabled() would be fine.
> + return false;
> +}
> +
> +static inline struct device_node *get_powerpc_os_sb_node(void)
> +{
> + return NULL;
> +}
> +
> +#endif
> +#endif
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index a7ca8fe62368..e2a54fa240ac 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -161,6 +161,8 @@ ifneq ($(CONFIG_PPC_POWERNV)$(CONFIG_PPC_SVM),)
> obj-y += ucall.o
> endif
>
> +obj-$(CONFIG_PPC_SECURE_BOOT) += secure_boot.o
> +
> # Disable GCOV, KCOV & sanitizers in odd or sensitive code
> GCOV_PROFILE_prom_init.o := n
> KCOV_INSTRUMENT_prom_init.o := n
> diff --git a/arch/powerpc/kernel/secure_boot.c b/arch/powerpc/kernel/secure_boot.c
> new file mode 100644
> index 000000000000..0488dbcab6b9
> --- /dev/null
> +++ b/arch/powerpc/kernel/secure_boot.c
> @@ -0,0 +1,42 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain
> + */
> +#include <linux/types.h>
> +#include <linux/of.h>
> +#include <asm/secure_boot.h>
> +
> +struct device_node *get_powerpc_os_sb_node(void)
> +{
> + return of_find_compatible_node(NULL, NULL, "ibm,secvar-v1");
> +}
Given that's only used in this file, once, it should just be inlined
into its caller.
> +
> +bool is_powerpc_os_secureboot_enabled(void)
> +{
> + struct device_node *node;
> +
> + node = get_powerpc_os_sb_node();
> + if (!node)
> + goto disabled;
> +
> + if (!of_device_is_available(node)) {
> + pr_err("Secure variables support is in error state, fail secure\n");
> + goto enabled;
> + }
> +
> + /*
> + * secureboot is enabled if os-secure-enforcing property exists,
> + * else disabled.
> + */
> + if (!of_find_property(node, "os-secure-enforcing", NULL))
Using of_property_read_bool() is preferable.
> + goto disabled;
> +
> +enabled:
> + pr_info("secureboot mode enabled\n");
> + return true;
> +
> +disabled:
> + pr_info("secureboot mode disabled\n");
> + return false;
> +}
You could make that tail a bit more concise by doing something like
below, but up to you:
bool enabled = false;
...
enabled = of_property_read_bool(node, "os-secure-enforcing");
out:
pr_info("secureboot mode %s\n", enabled ? "enabled" : "disabled");
return enabled;
}
cheers
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