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SubjectRe: [PATCH] ARM: tegra: add basic SecureOS support
On Thu, Jun 06, 2013 at 04:28:07PM +0900, Alexandre Courbot wrote:
> Boot loaders on some Tegra devices can be unlocked but do not let the
> system operate without SecureOS. SecureOS prevents access to some
> registers and requires the operating system to perform certain
> operations through Secure Monitor Calls instead of directly accessing
> the hardware.
>
> This patch introduces basic SecureOS support for Tegra. SecureOS support
> can be enabled by adding a "nvidia,secure-os" property to the "chosen"
> node of the device tree.
>
> Currently, only the bringup of secondary CPUs is performed by SMCs, but
> more operations will be added later.
>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
> Documentation/devicetree/bindings/arm/tegra.txt | 8 +++
> arch/arm/configs/tegra_defconfig | 1 +
> arch/arm/mach-tegra/Kconfig | 11 ++++
> arch/arm/mach-tegra/Makefile | 2 +
> arch/arm/mach-tegra/common.c | 2 +
> arch/arm/mach-tegra/reset.c | 30 +++++++----
> arch/arm/mach-tegra/secureos.c | 70 +++++++++++++++++++++++++
> arch/arm/mach-tegra/secureos.h | 31 +++++++++++
> 8 files changed, 145 insertions(+), 10 deletions(-)
> create mode 100644 arch/arm/mach-tegra/secureos.c
> create mode 100644 arch/arm/mach-tegra/secureos.h
>
> diff --git a/Documentation/devicetree/bindings/arm/tegra.txt b/Documentation/devicetree/bindings/arm/tegra.txt
> index ed9c853..b543091 100644
> --- a/Documentation/devicetree/bindings/arm/tegra.txt
> +++ b/Documentation/devicetree/bindings/arm/tegra.txt
> @@ -32,3 +32,11 @@ board-specific compatible values:
> nvidia,whistler
> toradex,colibri_t20-512
> toradex,iris
> +
> +Global properties
> +-------------------------------------------
> +
> +The following properties can be specified into the "chosen" root
> +node:
> +
> + nvidia,secure-os: enable SecureOS.
> diff --git a/arch/arm/configs/tegra_defconfig b/arch/arm/configs/tegra_defconfig
> index f7ba3161..f6ed0f5 100644
> --- a/arch/arm/configs/tegra_defconfig
> +++ b/arch/arm/configs/tegra_defconfig
> @@ -28,6 +28,7 @@ CONFIG_ARCH_TEGRA_3x_SOC=y
> CONFIG_ARCH_TEGRA_114_SOC=y
> CONFIG_TEGRA_PCI=y
> CONFIG_TEGRA_EMC_SCALING_ENABLE=y
> +CONFIG_TEGRA_SECUREOS=y
> CONFIG_SMP=y
> CONFIG_PREEMPT=y
> CONFIG_AEABI=y
> diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
> index 84d72fc..acb5d0a 100644
> --- a/arch/arm/mach-tegra/Kconfig
> +++ b/arch/arm/mach-tegra/Kconfig
> @@ -87,4 +87,15 @@ config TEGRA_AHB
> config TEGRA_EMC_SCALING_ENABLE
> bool "Enable scaling the memory frequency"
>
> +config TEGRA_SECUREOS
> + bool "Enable SecureOS support"
> + help
> + Support for Tegra devices which bootloader sets up a
> + SecureOS environment. This will use Secure Monitor Calls
> + instead of directly accessing the hardware for some protected
> + operations.
> +
> + SecureOS support is enabled by declaring a "nvidia,secure-os"
> + property into the "chosen" node of the device tree.
> +
> endmenu
> diff --git a/arch/arm/mach-tegra/Makefile b/arch/arm/mach-tegra/Makefile
> index d011f0a..3adafe6 100644
> --- a/arch/arm/mach-tegra/Makefile
> +++ b/arch/arm/mach-tegra/Makefile
> @@ -37,3 +37,5 @@ endif
> obj-$(CONFIG_ARCH_TEGRA_2x_SOC) += board-harmony-pcie.o
>
> obj-$(CONFIG_ARCH_TEGRA_2x_SOC) += board-paz00.o
> +
> +obj-$(CONFIG_TEGRA_SECUREOS) += secureos.o
> diff --git a/arch/arm/mach-tegra/common.c b/arch/arm/mach-tegra/common.c
> index 9f852c6..b7eea02 100644
> --- a/arch/arm/mach-tegra/common.c
> +++ b/arch/arm/mach-tegra/common.c
> @@ -37,6 +37,7 @@
> #include "sleep.h"
> #include "pm.h"
> #include "reset.h"
> +#include "secureos.h"
>
> /*
> * Storage for debug-macro.S's state.
> @@ -97,6 +98,7 @@ static void __init tegra_init_cache(void)
>
> void __init tegra_init_early(void)
> {
> + tegra_init_secureos();
> tegra_cpu_reset_handler_init();
> tegra_apb_io_init();
> tegra_init_fuse();
> diff --git a/arch/arm/mach-tegra/reset.c b/arch/arm/mach-tegra/reset.c
> index 1ac434e..4b9ebf9 100644
> --- a/arch/arm/mach-tegra/reset.c
> +++ b/arch/arm/mach-tegra/reset.c
> @@ -21,38 +21,32 @@
>
> #include <asm/cacheflush.h>
> #include <asm/hardware/cache-l2x0.h>
> +#include <asm/firmware.h>
>
> #include "iomap.h"
> #include "irammap.h"
> #include "reset.h"
> #include "sleep.h"
> #include "fuse.h"
> +#include "secureos.h"
>
> #define TEGRA_IRAM_RESET_BASE (TEGRA_IRAM_BASE + \
> TEGRA_IRAM_RESET_HANDLER_OFFSET)
>
> static bool is_enabled;
>
> -static void __init tegra_cpu_reset_handler_enable(void)
> +static void __init tegra_cpu_reset_handler_set(const u32 reset_address)
> {
> - void __iomem *iram_base = IO_ADDRESS(TEGRA_IRAM_RESET_BASE);
> void __iomem *evp_cpu_reset =
> IO_ADDRESS(TEGRA_EXCEPTION_VECTORS_BASE + 0x100);
> void __iomem *sb_ctrl = IO_ADDRESS(TEGRA_SB_BASE);
> u32 reg;
>
> - BUG_ON(is_enabled);
> - BUG_ON(tegra_cpu_reset_handler_size > TEGRA_IRAM_RESET_HANDLER_SIZE);
> -
> - memcpy(iram_base, (void *)__tegra_cpu_reset_handler_start,
> - tegra_cpu_reset_handler_size);
> -
> /*
> * NOTE: This must be the one and only write to the EVP CPU reset
> * vector in the entire system.
> */
> - writel(TEGRA_IRAM_RESET_BASE + tegra_cpu_reset_handler_offset,
> - evp_cpu_reset);
> + writel(reset_address, evp_cpu_reset);
> wmb();
> reg = readl(evp_cpu_reset);
>
> @@ -66,6 +60,22 @@ static void __init tegra_cpu_reset_handler_enable(void)
> writel(reg, sb_ctrl);
> wmb();
> }
> +}
> +
> +static void __init tegra_cpu_reset_handler_enable(void)
> +{
> + void __iomem *iram_base = IO_ADDRESS(TEGRA_IRAM_RESET_BASE);
> + const u32 reset_address = TEGRA_IRAM_RESET_BASE +
> + tegra_cpu_reset_handler_offset;
> +
> + BUG_ON(is_enabled);
> + BUG_ON(tegra_cpu_reset_handler_size > TEGRA_IRAM_RESET_HANDLER_SIZE);
> +
> + memcpy(iram_base, (void *)__tegra_cpu_reset_handler_start,
> + tegra_cpu_reset_handler_size);
> +
> + if (call_firmware_op(set_cpu_boot_addr, 0, reset_address) == -ENOSYS)
> + tegra_cpu_reset_handler_set(reset_address);
>
> is_enabled = true;
> }
> diff --git a/arch/arm/mach-tegra/secureos.c b/arch/arm/mach-tegra/secureos.c
> new file mode 100644
> index 0000000..44c3514
> --- /dev/null
> +++ b/arch/arm/mach-tegra/secureos.c
> @@ -0,0 +1,70 @@
> +/*
> + * SecureOS support for Tegra CPUs
> + *
> + * Copyright (c) 2013, NVIDIA Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/of.h>
> +#include <asm/firmware.h>
> +
> +static int __attribute__((used)) __tegra_smc_stack[10];

Use __used instead of using GCC attributes directly.

> +
> +/*
> + * With EABI, subtype and arg already end up in r0, r1 and r2 as they are
> + * function arguments, but we prefer to play safe here and explicitly move
> + * these values into the expected registers anyway. mov instructions without
> + * any side-effect are turned into nops by the assembler, which limits
> + * overhead.
> + */
> +static void tegra_generic_smc(u32 type, u32 subtype, u32 arg)
> +{
> + asm volatile(
> + ".arch_extension sec\n\t"
> + "ldr r3, =__tegra_smc_stack\n\t"

ldr= should be avoided in inline asm, because GCC can't guess it's size,
and can't guarantee that the literal pool word is close enough to be
addressable (though for small compilation units it's unlikely to be a
problem).

If you follow Russell's approach and define a naked function for this,
you can put an explicit literal word after the return:

ldr r3, 1f

/* ... */

/* return instruction */

.align 2
1: .long __tegra_smc_stack

> + "stmia r3, {r4-r12, lr}\n\t"
> + "mov r0, %[type]\n\t"
> + "mov r1, %[subtype]\n\t"
> + "mov r2, %[arg]\n\t"
> + "mov r3, #0\n\t"
> + "mov r4, #0\n\t"
> + "dsb\n\t"

Can you explain what this DSB is for?

> + "smc #0\n\t"
> + "ldr r3, =__tegra_smc_stack\n\t"
> + "ldmia r3, {r4-r12, lr}"
> + :
> + : [type] "r" (type),
> + [subtype] "r" (subtype),
> + [arg] "r" (arg)
> + : "r0", "r1", "r2", "r3", "r4", "memory");

If r5-r12 are not clobbered, why do you save and restore them?

In the ARM ABI, r12 is a caller-save register, so you probably
don't need to save/restore that even if it is clobbered.

Cheers
---Dave



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