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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v5 2/3] xen/arm32: Create the same boot-time MPU regions as arm64
On 07/04/2025 20:44, Ayan Kumar Halder wrote:
> We have created the same boot-time MPU protection regions as Armv8-R AArch64.
> Also, we have defined *_PRBAR macros for arm32. The only difference from
> arm64 is that XN is 1-bit for arm32.
> The macros have been defined in mpu/cpregs.h.
NIT: Describe your changes in imperative mood
>
> Also defined WRITE_SYSREG_ASM() to write to system registers in assembly.
>
> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> ---
> Changes from
>
> v1 -
>
> 1. enable_mpu() now sets HMAIR{0,1} registers. This is similar to what is
> being done in enable_mmu(). All the mm related configurations happen in this
> function.
>
> 2. Fixed some typos.
>
> v2 -
> 1. Include the common prepare_xen_region.inc in head.S.
>
> 2. Define LOAD_SYSREG()/STORE_SYSREG() for arm32.
>
> v3 -
> 1. Rename STORE_SYSREG() as WRITE_SYSREG_ASM()
>
> 2. enable_boot_cpu_mm() is defined in head.S
>
> v4 -
> 1. *_PRBAR is moved to arm32/sysregs.h.
>
> 2. MPU specific CP15 system registers are defined in mpu/cpregs.h.
>
> xen/arch/arm/arm32/Makefile | 1 +
> xen/arch/arm/arm32/mpu/Makefile | 1 +
> xen/arch/arm/arm32/mpu/head.S | 101 +++++++++++++++++++++++
> xen/arch/arm/include/asm/arm32/sysregs.h | 7 ++
> xen/arch/arm/include/asm/cpregs.h | 4 +
> xen/arch/arm/include/asm/mpu/cpregs.h | 24 ++++++
> 6 files changed, 138 insertions(+)
> create mode 100644 xen/arch/arm/arm32/mpu/Makefile
> create mode 100644 xen/arch/arm/arm32/mpu/head.S
> create mode 100644 xen/arch/arm/include/asm/mpu/cpregs.h
>
> diff --git a/xen/arch/arm/arm32/Makefile b/xen/arch/arm/arm32/Makefile
> index 40a2b4803f..537969d753 100644
> --- a/xen/arch/arm/arm32/Makefile
> +++ b/xen/arch/arm/arm32/Makefile
> @@ -1,5 +1,6 @@
> obj-y += lib/
> obj-$(CONFIG_MMU) += mmu/
> +obj-$(CONFIG_MPU) += mpu/
>
> obj-$(CONFIG_EARLY_PRINTK) += debug.o
> obj-y += domctl.o
> diff --git a/xen/arch/arm/arm32/mpu/Makefile b/xen/arch/arm/arm32/mpu/Makefile
> new file mode 100644
> index 0000000000..3340058c08
> --- /dev/null
> +++ b/xen/arch/arm/arm32/mpu/Makefile
> @@ -0,0 +1 @@
> +obj-y += head.o
> diff --git a/xen/arch/arm/arm32/mpu/head.S b/xen/arch/arm/arm32/mpu/head.S
> new file mode 100644
> index 0000000000..84e9f1f8ec
> --- /dev/null
> +++ b/xen/arch/arm/arm32/mpu/head.S
> @@ -0,0 +1,101 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Start-of-day code for an Armv8-R MPU system.
That's exactly the same text as for Aarch64. At least write Armv8A-R-AArch32.
> + */
> +
> +#include <asm/arm32/macros.h>
> +#include <asm/mpu/common.inc>
> +#include <asm/page.h>
> +
> +/*
> + * Set up the memory attribute type tables and enable EL2 MPU and data cache.
> + * If the Background region is enabled, then the MPU uses the default memory
> + * map as the Background region for generating the memory
> + * attributes when MPU is disabled.
> + * Since the default memory map of the Armv8-R AArch32 architecture is
> + * IMPLEMENTATION DEFINED, we intend to turn off the Background region here.
> + *
> + * Clobbers r0 - r1
> + */
> +FUNC_LOCAL(enable_mpu)
> + /* Set up memory attribute type tables */
> + mov_w r0, MAIR0VAL
> + mov_w r1, MAIR1VAL
> + mcr CP32(r0, HMAIR0)
> + mcr CP32(r1, HMAIR1)
Is there really a need to do these 2 writes one after another?
Why can't we use only r0 and save one clobbered reg?
mov_w r0, MAIR0VAL
mcr CP32(r0, HMAIR0)
mov_w r0, MAIR1VAL
mcr CP32(r0, HMAIR1)
> +
> + mrc CP32(r0, HSCTLR)
> + bic r0, r0, #SCTLR_ELx_BR /* Disable Background region */
> + orr r0, r0, #SCTLR_Axx_ELx_M /* Enable MPU */
> + orr r0, r0, #SCTLR_Axx_ELx_C /* Enable D-cache */
> + mcr CP32(r0, HSCTLR)
> + isb
> +
> + ret
> +END(enable_mpu)
> +
> +/*
> + * Maps the various sections of Xen (described in xen.lds.S) as different MPU
> + * regions.
> + *
> + * Clobbers r0 - r5
> + *
> + */
> +FUNC(enable_boot_cpu_mm)
> + /* Get the number of regions specified in MPUIR_EL2 */
> + mrc CP32(r5, MPUIR_EL2)
> + and r5, r5, #NUM_MPU_REGIONS_MASK
> +
> + /* x0: region sel */
> + mov r0, #0
> + /* Xen text section. */
> + mov_w r1, _stext
> + mov_w r2, _etext
> + prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prbar=REGION_TEXT_PRBAR
> +
> + /* Xen read-only data section. */
> + mov_w r1, _srodata
> + mov_w r2, _erodata
> + prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prbar=REGION_RO_PRBAR
> +
> + /* Xen read-only after init and data section. (RW data) */
> + mov_w r1, __ro_after_init_start
> + mov_w r2, __init_begin
> + prepare_xen_region r0, r1, r2, r3, r4, r5
> +
> + /* Xen code section. */
> + mov_w r1, __init_begin
> + mov_w r2, __init_data_begin
> + prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prbar=REGION_TEXT_PRBAR
> +
> + /* Xen data and BSS section. */
> + mov_w r1, __init_data_begin
> + mov_w r2, __bss_end
> + prepare_xen_region r0, r1, r2, r3, r4, r5
> +
> +#ifdef CONFIG_EARLY_PRINTK
> + /* Xen early UART section. */
> + mov_w r1, CONFIG_EARLY_UART_BASE_ADDRESS
> + mov_w r2, (CONFIG_EARLY_UART_BASE_ADDRESS + CONFIG_EARLY_UART_SIZE)
> + prepare_xen_region r0, r1, r2, r3, r4, r5,
> attr_prbar=REGION_DEVICE_PRBAR, attr_prlar=REGION_DEVICE_PRLAR
> +#endif
> +
> + b enable_mpu
> +END(enable_boot_cpu_mm)
> +
> +/*
> + * We don't yet support secondary CPUs bring-up. Implement a dummy helper to
> + * please the common code.
> + */
> +FUNC(enable_secondary_cpu_mm)
> + PRINT("- SMP not enabled yet -\r\n")
> +1: wfe
> + b 1b
> +END(enable_secondary_cpu_mm)
> +
> +/*
> + * Local variables:
> + * mode: ASM
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/arch/arm/include/asm/arm32/sysregs.h
> b/xen/arch/arm/include/asm/arm32/sysregs.h
> index 22871999af..a90d1610a1 100644
> --- a/xen/arch/arm/include/asm/arm32/sysregs.h
> +++ b/xen/arch/arm/include/asm/arm32/sysregs.h
> @@ -20,6 +20,13 @@
> * uses r0 as a placeholder register. */
> #define CMD_CP32(name...) "mcr " __stringify(CP32(r0, name)) ";"
>
> +#define REGION_TEXT_PRBAR 0x18 /* SH=11 AP=10 XN=0 */
> +#define REGION_RO_PRBAR 0x1D /* SH=11 AP=10 XN=1 */
> +#define REGION_DATA_PRBAR 0x19 /* SH=11 AP=00 XN=1 */
> +#define REGION_DEVICE_PRBAR 0x11 /* SH=10 AP=00 XN=1 */
> +
> +#define WRITE_SYSREG_ASM(v, name) mcr CP32(v, name)
Same comment as for previous patch.
> +
> #ifndef __ASSEMBLY__
>
> /* C wrappers */
> diff --git a/xen/arch/arm/include/asm/cpregs.h
> b/xen/arch/arm/include/asm/cpregs.h
> index aec9e8f329..6019a2cbdd 100644
> --- a/xen/arch/arm/include/asm/cpregs.h
> +++ b/xen/arch/arm/include/asm/cpregs.h
> @@ -1,6 +1,10 @@
> #ifndef __ASM_ARM_CPREGS_H
> #define __ASM_ARM_CPREGS_H
>
> +#ifdef CONFIG_MPU
NIT: Do we really need to protect this include? I thought we do the ifdefery if
we need to include either mmu or mpu. Here we don't have a choice and afaict
there's nothing problematic in mpu/cpregs.h
> +#include <asm/mpu/cpregs.h>
> +#endif
> +
> /*
> * AArch32 Co-processor registers.
> *
> diff --git a/xen/arch/arm/include/asm/mpu/cpregs.h
> b/xen/arch/arm/include/asm/mpu/cpregs.h
> new file mode 100644
> index 0000000000..6b20c7ceae
> --- /dev/null
> +++ b/xen/arch/arm/include/asm/mpu/cpregs.h
> @@ -0,0 +1,24 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef __ASM_ARM_MPU_CPREGS_H
> +#define __ASM_ARM_MPU_CPREGS_H
> +
> +/* CP15 CR0: MPU Type Register */
> +#define HMPUIR p15,4,c0,c0,4
> +
> +/* CP15 CR6: MPU Protection Region Base/Limit/Select Address Register */
> +#define HPRSELR p15,4,c6,c2,1
> +#define PRBAR_EL2 p15,4,c6,c3,0
> +#define PRLAR_EL2 p15,4,c6,c8,1
> +
> +#define MPUIR_EL2 HMPUIR
> +#define PRSELR_EL2 HPRSELR
AFAIK, these macros are there to use AArch64 sysreg names in common code when
compiling Arm32. This would mean they should be protected with #ifdef
CONFIG_ARM_32.
~Michal
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