ARM: Add base support for ARMv7-M
authorCatalin Marinas <catalin.marinas@arm.com>
Fri, 21 May 2010 17:06:41 +0000 (18:06 +0100)
committerUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Wed, 17 Apr 2013 19:38:10 +0000 (21:38 +0200)
This patch adds the base support for the ARMv7-M
architecture. It consists of the corresponding arch/arm/mm/ files and
various #ifdef's around the kernel. Exception handling is implemented by
a subsequent patch.

[ukleinek: squash in some changes originating from commit

b5717ba (Cortex-M3: Add support for the Microcontroller Prototyping System)

from the v2.6.33-arm1 patch stack, port to post 3.6, drop zImage
support, drop reorganisation of pt_regs, assert CONFIG_CPU_V7M doesn't
leak into installed headers and a few cosmetic changes]

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Jonathan Austin <jonathan.austin@arm.com>
Tested-by: Jonathan Austin <jonathan.austin@arm.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
16 files changed:
arch/arm/include/asm/assembler.h
arch/arm/include/asm/cputype.h
arch/arm/include/asm/glue-cache.h
arch/arm/include/asm/glue-df.h
arch/arm/include/asm/glue-proc.h
arch/arm/include/asm/irqflags.h
arch/arm/include/asm/ptrace.h
arch/arm/include/asm/system_info.h
arch/arm/include/asm/v7m.h [new file with mode: 0644]
arch/arm/include/uapi/asm/ptrace.h
arch/arm/kernel/head-nommu.S
arch/arm/kernel/setup.c
arch/arm/kernel/traps.c
arch/arm/mm/cache-nop.S [new file with mode: 0644]
arch/arm/mm/nommu.c
arch/arm/mm/proc-v7m.S [new file with mode: 0644]

index 05ee9ee..a5fef71 100644 (file)
  * assumes FIQs are enabled, and that the processor is in SVC mode.
  */
        .macro  save_and_disable_irqs, oldcpsr
+#ifdef CONFIG_CPU_V7M
+       mrs     \oldcpsr, primask
+#else
        mrs     \oldcpsr, cpsr
+#endif
        disable_irq
        .endm
 
  * guarantee that this will preserve the flags.
  */
        .macro  restore_irqs_notrace, oldcpsr
+#ifdef CONFIG_CPU_V7M
+       msr     primask, \oldcpsr
+#else
        msr     cpsr_c, \oldcpsr
+#endif
        .endm
 
        .macro restore_irqs, oldcpsr
 #endif
        .endm
 
-#ifdef CONFIG_THUMB2_KERNEL
+#if defined(CONFIG_CPU_V7M)
+       /*
+        * setmode is used to assert to be in svc mode during boot. For v7-M
+        * this is done in __v7m_setup, so setmode can be empty here.
+        */
+       .macro  setmode, mode, reg
+       .endm
+#elif defined(CONFIG_THUMB2_KERNEL)
        .macro  setmode, mode, reg
        mov     \reg, #\mode
        msr     cpsr_c, \reg
index 7652712..4eb94a3 100644 (file)
@@ -106,7 +106,17 @@ static inline unsigned int __attribute_const__ read_cpuid_id(void)
        return read_cpuid(CPUID_ID);
 }
 
-#else /* ifdef CONFIG_CPU_CP15 */
+#elif defined(CONFIG_CPU_V7M)
+
+#include <asm/io.h>
+#include <asm/v7m.h>
+
+static inline unsigned int __attribute_const__ read_cpuid_id(void)
+{
+       return readl(BASEADDR_V7M_SCB + V7M_SCB_CPUID);
+}
+
+#else /* ifdef CONFIG_CPU_CP15 / elif defined(CONFIG_CPU_V7M) */
 
 static inline unsigned int __attribute_const__ read_cpuid_id(void)
 {
index cca9f15..65c9faf 100644 (file)
 # endif
 #endif
 
+#if defined(CONFIG_CPU_V7M)
+# ifdef _CACHE
+#  define MULTI_CACHE 1
+# else
+#  define _CACHE nop
+# endif
+#endif
+
 #if !defined(_CACHE) && !defined(MULTI_CACHE)
 #error Unknown cache maintenance model
 #endif
 
+#ifndef __ASSEMBLER__
+extern inline void nop_flush_icache_all(void) { }
+extern inline void nop_flush_kern_cache_all(void) { }
+extern inline void nop_flush_kern_cache_louis(void) { }
+extern inline void nop_flush_user_cache_all(void) { }
+extern inline void nop_flush_user_cache_range(unsigned long a,
+               unsigned long b, unsigned int c) { }
+
+extern inline void nop_coherent_kern_range(unsigned long a, unsigned long b) { }
+extern inline int nop_coherent_user_range(unsigned long a,
+               unsigned long b) { return 0; }
+extern inline void nop_flush_kern_dcache_area(void *a, size_t s) { }
+
+extern inline void nop_dma_flush_range(const void *a, const void *b) { }
+
+extern inline void nop_dma_map_area(const void *s, size_t l, int f) { }
+extern inline void nop_dma_unmap_area(const void *s, size_t l, int f) { }
+#endif
+
 #ifndef MULTI_CACHE
 #define __cpuc_flush_icache_all                __glue(_CACHE,_flush_icache_all)
 #define __cpuc_flush_kern_all          __glue(_CACHE,_flush_kern_cache_all)
index b6e9f2c..6b70f1b 100644 (file)
 # endif
 #endif
 
+#ifdef CONFIG_CPU_ABRT_NOMMU
+# ifdef CPU_DABORT_HANDLER
+#  define MULTI_DABORT 1
+# else
+#  define CPU_DABORT_HANDLER nommu_early_abort
+# endif
+#endif
+
 #ifndef CPU_DABORT_HANDLER
 #error Unknown data abort handler type
 #endif
index ac1dd54..f2f39bc 100644 (file)
 # endif
 #endif
 
+#ifdef CONFIG_CPU_V7M
+# ifdef CPU_NAME
+#  undef  MULTI_CPU
+#  define MULTI_CPU
+# else
+#  define CPU_NAME cpu_v7m
+# endif
+#endif
+
 #ifndef MULTI_CPU
 #define cpu_proc_init                  __glue(CPU_NAME,_proc_init)
 #define cpu_proc_fin                   __glue(CPU_NAME,_proc_fin)
index 1e6cca5..3b763d6 100644 (file)
@@ -8,6 +8,16 @@
 /*
  * CPU interrupt mask handling.
  */
+#ifdef CONFIG_CPU_V7M
+#define IRQMASK_REG_NAME_R "primask"
+#define IRQMASK_REG_NAME_W "primask"
+#define IRQMASK_I_BIT  1
+#else
+#define IRQMASK_REG_NAME_R "cpsr"
+#define IRQMASK_REG_NAME_W "cpsr_c"
+#define IRQMASK_I_BIT  PSR_I_BIT
+#endif
+
 #if __LINUX_ARM_ARCH__ >= 6
 
 static inline unsigned long arch_local_irq_save(void)
@@ -15,7 +25,7 @@ static inline unsigned long arch_local_irq_save(void)
        unsigned long flags;
 
        asm volatile(
-               "       mrs     %0, cpsr        @ arch_local_irq_save\n"
+               "       mrs     %0, " IRQMASK_REG_NAME_R "      @ arch_local_irq_save\n"
                "       cpsid   i"
                : "=r" (flags) : : "memory", "cc");
        return flags;
@@ -129,7 +139,7 @@ static inline unsigned long arch_local_save_flags(void)
 {
        unsigned long flags;
        asm volatile(
-               "       mrs     %0, cpsr        @ local_save_flags"
+               "       mrs     %0, " IRQMASK_REG_NAME_R "      @ local_save_flags"
                : "=r" (flags) : : "memory", "cc");
        return flags;
 }
@@ -140,7 +150,7 @@ static inline unsigned long arch_local_save_flags(void)
 static inline void arch_local_irq_restore(unsigned long flags)
 {
        asm volatile(
-               "       msr     cpsr_c, %0      @ local_irq_restore"
+               "       msr     " IRQMASK_REG_NAME_W ", %0      @ local_irq_restore"
                :
                : "r" (flags)
                : "memory", "cc");
@@ -148,8 +158,8 @@ static inline void arch_local_irq_restore(unsigned long flags)
 
 static inline int arch_irqs_disabled_flags(unsigned long flags)
 {
-       return flags & PSR_I_BIT;
+       return flags & IRQMASK_I_BIT;
 }
 
-#endif
-#endif
+#endif /* ifdef __KERNEL__ */
+#endif /* ifndef __ASM_ARM_IRQFLAGS_H */
index 3d52ee1..04c99f3 100644 (file)
@@ -45,6 +45,7 @@ struct pt_regs {
  */
 static inline int valid_user_regs(struct pt_regs *regs)
 {
+#ifndef CONFIG_CPU_V7M
        unsigned long mode = regs->ARM_cpsr & MODE_MASK;
 
        /*
@@ -67,6 +68,9 @@ static inline int valid_user_regs(struct pt_regs *regs)
                regs->ARM_cpsr |= USR_MODE;
 
        return 0;
+#else /* ifndef CONFIG_CPU_V7M */
+       return 1;
+#endif
 }
 
 static inline long regs_return_value(struct pt_regs *regs)
index dfd386d..720ea03 100644 (file)
@@ -11,6 +11,7 @@
 #define CPU_ARCH_ARMv5TEJ      7
 #define CPU_ARCH_ARMv6         8
 #define CPU_ARCH_ARMv7         9
+#define CPU_ARCH_ARMv7M                10
 
 #ifndef __ASSEMBLY__
 
diff --git a/arch/arm/include/asm/v7m.h b/arch/arm/include/asm/v7m.h
new file mode 100644 (file)
index 0000000..fa88d09
--- /dev/null
@@ -0,0 +1,44 @@
+/*
+ * Common defines for v7m cpus
+ */
+#define V7M_SCS_ICTR                   IOMEM(0xe000e004)
+#define V7M_SCS_ICTR_INTLINESNUM_MASK          0x0000000f
+
+#define BASEADDR_V7M_SCB               IOMEM(0xe000ed00)
+
+#define V7M_SCB_CPUID                  0x00
+
+#define V7M_SCB_ICSR                   0x04
+#define V7M_SCB_ICSR_PENDSVSET                 (1 << 28)
+#define V7M_SCB_ICSR_PENDSVCLR                 (1 << 27)
+#define V7M_SCB_ICSR_RETTOBASE                 (1 << 11)
+
+#define V7M_SCB_VTOR                   0x08
+
+#define V7M_SCB_SCR                    0x10
+#define V7M_SCB_SCR_SLEEPDEEP                  (1 << 2)
+
+#define V7M_SCB_CCR                    0x14
+#define V7M_SCB_CCR_STKALIGN                   (1 << 9)
+
+#define V7M_SCB_SHPR2                  0x1c
+#define V7M_SCB_SHPR3                  0x20
+
+#define V7M_SCB_SHCSR                  0x24
+#define V7M_SCB_SHCSR_USGFAULTENA              (1 << 18)
+#define V7M_SCB_SHCSR_BUSFAULTENA              (1 << 17)
+#define V7M_SCB_SHCSR_MEMFAULTENA              (1 << 16)
+
+#define V7M_xPSR_FRAMEPTRALIGN                 0x00000200
+#define V7M_xPSR_EXCEPTIONNO                   0x000001ff
+
+/*
+ * When branching to an address that has bits [31:28] == 0xf an exception return
+ * occurs. Bits [27:5] are reserved (SBOP). If the processor implements the FP
+ * extension Bit [4] defines if the exception frame has space allocated for FP
+ * state information, SBOP otherwise. Bit [3] defines the mode that is returned
+ * to (0 -> handler mode; 1 -> thread mode). Bit [2] defines which sp is used
+ * (0 -> msp; 1 -> psp). Bits [1:0] are fixed to 0b01.
+ */
+#define EXC_RET_STACK_MASK                     0x00000004
+#define EXC_RET_THREADMODE_PROCESSSTACK                0xfffffffd
index 96ee092..5af0ed1 100644 (file)
 
 /*
  * PSR bits
+ * Note on V7M there is no mode contained in the PSR
  */
 #define USR26_MODE     0x00000000
 #define FIQ26_MODE     0x00000001
 #define IRQ26_MODE     0x00000002
 #define SVC26_MODE     0x00000003
+#if defined(__KERNEL__) && defined(CONFIG_CPU_V7M)
+/*
+ * Use 0 here to get code right that creates a userspace
+ * or kernel space thread.
+ */
+#define USR_MODE       0x00000000
+#define SVC_MODE       0x00000000
+#else
 #define USR_MODE       0x00000010
+#define SVC_MODE       0x00000013
+#endif
 #define FIQ_MODE       0x00000011
 #define IRQ_MODE       0x00000012
-#define SVC_MODE       0x00000013
 #define ABT_MODE       0x00000017
 #define HYP_MODE       0x0000001a
 #define UND_MODE       0x0000001b
 #define SYSTEM_MODE    0x0000001f
 #define MODE32_BIT     0x00000010
 #define MODE_MASK      0x0000001f
-#define PSR_T_BIT      0x00000020
-#define PSR_F_BIT      0x00000040
-#define PSR_I_BIT      0x00000080
-#define PSR_A_BIT      0x00000100
-#define PSR_E_BIT      0x00000200
-#define PSR_J_BIT      0x01000000
-#define PSR_Q_BIT      0x08000000
+
+#define V4_PSR_T_BIT   0x00000020      /* >= V4T, but not V7M */
+#define V7M_PSR_T_BIT  0x01000000
+#if defined(__KERNEL__) && defined(CONFIG_CPU_V7M)
+#define PSR_T_BIT      V7M_PSR_T_BIT
+#else
+/* for compatibility */
+#define PSR_T_BIT      V4_PSR_T_BIT
+#endif
+
+#define PSR_F_BIT      0x00000040      /* >= V4, but not V7M */
+#define PSR_I_BIT      0x00000080      /* >= V4, but not V7M */
+#define PSR_A_BIT      0x00000100      /* >= V6, but not V7M */
+#define PSR_E_BIT      0x00000200      /* >= V6, but not V7M */
+#define PSR_J_BIT      0x01000000      /* >= V5J, but not V7M */
+#define PSR_Q_BIT      0x08000000      /* >= V5E, including V7M */
 #define PSR_V_BIT      0x10000000
 #define PSR_C_BIT      0x20000000
 #define PSR_Z_BIT      0x40000000
index 6a2e09c..8812ce8 100644 (file)
@@ -19,6 +19,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/cp15.h>
 #include <asm/thread_info.h>
+#include <asm/v7m.h>
 
 /*
  * Kernel startup entry point.
@@ -50,10 +51,13 @@ ENTRY(stext)
 
        setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode
                                                @ and irqs disabled
-#ifndef CONFIG_CPU_CP15
-       ldr     r9, =CONFIG_PROCESSOR_ID
-#else
+#if defined(CONFIG_CPU_CP15)
        mrc     p15, 0, r9, c0, c0              @ get processor id
+#elif defined(CONFIG_CPU_V7M)
+       ldr     r9, =BASEADDR_V7M_SCB
+       ldr     r9, [r9, V7M_SCB_CPUID]
+#else
+       ldr     r9, =CONFIG_PROCESSOR_ID
 #endif
        bl      __lookup_processor_type         @ r5=procinfo r9=cpuid
        movs    r10, r5                         @ invalid processor (r5=0)?
index 1cc9e17..8291245 100644 (file)
@@ -128,7 +128,9 @@ struct stack {
        u32 und[3];
 } ____cacheline_aligned;
 
+#ifndef CONFIG_CPU_V7M
 static struct stack stacks[NR_CPUS];
+#endif
 
 char elf_platform[ELF_PLATFORM_SIZE];
 EXPORT_SYMBOL(elf_platform);
@@ -207,7 +209,7 @@ static const char *proc_arch[] = {
        "5TEJ",
        "6TEJ",
        "7",
-       "?(11)",
+       "7M",
        "?(12)",
        "?(13)",
        "?(14)",
@@ -216,6 +218,12 @@ static const char *proc_arch[] = {
        "?(17)",
 };
 
+#ifdef CONFIG_CPU_V7M
+static int __get_cpu_architecture(void)
+{
+       return CPU_ARCH_ARMv7M;
+}
+#else
 static int __get_cpu_architecture(void)
 {
        int cpu_arch;
@@ -248,6 +256,7 @@ static int __get_cpu_architecture(void)
 
        return cpu_arch;
 }
+#endif
 
 int __pure cpu_architecture(void)
 {
@@ -293,7 +302,9 @@ static void __init cacheid_init(void)
 {
        unsigned int arch = cpu_architecture();
 
-       if (arch >= CPU_ARCH_ARMv6) {
+       if (arch == CPU_ARCH_ARMv7M) {
+               cacheid = 0;
+       } else if (arch >= CPU_ARCH_ARMv6) {
                unsigned int cachetype = read_cpuid_cachetype();
                if ((cachetype & (7 << 29)) == 4 << 29) {
                        /* ARMv7 register format */
@@ -375,6 +386,7 @@ static void __init feat_v6_fixup(void)
  */
 void cpu_init(void)
 {
+#ifndef CONFIG_CPU_V7M
        unsigned int cpu = smp_processor_id();
        struct stack *stk = &stacks[cpu];
 
@@ -425,6 +437,7 @@ void cpu_init(void)
              "I" (offsetof(struct stack, und[0])),
              PLC (PSR_F_BIT | PSR_I_BIT | SVC_MODE)
            : "r14");
+#endif
 }
 
 int __cpu_logical_map[NR_CPUS];
index 1c08911..ec64571 100644 (file)
@@ -819,6 +819,7 @@ static void __init kuser_get_tls_init(unsigned long vectors)
 
 void __init early_trap_init(void *vectors_base)
 {
+#ifndef CONFIG_CPU_V7M
        unsigned long vectors = (unsigned long)vectors_base;
        extern char __stubs_start[], __stubs_end[];
        extern char __vectors_start[], __vectors_end[];
@@ -850,4 +851,11 @@ void __init early_trap_init(void *vectors_base)
 
        flush_icache_range(vectors, vectors + PAGE_SIZE);
        modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
+#else /* ifndef CONFIG_CPU_V7M */
+       /*
+        * on V7-M there is no need to copy the vector table to a dedicated
+        * memory area. The address is configurable and so a table in the kernel
+        * image can be used.
+        */
+#endif
 }
diff --git a/arch/arm/mm/cache-nop.S b/arch/arm/mm/cache-nop.S
new file mode 100644 (file)
index 0000000..8e12ddc
--- /dev/null
@@ -0,0 +1,50 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/linkage.h>
+#include <linux/init.h>
+
+#include "proc-macros.S"
+
+ENTRY(nop_flush_icache_all)
+       mov     pc, lr
+ENDPROC(nop_flush_icache_all)
+
+       .globl nop_flush_kern_cache_all
+       .equ nop_flush_kern_cache_all, nop_flush_icache_all
+
+       .globl nop_flush_kern_cache_louis
+       .equ nop_flush_kern_cache_louis, nop_flush_icache_all
+
+       .globl nop_flush_user_cache_all
+       .equ nop_flush_user_cache_all, nop_flush_icache_all
+
+       .globl nop_flush_user_cache_range
+       .equ nop_flush_user_cache_range, nop_flush_icache_all
+
+       .globl nop_coherent_kern_range
+       .equ nop_coherent_kern_range, nop_flush_icache_all
+
+ENTRY(nop_coherent_user_range)
+       mov     r0, 0
+       mov     pc, lr
+ENDPROC(nop_coherent_user_range)
+
+       .globl nop_flush_kern_dcache_area
+       .equ nop_flush_kern_dcache_area, nop_flush_icache_all
+
+       .globl nop_dma_flush_range
+       .equ nop_dma_flush_range, nop_flush_icache_all
+
+       .globl nop_dma_map_area
+       .equ nop_dma_map_area, nop_flush_icache_all
+
+       .globl nop_dma_unmap_area
+       .equ nop_dma_unmap_area, nop_flush_icache_all
+
+       __INITDATA
+
+       @ define struct cpu_cache_fns (see <asm/cacheflush.h> and proc-macros.S)
+       define_cache_functions nop
index d51225f..dd3a6c6 100644 (file)
 
 void __init arm_mm_memblock_reserve(void)
 {
+#ifndef CONFIG_CPU_V7M
        /*
         * Register the exception vector page.
         * some architectures which the DRAM is the exception vector to trap,
         * alloc_page breaks with error, although it is not NULL, but "0."
         */
        memblock_reserve(CONFIG_VECTORS_BASE, PAGE_SIZE);
+#else /* ifndef CONFIG_CPU_V7M */
+       /*
+        * There is no dedicated vector page on V7-M. So nothing needs to be
+        * reserved here.
+        */
+#endif
 }
 
 void __init sanity_check_meminfo(void)
diff --git a/arch/arm/mm/proc-v7m.S b/arch/arm/mm/proc-v7m.S
new file mode 100644 (file)
index 0000000..000499c
--- /dev/null
@@ -0,0 +1,157 @@
+/*
+ *  linux/arch/arm/mm/proc-v7m.S
+ *
+ *  Copyright (C) 2008 ARM Ltd.
+ *  Copyright (C) 2001 Deep Blue Solutions Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ *  This is the "shell" of the ARMv7-M processor support.
+ */
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <asm/v7m.h>
+#include "proc-macros.S"
+
+ENTRY(cpu_v7m_proc_init)
+       mov     pc, lr
+ENDPROC(cpu_v7m_proc_init)
+
+ENTRY(cpu_v7m_proc_fin)
+       mov     pc, lr
+ENDPROC(cpu_v7m_proc_fin)
+
+/*
+ *     cpu_v7m_reset(loc)
+ *
+ *     Perform a soft reset of the system.  Put the CPU into the
+ *     same state as it would be if it had been reset, and branch
+ *     to what would be the reset vector.
+ *
+ *     - loc   - location to jump to for soft reset
+ */
+       .align  5
+ENTRY(cpu_v7m_reset)
+       mov     pc, r0
+ENDPROC(cpu_v7m_reset)
+
+/*
+ *     cpu_v7m_do_idle()
+ *
+ *     Idle the processor (eg, wait for interrupt).
+ *
+ *     IRQs are already disabled.
+ */
+ENTRY(cpu_v7m_do_idle)
+       wfi
+       mov     pc, lr
+ENDPROC(cpu_v7m_do_idle)
+
+ENTRY(cpu_v7m_dcache_clean_area)
+       mov     pc, lr
+ENDPROC(cpu_v7m_dcache_clean_area)
+
+/*
+ * There is no MMU, so here is nothing to do.
+ */
+ENTRY(cpu_v7m_switch_mm)
+       mov     pc, lr
+ENDPROC(cpu_v7m_switch_mm)
+
+.globl cpu_v7m_suspend_size
+.equ   cpu_v7m_suspend_size, 0
+
+#ifdef CONFIG_ARM_CPU_SUSPEND
+ENTRY(cpu_v7m_do_suspend)
+       mov     pc, lr
+ENDPROC(cpu_v7m_do_suspend)
+
+ENTRY(cpu_v7m_do_resume)
+       mov     pc, lr
+ENDPROC(cpu_v7m_do_resume)
+#endif
+
+       .section ".text.init", #alloc, #execinstr
+
+/*
+ *     __v7m_setup
+ *
+ *     This should be able to cover all ARMv7-M cores.
+ */
+__v7m_setup:
+       @ Configure the vector table base address
+       ldr     r0, =BASEADDR_V7M_SCB
+       ldr     r12, =vector_table
+       str     r12, [r0, V7M_SCB_VTOR]
+
+       @ enable UsageFault, BusFault and MemManage fault.
+       ldr     r5, [r0, #V7M_SCB_SHCSR]
+       orr     r5, #(V7M_SCB_SHCSR_USGFAULTENA | V7M_SCB_SHCSR_BUSFAULTENA | V7M_SCB_SHCSR_MEMFAULTENA)
+       str     r5, [r0, #V7M_SCB_SHCSR]
+
+       @ Lower the priority of the SVC and PendSV exceptions
+       mov     r5, #0x80000000
+       str     r5, [r0, V7M_SCB_SHPR2] @ set SVC priority
+       mov     r5, #0x00800000
+       str     r5, [r0, V7M_SCB_SHPR3] @ set PendSV priority
+
+       @ SVC to run the kernel in this mode
+       adr     r1, BSYM(1f)
+       ldr     r5, [r12, #11 * 4]      @ read the SVC vector entry
+       str     r1, [r12, #11 * 4]      @ write the temporary SVC vector entry
+       mov     r6, lr                  @ save LR
+       mov     r7, sp                  @ save SP
+       ldr     sp, =__v7m_setup_stack_top
+       cpsie   i
+       svc     #0
+1:     cpsid   i
+       str     r5, [r12, #11 * 4]      @ restore the original SVC vector entry
+       mov     lr, r6                  @ restore LR
+       mov     sp, r7                  @ restore SP
+
+       @ Special-purpose control register
+       mov     r1, #1
+       msr     control, r1             @ Thread mode has unpriviledged access
+
+       @ Configure the System Control Register to ensure 8-byte stack alignment
+       @ Note the STKALIGN bit is either RW or RAO.
+       ldr     r12, [r0, V7M_SCB_CCR]  @ system control register
+       orr     r12, #V7M_SCB_CCR_STKALIGN
+       str     r12, [r0, V7M_SCB_CCR]
+       mov     pc, lr
+ENDPROC(__v7m_setup)
+
+       define_processor_functions v7m, dabort=nommu_early_abort, pabort=legacy_pabort, nommu=1
+
+       .section ".rodata"
+       string cpu_arch_name, "armv7m"
+       string cpu_elf_name "v7m"
+       string cpu_v7m_name "ARMv7-M"
+
+       .section ".proc.info.init", #alloc, #execinstr
+
+       /*
+        * Match any ARMv7-M processor core.
+        */
+       .type   __v7m_proc_info, #object
+__v7m_proc_info:
+       .long   0x000f0000              @ Required ID value
+       .long   0x000f0000              @ Mask for ID
+       .long   0                       @ proc_info_list.__cpu_mm_mmu_flags
+       .long   0                       @ proc_info_list.__cpu_io_mmu_flags
+       b       __v7m_setup             @ proc_info_list.__cpu_flush
+       .long   cpu_arch_name
+       .long   cpu_elf_name
+       .long   HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_IDIVT
+       .long   cpu_v7m_name
+       .long   v7m_processor_functions @ proc_info_list.proc
+       .long   0                       @ proc_info_list.tlb
+       .long   0                       @ proc_info_list.user
+       .long   nop_cache_fns           @ proc_info_list.cache
+       .size   __v7m_proc_info, . - __v7m_proc_info
+
+__v7m_setup_stack:
+       .space  4 * 8                           @ 8 registers
+__v7m_setup_stack_top: