Thumb-2: Implementation of the unified start-up and exceptions code

This patch implements the ARM/Thumb-2 unified kernel start-up and
exception handling code.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 87 insertions, 5 deletions

diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 87ab4e15799..a4eaf4f920c 100644
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -36,11 +36,6 @@
 #endif
         .endm
 
-        .macro  get_thread_info, rd
-        mov     \rd, sp, lsr #13
-        mov     \rd, \rd, lsl #13
-        .endm
-
         .macro  alignment_trap, rtemp
 #ifdef CONFIG_ALIGNMENT_TRAP
         ldr     \rtemp, .LCcralign
@@ -49,6 +44,93 @@
 #endif
         .endm
 
+        @
+        @ Store/load the USER SP and LR registers by switching to the SYS
+        @ mode. Useful in Thumb-2 mode where "stm/ldm rd, {sp, lr}^" is not
+        @ available. Should only be called from SVC mode
+        @
+        .macro  store_user_sp_lr, rd, rtemp, offset = 0
+        mrs     \rtemp, cpsr
+        eor     \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
+        msr     cpsr_c, \rtemp                  @ switch to the SYS mode
+
+        str     sp, [\rd, #\offset]             @ save sp_usr
+        str     lr, [\rd, #\offset + 4]         @ save lr_usr
+
+        eor     \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
+        msr     cpsr_c, \rtemp                  @ switch back to the SVC mode
+        .endm
+
+        .macro  load_user_sp_lr, rd, rtemp, offset = 0
+        mrs     \rtemp, cpsr
+        eor     \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
+        msr     cpsr_c, \rtemp                  @ switch to the SYS mode
+
+        ldr     sp, [\rd, #\offset]             @ load sp_usr
+        ldr     lr, [\rd, #\offset + 4]         @ load lr_usr
+
+        eor     \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
+        msr     cpsr_c, \rtemp                  @ switch back to the SVC mode
+        .endm
+
+#ifndef CONFIG_THUMB2_KERNEL
+        .macro  svc_exit, rpsr
+        msr     spsr_cxsf, \rpsr
+        ldmia   sp, {r0 - pc}^                  @ load r0 - pc, cpsr
+        .endm
+
+        .macro  restore_user_regs, fast = 0, offset = 0
+        ldr     r1, [sp, #\offset + S_PSR]      @ get calling cpsr
+        ldr     lr, [sp, #\offset + S_PC]!      @ get pc
+        msr     spsr_cxsf, r1                   @ save in spsr_svc
+        .if     \fast
+        ldmdb   sp, {r1 - lr}^                  @ get calling r1 - lr
+        .else
+        ldmdb   sp, {r0 - lr}^                  @ get calling r0 - lr
+        .endif
+        add     sp, sp, #S_FRAME_SIZE - S_PC
+        movs    pc, lr                          @ return & move spsr_svc into cpsr
+        .endm
+
+        .macro  get_thread_info, rd
+        mov     \rd, sp, lsr #13
+        mov     \rd, \rd, lsl #13
+        .endm
+#else   /* CONFIG_THUMB2_KERNEL */
+        .macro  svc_exit, rpsr
+        ldr     r0, [sp, #S_SP]                 @ top of the stack
+        ldr     r1, [sp, #S_PC]                 @ return address
+        tst     r0, #4                          @ orig stack 8-byte aligned?
+        stmdb   r0, {r1, \rpsr}                 @ rfe context
+        ldmia   sp, {r0 - r12}
+        ldr     lr, [sp, #S_LR]
+        addeq   sp, sp, #S_FRAME_SIZE - 8       @ aligned
+        addne   sp, sp, #S_FRAME_SIZE - 4       @ not aligned
+        rfeia   sp!
+        .endm
+
+        .macro  restore_user_regs, fast = 0, offset = 0
+        mov     r2, sp
+        load_user_sp_lr r2, r3, \offset + S_SP  @ calling sp, lr
+        ldr     r1, [sp, #\offset + S_PSR]      @ get calling cpsr
+        ldr     lr, [sp, #\offset + S_PC]       @ get pc
+        add     sp, sp, #\offset + S_SP
+        msr     spsr_cxsf, r1                   @ save in spsr_svc
+        .if     \fast
+        ldmdb   sp, {r1 - r12}                  @ get calling r1 - r12
+        .else
+        ldmdb   sp, {r0 - r12}                  @ get calling r0 - r12
+        .endif
+        add     sp, sp, #S_FRAME_SIZE - S_SP
+        movs    pc, lr                          @ return & move spsr_svc into cpsr
+        .endm
+
+        .macro  get_thread_info, rd
+        mov     \rd, sp
+        lsr     \rd, \rd, #13
+        mov     \rd, \rd, lsl #13
+        .endm
+#endif  /* !CONFIG_THUMB2_KERNEL */
 
 /*
  * These are the registers used in the syscall handler, and allow us to