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linux/arch/arm/kernel/entry-header.S

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/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/errno.h>
#include <asm/thread_info.h>
#include <asm/v7m.h>
@ Bad Abort numbers
@ -----------------
@
#define BAD_PREFETCH 0
#define BAD_DATA 1
#define BAD_ADDREXCPTN 2
#define BAD_IRQ 3
#define BAD_UNDEFINSTR 4
@
@ Most of the stack format comes from struct pt_regs, but with
@ the addition of 8 bytes for storing syscall args 5 and 6.
@ This _must_ remain a multiple of 8 for EABI.
@
#define S_OFF 8
/*
* The SWI code relies on the fact that R0 is at the bottom of the stack
* (due to slow/fast restore user regs).
*/
#if S_R0 != 0
#error "Please fix"
#endif
.macro zero_fp
#ifdef CONFIG_FRAME_POINTER
mov fp, #0
#endif
.endm
#ifdef CONFIG_ALIGNMENT_TRAP
#define ATRAP(x...) x
#else
#define ATRAP(x...)
#endif
.macro alignment_trap, rtmp1, rtmp2, label
#ifdef CONFIG_ALIGNMENT_TRAP
mrc p15, 0, \rtmp2, c1, c0, 0
ldr \rtmp1, \label
ldr \rtmp1, [\rtmp1]
teq \rtmp1, \rtmp2
mcrne p15, 0, \rtmp1, c1, c0, 0
#endif
.endm
#ifdef CONFIG_CPU_V7M
/*
* ARMv7-M exception entry/exit macros.
*
* xPSR, ReturnAddress(), LR (R14), R12, R3, R2, R1, and R0 are
* automatically saved on the current stack (32 words) before
* switching to the exception stack (SP_main).
*
* If exception is taken while in user mode, SP_main is
* empty. Otherwise, SP_main is aligned to 64 bit automatically
* (CCR.STKALIGN set).
*
* Linux assumes that the interrupts are disabled when entering an
* exception handler and it may BUG if this is not the case. Interrupts
* are disabled during entry and reenabled in the exit macro.
*
* v7m_exception_slow_exit is used when returning from SVC or PendSV.
* When returning to kernel mode, we don't return from exception.
*/
.macro v7m_exception_entry
@ determine the location of the registers saved by the core during
@ exception entry. Depending on the mode the cpu was in when the
@ exception happend that is either on the main or the process stack.
@ Bit 2 of EXC_RETURN stored in the lr register specifies which stack
@ was used.
tst lr, #EXC_RET_STACK_MASK
mrsne r12, psp
moveq r12, sp
@ we cannot rely on r0-r3 and r12 matching the value saved in the
@ exception frame because of tail-chaining. So these have to be
@ reloaded.
ldmia r12!, {r0-r3}
@ Linux expects to have irqs off. Do it here before taking stack space
cpsid i
sub sp, #PT_REGS_SIZE-S_IP
stmdb sp!, {r0-r11}
@ load saved r12, lr, return address and xPSR.
@ r0-r7 are used for signals and never touched from now on. Clobbering
@ r8-r12 is OK.
mov r9, r12
ldmia r9!, {r8, r10-r12}
@ calculate the original stack pointer value.
@ r9 currently points to the memory location just above the auto saved
@ xPSR.
@ The cpu might automatically 8-byte align the stack. Bit 9
@ of the saved xPSR specifies if stack aligning took place. In this case
@ another 32-bit value is included in the stack.
tst r12, V7M_xPSR_FRAMEPTRALIGN
addne r9, r9, #4
@ store saved r12 using str to have a register to hold the base for stm
str r8, [sp, #S_IP]
add r8, sp, #S_SP
@ store r13-r15, xPSR
stmia r8!, {r9-r12}
@ store old_r0
str r0, [r8]
.endm
/*
* PENDSV and SVCALL are configured to have the same exception
* priorities. As a kernel thread runs at SVCALL execution priority it
* can never be preempted and so we will never have to return to a
* kernel thread here.
*/
.macro v7m_exception_slow_exit ret_r0
cpsid i
ldr lr, =EXC_RET_THREADMODE_PROCESSSTACK
@ read original r12, sp, lr, pc and xPSR
add r12, sp, #S_IP
ldmia r12, {r1-r5}
@ an exception frame is always 8-byte aligned. To tell the hardware if
@ the sp to be restored is aligned or not set bit 9 of the saved xPSR
@ accordingly.
tst r2, #4
subne r2, r2, #4
orrne r5, V7M_xPSR_FRAMEPTRALIGN
biceq r5, V7M_xPSR_FRAMEPTRALIGN
@ ensure bit 0 is cleared in the PC, otherwise behaviour is
@ unpredictable
bic r4, #1
@ write basic exception frame
stmdb r2!, {r1, r3-r5}
ldmia sp, {r1, r3-r5}
.if \ret_r0
stmdb r2!, {r0, r3-r5}
.else
stmdb r2!, {r1, r3-r5}
.endif
@ restore process sp
msr psp, r2
@ restore original r4-r11
ldmia sp!, {r0-r11}
@ restore main sp
add sp, sp, #PT_REGS_SIZE-S_IP
cpsie i
bx lr
.endm
#endif /* CONFIG_CPU_V7M */
@
@ 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
.macro svc_exit, rpsr, irq = 0
.if \irq != 0
@ IRQs already off
#ifdef CONFIG_TRACE_IRQFLAGS
@ The parent context IRQs must have been enabled to get here in
@ the first place, so there's no point checking the PSR I bit.
bl trace_hardirqs_on
#endif
.else
@ IRQs off again before pulling preserved data off the stack
disable_irq_notrace
#ifdef CONFIG_TRACE_IRQFLAGS
tst \rpsr, #PSR_I_BIT
bleq trace_hardirqs_on
tst \rpsr, #PSR_I_BIT
blne trace_hardirqs_off
#endif
.endif
ldr r1, [sp, #SVC_ADDR_LIMIT]
uaccess_restore
str r1, [tsk, #TI_ADDR_LIMIT]
#ifndef CONFIG_THUMB2_KERNEL
@ ARM mode SVC restore
msr spsr_cxsf, \rpsr
#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K)
@ We must avoid clrex due to Cortex-A15 erratum #830321
sub r0, sp, #4 @ uninhabited address
strex r1, r2, [r0] @ clear the exclusive monitor
#endif
ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr
#else
@ Thumb mode SVC restore
ldr lr, [sp, #S_SP] @ top of the stack
ldrd r0, r1, [sp, #S_LR] @ calling lr and pc
@ We must avoid clrex due to Cortex-A15 erratum #830321
strex r2, r1, [sp, #S_LR] @ clear the exclusive monitor
stmdb lr!, {r0, r1, \rpsr} @ calling lr and rfe context
ldmia sp, {r0 - r12}
mov sp, lr
ldr lr, [sp], #4
rfeia sp!
#endif
.endm
@
@ svc_exit_via_fiq - like svc_exit but switches to FIQ mode before exit
@
@ This macro acts in a similar manner to svc_exit but switches to FIQ
@ mode to restore the final part of the register state.
@
@ We cannot use the normal svc_exit procedure because that would
@ clobber spsr_svc (FIQ could be delivered during the first few
@ instructions of vector_swi meaning its contents have not been
@ saved anywhere).
@
@ Note that, unlike svc_exit, this macro also does not allow a caller
@ supplied rpsr. This is because the FIQ exceptions are not re-entrant
@ and the handlers cannot call into the scheduler (meaning the value
@ on the stack remains correct).
@
.macro svc_exit_via_fiq
ldr r1, [sp, #SVC_ADDR_LIMIT]
uaccess_restore
str r1, [tsk, #TI_ADDR_LIMIT]
#ifndef CONFIG_THUMB2_KERNEL
@ ARM mode restore
mov r0, sp
ldmib r0, {r1 - r14} @ abort is deadly from here onward (it will
@ clobber state restored below)
msr cpsr_c, #FIQ_MODE | PSR_I_BIT | PSR_F_BIT
add r8, r0, #S_PC
ldr r9, [r0, #S_PSR]
msr spsr_cxsf, r9
ldr r0, [r0, #S_R0]
ldmia r8, {pc}^
#else
@ Thumb mode restore
add r0, sp, #S_R2
ldr lr, [sp, #S_LR]
ldr sp, [sp, #S_SP] @ abort is deadly from here onward (it will
@ clobber state restored below)
ldmia r0, {r2 - r12}
mov r1, #FIQ_MODE | PSR_I_BIT | PSR_F_BIT
msr cpsr_c, r1
sub r0, #S_R2
add r8, r0, #S_PC
ldmia r0, {r0 - r1}
rfeia r8
#endif
.endm
.macro restore_user_regs, fast = 0, offset = 0
uaccess_enable r1, isb=0
#ifndef CONFIG_THUMB2_KERNEL
@ ARM mode restore
mov r2, sp
ldr r1, [r2, #\offset + S_PSR] @ get calling cpsr
ldr lr, [r2, #\offset + S_PC]! @ get pc
tst r1, #PSR_I_BIT | 0x0f
bne 1f
msr spsr_cxsf, r1 @ save in spsr_svc
#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K)
@ We must avoid clrex due to Cortex-A15 erratum #830321
strex r1, r2, [r2] @ clear the exclusive monitor
#endif
.if \fast
ldmdb r2, {r1 - lr}^ @ get calling r1 - lr
.else
ldmdb r2, {r0 - lr}^ @ get calling r0 - lr
.endif
mov r0, r0 @ ARMv5T and earlier require a nop
@ after ldm {}^
add sp, sp, #\offset + PT_REGS_SIZE
movs pc, lr @ return & move spsr_svc into cpsr
1: bug "Returning to usermode but unexpected PSR bits set?", \@
#elif defined(CONFIG_CPU_V7M)
@ V7M restore.
@ Note that we don't need to do clrex here as clearing the local
@ monitor is part of the exception entry and exit sequence.
.if \offset
add sp, #\offset
.endif
v7m_exception_slow_exit ret_r0 = \fast
#else
@ Thumb mode restore
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
tst r1, #PSR_I_BIT | 0x0f
bne 1f
msr spsr_cxsf, r1 @ save in spsr_svc
@ We must avoid clrex due to Cortex-A15 erratum #830321
strex r1, r2, [sp] @ clear the exclusive monitor
.if \fast
ldmdb sp, {r1 - r12} @ get calling r1 - r12
.else
ldmdb sp, {r0 - r12} @ get calling r0 - r12
.endif
add sp, sp, #PT_REGS_SIZE - S_SP
movs pc, lr @ return & move spsr_svc into cpsr
1: bug "Returning to usermode but unexpected PSR bits set?", \@
#endif /* !CONFIG_THUMB2_KERNEL */
.endm
/*
* Context tracking subsystem. Used to instrument transitions
* between user and kernel mode.
*/
.macro ct_user_exit, save = 1
#ifdef CONFIG_CONTEXT_TRACKING
.if \save
stmdb sp!, {r0-r3, ip, lr}
bl context_tracking_user_exit
ldmia sp!, {r0-r3, ip, lr}
.else
bl context_tracking_user_exit
.endif
#endif
.endm
.macro ct_user_enter, save = 1
#ifdef CONFIG_CONTEXT_TRACKING
.if \save
stmdb sp!, {r0-r3, ip, lr}
bl context_tracking_user_enter
ldmia sp!, {r0-r3, ip, lr}
.else
bl context_tracking_user_enter
.endif
#endif
.endm
.macro invoke_syscall, table, nr, tmp, ret, reload=0
#ifdef CONFIG_CPU_SPECTRE
mov \tmp, \nr
cmp \tmp, #NR_syscalls @ check upper syscall limit
movcs \tmp, #0
csdb
badr lr, \ret @ return address
.if \reload
add r1, sp, #S_R0 + S_OFF @ pointer to regs
ldmccia r1, {r0 - r6} @ reload r0-r6
stmccia sp, {r4, r5} @ update stack arguments
.endif
ldrcc pc, [\table, \tmp, lsl #2] @ call sys_* routine
#else
cmp \nr, #NR_syscalls @ check upper syscall limit
badr lr, \ret @ return address
.if \reload
add r1, sp, #S_R0 + S_OFF @ pointer to regs
ldmccia r1, {r0 - r6} @ reload r0-r6
stmccia sp, {r4, r5} @ update stack arguments
.endif
ldrcc pc, [\table, \nr, lsl #2] @ call sys_* routine
#endif
.endm
/*
* These are the registers used in the syscall handler, and allow us to
* have in theory up to 7 arguments to a function - r0 to r6.
*
* r7 is reserved for the system call number for thumb mode.
*
* Note that tbl == why is intentional.
*
* We must set at least "tsk" and "why" when calling ret_with_reschedule.
*/
scno .req r7 @ syscall number
tbl .req r8 @ syscall table pointer
why .req r8 @ Linux syscall (!= 0)
tsk .req r9 @ current thread_info
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