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linux/arch/arm64/kernel/entry.S
Marc Zyngier 6468178767 arm64: let the core code deal with preempt_count 
Commit f27dde8dee (sched: Add NEED_RESCHED to the preempt_count)
introduced the use of bit 31 in preempt_count for obscure scheduling
purposes.

This causes interrupts taken from EL0 to hit the (open coded) BUG when
this flag is flipped while handling the interrupt (we compare the
values before and after, and kill the kernel if they are different).

The fix is to stop messing with the preempt count entirely, as this
is already being dealt with in the generic code (irq_enter/irq_exit).

Tested on a dual A53 FPGA running cyclictest.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2013-11-25 16:44:04 +00:00

681 lines
15 KiB
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/*
* Low-level exception handling code
*
* Copyright (C) 2012 ARM Ltd.
* Authors: Catalin Marinas <catalin.marinas@arm.com>
* Will Deacon <will.deacon@arm.com>
*
* 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 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.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/errno.h>
#include <asm/esr.h>
#include <asm/thread_info.h>
#include <asm/unistd.h>
#include <asm/unistd32.h>
/*
* Bad Abort numbers
*-----------------
*/
#define BAD_SYNC 0
#define BAD_IRQ 1
#define BAD_FIQ 2
#define BAD_ERROR 3
.macro kernel_entry, el, regsize = 64
sub sp, sp, #S_FRAME_SIZE - S_LR // room for LR, SP, SPSR, ELR
.if \regsize == 32
mov w0, w0 // zero upper 32 bits of x0
.endif
push x28, x29
push x26, x27
push x24, x25
push x22, x23
push x20, x21
push x18, x19
push x16, x17
push x14, x15
push x12, x13
push x10, x11
push x8, x9
push x6, x7
push x4, x5
push x2, x3
push x0, x1
.if \el == 0
mrs x21, sp_el0
.else
add x21, sp, #S_FRAME_SIZE
.endif
mrs x22, elr_el1
mrs x23, spsr_el1
stp lr, x21, [sp, #S_LR]
stp x22, x23, [sp, #S_PC]
/*
* Set syscallno to -1 by default (overridden later if real syscall).
*/
.if \el == 0
mvn x21, xzr
str x21, [sp, #S_SYSCALLNO]
.endif
/*
* Registers that may be useful after this macro is invoked:
*
* x21 - aborted SP
* x22 - aborted PC
* x23 - aborted PSTATE
*/
.endm
.macro kernel_exit, el, ret = 0
ldp x21, x22, [sp, #S_PC] // load ELR, SPSR
.if \el == 0
ldr x23, [sp, #S_SP] // load return stack pointer
.endif
.if \ret
ldr x1, [sp, #S_X1] // preserve x0 (syscall return)
add sp, sp, S_X2
.else
pop x0, x1
.endif
pop x2, x3 // load the rest of the registers
pop x4, x5
pop x6, x7
pop x8, x9
msr elr_el1, x21 // set up the return data
msr spsr_el1, x22
.if \el == 0
msr sp_el0, x23
.endif
pop x10, x11
pop x12, x13
pop x14, x15
pop x16, x17
pop x18, x19
pop x20, x21
pop x22, x23
pop x24, x25
pop x26, x27
pop x28, x29
ldr lr, [sp], #S_FRAME_SIZE - S_LR // load LR and restore SP
eret // return to kernel
.endm
.macro get_thread_info, rd
mov \rd, sp
and \rd, \rd, #~(THREAD_SIZE - 1) // top of stack
.endm
/*
* These are the registers used in the syscall handler, and allow us to
* have in theory up to 7 arguments to a function - x0 to x6.
*
* x7 is reserved for the system call number in 32-bit mode.
*/
sc_nr .req x25 // number of system calls
scno .req x26 // syscall number
stbl .req x27 // syscall table pointer
tsk .req x28 // current thread_info
/*
* Interrupt handling.
*/
.macro irq_handler
ldr x1, handle_arch_irq
mov x0, sp
blr x1
.endm
.text
/*
* Exception vectors.
*/
.align 11
ENTRY(vectors)
ventry el1_sync_invalid // Synchronous EL1t
ventry el1_irq_invalid // IRQ EL1t
ventry el1_fiq_invalid // FIQ EL1t
ventry el1_error_invalid // Error EL1t
ventry el1_sync // Synchronous EL1h
ventry el1_irq // IRQ EL1h
ventry el1_fiq_invalid // FIQ EL1h
ventry el1_error_invalid // Error EL1h
ventry el0_sync // Synchronous 64-bit EL0
ventry el0_irq // IRQ 64-bit EL0
ventry el0_fiq_invalid // FIQ 64-bit EL0
ventry el0_error_invalid // Error 64-bit EL0
#ifdef CONFIG_COMPAT
ventry el0_sync_compat // Synchronous 32-bit EL0
ventry el0_irq_compat // IRQ 32-bit EL0
ventry el0_fiq_invalid_compat // FIQ 32-bit EL0
ventry el0_error_invalid_compat // Error 32-bit EL0
#else
ventry el0_sync_invalid // Synchronous 32-bit EL0
ventry el0_irq_invalid // IRQ 32-bit EL0
ventry el0_fiq_invalid // FIQ 32-bit EL0
ventry el0_error_invalid // Error 32-bit EL0
#endif
END(vectors)
/*
* Invalid mode handlers
*/
.macro inv_entry, el, reason, regsize = 64
kernel_entry el, \regsize
mov x0, sp
mov x1, #\reason
mrs x2, esr_el1
b bad_mode
.endm
el0_sync_invalid:
inv_entry 0, BAD_SYNC
ENDPROC(el0_sync_invalid)
el0_irq_invalid:
inv_entry 0, BAD_IRQ
ENDPROC(el0_irq_invalid)
el0_fiq_invalid:
inv_entry 0, BAD_FIQ
ENDPROC(el0_fiq_invalid)
el0_error_invalid:
inv_entry 0, BAD_ERROR
ENDPROC(el0_error_invalid)
#ifdef CONFIG_COMPAT
el0_fiq_invalid_compat:
inv_entry 0, BAD_FIQ, 32
ENDPROC(el0_fiq_invalid_compat)
el0_error_invalid_compat:
inv_entry 0, BAD_ERROR, 32
ENDPROC(el0_error_invalid_compat)
#endif
el1_sync_invalid:
inv_entry 1, BAD_SYNC
ENDPROC(el1_sync_invalid)
el1_irq_invalid:
inv_entry 1, BAD_IRQ
ENDPROC(el1_irq_invalid)
el1_fiq_invalid:
inv_entry 1, BAD_FIQ
ENDPROC(el1_fiq_invalid)
el1_error_invalid:
inv_entry 1, BAD_ERROR
ENDPROC(el1_error_invalid)
/*
* EL1 mode handlers.
*/
.align 6
el1_sync:
kernel_entry 1
mrs x1, esr_el1 // read the syndrome register
lsr x24, x1, #ESR_EL1_EC_SHIFT // exception class
cmp x24, #ESR_EL1_EC_DABT_EL1 // data abort in EL1
b.eq el1_da
cmp x24, #ESR_EL1_EC_SYS64 // configurable trap
b.eq el1_undef
cmp x24, #ESR_EL1_EC_SP_ALIGN // stack alignment exception
b.eq el1_sp_pc
cmp x24, #ESR_EL1_EC_PC_ALIGN // pc alignment exception
b.eq el1_sp_pc
cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL1
b.eq el1_undef
cmp x24, #ESR_EL1_EC_BREAKPT_EL1 // debug exception in EL1
b.ge el1_dbg
b el1_inv
el1_da:
/*
* Data abort handling
*/
mrs x0, far_el1
enable_dbg_if_not_stepping x2
// re-enable interrupts if they were enabled in the aborted context
tbnz x23, #7, 1f // PSR_I_BIT
enable_irq
1:
mov x2, sp // struct pt_regs
bl do_mem_abort
// disable interrupts before pulling preserved data off the stack
disable_irq
kernel_exit 1
el1_sp_pc:
/*
* Stack or PC alignment exception handling
*/
mrs x0, far_el1
mov x1, x25
mov x2, sp
b do_sp_pc_abort
el1_undef:
/*
* Undefined instruction
*/
mov x0, sp
b do_undefinstr
el1_dbg:
/*
* Debug exception handling
*/
tbz x24, #0, el1_inv // EL1 only
mrs x0, far_el1
mov x2, sp // struct pt_regs
bl do_debug_exception
kernel_exit 1
el1_inv:
// TODO: add support for undefined instructions in kernel mode
mov x0, sp
mov x1, #BAD_SYNC
mrs x2, esr_el1
b bad_mode
ENDPROC(el1_sync)
.align 6
el1_irq:
kernel_entry 1
enable_dbg_if_not_stepping x0
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
irq_handler
#ifdef CONFIG_PREEMPT
get_thread_info tsk
ldr w24, [tsk, #TI_PREEMPT] // restore preempt count
cbnz w24, 1f // preempt count != 0
ldr x0, [tsk, #TI_FLAGS] // get flags
tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling?
bl el1_preempt
1:
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on
#endif
kernel_exit 1
ENDPROC(el1_irq)
#ifdef CONFIG_PREEMPT
el1_preempt:
mov x24, lr
1: enable_dbg
bl preempt_schedule_irq // irq en/disable is done inside
ldr x0, [tsk, #TI_FLAGS] // get new tasks TI_FLAGS
tbnz x0, #TIF_NEED_RESCHED, 1b // needs rescheduling?
ret x24
#endif
/*
* EL0 mode handlers.
*/
.align 6
el0_sync:
kernel_entry 0
mrs x25, esr_el1 // read the syndrome register
lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class
cmp x24, #ESR_EL1_EC_SVC64 // SVC in 64-bit state
b.eq el0_svc
adr lr, ret_from_exception
cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0
b.eq el0_da
cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0
b.eq el0_ia
cmp x24, #ESR_EL1_EC_FP_ASIMD // FP/ASIMD access
b.eq el0_fpsimd_acc
cmp x24, #ESR_EL1_EC_FP_EXC64 // FP/ASIMD exception
b.eq el0_fpsimd_exc
cmp x24, #ESR_EL1_EC_SYS64 // configurable trap
b.eq el0_undef
cmp x24, #ESR_EL1_EC_SP_ALIGN // stack alignment exception
b.eq el0_sp_pc
cmp x24, #ESR_EL1_EC_PC_ALIGN // pc alignment exception
b.eq el0_sp_pc
cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL0
b.eq el0_undef
cmp x24, #ESR_EL1_EC_BREAKPT_EL0 // debug exception in EL0
b.ge el0_dbg
b el0_inv
#ifdef CONFIG_COMPAT
.align 6
el0_sync_compat:
kernel_entry 0, 32
mrs x25, esr_el1 // read the syndrome register
lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class
cmp x24, #ESR_EL1_EC_SVC32 // SVC in 32-bit state
b.eq el0_svc_compat
adr lr, ret_from_exception
cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0
b.eq el0_da
cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0
b.eq el0_ia
cmp x24, #ESR_EL1_EC_FP_ASIMD // FP/ASIMD access
b.eq el0_fpsimd_acc
cmp x24, #ESR_EL1_EC_FP_EXC32 // FP/ASIMD exception
b.eq el0_fpsimd_exc
cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL0
b.eq el0_undef
cmp x24, #ESR_EL1_EC_CP15_32 // CP15 MRC/MCR trap
b.eq el0_undef
cmp x24, #ESR_EL1_EC_CP15_64 // CP15 MRRC/MCRR trap
b.eq el0_undef
cmp x24, #ESR_EL1_EC_CP14_MR // CP14 MRC/MCR trap
b.eq el0_undef
cmp x24, #ESR_EL1_EC_CP14_LS // CP14 LDC/STC trap
b.eq el0_undef
cmp x24, #ESR_EL1_EC_CP14_64 // CP14 MRRC/MCRR trap
b.eq el0_undef
cmp x24, #ESR_EL1_EC_BREAKPT_EL0 // debug exception in EL0
b.ge el0_dbg
b el0_inv
el0_svc_compat:
/*
* AArch32 syscall handling
*/
adr stbl, compat_sys_call_table // load compat syscall table pointer
uxtw scno, w7 // syscall number in w7 (r7)
mov sc_nr, #__NR_compat_syscalls
b el0_svc_naked
.align 6
el0_irq_compat:
kernel_entry 0, 32
b el0_irq_naked
#endif
el0_da:
/*
* Data abort handling
*/
mrs x0, far_el1
bic x0, x0, #(0xff << 56)
disable_step x1
isb
enable_dbg
// enable interrupts before calling the main handler
enable_irq
mov x1, x25
mov x2, sp
b do_mem_abort
el0_ia:
/*
* Instruction abort handling
*/
mrs x0, far_el1
disable_step x1
isb
enable_dbg
// enable interrupts before calling the main handler
enable_irq
orr x1, x25, #1 << 24 // use reserved ISS bit for instruction aborts
mov x2, sp
b do_mem_abort
el0_fpsimd_acc:
/*
* Floating Point or Advanced SIMD access
*/
mov x0, x25
mov x1, sp
b do_fpsimd_acc
el0_fpsimd_exc:
/*
* Floating Point or Advanced SIMD exception
*/
mov x0, x25
mov x1, sp
b do_fpsimd_exc
el0_sp_pc:
/*
* Stack or PC alignment exception handling
*/
mrs x0, far_el1
disable_step x1
isb
enable_dbg
// enable interrupts before calling the main handler
enable_irq
mov x1, x25
mov x2, sp
b do_sp_pc_abort
el0_undef:
/*
* Undefined instruction
*/
mov x0, sp
// enable interrupts before calling the main handler
enable_irq
b do_undefinstr
el0_dbg:
/*
* Debug exception handling
*/
tbnz x24, #0, el0_inv // EL0 only
mrs x0, far_el1
disable_step x1
mov x1, x25
mov x2, sp
b do_debug_exception
el0_inv:
mov x0, sp
mov x1, #BAD_SYNC
mrs x2, esr_el1
b bad_mode
ENDPROC(el0_sync)
.align 6
el0_irq:
kernel_entry 0
el0_irq_naked:
disable_step x1
isb
enable_dbg
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
irq_handler
get_thread_info tsk
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on
#endif
b ret_to_user
ENDPROC(el0_irq)
/*
* This is the return code to user mode for abort handlers
*/
ret_from_exception:
get_thread_info tsk
b ret_to_user
ENDPROC(ret_from_exception)
/*
* Register switch for AArch64. The callee-saved registers need to be saved
* and restored. On entry:
* x0 = previous task_struct (must be preserved across the switch)
* x1 = next task_struct
* Previous and next are guaranteed not to be the same.
*
*/
ENTRY(cpu_switch_to)
add x8, x0, #THREAD_CPU_CONTEXT
mov x9, sp
stp x19, x20, [x8], #16 // store callee-saved registers
stp x21, x22, [x8], #16
stp x23, x24, [x8], #16
stp x25, x26, [x8], #16
stp x27, x28, [x8], #16
stp x29, x9, [x8], #16
str lr, [x8]
add x8, x1, #THREAD_CPU_CONTEXT
ldp x19, x20, [x8], #16 // restore callee-saved registers
ldp x21, x22, [x8], #16
ldp x23, x24, [x8], #16
ldp x25, x26, [x8], #16
ldp x27, x28, [x8], #16
ldp x29, x9, [x8], #16
ldr lr, [x8]
mov sp, x9
ret
ENDPROC(cpu_switch_to)
/*
* This is the fast syscall return path. We do as little as possible here,
* and this includes saving x0 back into the kernel stack.
*/
ret_fast_syscall:
disable_irq // disable interrupts
ldr x1, [tsk, #TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
cbnz x2, fast_work_pending
tbz x1, #TIF_SINGLESTEP, fast_exit
disable_dbg
enable_step x2
fast_exit:
kernel_exit 0, ret = 1
/*
* Ok, we need to do extra processing, enter the slow path.
*/
fast_work_pending:
str x0, [sp, #S_X0] // returned x0
work_pending:
tbnz x1, #TIF_NEED_RESCHED, work_resched
/* TIF_SIGPENDING or TIF_NOTIFY_RESUME case */
ldr x2, [sp, #S_PSTATE]
mov x0, sp // 'regs'
tst x2, #PSR_MODE_MASK // user mode regs?
b.ne no_work_pending // returning to kernel
enable_irq // enable interrupts for do_notify_resume()
bl do_notify_resume
b ret_to_user
work_resched:
enable_dbg
bl schedule
/*
* "slow" syscall return path.
*/
ret_to_user:
disable_irq // disable interrupts
ldr x1, [tsk, #TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
tbz x1, #TIF_SINGLESTEP, no_work_pending
disable_dbg
enable_step x2
no_work_pending:
kernel_exit 0, ret = 0
ENDPROC(ret_to_user)
/*
* This is how we return from a fork.
*/
ENTRY(ret_from_fork)
bl schedule_tail
cbz x19, 1f // not a kernel thread
mov x0, x20
blr x19
1: get_thread_info tsk
b ret_to_user
ENDPROC(ret_from_fork)
/*
* SVC handler.
*/
.align 6
el0_svc:
adrp stbl, sys_call_table // load syscall table pointer
uxtw scno, w8 // syscall number in w8
mov sc_nr, #__NR_syscalls
el0_svc_naked: // compat entry point
stp x0, scno, [sp, #S_ORIG_X0] // save the original x0 and syscall number
disable_step x16
isb
enable_dbg
enable_irq
get_thread_info tsk
ldr x16, [tsk, #TI_FLAGS] // check for syscall tracing
tbnz x16, #TIF_SYSCALL_TRACE, __sys_trace // are we tracing syscalls?
adr lr, ret_fast_syscall // return address
cmp scno, sc_nr // check upper syscall limit
b.hs ni_sys
ldr x16, [stbl, scno, lsl #3] // address in the syscall table
br x16 // call sys_* routine
ni_sys:
mov x0, sp
b do_ni_syscall
ENDPROC(el0_svc)
/*
* This is the really slow path. We're going to be doing context
* switches, and waiting for our parent to respond.
*/
__sys_trace:
mov x1, sp
mov w0, #0 // trace entry
bl syscall_trace
adr lr, __sys_trace_return // return address
uxtw scno, w0 // syscall number (possibly new)
mov x1, sp // pointer to regs
cmp scno, sc_nr // check upper syscall limit
b.hs ni_sys
ldp x0, x1, [sp] // restore the syscall args
ldp x2, x3, [sp, #S_X2]
ldp x4, x5, [sp, #S_X4]
ldp x6, x7, [sp, #S_X6]
ldr x16, [stbl, scno, lsl #3] // address in the syscall table
br x16 // call sys_* routine
__sys_trace_return:
str x0, [sp] // save returned x0
mov x1, sp
mov w0, #1 // trace exit
bl syscall_trace
b ret_to_user
/*
* Special system call wrappers.
*/
ENTRY(sys_rt_sigreturn_wrapper)
mov x0, sp
b sys_rt_sigreturn
ENDPROC(sys_rt_sigreturn_wrapper)
ENTRY(handle_arch_irq)
.quad 0
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