ARM: 8150/3: fiq: Replace default FIQ handler

This patch introduces a new default FIQ handler that is structured in a
similar way to the existing ARM exception handler and result in the FIQ
being handled by C code running on the SVC stack (despite this code run
in the FIQ handler is subject to severe limitations with respect to
locking making normal interaction with the kernel impossible).

This default handler allows concepts that on x86 would be handled using
NMIs to be realized on ARM.

Credit:

    This patch is a near complete re-write of a patch originally
    provided by Anton Vorontsov. Today only a couple of small fragments
    survive, however without Anton's work to build from this patch would
    not exist. Thanks also to Russell King for spoonfeeding me a variety
    of fixes during the review cycle.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Daniel Thompson 2014-09-17 17:12:06 +01:00 committed by Russell King
parent 9e82bf0141
commit c0e7f7ee71
5 changed files with 180 additions and 16 deletions

View File

@ -146,7 +146,7 @@ ENDPROC(__und_invalid)
#define SPFIX(code...)
#endif
.macro svc_entry, stack_hole=0
.macro svc_entry, stack_hole=0, trace=1
UNWIND(.fnstart )
UNWIND(.save {r0 - pc} )
sub sp, sp, #(S_FRAME_SIZE + \stack_hole - 4)
@ -182,9 +182,11 @@ ENDPROC(__und_invalid)
@
stmia r7, {r2 - r6}
.if \trace
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
.endif
.endm
.align 5
@ -294,6 +296,15 @@ __pabt_svc:
UNWIND(.fnend )
ENDPROC(__pabt_svc)
.align 5
__fiq_svc:
svc_entry trace=0
mov r0, sp @ struct pt_regs *regs
bl handle_fiq_as_nmi
svc_exit_via_fiq
UNWIND(.fnend )
ENDPROC(__fiq_svc)
.align 5
.LCcralign:
.word cr_alignment
@ -304,6 +315,46 @@ ENDPROC(__pabt_svc)
.LCfp:
.word fp_enter
/*
* Abort mode handlers
*/
@
@ Taking a FIQ in abort mode is similar to taking a FIQ in SVC mode
@ and reuses the same macros. However in abort mode we must also
@ save/restore lr_abt and spsr_abt to make nested aborts safe.
@
.align 5
__fiq_abt:
svc_entry trace=0
ARM( msr cpsr_c, #ABT_MODE | PSR_I_BIT | PSR_F_BIT )
THUMB( mov r0, #ABT_MODE | PSR_I_BIT | PSR_F_BIT )
THUMB( msr cpsr_c, r0 )
mov r1, lr @ Save lr_abt
mrs r2, spsr @ Save spsr_abt, abort is now safe
ARM( msr cpsr_c, #SVC_MODE | PSR_I_BIT | PSR_F_BIT )
THUMB( mov r0, #SVC_MODE | PSR_I_BIT | PSR_F_BIT )
THUMB( msr cpsr_c, r0 )
stmfd sp!, {r1 - r2}
add r0, sp, #8 @ struct pt_regs *regs
bl handle_fiq_as_nmi
ldmfd sp!, {r1 - r2}
ARM( msr cpsr_c, #ABT_MODE | PSR_I_BIT | PSR_F_BIT )
THUMB( mov r0, #ABT_MODE | PSR_I_BIT | PSR_F_BIT )
THUMB( msr cpsr_c, r0 )
mov lr, r1 @ Restore lr_abt, abort is unsafe
msr spsr_cxsf, r2 @ Restore spsr_abt
ARM( msr cpsr_c, #SVC_MODE | PSR_I_BIT | PSR_F_BIT )
THUMB( mov r0, #SVC_MODE | PSR_I_BIT | PSR_F_BIT )
THUMB( msr cpsr_c, r0 )
svc_exit_via_fiq
UNWIND(.fnend )
ENDPROC(__fiq_abt)
/*
* User mode handlers
*
@ -314,7 +365,7 @@ ENDPROC(__pabt_svc)
#error "sizeof(struct pt_regs) must be a multiple of 8"
#endif
.macro usr_entry
.macro usr_entry, trace=1
UNWIND(.fnstart )
UNWIND(.cantunwind ) @ don't unwind the user space
sub sp, sp, #S_FRAME_SIZE
@ -351,10 +402,12 @@ ENDPROC(__pabt_svc)
@
zero_fp
.if \trace
#ifdef CONFIG_IRQSOFF_TRACER
bl trace_hardirqs_off
#endif
ct_user_exit save = 0
.endif
.endm
.macro kuser_cmpxchg_check
@ -683,6 +736,17 @@ ENTRY(ret_from_exception)
ENDPROC(__pabt_usr)
ENDPROC(ret_from_exception)
.align 5
__fiq_usr:
usr_entry trace=0
kuser_cmpxchg_check
mov r0, sp @ struct pt_regs *regs
bl handle_fiq_as_nmi
get_thread_info tsk
restore_user_regs fast = 0, offset = 0
UNWIND(.fnend )
ENDPROC(__fiq_usr)
/*
* Register switch for ARMv3 and ARMv4 processors
* r0 = previous task_struct, r1 = previous thread_info, r2 = next thread_info
@ -1118,17 +1182,29 @@ vector_addrexcptn:
b vector_addrexcptn
/*=============================================================================
* Undefined FIQs
* FIQ "NMI" handler
*-----------------------------------------------------------------------------
* Enter in FIQ mode, spsr = ANY CPSR, lr = ANY PC
* MUST PRESERVE SVC SPSR, but need to switch to SVC mode to show our msg.
* Basically to switch modes, we *HAVE* to clobber one register... brain
* damage alert! I don't think that we can execute any code in here in any
* other mode than FIQ... Ok you can switch to another mode, but you can't
* get out of that mode without clobbering one register.
* Handle a FIQ using the SVC stack allowing FIQ act like NMI on x86
* systems.
*/
vector_fiq:
subs pc, lr, #4
vector_stub fiq, FIQ_MODE, 4
.long __fiq_usr @ 0 (USR_26 / USR_32)
.long __fiq_svc @ 1 (FIQ_26 / FIQ_32)
.long __fiq_svc @ 2 (IRQ_26 / IRQ_32)
.long __fiq_svc @ 3 (SVC_26 / SVC_32)
.long __fiq_svc @ 4
.long __fiq_svc @ 5
.long __fiq_svc @ 6
.long __fiq_abt @ 7
.long __fiq_svc @ 8
.long __fiq_svc @ 9
.long __fiq_svc @ a
.long __fiq_svc @ b
.long __fiq_svc @ c
.long __fiq_svc @ d
.long __fiq_svc @ e
.long __fiq_svc @ f
.globl vector_fiq_offset
.equ vector_fiq_offset, vector_fiq

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@ -216,6 +216,34 @@
ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr
.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
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}^
.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
@ -267,6 +295,25 @@
rfeia sp!
.endm
@
@ svc_exit_via_fiq - like svc_exit but switches to FIQ mode before exit
@
@ For full details see non-Thumb implementation above.
@
.macro svc_exit_via_fiq
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
.endm
#ifdef CONFIG_CPU_V7M
/*
* Note we don't need to do clrex here as clearing the local monitor is

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@ -52,7 +52,8 @@
(unsigned)&vector_fiq_offset; \
})
static unsigned long no_fiq_insn;
static unsigned long dfl_fiq_insn;
static struct pt_regs dfl_fiq_regs;
/* Default reacquire function
* - we always relinquish FIQ control
@ -60,8 +61,15 @@ static unsigned long no_fiq_insn;
*/
static int fiq_def_op(void *ref, int relinquish)
{
if (!relinquish)
set_fiq_handler(&no_fiq_insn, sizeof(no_fiq_insn));
if (!relinquish) {
/* Restore default handler and registers */
local_fiq_disable();
set_fiq_regs(&dfl_fiq_regs);
set_fiq_handler(&dfl_fiq_insn, sizeof(dfl_fiq_insn));
local_fiq_enable();
/* FIXME: notify irq controller to standard enable FIQs */
}
return 0;
}
@ -150,6 +158,7 @@ EXPORT_SYMBOL(disable_fiq);
void __init init_FIQ(int start)
{
unsigned offset = FIQ_OFFSET;
no_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
dfl_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
get_fiq_regs(&dfl_fiq_regs);
fiq_start = start;
}

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@ -133,6 +133,7 @@ struct stack {
u32 irq[3];
u32 abt[3];
u32 und[3];
u32 fiq[3];
} ____cacheline_aligned;
#ifndef CONFIG_CPU_V7M
@ -470,7 +471,10 @@ void notrace cpu_init(void)
"msr cpsr_c, %5\n\t"
"add r14, %0, %6\n\t"
"mov sp, r14\n\t"
"msr cpsr_c, %7"
"msr cpsr_c, %7\n\t"
"add r14, %0, %8\n\t"
"mov sp, r14\n\t"
"msr cpsr_c, %9"
:
: "r" (stk),
PLC (PSR_F_BIT | PSR_I_BIT | IRQ_MODE),
@ -479,6 +483,8 @@ void notrace cpu_init(void)
"I" (offsetof(struct stack, abt[0])),
PLC (PSR_F_BIT | PSR_I_BIT | UND_MODE),
"I" (offsetof(struct stack, und[0])),
PLC (PSR_F_BIT | PSR_I_BIT | FIQ_MODE),
"I" (offsetof(struct stack, fiq[0])),
PLC (PSR_F_BIT | PSR_I_BIT | SVC_MODE)
: "r14");
#endif

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@ -25,6 +25,7 @@
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/irq.h>
#include <linux/atomic.h>
#include <asm/cacheflush.h>
@ -466,6 +467,31 @@ asmlinkage void do_unexp_fiq (struct pt_regs *regs)
printk("You may have a hardware problem...\n");
}
/*
* Handle FIQ similarly to NMI on x86 systems.
*
* The runtime environment for NMIs is extremely restrictive
* (NMIs can pre-empt critical sections meaning almost all locking is
* forbidden) meaning this default FIQ handling must only be used in
* circumstances where non-maskability improves robustness, such as
* watchdog or debug logic.
*
* This handler is not appropriate for general purpose use in drivers
* platform code and can be overrideen using set_fiq_handler.
*/
asmlinkage void __exception_irq_entry handle_fiq_as_nmi(struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
nmi_enter();
/* nop. FIQ handlers for special arch/arm features can be added here. */
nmi_exit();
set_irq_regs(old_regs);
}
/*
* bad_mode handles the impossible case in the vectors. If you see one of
* these, then it's extremely serious, and could mean you have buggy hardware.