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linux_dsm_epyc7002/arch/arm/vfp/vfphw.S
Dave Martin 7eb25ebee8 ARM: 6498/1: vfp: Correct data alignment for CONFIG_THUMB2_KERNEL 
Directives such as .long and .word do not magically cause the
assembler location counter to become aligned in gas.  As a result,
using these directives in code sections can result in misaligned
data words when building a Thumb-2 kernel (CONFIG_THUMB2_KERNEL).

This is a Bad Thing, since the ABI permits the compiler to assume
that fundamental types of word size or above are word- aligned when
accessing them from C.  If the data is not really word-aligned,
this can cause impaired performance and stray alignment faults in
some circumstances.

In general, the following rules should be applied when using data
word declaration directives inside code sections:

    * .quad and .double:
         .align 3

    * .long, .word, .single, .float:
         .align (or .align 2)

    * .short:
        No explicit alignment required, since Thumb-2
        instructions are always 2 or 4 bytes in size.
        immediately after an instruction.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-11-30 13:44:23 +00:00

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/*
* linux/arch/arm/vfp/vfphw.S
*
* Copyright (C) 2004 ARM Limited.
* Written by Deep Blue Solutions Limited.
*
* 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 code is called from the kernel's undefined instruction trap.
* r9 holds the return address for successful handling.
* lr holds the return address for unrecognised instructions.
* r10 points at the start of the private FP workspace in the thread structure
* sp points to a struct pt_regs (as defined in include/asm/proc/ptrace.h)
*/
#include <asm/thread_info.h>
#include <asm/vfpmacros.h>
#include "../kernel/entry-header.S"
.macro DBGSTR, str
#ifdef DEBUG
stmfd sp!, {r0-r3, ip, lr}
add r0, pc, #4
bl printk
b 1f
.asciz "<7>VFP: \str\n"
.balign 4
1: ldmfd sp!, {r0-r3, ip, lr}
#endif
.endm
.macro DBGSTR1, str, arg
#ifdef DEBUG
stmfd sp!, {r0-r3, ip, lr}
mov r1, \arg
add r0, pc, #4
bl printk
b 1f
.asciz "<7>VFP: \str\n"
.balign 4
1: ldmfd sp!, {r0-r3, ip, lr}
#endif
.endm
.macro DBGSTR3, str, arg1, arg2, arg3
#ifdef DEBUG
stmfd sp!, {r0-r3, ip, lr}
mov r3, \arg3
mov r2, \arg2
mov r1, \arg1
add r0, pc, #4
bl printk
b 1f
.asciz "<7>VFP: \str\n"
.balign 4
1: ldmfd sp!, {r0-r3, ip, lr}
#endif
.endm
@ VFP hardware support entry point.
@
@ r0 = faulted instruction
@ r2 = faulted PC+4
@ r9 = successful return
@ r10 = vfp_state union
@ r11 = CPU number
@ lr = failure return
ENTRY(vfp_support_entry)
DBGSTR3 "instr %08x pc %08x state %p", r0, r2, r10
VFPFMRX r1, FPEXC @ Is the VFP enabled?
DBGSTR1 "fpexc %08x", r1
tst r1, #FPEXC_EN
bne look_for_VFP_exceptions @ VFP is already enabled
DBGSTR1 "enable %x", r10
ldr r3, last_VFP_context_address
orr r1, r1, #FPEXC_EN @ user FPEXC has the enable bit set
ldr r4, [r3, r11, lsl #2] @ last_VFP_context pointer
bic r5, r1, #FPEXC_EX @ make sure exceptions are disabled
cmp r4, r10
beq check_for_exception @ we are returning to the same
@ process, so the registers are
@ still there. In this case, we do
@ not want to drop a pending exception.
VFPFMXR FPEXC, r5 @ enable VFP, disable any pending
@ exceptions, so we can get at the
@ rest of it
#ifndef CONFIG_SMP
@ Save out the current registers to the old thread state
@ No need for SMP since this is not done lazily
DBGSTR1 "save old state %p", r4
cmp r4, #0
beq no_old_VFP_process
VFPFSTMIA r4, r5 @ save the working registers
VFPFMRX r5, FPSCR @ current status
#ifndef CONFIG_CPU_FEROCEON
tst r1, #FPEXC_EX @ is there additional state to save?
beq 1f
VFPFMRX r6, FPINST @ FPINST (only if FPEXC.EX is set)
tst r1, #FPEXC_FP2V @ is there an FPINST2 to read?
beq 1f
VFPFMRX r8, FPINST2 @ FPINST2 if needed (and present)
1:
#endif
stmia r4, {r1, r5, r6, r8} @ save FPEXC, FPSCR, FPINST, FPINST2
@ and point r4 at the word at the
@ start of the register dump
#endif
no_old_VFP_process:
DBGSTR1 "load state %p", r10
str r10, [r3, r11, lsl #2] @ update the last_VFP_context pointer
@ Load the saved state back into the VFP
VFPFLDMIA r10, r5 @ reload the working registers while
@ FPEXC is in a safe state
ldmia r10, {r1, r5, r6, r8} @ load FPEXC, FPSCR, FPINST, FPINST2
#ifndef CONFIG_CPU_FEROCEON
tst r1, #FPEXC_EX @ is there additional state to restore?
beq 1f
VFPFMXR FPINST, r6 @ restore FPINST (only if FPEXC.EX is set)
tst r1, #FPEXC_FP2V @ is there an FPINST2 to write?
beq 1f
VFPFMXR FPINST2, r8 @ FPINST2 if needed (and present)
1:
#endif
VFPFMXR FPSCR, r5 @ restore status
check_for_exception:
tst r1, #FPEXC_EX
bne process_exception @ might as well handle the pending
@ exception before retrying branch
@ out before setting an FPEXC that
@ stops us reading stuff
VFPFMXR FPEXC, r1 @ restore FPEXC last
sub r2, r2, #4
str r2, [sp, #S_PC] @ retry the instruction
#ifdef CONFIG_PREEMPT
get_thread_info r10
ldr r4, [r10, #TI_PREEMPT] @ get preempt count
sub r11, r4, #1 @ decrement it
str r11, [r10, #TI_PREEMPT]
#endif
mov pc, r9 @ we think we have handled things
look_for_VFP_exceptions:
@ Check for synchronous or asynchronous exception
tst r1, #FPEXC_EX | FPEXC_DEX
bne process_exception
@ On some implementations of the VFP subarch 1, setting FPSCR.IXE
@ causes all the CDP instructions to be bounced synchronously without
@ setting the FPEXC.EX bit
VFPFMRX r5, FPSCR
tst r5, #FPSCR_IXE
bne process_exception
@ Fall into hand on to next handler - appropriate coproc instr
@ not recognised by VFP
DBGSTR "not VFP"
#ifdef CONFIG_PREEMPT
get_thread_info r10
ldr r4, [r10, #TI_PREEMPT] @ get preempt count
sub r11, r4, #1 @ decrement it
str r11, [r10, #TI_PREEMPT]
#endif
mov pc, lr
process_exception:
DBGSTR "bounce"
mov r2, sp @ nothing stacked - regdump is at TOS
mov lr, r9 @ setup for a return to the user code.
@ Now call the C code to package up the bounce to the support code
@ r0 holds the trigger instruction
@ r1 holds the FPEXC value
@ r2 pointer to register dump
b VFP_bounce @ we have handled this - the support
@ code will raise an exception if
@ required. If not, the user code will
@ retry the faulted instruction
ENDPROC(vfp_support_entry)
ENTRY(vfp_save_state)
@ Save the current VFP state
@ r0 - save location
@ r1 - FPEXC
DBGSTR1 "save VFP state %p", r0
VFPFSTMIA r0, r2 @ save the working registers
VFPFMRX r2, FPSCR @ current status
tst r1, #FPEXC_EX @ is there additional state to save?
beq 1f
VFPFMRX r3, FPINST @ FPINST (only if FPEXC.EX is set)
tst r1, #FPEXC_FP2V @ is there an FPINST2 to read?
beq 1f
VFPFMRX r12, FPINST2 @ FPINST2 if needed (and present)
1:
stmia r0, {r1, r2, r3, r12} @ save FPEXC, FPSCR, FPINST, FPINST2
mov pc, lr
ENDPROC(vfp_save_state)
.align
last_VFP_context_address:
.word last_VFP_context
.macro tbl_branch, base, tmp, shift
#ifdef CONFIG_THUMB2_KERNEL
adr \tmp, 1f
add \tmp, \tmp, \base, lsl \shift
mov pc, \tmp
#else
add pc, pc, \base, lsl \shift
mov r0, r0
#endif
1:
.endm
ENTRY(vfp_get_float)
tbl_branch r0, r3, #3
.irp dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
1: mrc p10, 0, r0, c\dr, c0, 0 @ fmrs r0, s0
mov pc, lr
.org 1b + 8
1: mrc p10, 0, r0, c\dr, c0, 4 @ fmrs r0, s1
mov pc, lr
.org 1b + 8
.endr
ENDPROC(vfp_get_float)
ENTRY(vfp_put_float)
tbl_branch r1, r3, #3
.irp dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
1: mcr p10, 0, r0, c\dr, c0, 0 @ fmsr r0, s0
mov pc, lr
.org 1b + 8
1: mcr p10, 0, r0, c\dr, c0, 4 @ fmsr r0, s1
mov pc, lr
.org 1b + 8
.endr
ENDPROC(vfp_put_float)
ENTRY(vfp_get_double)
tbl_branch r0, r3, #3
.irp dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
1: fmrrd r0, r1, d\dr
mov pc, lr
.org 1b + 8
.endr
#ifdef CONFIG_VFPv3
@ d16 - d31 registers
.irp dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
1: mrrc p11, 3, r0, r1, c\dr @ fmrrd r0, r1, d\dr
mov pc, lr
.org 1b + 8
.endr
#endif
@ virtual register 16 (or 32 if VFPv3) for compare with zero
mov r0, #0
mov r1, #0
mov pc, lr
ENDPROC(vfp_get_double)
ENTRY(vfp_put_double)
tbl_branch r2, r3, #3
.irp dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
1: fmdrr d\dr, r0, r1
mov pc, lr
.org 1b + 8
.endr
#ifdef CONFIG_VFPv3
@ d16 - d31 registers
.irp dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
1: mcrr p11, 3, r0, r1, c\dr @ fmdrr r0, r1, d\dr
mov pc, lr
.org 1b + 8
.endr
#endif
ENDPROC(vfp_put_double)
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