ARM: vfp: Use undef hook for handling VFP exceptions

Now that the VFP support code has been reimplemented as a C function
that takes a struct pt_regs pointer and an opcode, we can use the
existing undef_hook framework to deal with undef exceptions triggered by
VFP instructions instead of having special handling in assembler.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Ard Biesheuvel 2023-03-19 00:28:35 +01:00
parent 6ee1e6772e
commit cdd87465ad
4 changed files with 54 additions and 141 deletions

View file

@ -557,13 +557,6 @@ ENDPROC(__und_usr)
* co-processor instructions. However, we have to watch out
* for the ARM6/ARM7 SWI bug.
*
* NEON is a special case that has to be handled here. Not all
* NEON instructions are co-processor instructions, so we have
* to make a special case of checking for them. Plus, there's
* five groups of them, so we have a table of mask/opcode pairs
* to check against, and if any match then we branch off into the
* NEON handler code.
*
* Emulators may wish to make use of the following registers:
* r0 = instruction opcode (32-bit ARM or two 16-bit Thumb)
* r2 = PC value to resume execution after successful emulation
@ -575,25 +568,8 @@ ENDPROC(__und_usr)
@
@ Fall-through from Thumb-2 __und_usr
@
#ifdef CONFIG_NEON
get_thread_info r10 @ get current thread
adr r6, .LCneon_thumb_opcodes
b 2f
#endif
call_fpe:
get_thread_info r10 @ get current thread
#ifdef CONFIG_NEON
adr r6, .LCneon_arm_opcodes
2: ldr r5, [r6], #4 @ mask value
ldr r7, [r6], #4 @ opcode bits matching in mask
cmp r5, #0 @ end mask?
beq 1f
and r8, r0, r5
cmp r8, r7 @ NEON instruction?
bne 2b
b do_vfp @ let VFP handler handle this
1:
#endif
tst r0, #0x08000000 @ only CDP/CPRT/LDC/STC have bit 27
tstne r0, #0x04000000 @ bit 26 set on both ARM and Thumb-2
reteq lr
@ -620,42 +596,13 @@ call_fpe:
ret.w lr @ CP#7
ret.w lr @ CP#8
ret.w lr @ CP#9
#ifdef CONFIG_VFP
W(b) do_vfp @ CP#10 (VFP)
W(b) do_vfp @ CP#11 (VFP)
#else
ret.w lr @ CP#10 (VFP)
ret.w lr @ CP#11 (VFP)
#endif
ret.w lr @ CP#12
ret.w lr @ CP#13
ret.w lr @ CP#14 (Debug)
ret.w lr @ CP#15 (Control)
#ifdef CONFIG_NEON
.align 6
.LCneon_arm_opcodes:
.word 0xfe000000 @ mask
.word 0xf2000000 @ opcode
.word 0xff100000 @ mask
.word 0xf4000000 @ opcode
.word 0x00000000 @ mask
.word 0x00000000 @ opcode
.LCneon_thumb_opcodes:
.word 0xef000000 @ mask
.word 0xef000000 @ opcode
.word 0xff100000 @ mask
.word 0xf9000000 @ opcode
.word 0x00000000 @ mask
.word 0x00000000 @ opcode
#endif
do_fpe:
add r10, r10, #TI_FPSTATE @ r10 = workspace
ldr_va pc, fp_enter, tmp=r4 @ Call FP module USR entry point

View file

@ -8,4 +8,4 @@
# ccflags-y := -DDEBUG
# asflags-y := -DDEBUG
obj-y += vfpmodule.o entry.o vfphw.o vfpsingle.o vfpdouble.o
obj-y += vfpmodule.o vfphw.o vfpsingle.o vfpdouble.o

View file

@ -1,31 +0,0 @@
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* linux/arch/arm/vfp/entry.S
*
* Copyright (C) 2004 ARM Limited.
* Written by Deep Blue Solutions Limited.
*/
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/thread_info.h>
#include <asm/vfpmacros.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
@ VFP entry point.
@
@ r0 = instruction opcode (32-bit ARM or two 16-bit Thumb)
@ r2 = PC value to resume execution after successful emulation
@ r9 = normal "successful" return address
@ r10 = this threads thread_info structure
@ lr = unrecognised instruction return address
@ IRQs enabled.
@
ENTRY(do_vfp)
mov r1, r0 @ pass trigger opcode via R1
mov r0, sp @ pass struct pt_regs via R0
bl vfp_support_entry @ dispatch the VFP exception
cmp r0, #0 @ handled successfully?
reteq r9 @ then use R9 as return address
ret lr @ pass to undef handler
ENDPROC(do_vfp)

View file

@ -641,15 +641,37 @@ static int vfp_starting_cpu(unsigned int unused)
return 0;
}
static int vfp_kmode_exception(struct pt_regs *regs, unsigned int instr)
{
/*
* If we reach this point, a floating point exception has been raised
* while running in kernel mode. If the NEON/VFP unit was enabled at the
* time, it means a VFP instruction has been issued that requires
* software assistance to complete, something which is not currently
* supported in kernel mode.
* If the NEON/VFP unit was disabled, and the location pointed to below
* is properly preceded by a call to kernel_neon_begin(), something has
* caused the task to be scheduled out and back in again. In this case,
* rebuilding and running with CONFIG_DEBUG_ATOMIC_SLEEP enabled should
* be helpful in localizing the problem.
*/
if (fmrx(FPEXC) & FPEXC_EN)
pr_crit("BUG: unsupported FP instruction in kernel mode\n");
else
pr_crit("BUG: FP instruction issued in kernel mode with FP unit disabled\n");
pr_crit("FPEXC == 0x%08x\n", fmrx(FPEXC));
return 1;
}
/*
* vfp_support_entry - Handle VFP exception from user mode
* vfp_support_entry - Handle VFP exception
*
* @regs: pt_regs structure holding the register state at exception entry
* @trigger: The opcode of the instruction that triggered the exception
*
* Returns 0 if the exception was handled, or an error code otherwise.
*/
asmlinkage int vfp_support_entry(struct pt_regs *regs, u32 trigger)
static int vfp_support_entry(struct pt_regs *regs, u32 trigger)
{
struct thread_info *ti = current_thread_info();
u32 fpexc;
@ -657,6 +679,9 @@ asmlinkage int vfp_support_entry(struct pt_regs *regs, u32 trigger)
if (unlikely(!have_vfp))
return -ENODEV;
if (!user_mode(regs))
return vfp_kmode_exception(regs, trigger);
local_bh_disable();
fpexc = fmrx(FPEXC);
@ -722,7 +747,6 @@ asmlinkage int vfp_support_entry(struct pt_regs *regs, u32 trigger)
* replay the instruction that trapped.
*/
fmxr(FPEXC, fpexc);
regs->ARM_pc -= 4;
} else {
/* Check for synchronous or asynchronous exceptions */
if (!(fpexc & (FPEXC_EX | FPEXC_DEX))) {
@ -743,78 +767,47 @@ asmlinkage int vfp_support_entry(struct pt_regs *regs, u32 trigger)
fpexc |= FPEXC_DEX;
}
}
bounce: VFP_bounce(trigger, fpexc, regs);
bounce: regs->ARM_pc += 4;
VFP_bounce(trigger, fpexc, regs);
}
local_bh_enable();
return 0;
}
#ifdef CONFIG_KERNEL_MODE_NEON
static int vfp_kmode_exception(struct pt_regs *regs, unsigned int instr)
{
/*
* If we reach this point, a floating point exception has been raised
* while running in kernel mode. If the NEON/VFP unit was enabled at the
* time, it means a VFP instruction has been issued that requires
* software assistance to complete, something which is not currently
* supported in kernel mode.
* If the NEON/VFP unit was disabled, and the location pointed to below
* is properly preceded by a call to kernel_neon_begin(), something has
* caused the task to be scheduled out and back in again. In this case,
* rebuilding and running with CONFIG_DEBUG_ATOMIC_SLEEP enabled should
* be helpful in localizing the problem.
*/
if (fmrx(FPEXC) & FPEXC_EN)
pr_crit("BUG: unsupported FP instruction in kernel mode\n");
else
pr_crit("BUG: FP instruction issued in kernel mode with FP unit disabled\n");
pr_crit("FPEXC == 0x%08x\n", fmrx(FPEXC));
return 1;
}
static struct undef_hook vfp_kmode_exception_hook[] = {{
static struct undef_hook neon_support_hook[] = {{
.instr_mask = 0xfe000000,
.instr_val = 0xf2000000,
.cpsr_mask = MODE_MASK | PSR_T_BIT,
.cpsr_val = SVC_MODE,
.fn = vfp_kmode_exception,
.cpsr_mask = PSR_T_BIT,
.cpsr_val = 0,
.fn = vfp_support_entry,
}, {
.instr_mask = 0xff100000,
.instr_val = 0xf4000000,
.cpsr_mask = MODE_MASK | PSR_T_BIT,
.cpsr_val = SVC_MODE,
.fn = vfp_kmode_exception,
.cpsr_mask = PSR_T_BIT,
.cpsr_val = 0,
.fn = vfp_support_entry,
}, {
.instr_mask = 0xef000000,
.instr_val = 0xef000000,
.cpsr_mask = MODE_MASK | PSR_T_BIT,
.cpsr_val = SVC_MODE | PSR_T_BIT,
.fn = vfp_kmode_exception,
.cpsr_mask = PSR_T_BIT,
.cpsr_val = PSR_T_BIT,
.fn = vfp_support_entry,
}, {
.instr_mask = 0xff100000,
.instr_val = 0xf9000000,
.cpsr_mask = MODE_MASK | PSR_T_BIT,
.cpsr_val = SVC_MODE | PSR_T_BIT,
.fn = vfp_kmode_exception,
}, {
.instr_mask = 0x0c000e00,
.instr_val = 0x0c000a00,
.cpsr_mask = MODE_MASK,
.cpsr_val = SVC_MODE,
.fn = vfp_kmode_exception,
.cpsr_mask = PSR_T_BIT,
.cpsr_val = PSR_T_BIT,
.fn = vfp_support_entry,
}};
static int __init vfp_kmode_exception_hook_init(void)
{
int i;
static struct undef_hook vfp_support_hook = {
.instr_mask = 0x0c000e00,
.instr_val = 0x0c000a00,
.fn = vfp_support_entry,
};
for (i = 0; i < ARRAY_SIZE(vfp_kmode_exception_hook); i++)
register_undef_hook(&vfp_kmode_exception_hook[i]);
return 0;
}
subsys_initcall(vfp_kmode_exception_hook_init);
#ifdef CONFIG_KERNEL_MODE_NEON
/*
* Kernel-side NEON support functions
@ -919,8 +912,11 @@ static int __init vfp_init(void)
* for NEON if the hardware has the MVFR registers.
*/
if (IS_ENABLED(CONFIG_NEON) &&
(fmrx(MVFR1) & 0x000fff00) == 0x00011100)
(fmrx(MVFR1) & 0x000fff00) == 0x00011100) {
elf_hwcap |= HWCAP_NEON;
for (int i = 0; i < ARRAY_SIZE(neon_support_hook); i++)
register_undef_hook(&neon_support_hook[i]);
}
if (IS_ENABLED(CONFIG_VFPv3)) {
u32 mvfr0 = fmrx(MVFR0);
@ -989,6 +985,7 @@ static int __init vfp_init(void)
have_vfp = true;
register_undef_hook(&vfp_support_hook);
thread_register_notifier(&vfp_notifier_block);
vfp_pm_init();