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linux/arch/arm/mm/alignment.c
Ard Biesheuvel e5c46fde75 ARM: 9214/1: alignment: advance IT state after emulating Thumb instruction 
After emulating a misaligned load or store issued in Thumb mode, we have
to advance the IT state by hand, or it will get out of sync with the
actual instruction stream, which means we'll end up applying the wrong
condition code to subsequent instructions. This might corrupt the
program state rather catastrophically.

So borrow the it_advance() helper from the probing code, and use it on
CPSR if the emulated instruction is Thumb.

Cc: <stable@vger.kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
2022-07-06 22:44:49 +01:00

1053 lines
27 KiB
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// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/arch/arm/mm/alignment.c
*
* Copyright (C) 1995 Linus Torvalds
* Modifications for ARM processor (c) 1995-2001 Russell King
* Thumb alignment fault fixups (c) 2004 MontaVista Software, Inc.
* - Adapted from gdb/sim/arm/thumbemu.c -- Thumb instruction emulation.
* Copyright (C) 1996, Cygnus Software Technologies Ltd.
*/
#include <linux/moduleparam.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/sched/debug.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <asm/cp15.h>
#include <asm/system_info.h>
#include <asm/unaligned.h>
#include <asm/opcodes.h>
#include "fault.h"
#include "mm.h"
/*
* 32-bit misaligned trap handler (c) 1998 San Mehat (CCC) -July 1998
* /proc/sys/debug/alignment, modified and integrated into
* Linux 2.1 by Russell King
*
* Speed optimisations and better fault handling by Russell King.
*
* *** NOTE ***
* This code is not portable to processors with late data abort handling.
*/
#define CODING_BITS(i) (i & 0x0e000000)
#define COND_BITS(i) (i & 0xf0000000)
#define LDST_I_BIT(i) (i & (1 << 26)) /* Immediate constant */
#define LDST_P_BIT(i) (i & (1 << 24)) /* Preindex */
#define LDST_U_BIT(i) (i & (1 << 23)) /* Add offset */
#define LDST_W_BIT(i) (i & (1 << 21)) /* Writeback */
#define LDST_L_BIT(i) (i & (1 << 20)) /* Load */
#define LDST_P_EQ_U(i) ((((i) ^ ((i) >> 1)) & (1 << 23)) == 0)
#define LDSTHD_I_BIT(i) (i & (1 << 22)) /* double/half-word immed */
#define LDM_S_BIT(i) (i & (1 << 22)) /* write CPSR from SPSR */
#define RN_BITS(i) ((i >> 16) & 15) /* Rn */
#define RD_BITS(i) ((i >> 12) & 15) /* Rd */
#define RM_BITS(i) (i & 15) /* Rm */
#define REGMASK_BITS(i) (i & 0xffff)
#define OFFSET_BITS(i) (i & 0x0fff)
#define IS_SHIFT(i) (i & 0x0ff0)
#define SHIFT_BITS(i) ((i >> 7) & 0x1f)
#define SHIFT_TYPE(i) (i & 0x60)
#define SHIFT_LSL 0x00
#define SHIFT_LSR 0x20
#define SHIFT_ASR 0x40
#define SHIFT_RORRRX 0x60
#define BAD_INSTR 0xdeadc0de
/* Thumb-2 32 bit format per ARMv7 DDI0406A A6.3, either f800h,e800h,f800h */
#define IS_T32(hi16) \
(((hi16) & 0xe000) == 0xe000 && ((hi16) & 0x1800))
static unsigned long ai_user;
static unsigned long ai_sys;
static void *ai_sys_last_pc;
static unsigned long ai_skipped;
static unsigned long ai_half;
static unsigned long ai_word;
static unsigned long ai_dword;
static unsigned long ai_multi;
static int ai_usermode;
static unsigned long cr_no_alignment;
core_param(alignment, ai_usermode, int, 0600);
#define UM_WARN (1 << 0)
#define UM_FIXUP (1 << 1)
#define UM_SIGNAL (1 << 2)
/* Return true if and only if the ARMv6 unaligned access model is in use. */
static bool cpu_is_v6_unaligned(void)
{
return cpu_architecture() >= CPU_ARCH_ARMv6 && get_cr() & CR_U;
}
static int safe_usermode(int new_usermode, bool warn)
{
/*
* ARMv6 and later CPUs can perform unaligned accesses for
* most single load and store instructions up to word size.
* LDM, STM, LDRD and STRD still need to be handled.
*
* Ignoring the alignment fault is not an option on these
* CPUs since we spin re-faulting the instruction without
* making any progress.
*/
if (cpu_is_v6_unaligned() && !(new_usermode & (UM_FIXUP | UM_SIGNAL))) {
new_usermode |= UM_FIXUP;
if (warn)
pr_warn("alignment: ignoring faults is unsafe on this CPU. Defaulting to fixup mode.\n");
}
return new_usermode;
}
#ifdef CONFIG_PROC_FS
static const char *usermode_action[] = {
"ignored",
"warn",
"fixup",
"fixup+warn",
"signal",
"signal+warn"
};
static int alignment_proc_show(struct seq_file *m, void *v)
{
seq_printf(m, "User:\t\t%lu\n", ai_user);
seq_printf(m, "System:\t\t%lu (%pS)\n", ai_sys, ai_sys_last_pc);
seq_printf(m, "Skipped:\t%lu\n", ai_skipped);
seq_printf(m, "Half:\t\t%lu\n", ai_half);
seq_printf(m, "Word:\t\t%lu\n", ai_word);
if (cpu_architecture() >= CPU_ARCH_ARMv5TE)
seq_printf(m, "DWord:\t\t%lu\n", ai_dword);
seq_printf(m, "Multi:\t\t%lu\n", ai_multi);
seq_printf(m, "User faults:\t%i (%s)\n", ai_usermode,
usermode_action[ai_usermode]);
return 0;
}
static int alignment_proc_open(struct inode *inode, struct file *file)
{
return single_open(file, alignment_proc_show, NULL);
}
static ssize_t alignment_proc_write(struct file *file, const char __user *buffer,
size_t count, loff_t *pos)
{
char mode;
if (count > 0) {
if (get_user(mode, buffer))
return -EFAULT;
if (mode >= '0' && mode <= '5')
ai_usermode = safe_usermode(mode - '0', true);
}
return count;
}
static const struct proc_ops alignment_proc_ops = {
.proc_open = alignment_proc_open,
.proc_read = seq_read,
.proc_lseek = seq_lseek,
.proc_release = single_release,
.proc_write = alignment_proc_write,
};
#endif /* CONFIG_PROC_FS */
union offset_union {
unsigned long un;
signed long sn;
};
#define TYPE_ERROR 0
#define TYPE_FAULT 1
#define TYPE_LDST 2
#define TYPE_DONE 3
#ifdef __ARMEB__
#define BE 1
#define FIRST_BYTE_16 "mov %1, %1, ror #8\n"
#define FIRST_BYTE_32 "mov %1, %1, ror #24\n"
#define NEXT_BYTE "ror #24"
#else
#define BE 0
#define FIRST_BYTE_16
#define FIRST_BYTE_32
#define NEXT_BYTE "lsr #8"
#endif
#define __get8_unaligned_check(ins,val,addr,err) \
__asm__( \
ARM( "1: "ins" %1, [%2], #1\n" ) \
THUMB( "1: "ins" %1, [%2]\n" ) \
THUMB( " add %2, %2, #1\n" ) \
"2:\n" \
" .pushsection .text.fixup,\"ax\"\n" \
" .align 2\n" \
"3: mov %0, #1\n" \
" b 2b\n" \
" .popsection\n" \
" .pushsection __ex_table,\"a\"\n" \
" .align 3\n" \
" .long 1b, 3b\n" \
" .popsection\n" \
: "=r" (err), "=&r" (val), "=r" (addr) \
: "0" (err), "2" (addr))
#define __get16_unaligned_check(ins,val,addr) \
do { \
unsigned int err = 0, v, a = addr; \
__get8_unaligned_check(ins,v,a,err); \
val = v << ((BE) ? 8 : 0); \
__get8_unaligned_check(ins,v,a,err); \
val |= v << ((BE) ? 0 : 8); \
if (err) \
goto fault; \
} while (0)
#define get16_unaligned_check(val,addr) \
__get16_unaligned_check("ldrb",val,addr)
#define get16t_unaligned_check(val,addr) \
__get16_unaligned_check("ldrbt",val,addr)
#define __get32_unaligned_check(ins,val,addr) \
do { \
unsigned int err = 0, v, a = addr; \
__get8_unaligned_check(ins,v,a,err); \
val = v << ((BE) ? 24 : 0); \
__get8_unaligned_check(ins,v,a,err); \
val |= v << ((BE) ? 16 : 8); \
__get8_unaligned_check(ins,v,a,err); \
val |= v << ((BE) ? 8 : 16); \
__get8_unaligned_check(ins,v,a,err); \
val |= v << ((BE) ? 0 : 24); \
if (err) \
goto fault; \
} while (0)
#define get32_unaligned_check(val,addr) \
__get32_unaligned_check("ldrb",val,addr)
#define get32t_unaligned_check(val,addr) \
__get32_unaligned_check("ldrbt",val,addr)
#define __put16_unaligned_check(ins,val,addr) \
do { \
unsigned int err = 0, v = val, a = addr; \
__asm__( FIRST_BYTE_16 \
ARM( "1: "ins" %1, [%2], #1\n" ) \
THUMB( "1: "ins" %1, [%2]\n" ) \
THUMB( " add %2, %2, #1\n" ) \
" mov %1, %1, "NEXT_BYTE"\n" \
"2: "ins" %1, [%2]\n" \
"3:\n" \
" .pushsection .text.fixup,\"ax\"\n" \
" .align 2\n" \
"4: mov %0, #1\n" \
" b 3b\n" \
" .popsection\n" \
" .pushsection __ex_table,\"a\"\n" \
" .align 3\n" \
" .long 1b, 4b\n" \
" .long 2b, 4b\n" \
" .popsection\n" \
: "=r" (err), "=&r" (v), "=&r" (a) \
: "0" (err), "1" (v), "2" (a)); \
if (err) \
goto fault; \
} while (0)
#define put16_unaligned_check(val,addr) \
__put16_unaligned_check("strb",val,addr)
#define put16t_unaligned_check(val,addr) \
__put16_unaligned_check("strbt",val,addr)
#define __put32_unaligned_check(ins,val,addr) \
do { \
unsigned int err = 0, v = val, a = addr; \
__asm__( FIRST_BYTE_32 \
ARM( "1: "ins" %1, [%2], #1\n" ) \
THUMB( "1: "ins" %1, [%2]\n" ) \
THUMB( " add %2, %2, #1\n" ) \
" mov %1, %1, "NEXT_BYTE"\n" \
ARM( "2: "ins" %1, [%2], #1\n" ) \
THUMB( "2: "ins" %1, [%2]\n" ) \
THUMB( " add %2, %2, #1\n" ) \
" mov %1, %1, "NEXT_BYTE"\n" \
ARM( "3: "ins" %1, [%2], #1\n" ) \
THUMB( "3: "ins" %1, [%2]\n" ) \
THUMB( " add %2, %2, #1\n" ) \
" mov %1, %1, "NEXT_BYTE"\n" \
"4: "ins" %1, [%2]\n" \
"5:\n" \
" .pushsection .text.fixup,\"ax\"\n" \
" .align 2\n" \
"6: mov %0, #1\n" \
" b 5b\n" \
" .popsection\n" \
" .pushsection __ex_table,\"a\"\n" \
" .align 3\n" \
" .long 1b, 6b\n" \
" .long 2b, 6b\n" \
" .long 3b, 6b\n" \
" .long 4b, 6b\n" \
" .popsection\n" \
: "=r" (err), "=&r" (v), "=&r" (a) \
: "0" (err), "1" (v), "2" (a)); \
if (err) \
goto fault; \
} while (0)
#define put32_unaligned_check(val,addr) \
__put32_unaligned_check("strb", val, addr)
#define put32t_unaligned_check(val,addr) \
__put32_unaligned_check("strbt", val, addr)
static void
do_alignment_finish_ldst(unsigned long addr, u32 instr, struct pt_regs *regs, union offset_union offset)
{
if (!LDST_U_BIT(instr))
offset.un = -offset.un;
if (!LDST_P_BIT(instr))
addr += offset.un;
if (!LDST_P_BIT(instr) || LDST_W_BIT(instr))
regs->uregs[RN_BITS(instr)] = addr;
}
static int
do_alignment_ldrhstrh(unsigned long addr, u32 instr, struct pt_regs *regs)
{
unsigned int rd = RD_BITS(instr);
ai_half += 1;
if (user_mode(regs))
goto user;
if (LDST_L_BIT(instr)) {
unsigned long val;
get16_unaligned_check(val, addr);
/* signed half-word? */
if (instr & 0x40)
val = (signed long)((signed short) val);
regs->uregs[rd] = val;
} else
put16_unaligned_check(regs->uregs[rd], addr);
return TYPE_LDST;
user:
if (LDST_L_BIT(instr)) {
unsigned long val;
unsigned int __ua_flags = uaccess_save_and_enable();
get16t_unaligned_check(val, addr);
uaccess_restore(__ua_flags);
/* signed half-word? */
if (instr & 0x40)
val = (signed long)((signed short) val);
regs->uregs[rd] = val;
} else {
unsigned int __ua_flags = uaccess_save_and_enable();
put16t_unaligned_check(regs->uregs[rd], addr);
uaccess_restore(__ua_flags);
}
return TYPE_LDST;
fault:
return TYPE_FAULT;
}
static int
do_alignment_ldrdstrd(unsigned long addr, u32 instr, struct pt_regs *regs)
{
unsigned int rd = RD_BITS(instr);
unsigned int rd2;
int load;
if ((instr & 0xfe000000) == 0xe8000000) {
/* ARMv7 Thumb-2 32-bit LDRD/STRD */
rd2 = (instr >> 8) & 0xf;
load = !!(LDST_L_BIT(instr));
} else if (((rd & 1) == 1) || (rd == 14))
goto bad;
else {
load = ((instr & 0xf0) == 0xd0);
rd2 = rd + 1;
}
ai_dword += 1;
if (user_mode(regs))
goto user;
if (load) {
unsigned long val;
get32_unaligned_check(val, addr);
regs->uregs[rd] = val;
get32_unaligned_check(val, addr + 4);
regs->uregs[rd2] = val;
} else {
put32_unaligned_check(regs->uregs[rd], addr);
put32_unaligned_check(regs->uregs[rd2], addr + 4);
}
return TYPE_LDST;
user:
if (load) {
unsigned long val, val2;
unsigned int __ua_flags = uaccess_save_and_enable();
get32t_unaligned_check(val, addr);
get32t_unaligned_check(val2, addr + 4);
uaccess_restore(__ua_flags);
regs->uregs[rd] = val;
regs->uregs[rd2] = val2;
} else {
unsigned int __ua_flags = uaccess_save_and_enable();
put32t_unaligned_check(regs->uregs[rd], addr);
put32t_unaligned_check(regs->uregs[rd2], addr + 4);
uaccess_restore(__ua_flags);
}
return TYPE_LDST;
bad:
return TYPE_ERROR;
fault:
return TYPE_FAULT;
}
static int
do_alignment_ldrstr(unsigned long addr, u32 instr, struct pt_regs *regs)
{
unsigned int rd = RD_BITS(instr);
ai_word += 1;
if ((!LDST_P_BIT(instr) && LDST_W_BIT(instr)) || user_mode(regs))
goto trans;
if (LDST_L_BIT(instr)) {
unsigned int val;
get32_unaligned_check(val, addr);
regs->uregs[rd] = val;
} else
put32_unaligned_check(regs->uregs[rd], addr);
return TYPE_LDST;
trans:
if (LDST_L_BIT(instr)) {
unsigned int val;
unsigned int __ua_flags = uaccess_save_and_enable();
get32t_unaligned_check(val, addr);
uaccess_restore(__ua_flags);
regs->uregs[rd] = val;
} else {
unsigned int __ua_flags = uaccess_save_and_enable();
put32t_unaligned_check(regs->uregs[rd], addr);
uaccess_restore(__ua_flags);
}
return TYPE_LDST;
fault:
return TYPE_FAULT;
}
/*
* LDM/STM alignment handler.
*
* There are 4 variants of this instruction:
*
* B = rn pointer before instruction, A = rn pointer after instruction
* ------ increasing address ----->
* | | r0 | r1 | ... | rx | |
* PU = 01 B A
* PU = 11 B A
* PU = 00 A B
* PU = 10 A B
*/
static int
do_alignment_ldmstm(unsigned long addr, u32 instr, struct pt_regs *regs)
{
unsigned int rd, rn, correction, nr_regs, regbits;
unsigned long eaddr, newaddr;
if (LDM_S_BIT(instr))
goto bad;
correction = 4; /* processor implementation defined */
regs->ARM_pc += correction;
ai_multi += 1;
/* count the number of registers in the mask to be transferred */
nr_regs = hweight16(REGMASK_BITS(instr)) * 4;
rn = RN_BITS(instr);
newaddr = eaddr = regs->uregs[rn];
if (!LDST_U_BIT(instr))
nr_regs = -nr_regs;
newaddr += nr_regs;
if (!LDST_U_BIT(instr))
eaddr = newaddr;
if (LDST_P_EQ_U(instr)) /* U = P */
eaddr += 4;
/*
* For alignment faults on the ARM922T/ARM920T the MMU makes
* the FSR (and hence addr) equal to the updated base address
* of the multiple access rather than the restored value.
* Switch this message off if we've got a ARM92[02], otherwise
* [ls]dm alignment faults are noisy!
*/
#if !(defined CONFIG_CPU_ARM922T) && !(defined CONFIG_CPU_ARM920T)
/*
* This is a "hint" - we already have eaddr worked out by the
* processor for us.
*/
if (addr != eaddr) {
pr_err("LDMSTM: PC = %08lx, instr = %08x, "
"addr = %08lx, eaddr = %08lx\n",
instruction_pointer(regs), instr, addr, eaddr);
show_regs(regs);
}
#endif
if (user_mode(regs)) {
unsigned int __ua_flags = uaccess_save_and_enable();
for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
regbits >>= 1, rd += 1)
if (regbits & 1) {
if (LDST_L_BIT(instr)) {
unsigned int val;
get32t_unaligned_check(val, eaddr);
regs->uregs[rd] = val;
} else
put32t_unaligned_check(regs->uregs[rd], eaddr);
eaddr += 4;
}
uaccess_restore(__ua_flags);
} else {
for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
regbits >>= 1, rd += 1)
if (regbits & 1) {
if (LDST_L_BIT(instr)) {
unsigned int val;
get32_unaligned_check(val, eaddr);
regs->uregs[rd] = val;
} else
put32_unaligned_check(regs->uregs[rd], eaddr);
eaddr += 4;
}
}
if (LDST_W_BIT(instr))
regs->uregs[rn] = newaddr;
if (!LDST_L_BIT(instr) || !(REGMASK_BITS(instr) & (1 << 15)))
regs->ARM_pc -= correction;
return TYPE_DONE;
fault:
regs->ARM_pc -= correction;
return TYPE_FAULT;
bad:
pr_err("Alignment trap: not handling ldm with s-bit set\n");
return TYPE_ERROR;
}
/*
* Convert Thumb ld/st instruction forms to equivalent ARM instructions so
* we can reuse ARM userland alignment fault fixups for Thumb.
*
* This implementation was initially based on the algorithm found in
* gdb/sim/arm/thumbemu.c. It is basically just a code reduction of same
* to convert only Thumb ld/st instruction forms to equivalent ARM forms.
*
* NOTES:
* 1. Comments below refer to ARM ARM DDI0100E Thumb Instruction sections.
* 2. If for some reason we're passed an non-ld/st Thumb instruction to
* decode, we return 0xdeadc0de. This should never happen under normal
* circumstances but if it does, we've got other problems to deal with
* elsewhere and we obviously can't fix those problems here.
*/
static unsigned long
thumb2arm(u16 tinstr)
{
u32 L = (tinstr & (1<<11)) >> 11;
switch ((tinstr & 0xf800) >> 11) {
/* 6.5.1 Format 1: */
case 0x6000 >> 11: /* 7.1.52 STR(1) */
case 0x6800 >> 11: /* 7.1.26 LDR(1) */
case 0x7000 >> 11: /* 7.1.55 STRB(1) */
case 0x7800 >> 11: /* 7.1.30 LDRB(1) */
return 0xe5800000 |
((tinstr & (1<<12)) << (22-12)) | /* fixup */
(L<<20) | /* L==1? */
((tinstr & (7<<0)) << (12-0)) | /* Rd */
((tinstr & (7<<3)) << (16-3)) | /* Rn */
((tinstr & (31<<6)) >> /* immed_5 */
(6 - ((tinstr & (1<<12)) ? 0 : 2)));
case 0x8000 >> 11: /* 7.1.57 STRH(1) */
case 0x8800 >> 11: /* 7.1.32 LDRH(1) */
return 0xe1c000b0 |
(L<<20) | /* L==1? */
((tinstr & (7<<0)) << (12-0)) | /* Rd */
((tinstr & (7<<3)) << (16-3)) | /* Rn */
((tinstr & (7<<6)) >> (6-1)) | /* immed_5[2:0] */
((tinstr & (3<<9)) >> (9-8)); /* immed_5[4:3] */
/* 6.5.1 Format 2: */
case 0x5000 >> 11:
case 0x5800 >> 11:
{
static const u32 subset[8] = {
0xe7800000, /* 7.1.53 STR(2) */
0xe18000b0, /* 7.1.58 STRH(2) */
0xe7c00000, /* 7.1.56 STRB(2) */
0xe19000d0, /* 7.1.34 LDRSB */
0xe7900000, /* 7.1.27 LDR(2) */
0xe19000b0, /* 7.1.33 LDRH(2) */
0xe7d00000, /* 7.1.31 LDRB(2) */
0xe19000f0 /* 7.1.35 LDRSH */
};
return subset[(tinstr & (7<<9)) >> 9] |
((tinstr & (7<<0)) << (12-0)) | /* Rd */
((tinstr & (7<<3)) << (16-3)) | /* Rn */
((tinstr & (7<<6)) >> (6-0)); /* Rm */
}
/* 6.5.1 Format 3: */
case 0x4800 >> 11: /* 7.1.28 LDR(3) */
/* NOTE: This case is not technically possible. We're
* loading 32-bit memory data via PC relative
* addressing mode. So we can and should eliminate
* this case. But I'll leave it here for now.
*/
return 0xe59f0000 |
((tinstr & (7<<8)) << (12-8)) | /* Rd */
((tinstr & 255) << (2-0)); /* immed_8 */
/* 6.5.1 Format 4: */
case 0x9000 >> 11: /* 7.1.54 STR(3) */
case 0x9800 >> 11: /* 7.1.29 LDR(4) */
return 0xe58d0000 |
(L<<20) | /* L==1? */
((tinstr & (7<<8)) << (12-8)) | /* Rd */
((tinstr & 255) << 2); /* immed_8 */
/* 6.6.1 Format 1: */
case 0xc000 >> 11: /* 7.1.51 STMIA */
case 0xc800 >> 11: /* 7.1.25 LDMIA */
{
u32 Rn = (tinstr & (7<<8)) >> 8;
u32 W = ((L<<Rn) & (tinstr&255)) ? 0 : 1<<21;
return 0xe8800000 | W | (L<<20) | (Rn<<16) |
(tinstr&255);
}
/* 6.6.1 Format 2: */
case 0xb000 >> 11: /* 7.1.48 PUSH */
case 0xb800 >> 11: /* 7.1.47 POP */
if ((tinstr & (3 << 9)) == 0x0400) {
static const u32 subset[4] = {
0xe92d0000, /* STMDB sp!,{registers} */
0xe92d4000, /* STMDB sp!,{registers,lr} */
0xe8bd0000, /* LDMIA sp!,{registers} */
0xe8bd8000 /* LDMIA sp!,{registers,pc} */
};
return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
(tinstr & 255); /* register_list */
}
fallthrough; /* for illegal instruction case */
default:
return BAD_INSTR;
}
}
/*
* Convert Thumb-2 32 bit LDM, STM, LDRD, STRD to equivalent instruction
* handlable by ARM alignment handler, also find the corresponding handler,
* so that we can reuse ARM userland alignment fault fixups for Thumb.
*
* @pinstr: original Thumb-2 instruction; returns new handlable instruction
* @regs: register context.
* @poffset: return offset from faulted addr for later writeback
*
* NOTES:
* 1. Comments below refer to ARMv7 DDI0406A Thumb Instruction sections.
* 2. Register name Rt from ARMv7 is same as Rd from ARMv6 (Rd is Rt)
*/
static void *
do_alignment_t32_to_handler(u32 *pinstr, struct pt_regs *regs,
union offset_union *poffset)
{
u32 instr = *pinstr;
u16 tinst1 = (instr >> 16) & 0xffff;
u16 tinst2 = instr & 0xffff;
switch (tinst1 & 0xffe0) {
/* A6.3.5 Load/Store multiple */
case 0xe880: /* STM/STMIA/STMEA,LDM/LDMIA, PUSH/POP T2 */
case 0xe8a0: /* ...above writeback version */
case 0xe900: /* STMDB/STMFD, LDMDB/LDMEA */
case 0xe920: /* ...above writeback version */
/* no need offset decision since handler calculates it */
return do_alignment_ldmstm;
case 0xf840: /* POP/PUSH T3 (single register) */
if (RN_BITS(instr) == 13 && (tinst2 & 0x09ff) == 0x0904) {
u32 L = !!(LDST_L_BIT(instr));
const u32 subset[2] = {
0xe92d0000, /* STMDB sp!,{registers} */
0xe8bd0000, /* LDMIA sp!,{registers} */
};
*pinstr = subset[L] | (1<<RD_BITS(instr));
return do_alignment_ldmstm;
}
/* Else fall through for illegal instruction case */
break;
/* A6.3.6 Load/store double, STRD/LDRD(immed, lit, reg) */
case 0xe860:
case 0xe960:
case 0xe8e0:
case 0xe9e0:
poffset->un = (tinst2 & 0xff) << 2;
fallthrough;
case 0xe940:
case 0xe9c0:
return do_alignment_ldrdstrd;
/*
* No need to handle load/store instructions up to word size
* since ARMv6 and later CPUs can perform unaligned accesses.
*/
default:
break;
}
return NULL;
}
static int alignment_get_arm(struct pt_regs *regs, u32 *ip, u32 *inst)
{
u32 instr = 0;
int fault;
if (user_mode(regs))
fault = get_user(instr, ip);
else
fault = get_kernel_nofault(instr, ip);
*inst = __mem_to_opcode_arm(instr);
return fault;
}
static int alignment_get_thumb(struct pt_regs *regs, u16 *ip, u16 *inst)
{
u16 instr = 0;
int fault;
if (user_mode(regs))
fault = get_user(instr, ip);
else
fault = get_kernel_nofault(instr, ip);
*inst = __mem_to_opcode_thumb16(instr);
return fault;
}
static int
do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
union offset_union offset;
unsigned long instrptr;
int (*handler)(unsigned long addr, u32 instr, struct pt_regs *regs);
unsigned int type;
u32 instr = 0;
u16 tinstr = 0;
int isize = 4;
int thumb2_32b = 0;
int fault;
if (interrupts_enabled(regs))
local_irq_enable();
instrptr = instruction_pointer(regs);
if (thumb_mode(regs)) {
u16 *ptr = (u16 *)(instrptr & ~1);
fault = alignment_get_thumb(regs, ptr, &tinstr);
if (!fault) {
if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
IS_T32(tinstr)) {
/* Thumb-2 32-bit */
u16 tinst2;
fault = alignment_get_thumb(regs, ptr + 1, &tinst2);
instr = __opcode_thumb32_compose(tinstr, tinst2);
thumb2_32b = 1;
} else {
isize = 2;
instr = thumb2arm(tinstr);
}
}
} else {
fault = alignment_get_arm(regs, (void *)instrptr, &instr);
}
if (fault) {
type = TYPE_FAULT;
goto bad_or_fault;
}
if (user_mode(regs))
goto user;
ai_sys += 1;
ai_sys_last_pc = (void *)instruction_pointer(regs);
fixup:
regs->ARM_pc += isize;
switch (CODING_BITS(instr)) {
case 0x00000000: /* 3.13.4 load/store instruction extensions */
if (LDSTHD_I_BIT(instr))
offset.un = (instr & 0xf00) >> 4 | (instr & 15);
else
offset.un = regs->uregs[RM_BITS(instr)];
if ((instr & 0x000000f0) == 0x000000b0 || /* LDRH, STRH */
(instr & 0x001000f0) == 0x001000f0) /* LDRSH */
handler = do_alignment_ldrhstrh;
else if ((instr & 0x001000f0) == 0x000000d0 || /* LDRD */
(instr & 0x001000f0) == 0x000000f0) /* STRD */
handler = do_alignment_ldrdstrd;
else if ((instr & 0x01f00ff0) == 0x01000090) /* SWP */
goto swp;
else
goto bad;
break;
case 0x04000000: /* ldr or str immediate */
if (COND_BITS(instr) == 0xf0000000) /* NEON VLDn, VSTn */
goto bad;
offset.un = OFFSET_BITS(instr);
handler = do_alignment_ldrstr;
break;
case 0x06000000: /* ldr or str register */
offset.un = regs->uregs[RM_BITS(instr)];
if (IS_SHIFT(instr)) {
unsigned int shiftval = SHIFT_BITS(instr);
switch(SHIFT_TYPE(instr)) {
case SHIFT_LSL:
offset.un <<= shiftval;
break;
case SHIFT_LSR:
offset.un >>= shiftval;
break;
case SHIFT_ASR:
offset.sn >>= shiftval;
break;
case SHIFT_RORRRX:
if (shiftval == 0) {
offset.un >>= 1;
if (regs->ARM_cpsr & PSR_C_BIT)
offset.un |= 1 << 31;
} else
offset.un = offset.un >> shiftval |
offset.un << (32 - shiftval);
break;
}
}
handler = do_alignment_ldrstr;
break;
case 0x08000000: /* ldm or stm, or thumb-2 32bit instruction */
if (thumb2_32b) {
offset.un = 0;
handler = do_alignment_t32_to_handler(&instr, regs, &offset);
} else {
offset.un = 0;
handler = do_alignment_ldmstm;
}
break;
default:
goto bad;
}
if (!handler)
goto bad;
type = handler(addr, instr, regs);
if (type == TYPE_ERROR || type == TYPE_FAULT) {
regs->ARM_pc -= isize;
goto bad_or_fault;
}
if (type == TYPE_LDST)
do_alignment_finish_ldst(addr, instr, regs, offset);
if (thumb_mode(regs))
regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
return 0;
bad_or_fault:
if (type == TYPE_ERROR)
goto bad;
/*
* We got a fault - fix it up, or die.
*/
do_bad_area(addr, fsr, regs);
return 0;
swp:
pr_err("Alignment trap: not handling swp instruction\n");
bad:
/*
* Oops, we didn't handle the instruction.
*/
pr_err("Alignment trap: not handling instruction "
"%0*x at [<%08lx>]\n",
isize << 1,
isize == 2 ? tinstr : instr, instrptr);
ai_skipped += 1;
return 1;
user:
ai_user += 1;
if (ai_usermode & UM_WARN)
printk("Alignment trap: %s (%d) PC=0x%08lx Instr=0x%0*x "
"Address=0x%08lx FSR 0x%03x\n", current->comm,
task_pid_nr(current), instrptr,
isize << 1,
isize == 2 ? tinstr : instr,
addr, fsr);
if (ai_usermode & UM_FIXUP)
goto fixup;
if (ai_usermode & UM_SIGNAL) {
force_sig_fault(SIGBUS, BUS_ADRALN, (void __user *)addr);
} else {
/*
* We're about to disable the alignment trap and return to
* user space. But if an interrupt occurs before actually
* reaching user space, then the IRQ vector entry code will
* notice that we were still in kernel space and therefore
* the alignment trap won't be re-enabled in that case as it
* is presumed to be always on from kernel space.
* Let's prevent that race by disabling interrupts here (they
* are disabled on the way back to user space anyway in
* entry-common.S) and disable the alignment trap only if
* there is no work pending for this thread.
*/
raw_local_irq_disable();
if (!(read_thread_flags() & _TIF_WORK_MASK))
set_cr(cr_no_alignment);
}
return 0;
}
static int __init noalign_setup(char *__unused)
{
set_cr(__clear_cr(CR_A));
return 1;
}
__setup("noalign", noalign_setup);
/*
* This needs to be done after sysctl_init_bases(), otherwise sys/ will be
* overwritten. Actually, this shouldn't be in sys/ at all since
* it isn't a sysctl, and it doesn't contain sysctl information.
* We now locate it in /proc/cpu/alignment instead.
*/
static int __init alignment_init(void)
{
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *res;
res = proc_create("cpu/alignment", S_IWUSR | S_IRUGO, NULL,
&alignment_proc_ops);
if (!res)
return -ENOMEM;
#endif
if (cpu_is_v6_unaligned()) {
set_cr(__clear_cr(CR_A));
ai_usermode = safe_usermode(ai_usermode, false);
}
cr_no_alignment = get_cr() & ~CR_A;
hook_fault_code(FAULT_CODE_ALIGNMENT, do_alignment, SIGBUS, BUS_ADRALN,
"alignment exception");
/*
* ARMv6K and ARMv7 use fault status 3 (0b00011) as Access Flag section
* fault, not as alignment error.
*
* TODO: handle ARMv6K properly. Runtime check for 'K' extension is
* needed.
*/
if (cpu_architecture() <= CPU_ARCH_ARMv6) {
hook_fault_code(3, do_alignment, SIGBUS, BUS_ADRALN,
"alignment exception");
}
return 0;
}
fs_initcall(alignment_init);
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