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Diffstat (limited to 'kernel/arch/arm/mm/alignment.c')
| -rw-r--r-- | kernel/arch/arm/mm/alignment.c | 1008 |
1 files changed, 1008 insertions, 0 deletions
diff --git a/kernel/arch/arm/mm/alignment.c b/kernel/arch/arm/mm/alignment.c new file mode 100644 index 000000000..9769f1eef --- /dev/null +++ b/kernel/arch/arm/mm/alignment.c @@ -0,0 +1,1008 @@ +/* + * 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. + * + * 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. + */ +#include <linux/moduleparam.h> +#include <linux/compiler.h> +#include <linux/kernel.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.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 (%pF)\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 file_operations alignment_proc_fops = { + .open = alignment_proc_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, + .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, unsigned long 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, unsigned long 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; + get16t_unaligned_check(val, addr); + + /* signed half-word? */ + if (instr & 0x40) + val = (signed long)((signed short) val); + + regs->uregs[rd] = val; + } else + put16t_unaligned_check(regs->uregs[rd], addr); + + return TYPE_LDST; + + fault: + return TYPE_FAULT; +} + +static int +do_alignment_ldrdstrd(unsigned long addr, unsigned long 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; + get32t_unaligned_check(val, addr); + regs->uregs[rd] = val; + get32t_unaligned_check(val, addr + 4); + regs->uregs[rd2] = val; + } else { + put32t_unaligned_check(regs->uregs[rd], addr); + put32t_unaligned_check(regs->uregs[rd2], addr + 4); + } + + return TYPE_LDST; + bad: + return TYPE_ERROR; + fault: + return TYPE_FAULT; +} + +static int +do_alignment_ldrstr(unsigned long addr, unsigned long 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; + get32t_unaligned_check(val, addr); + regs->uregs[rd] = val; + } else + put32t_unaligned_check(regs->uregs[rd], addr); + 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, unsigned long 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 = %08lx, " + "addr = %08lx, eaddr = %08lx\n", + instruction_pointer(regs), instr, addr, eaddr); + show_regs(regs); + } +#endif + + if (user_mode(regs)) { + 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; + } + } 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 */ + } + /* Else fall through 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(unsigned long *pinstr, struct pt_regs *regs, + union offset_union *poffset) +{ + unsigned long 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; + 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 +do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs) +{ + union offset_union uninitialized_var(offset); + unsigned long instr = 0, instrptr; + int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs); + unsigned int type; + unsigned int fault; + u16 tinstr = 0; + int isize = 4; + int thumb2_32b = 0; + + if (interrupts_enabled(regs)) + local_irq_enable(); + + instrptr = instruction_pointer(regs); + + if (thumb_mode(regs)) { + u16 *ptr = (u16 *)(instrptr & ~1); + fault = probe_kernel_address(ptr, tinstr); + tinstr = __mem_to_opcode_thumb16(tinstr); + if (!fault) { + if (cpu_architecture() >= CPU_ARCH_ARMv7 && + IS_T32(tinstr)) { + /* Thumb-2 32-bit */ + u16 tinst2 = 0; + fault = probe_kernel_address(ptr + 1, tinst2); + tinst2 = __mem_to_opcode_thumb16(tinst2); + instr = __opcode_thumb32_compose(tinstr, tinst2); + thumb2_32b = 1; + } else { + isize = 2; + instr = thumb2arm(tinstr); + } + } + } else { + fault = probe_kernel_address(instrptr, instr); + instr = __mem_to_opcode_arm(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); + + 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*lx 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*lx " + "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) { + siginfo_t si; + + si.si_signo = SIGBUS; + si.si_errno = 0; + si.si_code = BUS_ADRALN; + si.si_addr = (void __user *)addr; + + force_sig_info(si.si_signo, &si, current); + } 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 (!(current_thread_info()->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, 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_fops); + 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); |