| /* |
| * linux/arch/arm/kernel/swp_emulate.c |
| * |
| * Copyright (C) 2009 ARM Limited |
| * __user_* functions adapted from include/asm/uaccess.h |
| * |
| * 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. |
| * |
| * Implements emulation of the SWP/SWPB instructions using load-exclusive and |
| * store-exclusive for processors that have them disabled (or future ones that |
| * might not implement them). |
| * |
| * Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>] |
| * Where: Rt = destination |
| * Rt2 = source |
| * Rn = address |
| */ |
| |
| #include <linux/init.h> |
| #include <linux/kernel.h> |
| #include <linux/proc_fs.h> |
| #include <linux/seq_file.h> |
| #include <linux/sched.h> |
| #include <linux/sched/mm.h> |
| #include <linux/syscalls.h> |
| #include <linux/perf_event.h> |
| |
| #include <asm/opcodes.h> |
| #include <asm/system_info.h> |
| #include <asm/traps.h> |
| #include <linux/uaccess.h> |
| |
| /* |
| * Error-checking SWP macros implemented using ldrex{b}/strex{b} |
| */ |
| #define __user_swpX_asm(data, addr, res, temp, B) \ |
| __asm__ __volatile__( \ |
| "0: ldrex"B" %2, [%3]\n" \ |
| "1: strex"B" %0, %1, [%3]\n" \ |
| " cmp %0, #0\n" \ |
| " moveq %1, %2\n" \ |
| " movne %0, %4\n" \ |
| "2:\n" \ |
| " .section .text.fixup,\"ax\"\n" \ |
| " .align 2\n" \ |
| "3: mov %0, %5\n" \ |
| " b 2b\n" \ |
| " .previous\n" \ |
| " .section __ex_table,\"a\"\n" \ |
| " .align 3\n" \ |
| " .long 0b, 3b\n" \ |
| " .long 1b, 3b\n" \ |
| " .previous" \ |
| : "=&r" (res), "+r" (data), "=&r" (temp) \ |
| : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT) \ |
| : "cc", "memory") |
| |
| #define __user_swp_asm(data, addr, res, temp) \ |
| __user_swpX_asm(data, addr, res, temp, "") |
| #define __user_swpb_asm(data, addr, res, temp) \ |
| __user_swpX_asm(data, addr, res, temp, "b") |
| |
| /* |
| * Macros/defines for extracting register numbers from instruction. |
| */ |
| #define EXTRACT_REG_NUM(instruction, offset) \ |
| (((instruction) & (0xf << (offset))) >> (offset)) |
| #define RN_OFFSET 16 |
| #define RT_OFFSET 12 |
| #define RT2_OFFSET 0 |
| /* |
| * Bit 22 of the instruction encoding distinguishes between |
| * the SWP and SWPB variants (bit set means SWPB). |
| */ |
| #define TYPE_SWPB (1 << 22) |
| |
| static unsigned long swpcounter; |
| static unsigned long swpbcounter; |
| static unsigned long abtcounter; |
| static pid_t previous_pid; |
| |
| #ifdef CONFIG_PROC_FS |
| static int proc_status_show(struct seq_file *m, void *v) |
| { |
| seq_printf(m, "Emulated SWP:\t\t%lu\n", swpcounter); |
| seq_printf(m, "Emulated SWPB:\t\t%lu\n", swpbcounter); |
| seq_printf(m, "Aborted SWP{B}:\t\t%lu\n", abtcounter); |
| if (previous_pid != 0) |
| seq_printf(m, "Last process:\t\t%d\n", previous_pid); |
| return 0; |
| } |
| #endif |
| |
| /* |
| * Set up process info to signal segmentation fault - called on access error. |
| */ |
| static void set_segfault(struct pt_regs *regs, unsigned long addr) |
| { |
| int si_code; |
| |
| down_read(¤t->mm->mmap_sem); |
| if (find_vma(current->mm, addr) == NULL) |
| si_code = SEGV_MAPERR; |
| else |
| si_code = SEGV_ACCERR; |
| up_read(¤t->mm->mmap_sem); |
| |
| pr_debug("SWP{B} emulation: access caused memory abort!\n"); |
| arm_notify_die("Illegal memory access", regs, |
| SIGSEGV, si_code, |
| (void __user *)instruction_pointer(regs), |
| 0, 0); |
| |
| abtcounter++; |
| } |
| |
| static int emulate_swpX(unsigned int address, unsigned int *data, |
| unsigned int type) |
| { |
| unsigned int res = 0; |
| |
| if ((type != TYPE_SWPB) && (address & 0x3)) { |
| /* SWP to unaligned address not permitted */ |
| pr_debug("SWP instruction on unaligned pointer!\n"); |
| return -EFAULT; |
| } |
| |
| while (1) { |
| unsigned long temp; |
| unsigned int __ua_flags; |
| |
| __ua_flags = uaccess_save_and_enable(); |
| if (type == TYPE_SWPB) |
| __user_swpb_asm(*data, address, res, temp); |
| else |
| __user_swp_asm(*data, address, res, temp); |
| uaccess_restore(__ua_flags); |
| |
| if (likely(res != -EAGAIN) || signal_pending(current)) |
| break; |
| |
| cond_resched(); |
| } |
| |
| if (res == 0) { |
| if (type == TYPE_SWPB) |
| swpbcounter++; |
| else |
| swpcounter++; |
| } |
| |
| return res; |
| } |
| |
| /* |
| * swp_handler logs the id of calling process, dissects the instruction, sanity |
| * checks the memory location, calls emulate_swpX for the actual operation and |
| * deals with fixup/error handling before returning |
| */ |
| static int swp_handler(struct pt_regs *regs, unsigned int instr) |
| { |
| unsigned int address, destreg, data, type; |
| unsigned int res = 0; |
| |
| perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc); |
| |
| res = arm_check_condition(instr, regs->ARM_cpsr); |
| switch (res) { |
| case ARM_OPCODE_CONDTEST_PASS: |
| break; |
| case ARM_OPCODE_CONDTEST_FAIL: |
| /* Condition failed - return to next instruction */ |
| regs->ARM_pc += 4; |
| return 0; |
| case ARM_OPCODE_CONDTEST_UNCOND: |
| /* If unconditional encoding - not a SWP, undef */ |
| return -EFAULT; |
| default: |
| return -EINVAL; |
| } |
| |
| if (current->pid != previous_pid) { |
| pr_debug("\"%s\" (%ld) uses deprecated SWP{B} instruction\n", |
| current->comm, (unsigned long)current->pid); |
| previous_pid = current->pid; |
| } |
| |
| address = regs->uregs[EXTRACT_REG_NUM(instr, RN_OFFSET)]; |
| data = regs->uregs[EXTRACT_REG_NUM(instr, RT2_OFFSET)]; |
| destreg = EXTRACT_REG_NUM(instr, RT_OFFSET); |
| |
| type = instr & TYPE_SWPB; |
| |
| pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n", |
| EXTRACT_REG_NUM(instr, RN_OFFSET), address, |
| destreg, EXTRACT_REG_NUM(instr, RT2_OFFSET), data); |
| |
| /* Check access in reasonable access range for both SWP and SWPB */ |
| if (!access_ok((address & ~3), 4)) { |
| pr_debug("SWP{B} emulation: access to %p not allowed!\n", |
| (void *)address); |
| res = -EFAULT; |
| } else { |
| res = emulate_swpX(address, &data, type); |
| } |
| |
| if (res == 0) { |
| /* |
| * On successful emulation, revert the adjustment to the PC |
| * made in kernel/traps.c in order to resume execution at the |
| * instruction following the SWP{B}. |
| */ |
| regs->ARM_pc += 4; |
| regs->uregs[destreg] = data; |
| } else if (res == -EFAULT) { |
| /* |
| * Memory errors do not mean emulation failed. |
| * Set up signal info to return SEGV, then return OK |
| */ |
| set_segfault(regs, address); |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * Only emulate SWP/SWPB executed in ARM state/User mode. |
| * The kernel must be SWP free and SWP{B} does not exist in Thumb/ThumbEE. |
| */ |
| static struct undef_hook swp_hook = { |
| .instr_mask = 0x0fb00ff0, |
| .instr_val = 0x01000090, |
| .cpsr_mask = MODE_MASK | PSR_T_BIT | PSR_J_BIT, |
| .cpsr_val = USR_MODE, |
| .fn = swp_handler |
| }; |
| |
| /* |
| * Register handler and create status file in /proc/cpu |
| * Invoked as late_initcall, since not needed before init spawned. |
| */ |
| static int __init swp_emulation_init(void) |
| { |
| if (cpu_architecture() < CPU_ARCH_ARMv7) |
| return 0; |
| |
| #ifdef CONFIG_PROC_FS |
| if (!proc_create_single("cpu/swp_emulation", S_IRUGO, NULL, |
| proc_status_show)) |
| return -ENOMEM; |
| #endif /* CONFIG_PROC_FS */ |
| |
| pr_notice("Registering SWP/SWPB emulation handler\n"); |
| register_undef_hook(&swp_hook); |
| |
| return 0; |
| } |
| |
| late_initcall(swp_emulation_init); |