From 2e651ea1596b0ee25af4fcdc4cd13cbb33ffc254 Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Wed, 23 Jan 2013 16:30:36 +0530 Subject: ARC: Unaligned access emulation ARC700 doesn't natively support unaligned access, but can be emulated -Unaligned Access Exception -Disassembly at the Fault address to find the exact insn (long/short) Also per Arnd's comment, we runtime control it using 2 sysctl knobs: * SYSCTL_ARCH_UNALIGN_ALLOW: Runtime enable/disble * SYSCTL_ARCH_UNALIGN_NO_WARN: Warn on each emulation attempt Originally contributed by Tim Yao Signed-off-by: Vineet Gupta Cc: Tim Yao Acked-by: Arnd Bergmann --- arch/arc/Kconfig | 11 ++ arch/arc/include/asm/Kbuild | 1 - arch/arc/include/asm/ptrace.h | 3 + arch/arc/include/asm/unaligned.h | 29 +++++ arch/arc/kernel/Makefile | 1 + arch/arc/kernel/disasm.c | 2 +- arch/arc/kernel/entry.S | 13 +++ arch/arc/kernel/traps.c | 26 +++++ arch/arc/kernel/unaligned.c | 245 +++++++++++++++++++++++++++++++++++++++ 9 files changed, 329 insertions(+), 2 deletions(-) create mode 100644 arch/arc/include/asm/unaligned.h create mode 100644 arch/arc/kernel/unaligned.c (limited to 'arch/arc') diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index cde8d3fcec9..f8042835e74 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -336,6 +336,17 @@ config ARC_CURR_IN_REG This reserved Register R25 to point to Current Task in kernel mode. This saves memory access for each such access + +config ARC_MISALIGN_ACCESS + bool "Emulate unaligned memory access (userspace only)" + default N + select SYSCTL_ARCH_UNALIGN_NO_WARN + select SYSCTL_ARCH_UNALIGN_ALLOW + help + This enables misaligned 16 & 32 bit memory access from user space. + Use ONLY-IF-ABS-NECESSARY as it will be very slow and also can hide + potential bugs in code + config ARC_STACK_NONEXEC bool "Make stack non-executable" default n diff --git a/arch/arc/include/asm/Kbuild b/arch/arc/include/asm/Kbuild index 78e982dad53..b24089c974a 100644 --- a/arch/arc/include/asm/Kbuild +++ b/arch/arc/include/asm/Kbuild @@ -52,7 +52,6 @@ generic-y += topology.h generic-y += trace_clock.h generic-y += types.h generic-y += ucontext.h -generic-y += unaligned.h generic-y += user.h generic-y += vga.h generic-y += xor.h diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h index 063ed0040ef..df5b9521377 100644 --- a/arch/arc/include/asm/ptrace.h +++ b/arch/arc/include/asm/ptrace.h @@ -97,6 +97,9 @@ struct callee_regs { sp; \ }) +/* return 1 if PC in delay slot */ +#define delay_mode(regs) ((regs->status32 & STATUS_DE_MASK) == STATUS_DE_MASK) + #define in_syscall(regs) (regs->event & orig_r8_IS_SCALL) #define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT) diff --git a/arch/arc/include/asm/unaligned.h b/arch/arc/include/asm/unaligned.h new file mode 100644 index 00000000000..5dbe63f17b6 --- /dev/null +++ b/arch/arc/include/asm/unaligned.h @@ -0,0 +1,29 @@ +/* + * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) + * + * 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. + */ + +#ifndef _ASM_ARC_UNALIGNED_H +#define _ASM_ARC_UNALIGNED_H + +/* ARC700 can't handle unaligned Data accesses. */ + +#include +#include + +#ifdef CONFIG_ARC_MISALIGN_ACCESS +int misaligned_fixup(unsigned long address, struct pt_regs *regs, + unsigned long cause, struct callee_regs *cregs); +#else +static inline int +misaligned_fixup(unsigned long address, struct pt_regs *regs, + unsigned long cause, struct callee_regs *cregs) +{ + return 0; +} +#endif + +#endif /* _ASM_ARC_UNALIGNED_H */ diff --git a/arch/arc/kernel/Makefile b/arch/arc/kernel/Makefile index d331bd7047a..507a33d4a25 100644 --- a/arch/arc/kernel/Makefile +++ b/arch/arc/kernel/Makefile @@ -16,6 +16,7 @@ obj-$(CONFIG_MODULES) += arcksyms.o module.o obj-$(CONFIG_SMP) += smp.o obj-$(CONFIG_ARC_DW2_UNWIND) += unwind.o obj-$(CONFIG_KPROBES) += kprobes.o +obj-$(CONFIG_ARC_MISALIGN_ACCESS) += unaligned.o obj-$(CONFIG_ARC_FPU_SAVE_RESTORE) += fpu.o CFLAGS_fpu.o += -mdpfp diff --git a/arch/arc/kernel/disasm.c b/arch/arc/kernel/disasm.c index 51bad8ff373..2f390289a79 100644 --- a/arch/arc/kernel/disasm.c +++ b/arch/arc/kernel/disasm.c @@ -15,7 +15,7 @@ #include #include -#if defined(CONFIG_KGDB) || defined(CONFIG_MISALIGN_ACCESS) || \ +#if defined(CONFIG_KGDB) || defined(CONFIG_ARC_MISALIGN_ACCESS) || \ defined(CONFIG_KPROBES) /* disasm_instr: Analyses instruction at addr, stores diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S index 021cfa46a1d..f8efade1536 100644 --- a/arch/arc/kernel/entry.S +++ b/arch/arc/kernel/entry.S @@ -7,6 +7,9 @@ * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * + * vineetg: May 2011 + * -Userspace unaligned access emulation + * * vineetg: Feb 2011 (ptrace low level code fixes) * -traced syscall return code (r0) was not saved into pt_regs for restoring * into user reg-file when traded task rets to user space. @@ -387,7 +390,17 @@ ARC_ENTRY EV_TLBProtV mov r1, r4 ; faulting address mov r2, sp ; pt_regs +#ifdef CONFIG_ARC_MISALIGN_ACCESS + SAVE_CALLEE_SAVED_USER + mov r3, sp ; callee_regs +#endif + bl do_misaligned_access + +#ifdef CONFIG_ARC_MISALIGN_ACCESS + DISCARD_CALLEE_SAVED_USER +#endif + b ret_from_exception ARC_EXIT EV_TLBProtV diff --git a/arch/arc/kernel/traps.c b/arch/arc/kernel/traps.c index c6396b48fcd..ec802c52a1c 100644 --- a/arch/arc/kernel/traps.c +++ b/arch/arc/kernel/traps.c @@ -7,6 +7,9 @@ * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * + * vineetg: May 2011 + * -user-space unaligned access emulation + * * Rahul Trivedi: Codito Technologies 2004 */ @@ -16,6 +19,7 @@ #include #include #include +#include void __init trap_init(void) { @@ -79,7 +83,29 @@ DO_ERROR_INFO(SIGILL, "Illegal Insn (or Seq)", insterror_is_error, ILL_ILLOPC) DO_ERROR_INFO(SIGBUS, "Invalid Mem Access", do_memory_error, BUS_ADRERR) DO_ERROR_INFO(SIGTRAP, "Breakpoint Set", trap_is_brkpt, TRAP_BRKPT) +#ifdef CONFIG_ARC_MISALIGN_ACCESS +/* + * Entry Point for Misaligned Data access Exception, for emulating in software + */ +int do_misaligned_access(unsigned long cause, unsigned long address, + struct pt_regs *regs, struct callee_regs *cregs) +{ + if (misaligned_fixup(address, regs, cause, cregs) != 0) { + siginfo_t info; + + info.si_signo = SIGBUS; + info.si_errno = 0; + info.si_code = BUS_ADRALN; + info.si_addr = (void __user *)address; + return handle_exception(cause, "Misaligned Access", regs, + &info); + } + return 0; +} + +#else DO_ERROR_INFO(SIGSEGV, "Misaligned Access", do_misaligned_access, SEGV_ACCERR) +#endif /* * Entry point for miscll errors such as Nested Exceptions diff --git a/arch/arc/kernel/unaligned.c b/arch/arc/kernel/unaligned.c new file mode 100644 index 00000000000..4cd81633feb --- /dev/null +++ b/arch/arc/kernel/unaligned.c @@ -0,0 +1,245 @@ +/* + * Copyright (C) 2011-2012 Synopsys (www.synopsys.com) + * + * 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. + * + * vineetg : May 2011 + * -Adapted (from .26 to .35) + * -original contribution by Tim.yao@amlogic.com + * + */ + +#include +#include +#include +#include + +#define __get8_unaligned_check(val, addr, err) \ + __asm__( \ + "1: ldb.ab %1, [%2, 1]\n" \ + "2:\n" \ + " .section .fixup,\"ax\"\n" \ + " .align 4\n" \ + "3: mov %0, 1\n" \ + " b 2b\n" \ + " .previous\n" \ + " .section __ex_table,\"a\"\n" \ + " .align 4\n" \ + " .long 1b, 3b\n" \ + " .previous\n" \ + : "=r" (err), "=&r" (val), "=r" (addr) \ + : "0" (err), "2" (addr)) + +#define get16_unaligned_check(val, addr) \ + do { \ + unsigned int err = 0, v, a = addr; \ + __get8_unaligned_check(v, a, err); \ + val = v ; \ + __get8_unaligned_check(v, a, err); \ + val |= v << 8; \ + if (err) \ + goto fault; \ + } while (0) + +#define get32_unaligned_check(val, addr) \ + do { \ + unsigned int err = 0, v, a = addr; \ + __get8_unaligned_check(v, a, err); \ + val = v << 0; \ + __get8_unaligned_check(v, a, err); \ + val |= v << 8; \ + __get8_unaligned_check(v, a, err); \ + val |= v << 16; \ + __get8_unaligned_check(v, a, err); \ + val |= v << 24; \ + if (err) \ + goto fault; \ + } while (0) + +#define put16_unaligned_check(val, addr) \ + do { \ + unsigned int err = 0, v = val, a = addr;\ + \ + __asm__( \ + "1: stb.ab %1, [%2, 1]\n" \ + " lsr %1, %1, 8\n" \ + "2: stb %1, [%2]\n" \ + "3:\n" \ + " .section .fixup,\"ax\"\n" \ + " .align 4\n" \ + "4: mov %0, 1\n" \ + " b 3b\n" \ + " .previous\n" \ + " .section __ex_table,\"a\"\n" \ + " .align 4\n" \ + " .long 1b, 4b\n" \ + " .long 2b, 4b\n" \ + " .previous\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) \ + do { \ + unsigned int err = 0, v = val, a = addr;\ + __asm__( \ + \ + "1: stb.ab %1, [%2, 1]\n" \ + " lsr %1, %1, 8\n" \ + "2: stb.ab %1, [%2, 1]\n" \ + " lsr %1, %1, 8\n" \ + "3: stb.ab %1, [%2, 1]\n" \ + " lsr %1, %1, 8\n" \ + "4: stb %1, [%2]\n" \ + "5:\n" \ + " .section .fixup,\"ax\"\n" \ + " .align 4\n" \ + "6: mov %0, 1\n" \ + " b 5b\n" \ + " .previous\n" \ + " .section __ex_table,\"a\"\n" \ + " .align 4\n" \ + " .long 1b, 6b\n" \ + " .long 2b, 6b\n" \ + " .long 3b, 6b\n" \ + " .long 4b, 6b\n" \ + " .previous\n" \ + : "=r" (err), "=&r" (v), "=&r" (a) \ + : "0" (err), "1" (v), "2" (a)); \ + \ + if (err) \ + goto fault; \ + } while (0) + +/* sysctl hooks */ +int unaligned_enabled __read_mostly = 1; /* Enabled by default */ +int no_unaligned_warning __read_mostly = 1; /* Only 1 warning by default */ + +static void fixup_load(struct disasm_state *state, struct pt_regs *regs, + struct callee_regs *cregs) +{ + int val; + + /* register write back */ + if ((state->aa == 1) || (state->aa == 2)) { + set_reg(state->wb_reg, state->src1 + state->src2, regs, cregs); + + if (state->aa == 2) + state->src2 = 0; + } + + if (state->zz == 0) { + get32_unaligned_check(val, state->src1 + state->src2); + } else { + get16_unaligned_check(val, state->src1 + state->src2); + + if (state->x) + val = (val << 16) >> 16; + } + + if (state->pref == 0) + set_reg(state->dest, val, regs, cregs); + + return; + +fault: state->fault = 1; +} + +static void fixup_store(struct disasm_state *state, struct pt_regs *regs, + struct callee_regs *cregs) +{ + /* register write back */ + if ((state->aa == 1) || (state->aa == 2)) { + set_reg(state->wb_reg, state->src2 + state->src3, regs, cregs); + + if (state->aa == 3) + state->src3 = 0; + } else if (state->aa == 3) { + if (state->zz == 2) { + set_reg(state->wb_reg, state->src2 + (state->src3 << 1), + regs, cregs); + } else if (!state->zz) { + set_reg(state->wb_reg, state->src2 + (state->src3 << 2), + regs, cregs); + } else { + goto fault; + } + } + + /* write fix-up */ + if (!state->zz) + put32_unaligned_check(state->src1, state->src2 + state->src3); + else + put16_unaligned_check(state->src1, state->src2 + state->src3); + + return; + +fault: state->fault = 1; +} + +/* + * Handle an unaligned access + * Returns 0 if successfully handled, 1 if some error happened + */ +int misaligned_fixup(unsigned long address, struct pt_regs *regs, + unsigned long cause, struct callee_regs *cregs) +{ + struct disasm_state state; + char buf[TASK_COMM_LEN]; + + /* handle user mode only and only if enabled by sysadmin */ + if (!user_mode(regs) || !unaligned_enabled) + return 1; + + if (no_unaligned_warning) { + pr_warn_once("%s(%d) made unaligned access which was emulated" + " by kernel assist\n. This can degrade application" + " performance significantly\n. To enable further" + " logging of such instances, please \n" + " echo 0 > /proc/sys/kernel/ignore-unaligned-usertrap\n", + get_task_comm(buf, current), task_pid_nr(current)); + } else { + /* Add rate limiting if it gets down to it */ + pr_warn("%s(%d): unaligned access to/from 0x%lx by PC: 0x%lx\n", + get_task_comm(buf, current), task_pid_nr(current), + address, regs->ret); + + } + + disasm_instr(regs->ret, &state, 1, regs, cregs); + + if (state.fault) + goto fault; + + /* ldb/stb should not have unaligned exception */ + if ((state.zz == 1) || (state.di)) + goto fault; + + if (!state.write) + fixup_load(&state, regs, cregs); + else + fixup_store(&state, regs, cregs); + + if (state.fault) + goto fault; + + if (delay_mode(regs)) { + regs->ret = regs->bta; + regs->status32 &= ~STATUS_DE_MASK; + } else { + regs->ret += state.instr_len; + } + + return 0; + +fault: + pr_err("Alignment trap: fault in fix-up %08lx at [<%08lx>]\n", + state.words[0], address); + + return 1; +} -- cgit v1.2.3