diff options
Diffstat (limited to 'arch/tile/kernel/single_step.c')
| -rw-r--r-- | arch/tile/kernel/single_step.c | 663 |
1 files changed, 663 insertions, 0 deletions
diff --git a/arch/tile/kernel/single_step.c b/arch/tile/kernel/single_step.c new file mode 100644 index 000000000000..5ec4b9c651f2 --- /dev/null +++ b/arch/tile/kernel/single_step.c @@ -0,0 +1,663 @@ +/* + * Copyright 2010 Tilera Corporation. All Rights Reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, version 2. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for + * more details. + * + * A code-rewriter that enables instruction single-stepping. + * Derived from iLib's single-stepping code. + */ + +#ifndef __tilegx__ /* No support for single-step yet. */ + +/* These functions are only used on the TILE platform */ +#include <linux/slab.h> +#include <linux/thread_info.h> +#include <linux/uaccess.h> +#include <linux/mman.h> +#include <linux/types.h> +#include <linux/err.h> +#include <asm/cacheflush.h> +#include <asm/opcode-tile.h> +#include <asm/opcode_constants.h> +#include <arch/abi.h> + +#define signExtend17(val) sign_extend((val), 17) +#define TILE_X1_MASK (0xffffffffULL << 31) + +int unaligned_printk; + +static int __init setup_unaligned_printk(char *str) +{ + long val; + if (strict_strtol(str, 0, &val) != 0) + return 0; + unaligned_printk = val; + pr_info("Printk for each unaligned data accesses is %s\n", + unaligned_printk ? "enabled" : "disabled"); + return 1; +} +__setup("unaligned_printk=", setup_unaligned_printk); + +unsigned int unaligned_fixup_count; + +enum mem_op { + MEMOP_NONE, + MEMOP_LOAD, + MEMOP_STORE, + MEMOP_LOAD_POSTINCR, + MEMOP_STORE_POSTINCR +}; + +static inline tile_bundle_bits set_BrOff_X1(tile_bundle_bits n, int32_t offset) +{ + tile_bundle_bits result; + + /* mask out the old offset */ + tile_bundle_bits mask = create_BrOff_X1(-1); + result = n & (~mask); + + /* or in the new offset */ + result |= create_BrOff_X1(offset); + + return result; +} + +static inline tile_bundle_bits move_X1(tile_bundle_bits n, int dest, int src) +{ + tile_bundle_bits result; + tile_bundle_bits op; + + result = n & (~TILE_X1_MASK); + + op = create_Opcode_X1(SPECIAL_0_OPCODE_X1) | + create_RRROpcodeExtension_X1(OR_SPECIAL_0_OPCODE_X1) | + create_Dest_X1(dest) | + create_SrcB_X1(TREG_ZERO) | + create_SrcA_X1(src) ; + + result |= op; + return result; +} + +static inline tile_bundle_bits nop_X1(tile_bundle_bits n) +{ + return move_X1(n, TREG_ZERO, TREG_ZERO); +} + +static inline tile_bundle_bits addi_X1( + tile_bundle_bits n, int dest, int src, int imm) +{ + n &= ~TILE_X1_MASK; + + n |= (create_SrcA_X1(src) | + create_Dest_X1(dest) | + create_Imm8_X1(imm) | + create_S_X1(0) | + create_Opcode_X1(IMM_0_OPCODE_X1) | + create_ImmOpcodeExtension_X1(ADDI_IMM_0_OPCODE_X1)); + + return n; +} + +static tile_bundle_bits rewrite_load_store_unaligned( + struct single_step_state *state, + tile_bundle_bits bundle, + struct pt_regs *regs, + enum mem_op mem_op, + int size, int sign_ext) +{ + unsigned char __user *addr; + int val_reg, addr_reg, err, val; + + /* Get address and value registers */ + if (bundle & TILE_BUNDLE_Y_ENCODING_MASK) { + addr_reg = get_SrcA_Y2(bundle); + val_reg = get_SrcBDest_Y2(bundle); + } else if (mem_op == MEMOP_LOAD || mem_op == MEMOP_LOAD_POSTINCR) { + addr_reg = get_SrcA_X1(bundle); + val_reg = get_Dest_X1(bundle); + } else { + addr_reg = get_SrcA_X1(bundle); + val_reg = get_SrcB_X1(bundle); + } + + /* + * If registers are not GPRs, don't try to handle it. + * + * FIXME: we could handle non-GPR loads by getting the real value + * from memory, writing it to the single step buffer, using a + * temp_reg to hold a pointer to that memory, then executing that + * instruction and resetting temp_reg. For non-GPR stores, it's a + * little trickier; we could use the single step buffer for that + * too, but we'd have to add some more state bits so that we could + * call back in here to copy that value to the real target. For + * now, we just handle the simple case. + */ + if ((val_reg >= PTREGS_NR_GPRS && + (val_reg != TREG_ZERO || + mem_op == MEMOP_LOAD || + mem_op == MEMOP_LOAD_POSTINCR)) || + addr_reg >= PTREGS_NR_GPRS) + return bundle; + + /* If it's aligned, don't handle it specially */ + addr = (void __user *)regs->regs[addr_reg]; + if (((unsigned long)addr % size) == 0) + return bundle; + +#ifndef __LITTLE_ENDIAN +# error We assume little-endian representation with copy_xx_user size 2 here +#endif + /* Handle unaligned load/store */ + if (mem_op == MEMOP_LOAD || mem_op == MEMOP_LOAD_POSTINCR) { + unsigned short val_16; + switch (size) { + case 2: + err = copy_from_user(&val_16, addr, sizeof(val_16)); + val = sign_ext ? ((short)val_16) : val_16; + break; + case 4: + err = copy_from_user(&val, addr, sizeof(val)); + break; + default: + BUG(); + } + if (err == 0) { + state->update_reg = val_reg; + state->update_value = val; + state->update = 1; + } + } else { + val = (val_reg == TREG_ZERO) ? 0 : regs->regs[val_reg]; + err = copy_to_user(addr, &val, size); + } + + if (err) { + siginfo_t info = { + .si_signo = SIGSEGV, + .si_code = SEGV_MAPERR, + .si_addr = addr + }; + force_sig_info(info.si_signo, &info, current); + return (tile_bundle_bits) 0; + } + + if (unaligned_fixup == 0) { + siginfo_t info = { + .si_signo = SIGBUS, + .si_code = BUS_ADRALN, + .si_addr = addr + }; + force_sig_info(info.si_signo, &info, current); + return (tile_bundle_bits) 0; + } + + if (unaligned_printk || unaligned_fixup_count == 0) { + pr_info("Process %d/%s: PC %#lx: Fixup of" + " unaligned %s at %#lx.\n", + current->pid, current->comm, regs->pc, + (mem_op == MEMOP_LOAD || + mem_op == MEMOP_LOAD_POSTINCR) ? + "load" : "store", + (unsigned long)addr); + if (!unaligned_printk) { +#define P pr_info +P("\n"); +P("Unaligned fixups in the kernel will slow your application considerably.\n"); +P("To find them, write a \"1\" to /proc/sys/tile/unaligned_fixup/printk,\n"); +P("which requests the kernel show all unaligned fixups, or write a \"0\"\n"); +P("to /proc/sys/tile/unaligned_fixup/enabled, in which case each unaligned\n"); +P("access will become a SIGBUS you can debug. No further warnings will be\n"); +P("shown so as to avoid additional slowdown, but you can track the number\n"); +P("of fixups performed via /proc/sys/tile/unaligned_fixup/count.\n"); +P("Use the tile-addr2line command (see \"info addr2line\") to decode PCs.\n"); +P("\n"); +#undef P + } + } + ++unaligned_fixup_count; + + if (bundle & TILE_BUNDLE_Y_ENCODING_MASK) { + /* Convert the Y2 instruction to a prefetch. */ + bundle &= ~(create_SrcBDest_Y2(-1) | + create_Opcode_Y2(-1)); + bundle |= (create_SrcBDest_Y2(TREG_ZERO) | + create_Opcode_Y2(LW_OPCODE_Y2)); + /* Replace the load postincr with an addi */ + } else if (mem_op == MEMOP_LOAD_POSTINCR) { + bundle = addi_X1(bundle, addr_reg, addr_reg, + get_Imm8_X1(bundle)); + /* Replace the store postincr with an addi */ + } else if (mem_op == MEMOP_STORE_POSTINCR) { + bundle = addi_X1(bundle, addr_reg, addr_reg, + get_Dest_Imm8_X1(bundle)); + } else { + /* Convert the X1 instruction to a nop. */ + bundle &= ~(create_Opcode_X1(-1) | + create_UnShOpcodeExtension_X1(-1) | + create_UnOpcodeExtension_X1(-1)); + bundle |= (create_Opcode_X1(SHUN_0_OPCODE_X1) | + create_UnShOpcodeExtension_X1( + UN_0_SHUN_0_OPCODE_X1) | + create_UnOpcodeExtension_X1( + NOP_UN_0_SHUN_0_OPCODE_X1)); + } + + return bundle; +} + +/** + * single_step_once() - entry point when single stepping has been triggered. + * @regs: The machine register state + * + * When we arrive at this routine via a trampoline, the single step + * engine copies the executing bundle to the single step buffer. + * If the instruction is a condition branch, then the target is + * reset to one past the next instruction. If the instruction + * sets the lr, then that is noted. If the instruction is a jump + * or call, then the new target pc is preserved and the current + * bundle instruction set to null. + * + * The necessary post-single-step rewriting information is stored in + * single_step_state-> We use data segment values because the + * stack will be rewound when we run the rewritten single-stepped + * instruction. + */ +void single_step_once(struct pt_regs *regs) +{ + extern tile_bundle_bits __single_step_ill_insn; + extern tile_bundle_bits __single_step_j_insn; + extern tile_bundle_bits __single_step_addli_insn; + extern tile_bundle_bits __single_step_auli_insn; + struct thread_info *info = (void *)current_thread_info(); + struct single_step_state *state = info->step_state; + int is_single_step = test_ti_thread_flag(info, TIF_SINGLESTEP); + tile_bundle_bits __user *buffer, *pc; + tile_bundle_bits bundle; + int temp_reg; + int target_reg = TREG_LR; + int err; + enum mem_op mem_op = MEMOP_NONE; + int size = 0, sign_ext = 0; /* happy compiler */ + + asm( +" .pushsection .rodata.single_step\n" +" .align 8\n" +" .globl __single_step_ill_insn\n" +"__single_step_ill_insn:\n" +" ill\n" +" .globl __single_step_addli_insn\n" +"__single_step_addli_insn:\n" +" { nop; addli r0, zero, 0 }\n" +" .globl __single_step_auli_insn\n" +"__single_step_auli_insn:\n" +" { nop; auli r0, r0, 0 }\n" +" .globl __single_step_j_insn\n" +"__single_step_j_insn:\n" +" j .\n" +" .popsection\n" + ); + + if (state == NULL) { + /* allocate a page of writable, executable memory */ + state = kmalloc(sizeof(struct single_step_state), GFP_KERNEL); + if (state == NULL) { + pr_err("Out of kernel memory trying to single-step\n"); + return; + } + + /* allocate a cache line of writable, executable memory */ + down_write(¤t->mm->mmap_sem); + buffer = (void __user *) do_mmap(NULL, 0, 64, + PROT_EXEC | PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, + 0); + up_write(¤t->mm->mmap_sem); + + if (IS_ERR((void __force *)buffer)) { + kfree(state); + pr_err("Out of kernel pages trying to single-step\n"); + return; + } + + state->buffer = buffer; + state->is_enabled = 0; + + info->step_state = state; + + /* Validate our stored instruction patterns */ + BUG_ON(get_Opcode_X1(__single_step_addli_insn) != + ADDLI_OPCODE_X1); + BUG_ON(get_Opcode_X1(__single_step_auli_insn) != + AULI_OPCODE_X1); + BUG_ON(get_SrcA_X1(__single_step_addli_insn) != TREG_ZERO); + BUG_ON(get_Dest_X1(__single_step_addli_insn) != 0); + BUG_ON(get_JOffLong_X1(__single_step_j_insn) != 0); + } + + /* + * If we are returning from a syscall, we still haven't hit the + * "ill" for the swint1 instruction. So back the PC up to be + * pointing at the swint1, but we'll actually return directly + * back to the "ill" so we come back in via SIGILL as if we + * had "executed" the swint1 without ever being in kernel space. + */ + if (regs->faultnum == INT_SWINT_1) + regs->pc -= 8; + + pc = (tile_bundle_bits __user *)(regs->pc); + if (get_user(bundle, pc) != 0) { + pr_err("Couldn't read instruction at %p trying to step\n", pc); + return; + } + + /* We'll follow the instruction with 2 ill op bundles */ + state->orig_pc = (unsigned long)pc; + state->next_pc = (unsigned long)(pc + 1); + state->branch_next_pc = 0; + state->update = 0; + + if (!(bundle & TILE_BUNDLE_Y_ENCODING_MASK)) { + /* two wide, check for control flow */ + int opcode = get_Opcode_X1(bundle); + + switch (opcode) { + /* branches */ + case BRANCH_OPCODE_X1: + { + int32_t offset = signExtend17(get_BrOff_X1(bundle)); + + /* + * For branches, we use a rewriting trick to let the + * hardware evaluate whether the branch is taken or + * untaken. We record the target offset and then + * rewrite the branch instruction to target 1 insn + * ahead if the branch is taken. We then follow the + * rewritten branch with two bundles, each containing + * an "ill" instruction. The supervisor examines the + * pc after the single step code is executed, and if + * the pc is the first ill instruction, then the + * branch (if any) was not taken. If the pc is the + * second ill instruction, then the branch was + * taken. The new pc is computed for these cases, and + * inserted into the registers for the thread. If + * the pc is the start of the single step code, then + * an exception or interrupt was taken before the + * code started processing, and the same "original" + * pc is restored. This change, different from the + * original implementation, has the advantage of + * executing a single user instruction. + */ + state->branch_next_pc = (unsigned long)(pc + offset); + + /* rewrite branch offset to go forward one bundle */ + bundle = set_BrOff_X1(bundle, 2); + } + break; + + /* jumps */ + case JALB_OPCODE_X1: + case JALF_OPCODE_X1: + state->update = 1; + state->next_pc = + (unsigned long) (pc + get_JOffLong_X1(bundle)); + break; + + case JB_OPCODE_X1: + case JF_OPCODE_X1: + state->next_pc = + (unsigned long) (pc + get_JOffLong_X1(bundle)); + bundle = nop_X1(bundle); + break; + + case SPECIAL_0_OPCODE_X1: + switch (get_RRROpcodeExtension_X1(bundle)) { + /* jump-register */ + case JALRP_SPECIAL_0_OPCODE_X1: + case JALR_SPECIAL_0_OPCODE_X1: + state->update = 1; + state->next_pc = + regs->regs[get_SrcA_X1(bundle)]; + break; + + case JRP_SPECIAL_0_OPCODE_X1: + case JR_SPECIAL_0_OPCODE_X1: + state->next_pc = + regs->regs[get_SrcA_X1(bundle)]; + bundle = nop_X1(bundle); + break; + + case LNK_SPECIAL_0_OPCODE_X1: + state->update = 1; + target_reg = get_Dest_X1(bundle); + break; + + /* stores */ + case SH_SPECIAL_0_OPCODE_X1: + mem_op = MEMOP_STORE; + size = 2; + break; + + case SW_SPECIAL_0_OPCODE_X1: + mem_op = MEMOP_STORE; + size = 4; + break; + } + break; + + /* loads and iret */ + case SHUN_0_OPCODE_X1: + if (get_UnShOpcodeExtension_X1(bundle) == + UN_0_SHUN_0_OPCODE_X1) { + switch (get_UnOpcodeExtension_X1(bundle)) { + case LH_UN_0_SHUN_0_OPCODE_X1: + mem_op = MEMOP_LOAD; + size = 2; + sign_ext = 1; + break; + + case LH_U_UN_0_SHUN_0_OPCODE_X1: + mem_op = MEMOP_LOAD; + size = 2; + sign_ext = 0; + break; + + case LW_UN_0_SHUN_0_OPCODE_X1: + mem_op = MEMOP_LOAD; + size = 4; + break; + + case IRET_UN_0_SHUN_0_OPCODE_X1: + { + unsigned long ex0_0 = __insn_mfspr( + SPR_EX_CONTEXT_0_0); + unsigned long ex0_1 = __insn_mfspr( + SPR_EX_CONTEXT_0_1); + /* + * Special-case it if we're iret'ing + * to PL0 again. Otherwise just let + * it run and it will generate SIGILL. + */ + if (EX1_PL(ex0_1) == USER_PL) { + state->next_pc = ex0_0; + regs->ex1 = ex0_1; + bundle = nop_X1(bundle); + } + } + } + } + break; + +#if CHIP_HAS_WH64() + /* postincrement operations */ + case IMM_0_OPCODE_X1: + switch (get_ImmOpcodeExtension_X1(bundle)) { + case LWADD_IMM_0_OPCODE_X1: + mem_op = MEMOP_LOAD_POSTINCR; + size = 4; + break; + + case LHADD_IMM_0_OPCODE_X1: + mem_op = MEMOP_LOAD_POSTINCR; + size = 2; + sign_ext = 1; + break; + + case LHADD_U_IMM_0_OPCODE_X1: + mem_op = MEMOP_LOAD_POSTINCR; + size = 2; + sign_ext = 0; + break; + + case SWADD_IMM_0_OPCODE_X1: + mem_op = MEMOP_STORE_POSTINCR; + size = 4; + break; + + case SHADD_IMM_0_OPCODE_X1: + mem_op = MEMOP_STORE_POSTINCR; + size = 2; + break; + + default: + break; + } + break; +#endif /* CHIP_HAS_WH64() */ + } + + if (state->update) { + /* + * Get an available register. We start with a + * bitmask with 1's for available registers. + * We truncate to the low 32 registers since + * we are guaranteed to have set bits in the + * low 32 bits, then use ctz to pick the first. + */ + u32 mask = (u32) ~((1ULL << get_Dest_X0(bundle)) | + (1ULL << get_SrcA_X0(bundle)) | + (1ULL << get_SrcB_X0(bundle)) | + (1ULL << target_reg)); + temp_reg = __builtin_ctz(mask); + state->update_reg = temp_reg; + state->update_value = regs->regs[temp_reg]; + regs->regs[temp_reg] = (unsigned long) (pc+1); + regs->flags |= PT_FLAGS_RESTORE_REGS; + bundle = move_X1(bundle, target_reg, temp_reg); + } + } else { + int opcode = get_Opcode_Y2(bundle); + + switch (opcode) { + /* loads */ + case LH_OPCODE_Y2: + mem_op = MEMOP_LOAD; + size = 2; + sign_ext = 1; + break; + + case LH_U_OPCODE_Y2: + mem_op = MEMOP_LOAD; + size = 2; + sign_ext = 0; + break; + + case LW_OPCODE_Y2: + mem_op = MEMOP_LOAD; + size = 4; + break; + + /* stores */ + case SH_OPCODE_Y2: + mem_op = MEMOP_STORE; + size = 2; + break; + + case SW_OPCODE_Y2: + mem_op = MEMOP_STORE; + size = 4; + break; + } + } + + /* + * Check if we need to rewrite an unaligned load/store. + * Returning zero is a special value meaning we need to SIGSEGV. + */ + if (mem_op != MEMOP_NONE && unaligned_fixup >= 0) { + bundle = rewrite_load_store_unaligned(state, bundle, regs, + mem_op, size, sign_ext); + if (bundle == 0) + return; + } + + /* write the bundle to our execution area */ + buffer = state->buffer; + err = __put_user(bundle, buffer++); + + /* + * If we're really single-stepping, we take an INT_ILL after. + * If we're just handling an unaligned access, we can just + * jump directly back to where we were in user code. + */ + if (is_single_step) { + err |= __put_user(__single_step_ill_insn, buffer++); + err |= __put_user(__single_step_ill_insn, buffer++); + } else { + long delta; + + if (state->update) { + /* We have some state to update; do it inline */ + int ha16; + bundle = __single_step_addli_insn; + bundle |= create_Dest_X1(state->update_reg); + bundle |= create_Imm16_X1(state->update_value); + err |= __put_user(bundle, buffer++); + bundle = __single_step_auli_insn; + bundle |= create_Dest_X1(state->update_reg); + bundle |= create_SrcA_X1(state->update_reg); + ha16 = (state->update_value + 0x8000) >> 16; + bundle |= create_Imm16_X1(ha16); + err |= __put_user(bundle, buffer++); + state->update = 0; + } + + /* End with a jump back to the next instruction */ + delta = ((regs->pc + TILE_BUNDLE_SIZE_IN_BYTES) - + (unsigned long)buffer) >> + TILE_LOG2_BUNDLE_ALIGNMENT_IN_BYTES; + bundle = __single_step_j_insn; + bundle |= create_JOffLong_X1(delta); + err |= __put_user(bundle, buffer++); + } + + if (err) { + pr_err("Fault when writing to single-step buffer\n"); + return; + } + + /* + * Flush the buffer. + * We do a local flush only, since this is a thread-specific buffer. + */ + __flush_icache_range((unsigned long)state->buffer, + (unsigned long)buffer); + + /* Indicate enabled */ + state->is_enabled = is_single_step; + regs->pc = (unsigned long)state->buffer; + + /* Fault immediately if we are coming back from a syscall. */ + if (regs->faultnum == INT_SWINT_1) + regs->pc += 8; +} + +#endif /* !__tilegx__ */ |