- 根目录:
- arch
- tile
- kernel
- single_step.c
/*
* 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.
*/
#include <linux/smp.h>
#include <linux/ptrace.h>
#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 <linux/prctl.h>
#include <asm/cacheflush.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
#include <asm/unaligned.h>
#include <arch/abi.h>
#include <arch/spr_def.h>
#include <arch/opcode.h>
#ifndef __tilegx__ /* Hardware support for single step unavailable. */
#define signExtend17(val) sign_extend((val), 17)
#define TILE_X1_MASK (0xffffffffULL << 31)
enum mem_op {
MEMOP_NONE,
MEMOP_LOAD,
MEMOP_STORE,
MEMOP_LOAD_POSTINCR,
MEMOP_STORE_POSTINCR
};
static inline tilepro_bundle_bits set_BrOff_X1(tilepro_bundle_bits n,
s32 offset)
{
tilepro_bundle_bits result;
/* mask out the old offset */
tilepro_bundle_bits mask = create_BrOff_X1(-1);
result = n & (~mask);
/* or in the new offset */
result |= create_BrOff_X1(offset);
return result;
}
static inline tilepro_bundle_bits move_X1(tilepro_bundle_bits n, int dest,
int src)
{
tilepro_bundle_bits result;
tilepro_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 tilepro_bundle_bits nop_X1(tilepro_bundle_bits n)
{
return move_X1(n, TREG_ZERO, TREG_ZERO);
}
static inline tilepro_bundle_bits addi_X1(
tilepro_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 tilepro_bundle_bits rewrite_load_store_unaligned(
struct single_step_state *state,
tilepro_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;
int align_ctl;
align_ctl = unaligned_fixup;
switch (task_thread_info(current)->align_ctl) {
case PR_UNALIGN_NOPRINT:
align_ctl = 1;
break;
case PR_UNALIGN_SIGBUS:
align_ctl = 0;
break;
}
/* Get address and value registers */
if (bundle & TILEPRO_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;
/*
* Return SIGBUS with the unaligned address, if requested.
* Note that we return SIGBUS even for completely invalid addresses
* as long as they are in fact unaligned; this matches what the
* tilepro hardware would be doing, if it could provide us with the
* actual bad address in an SPR, which it doesn't.
*/
if (align_ctl == 0) {
siginfo_t info = {
.si_signo = SIGBUS,
.si_code = BUS_ADRALN,
.si_addr = addr
};
trace_unhandled_signal("unaligned trap", regs,
(unsigned long)addr, SIGBUS);
force_sig_info(info.si_signo, &info, current);
return (tilepro_bundle_bits) 0;
}
/* 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 {
unsigned short val_16;
val = (val_reg == TREG_ZERO) ? 0 : regs->regs[val_reg];
switch (size) {
case 2:
val_16 = val;
err = copy_to_user(addr, &val_16, sizeof(val_16));
break;
case 4:
err = copy_to_user(addr, &val, sizeof(val));
break;
default:
BUG();
}
}
if (err) {
siginfo_t info = {
.si_signo = SIGBUS,
.si_code = BUS_ADRALN,
.si_addr = addr
};
trace_unhandled_signal("bad address for unaligned fixup", regs,
(unsigned long)addr, SIGBUS);
force_sig_info(info.si_signo, &info, current);
return (tilepro_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 & TILEPRO_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;
}
/*
* Called after execve() has started the new image. This allows us
* to reset the info state. Note that the the mmap'ed memory, if there
* was any, has already been unmapped by the exec.
*/
void single_step_execve(void)
{
struct thread_info *ti = current_thread_info();
kfree(ti->step_state);
ti->step_state = NULL;
}
/*
* 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 tilepro_bundle_bits __single_step_ill_insn;
extern tilepro_bundle_bits __single_step_j_insn;
extern tilepro_bundle_bits __single_step_addli_insn;
extern tilepro_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);
tilepro_bundle_bits __user *buffer, *pc;
tilepro_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 */
int align_ctl;
align_ctl = unaligned_fixup;
switch (task_thread_info(current)->align_ctl) {
case PR_UNALIGN_NOPRINT:
align_ctl = 1;
break;
case PR_UNALIGN_SIGBUS:
align_ctl = 0;
break;
}
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"
);
/*
* Enable interrupts here to allow touching userspace and the like.
* The callers expect this: do_trap() already has interrupts
* enabled, and do_work_pending() handles functions that enable
* interrupts internally.
*/
local_irq_enable();
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 */
buffer = (void __user *) vm_mmap(NULL, 0, 64,
PROT_EXEC | PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS,
0);
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 = (tilepro_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 & TILEPRO_BUNDLE_Y_ENCODING_MASK)) {
/* two wide, check for control flow */
int opcode = get_Opcode_X1(bundle);
switch (opcode) {
/* branches */
case BRANCH_OPCODE_X1:
{
s32 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;
/* 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;
}
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 generated a signal.
*/
if (mem_op != MEMOP_NONE && align_ctl >= 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 + TILEPRO_BUNDLE_SIZE_IN_BYTES) -
(unsigned long)buffer) >>
TILEPRO_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;
}
#else
static DEFINE_PER_CPU(unsigned long, ss_saved_pc);
/*
* Called directly on the occasion of an interrupt.
*
* If the process doesn't have single step set, then we use this as an
* opportunity to turn single step off.
*
* It has been mentioned that we could conditionally turn off single stepping
* on each entry into the kernel and rely on single_step_once to turn it
* on for the processes that matter (as we already do), but this
* implementation is somewhat more efficient in that we muck with registers
* once on a bum interrupt rather than on every entry into the kernel.
*
* If SINGLE_STEP_CONTROL_K has CANCELED set, then an interrupt occurred,
* so we have to run through this process again before we can say that an
* instruction has executed.
*
* swint will set CANCELED, but it's a legitimate instruction. Fortunately
* it changes the PC. If it hasn't changed, then we know that the interrupt
* wasn't generated by swint and we'll need to run this process again before
* we can say an instruction has executed.
*
* If either CANCELED == 0 or the PC's changed, we send out SIGTRAPs and get
* on with our lives.
*/
void gx_singlestep_handle(struct pt_regs *regs, int fault_num)
{
unsigned long *ss_pc = &__get_cpu_var(ss_saved_pc);
struct thread_info *info = (void *)current_thread_info();
int is_single_step = test_ti_thread_flag(info, TIF_SINGLESTEP);
unsigned long control = __insn_mfspr(SPR_SINGLE_STEP_CONTROL_K);
if (is_single_step == 0) {
__insn_mtspr(SPR_SINGLE_STEP_EN_K_K, 0);
} else if ((*ss_pc != regs->pc) ||
(!(control & SPR_SINGLE_STEP_CONTROL_1__CANCELED_MASK))) {
control |= SPR_SINGLE_STEP_CONTROL_1__CANCELED_MASK;
control |= SPR_SINGLE_STEP_CONTROL_1__INHIBIT_MASK;
__insn_mtspr(SPR_SINGLE_STEP_CONTROL_K, control);
send_sigtrap(current, regs);
}
}
/*
* Called from need_singlestep. Set up the control registers and the enable
* register, then return back.
*/
void single_step_once(struct pt_regs *regs)
{
unsigned long *ss_pc = &__get_cpu_var(ss_saved_pc);
unsigned long control = __insn_mfspr(SPR_SINGLE_STEP_CONTROL_K);
*ss_pc = regs->pc;
control |= SPR_SINGLE_STEP_CONTROL_1__CANCELED_MASK;
control |= SPR_SINGLE_STEP_CONTROL_1__INHIBIT_MASK;
__insn_mtspr(SPR_SINGLE_STEP_CONTROL_K, control);
__insn_mtspr(SPR_SINGLE_STEP_EN_K_K, 1 << USER_PL);
}
void single_step_execve(void)
{
/* Nothing */
}
#endif /* !__tilegx__ */