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linux-next/arch/sparc/kernel/kprobes.c
Christoph Lameter 494fc42170 sparc: Replace __get_cpu_var uses 
__get_cpu_var() is used for multiple purposes in the kernel source. One of
them is address calculation via the form &__get_cpu_var(x).  This calculates
the address for the instance of the percpu variable of the current processor
based on an offset.

Other use cases are for storing and retrieving data from the current
processors percpu area.  __get_cpu_var() can be used as an lvalue when
writing data or on the right side of an assignment.

__get_cpu_var() is defined as :

#define __get_cpu_var(var) (*this_cpu_ptr(&(var)))

__get_cpu_var() always only does an address determination. However, store
and retrieve operations could use a segment prefix (or global register on
other platforms) to avoid the address calculation.

this_cpu_write() and this_cpu_read() can directly take an offset into a
percpu area and use optimized assembly code to read and write per cpu
variables.

This patch converts __get_cpu_var into either an explicit address
calculation using this_cpu_ptr() or into a use of this_cpu operations that
use the offset.  Thereby address calculations are avoided and less registers
are used when code is generated.

At the end of the patch set all uses of __get_cpu_var have been removed so
the macro is removed too.

The patch set includes passes over all arches as well. Once these operations
are used throughout then specialized macros can be defined in non -x86
arches as well in order to optimize per cpu access by f.e.  using a global
register that may be set to the per cpu base.

Transformations done to __get_cpu_var()

1. Determine the address of the percpu instance of the current processor.

	DEFINE_PER_CPU(int, y);
	int *x = &__get_cpu_var(y);

    Converts to

	int *x = this_cpu_ptr(&y);

2. Same as #1 but this time an array structure is involved.

	DEFINE_PER_CPU(int, y[20]);
	int *x = __get_cpu_var(y);

    Converts to

	int *x = this_cpu_ptr(y);

3. Retrieve the content of the current processors instance of a per cpu
variable.

	DEFINE_PER_CPU(int, y);
	int x = __get_cpu_var(y)

   Converts to

	int x = __this_cpu_read(y);

4. Retrieve the content of a percpu struct

	DEFINE_PER_CPU(struct mystruct, y);
	struct mystruct x = __get_cpu_var(y);

   Converts to

	memcpy(&x, this_cpu_ptr(&y), sizeof(x));

5. Assignment to a per cpu variable

	DEFINE_PER_CPU(int, y)
	__get_cpu_var(y) = x;

   Converts to

	__this_cpu_write(y, x);

6. Increment/Decrement etc of a per cpu variable

	DEFINE_PER_CPU(int, y);
	__get_cpu_var(y)++

   Converts to

	__this_cpu_inc(y)

Cc: sparclinux@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2014-08-26 13:45:55 -04:00

604 lines
16 KiB
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/* arch/sparc64/kernel/kprobes.c
*
* Copyright (C) 2004 David S. Miller <davem@davemloft.net>
*/
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/kdebug.h>
#include <linux/slab.h>
#include <linux/context_tracking.h>
#include <asm/signal.h>
#include <asm/cacheflush.h>
#include <asm/uaccess.h>
/* We do not have hardware single-stepping on sparc64.
* So we implement software single-stepping with breakpoint
* traps. The top-level scheme is similar to that used
* in the x86 kprobes implementation.
*
* In the kprobe->ainsn.insn[] array we store the original
* instruction at index zero and a break instruction at
* index one.
*
* When we hit a kprobe we:
* - Run the pre-handler
* - Remember "regs->tnpc" and interrupt level stored in
* "regs->tstate" so we can restore them later
* - Disable PIL interrupts
* - Set regs->tpc to point to kprobe->ainsn.insn[0]
* - Set regs->tnpc to point to kprobe->ainsn.insn[1]
* - Mark that we are actively in a kprobe
*
* At this point we wait for the second breakpoint at
* kprobe->ainsn.insn[1] to hit. When it does we:
* - Run the post-handler
* - Set regs->tpc to "remembered" regs->tnpc stored above,
* restore the PIL interrupt level in "regs->tstate" as well
* - Make any adjustments necessary to regs->tnpc in order
* to handle relative branches correctly. See below.
* - Mark that we are no longer actively in a kprobe.
*/
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
if ((unsigned long) p->addr & 0x3UL)
return -EILSEQ;
p->ainsn.insn[0] = *p->addr;
flushi(&p->ainsn.insn[0]);
p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
flushi(&p->ainsn.insn[1]);
p->opcode = *p->addr;
return 0;
}
void __kprobes arch_arm_kprobe(struct kprobe *p)
{
*p->addr = BREAKPOINT_INSTRUCTION;
flushi(p->addr);
}
void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
*p->addr = p->opcode;
flushi(p->addr);
}
static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
kcb->prev_kprobe.kp = kprobe_running();
kcb->prev_kprobe.status = kcb->kprobe_status;
kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
}
static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
kcb->kprobe_status = kcb->prev_kprobe.status;
kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
}
static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, p);
kcb->kprobe_orig_tnpc = regs->tnpc;
kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
}
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
regs->tstate |= TSTATE_PIL;
/*single step inline, if it a breakpoint instruction*/
if (p->opcode == BREAKPOINT_INSTRUCTION) {
regs->tpc = (unsigned long) p->addr;
regs->tnpc = kcb->kprobe_orig_tnpc;
} else {
regs->tpc = (unsigned long) &p->ainsn.insn[0];
regs->tnpc = (unsigned long) &p->ainsn.insn[1];
}
}
static int __kprobes kprobe_handler(struct pt_regs *regs)
{
struct kprobe *p;
void *addr = (void *) regs->tpc;
int ret = 0;
struct kprobe_ctlblk *kcb;
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
if (kprobe_running()) {
p = get_kprobe(addr);
if (p) {
if (kcb->kprobe_status == KPROBE_HIT_SS) {
regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
kcb->kprobe_orig_tstate_pil);
goto no_kprobe;
}
/* We have reentered the kprobe_handler(), since
* another probe was hit while within the handler.
* We here save the original kprobes variables and
* just single step on the instruction of the new probe
* without calling any user handlers.
*/
save_previous_kprobe(kcb);
set_current_kprobe(p, regs, kcb);
kprobes_inc_nmissed_count(p);
kcb->kprobe_status = KPROBE_REENTER;
prepare_singlestep(p, regs, kcb);
return 1;
} else {
if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
/* The breakpoint instruction was removed by
* another cpu right after we hit, no further
* handling of this interrupt is appropriate
*/
ret = 1;
goto no_kprobe;
}
p = __this_cpu_read(current_kprobe);
if (p->break_handler && p->break_handler(p, regs))
goto ss_probe;
}
goto no_kprobe;
}
p = get_kprobe(addr);
if (!p) {
if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
/*
* The breakpoint instruction was removed right
* after we hit it. Another cpu has removed
* either a probepoint or a debugger breakpoint
* at this address. In either case, no further
* handling of this interrupt is appropriate.
*/
ret = 1;
}
/* Not one of ours: let kernel handle it */
goto no_kprobe;
}
set_current_kprobe(p, regs, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
if (p->pre_handler && p->pre_handler(p, regs))
return 1;
ss_probe:
prepare_singlestep(p, regs, kcb);
kcb->kprobe_status = KPROBE_HIT_SS;
return 1;
no_kprobe:
preempt_enable_no_resched();
return ret;
}
/* If INSN is a relative control transfer instruction,
* return the corrected branch destination value.
*
* regs->tpc and regs->tnpc still hold the values of the
* program counters at the time of trap due to the execution
* of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1]
*
*/
static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p,
struct pt_regs *regs)
{
unsigned long real_pc = (unsigned long) p->addr;
/* Branch not taken, no mods necessary. */
if (regs->tnpc == regs->tpc + 0x4UL)
return real_pc + 0x8UL;
/* The three cases are call, branch w/prediction,
* and traditional branch.
*/
if ((insn & 0xc0000000) == 0x40000000 ||
(insn & 0xc1c00000) == 0x00400000 ||
(insn & 0xc1c00000) == 0x00800000) {
unsigned long ainsn_addr;
ainsn_addr = (unsigned long) &p->ainsn.insn[0];
/* The instruction did all the work for us
* already, just apply the offset to the correct
* instruction location.
*/
return (real_pc + (regs->tnpc - ainsn_addr));
}
/* It is jmpl or some other absolute PC modification instruction,
* leave NPC as-is.
*/
return regs->tnpc;
}
/* If INSN is an instruction which writes it's PC location
* into a destination register, fix that up.
*/
static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
unsigned long real_pc)
{
unsigned long *slot = NULL;
/* Simplest case is 'call', which always uses %o7 */
if ((insn & 0xc0000000) == 0x40000000) {
slot = &regs->u_regs[UREG_I7];
}
/* 'jmpl' encodes the register inside of the opcode */
if ((insn & 0xc1f80000) == 0x81c00000) {
unsigned long rd = ((insn >> 25) & 0x1f);
if (rd <= 15) {
slot = &regs->u_regs[rd];
} else {
/* Hard case, it goes onto the stack. */
flushw_all();
rd -= 16;
slot = (unsigned long *)
(regs->u_regs[UREG_FP] + STACK_BIAS);
slot += rd;
}
}
if (slot != NULL)
*slot = real_pc;
}
/*
* Called after single-stepping. p->addr is the address of the
* instruction which has been replaced by the breakpoint
* instruction. To avoid the SMP problems that can occur when we
* temporarily put back the original opcode to single-step, we
* single-stepped a copy of the instruction. The address of this
* copy is &p->ainsn.insn[0].
*
* This function prepares to return from the post-single-step
* breakpoint trap.
*/
static void __kprobes resume_execution(struct kprobe *p,
struct pt_regs *regs, struct kprobe_ctlblk *kcb)
{
u32 insn = p->ainsn.insn[0];
regs->tnpc = relbranch_fixup(insn, p, regs);
/* This assignment must occur after relbranch_fixup() */
regs->tpc = kcb->kprobe_orig_tnpc;
retpc_fixup(regs, insn, (unsigned long) p->addr);
regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
kcb->kprobe_orig_tstate_pil);
}
static int __kprobes post_kprobe_handler(struct pt_regs *regs)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if (!cur)
return 0;
if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
kcb->kprobe_status = KPROBE_HIT_SSDONE;
cur->post_handler(cur, regs, 0);
}
resume_execution(cur, regs, kcb);
/*Restore back the original saved kprobes variables and continue. */
if (kcb->kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe(kcb);
goto out;
}
reset_current_kprobe();
out:
preempt_enable_no_resched();
return 1;
}
int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
const struct exception_table_entry *entry;
switch(kcb->kprobe_status) {
case KPROBE_HIT_SS:
case KPROBE_REENTER:
/*
* We are here because the instruction being single
* stepped caused a page fault. We reset the current
* kprobe and the tpc points back to the probe address
* and allow the page fault handler to continue as a
* normal page fault.
*/
regs->tpc = (unsigned long)cur->addr;
regs->tnpc = kcb->kprobe_orig_tnpc;
regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
kcb->kprobe_orig_tstate_pil);
if (kcb->kprobe_status == KPROBE_REENTER)
restore_previous_kprobe(kcb);
else
reset_current_kprobe();
preempt_enable_no_resched();
break;
case KPROBE_HIT_ACTIVE:
case KPROBE_HIT_SSDONE:
/*
* We increment the nmissed count for accounting,
* we can also use npre/npostfault count for accounting
* these specific fault cases.
*/
kprobes_inc_nmissed_count(cur);
/*
* We come here because instructions in the pre/post
* handler caused the page_fault, this could happen
* if handler tries to access user space by
* copy_from_user(), get_user() etc. Let the
* user-specified handler try to fix it first.
*/
if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
return 1;
/*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
entry = search_exception_tables(regs->tpc);
if (entry) {
regs->tpc = entry->fixup;
regs->tnpc = regs->tpc + 4;
return 1;
}
/*
* fixup_exception() could not handle it,
* Let do_page_fault() fix it.
*/
break;
default:
break;
}
return 0;
}
/*
* Wrapper routine to for handling exceptions.
*/
int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
unsigned long val, void *data)
{
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
if (args->regs && user_mode(args->regs))
return ret;
switch (val) {
case DIE_DEBUG:
if (kprobe_handler(args->regs))
ret = NOTIFY_STOP;
break;
case DIE_DEBUG_2:
if (post_kprobe_handler(args->regs))
ret = NOTIFY_STOP;
break;
default:
break;
}
return ret;
}
asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
struct pt_regs *regs)
{
enum ctx_state prev_state = exception_enter();
BUG_ON(trap_level != 0x170 && trap_level != 0x171);
if (user_mode(regs)) {
local_irq_enable();
bad_trap(regs, trap_level);
goto out;
}
/* trap_level == 0x170 --> ta 0x70
* trap_level == 0x171 --> ta 0x71
*/
if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
(trap_level == 0x170) ? "debug" : "debug_2",
regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
bad_trap(regs, trap_level);
out:
exception_exit(prev_state);
}
/* Jprobes support. */
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
struct jprobe *jp = container_of(p, struct jprobe, kp);
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
regs->tpc = (unsigned long) jp->entry;
regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
regs->tstate |= TSTATE_PIL;
return 1;
}
void __kprobes jprobe_return(void)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
register unsigned long orig_fp asm("g1");
orig_fp = kcb->jprobe_saved_regs.u_regs[UREG_FP];
__asm__ __volatile__("\n"
"1: cmp %%sp, %0\n\t"
"blu,a,pt %%xcc, 1b\n\t"
" restore\n\t"
".globl jprobe_return_trap_instruction\n"
"jprobe_return_trap_instruction:\n\t"
"ta 0x70"
: /* no outputs */
: "r" (orig_fp));
}
extern void jprobe_return_trap_instruction(void);
int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
u32 *addr = (u32 *) regs->tpc;
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if (addr == (u32 *) jprobe_return_trap_instruction) {
memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
preempt_enable_no_resched();
return 1;
}
return 0;
}
/* The value stored in the return address register is actually 2
* instructions before where the callee will return to.
* Sequences usually look something like this
*
* call some_function <--- return register points here
* nop <--- call delay slot
* whatever <--- where callee returns to
*
* To keep trampoline_probe_handler logic simpler, we normalize the
* value kept in ri->ret_addr so we don't need to keep adjusting it
* back and forth.
*/
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8);
/* Replace the return addr with trampoline addr */
regs->u_regs[UREG_RETPC] =
((unsigned long)kretprobe_trampoline) - 8;
}
/*
* Called when the probe at kretprobe trampoline is hit
*/
static int __kprobes trampoline_probe_handler(struct kprobe *p,
struct pt_regs *regs)
{
struct kretprobe_instance *ri = NULL;
struct hlist_head *head, empty_rp;
struct hlist_node *tmp;
unsigned long flags, orig_ret_address = 0;
unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
INIT_HLIST_HEAD(&empty_rp);
kretprobe_hash_lock(current, &head, &flags);
/*
* It is possible to have multiple instances associated with a given
* task either because an multiple functions in the call path
* have a return probe installed on them, and/or more than one return
* return probe was registered for a target function.
*
* We can handle this because:
* - instances are always inserted at the head of the list
* - when multiple return probes are registered for the same
* function, the first instance's ret_addr will point to the
* real return address, and all the rest will point to
* kretprobe_trampoline
*/
hlist_for_each_entry_safe(ri, tmp, head, hlist) {
if (ri->task != current)
/* another task is sharing our hash bucket */
continue;
if (ri->rp && ri->rp->handler)
ri->rp->handler(ri, regs);
orig_ret_address = (unsigned long)ri->ret_addr;
recycle_rp_inst(ri, &empty_rp);
if (orig_ret_address != trampoline_address)
/*
* This is the real return address. Any other
* instances associated with this task are for
* other calls deeper on the call stack
*/
break;
}
kretprobe_assert(ri, orig_ret_address, trampoline_address);
regs->tpc = orig_ret_address;
regs->tnpc = orig_ret_address + 4;
reset_current_kprobe();
kretprobe_hash_unlock(current, &flags);
preempt_enable_no_resched();
hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
hlist_del(&ri->hlist);
kfree(ri);
}
/*
* By returning a non-zero value, we are telling
* kprobe_handler() that we don't want the post_handler
* to run (and have re-enabled preemption)
*/
return 1;
}
static void __used kretprobe_trampoline_holder(void)
{
asm volatile(".global kretprobe_trampoline\n"
"kretprobe_trampoline:\n"
"\tnop\n"
"\tnop\n");
}
static struct kprobe trampoline_p = {
.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
.pre_handler = trampoline_probe_handler
};
int __init arch_init_kprobes(void)
{
return register_kprobe(&trampoline_p);
}
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
return 1;
return 0;
}
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