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![Christoph Lameter](/assets/img/avatar_default.png)
This still has not been merged and now powerpc is the only arch that does not have this change. Sorry about missing linuxppc-dev before. V2->V2 - Fix up to work against 3.18-rc1 __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 : __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: Benjamin Herrenschmidt <benh@kernel.crashing.org> CC: Paul Mackerras <paulus@samba.org> Signed-off-by: Christoph Lameter <cl@linux.com> [mpe: Fix build errors caused by set/or_softirq_pending(), and rework assignment in __set_breakpoint() to use memcpy().] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
559 lines
15 KiB
C
559 lines
15 KiB
C
/*
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* Kernel Probes (KProbes)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2002, 2004
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*
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* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
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* Probes initial implementation ( includes contributions from
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* Rusty Russell).
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* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
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* interface to access function arguments.
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* 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
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* for PPC64
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*/
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#include <linux/kprobes.h>
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#include <linux/ptrace.h>
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#include <linux/preempt.h>
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#include <linux/module.h>
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#include <linux/kdebug.h>
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#include <linux/slab.h>
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#include <asm/code-patching.h>
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#include <asm/cacheflush.h>
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#include <asm/sstep.h>
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#include <asm/uaccess.h>
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DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
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struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
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int __kprobes arch_prepare_kprobe(struct kprobe *p)
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{
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int ret = 0;
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kprobe_opcode_t insn = *p->addr;
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if ((unsigned long)p->addr & 0x03) {
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printk("Attempt to register kprobe at an unaligned address\n");
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ret = -EINVAL;
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} else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
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printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
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ret = -EINVAL;
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}
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/* insn must be on a special executable page on ppc64. This is
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* not explicitly required on ppc32 (right now), but it doesn't hurt */
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if (!ret) {
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p->ainsn.insn = get_insn_slot();
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if (!p->ainsn.insn)
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ret = -ENOMEM;
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}
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if (!ret) {
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memcpy(p->ainsn.insn, p->addr,
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MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
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p->opcode = *p->addr;
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flush_icache_range((unsigned long)p->ainsn.insn,
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(unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
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}
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p->ainsn.boostable = 0;
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return ret;
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}
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void __kprobes arch_arm_kprobe(struct kprobe *p)
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{
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*p->addr = BREAKPOINT_INSTRUCTION;
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flush_icache_range((unsigned long) p->addr,
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(unsigned long) p->addr + sizeof(kprobe_opcode_t));
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}
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void __kprobes arch_disarm_kprobe(struct kprobe *p)
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{
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*p->addr = p->opcode;
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flush_icache_range((unsigned long) p->addr,
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(unsigned long) p->addr + sizeof(kprobe_opcode_t));
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}
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void __kprobes arch_remove_kprobe(struct kprobe *p)
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{
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if (p->ainsn.insn) {
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free_insn_slot(p->ainsn.insn, 0);
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p->ainsn.insn = NULL;
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}
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}
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static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
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{
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enable_single_step(regs);
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/*
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* On powerpc we should single step on the original
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* instruction even if the probed insn is a trap
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* variant as values in regs could play a part in
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* if the trap is taken or not
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*/
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regs->nip = (unsigned long)p->ainsn.insn;
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}
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static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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kcb->prev_kprobe.kp = kprobe_running();
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kcb->prev_kprobe.status = kcb->kprobe_status;
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kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
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}
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static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
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kcb->kprobe_status = kcb->prev_kprobe.status;
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kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
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}
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static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
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struct kprobe_ctlblk *kcb)
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{
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__this_cpu_write(current_kprobe, p);
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kcb->kprobe_saved_msr = regs->msr;
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}
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void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
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struct pt_regs *regs)
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{
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ri->ret_addr = (kprobe_opcode_t *)regs->link;
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/* Replace the return addr with trampoline addr */
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regs->link = (unsigned long)kretprobe_trampoline;
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}
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static int __kprobes kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *p;
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int ret = 0;
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unsigned int *addr = (unsigned int *)regs->nip;
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struct kprobe_ctlblk *kcb;
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/*
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* We don't want to be preempted for the entire
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* duration of kprobe processing
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*/
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preempt_disable();
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kcb = get_kprobe_ctlblk();
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/* Check we're not actually recursing */
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if (kprobe_running()) {
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p = get_kprobe(addr);
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if (p) {
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kprobe_opcode_t insn = *p->ainsn.insn;
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if (kcb->kprobe_status == KPROBE_HIT_SS &&
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is_trap(insn)) {
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/* Turn off 'trace' bits */
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regs->msr &= ~MSR_SINGLESTEP;
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regs->msr |= kcb->kprobe_saved_msr;
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goto no_kprobe;
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}
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/* We have reentered the kprobe_handler(), since
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* another probe was hit while within the handler.
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* We here save the original kprobes variables and
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* just single step on the instruction of the new probe
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* without calling any user handlers.
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*/
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save_previous_kprobe(kcb);
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set_current_kprobe(p, regs, kcb);
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kcb->kprobe_saved_msr = regs->msr;
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kprobes_inc_nmissed_count(p);
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prepare_singlestep(p, regs);
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kcb->kprobe_status = KPROBE_REENTER;
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return 1;
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} else {
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if (*addr != BREAKPOINT_INSTRUCTION) {
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/* If trap variant, then it belongs not to us */
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kprobe_opcode_t cur_insn = *addr;
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if (is_trap(cur_insn))
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goto no_kprobe;
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/* The breakpoint instruction was removed by
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* another cpu right after we hit, no further
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* handling of this interrupt is appropriate
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*/
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ret = 1;
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goto no_kprobe;
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}
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p = __this_cpu_read(current_kprobe);
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if (p->break_handler && p->break_handler(p, regs)) {
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goto ss_probe;
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}
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}
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goto no_kprobe;
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}
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p = get_kprobe(addr);
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if (!p) {
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if (*addr != BREAKPOINT_INSTRUCTION) {
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/*
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* PowerPC has multiple variants of the "trap"
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* instruction. If the current instruction is a
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* trap variant, it could belong to someone else
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*/
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kprobe_opcode_t cur_insn = *addr;
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if (is_trap(cur_insn))
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goto no_kprobe;
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/*
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* The breakpoint instruction was removed right
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* after we hit it. Another cpu has removed
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* either a probepoint or a debugger breakpoint
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* at this address. In either case, no further
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* handling of this interrupt is appropriate.
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*/
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ret = 1;
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}
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/* Not one of ours: let kernel handle it */
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goto no_kprobe;
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}
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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set_current_kprobe(p, regs, kcb);
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if (p->pre_handler && p->pre_handler(p, regs))
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/* handler has already set things up, so skip ss setup */
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return 1;
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ss_probe:
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if (p->ainsn.boostable >= 0) {
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unsigned int insn = *p->ainsn.insn;
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/* regs->nip is also adjusted if emulate_step returns 1 */
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ret = emulate_step(regs, insn);
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if (ret > 0) {
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/*
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* Once this instruction has been boosted
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* successfully, set the boostable flag
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*/
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if (unlikely(p->ainsn.boostable == 0))
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p->ainsn.boostable = 1;
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if (p->post_handler)
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p->post_handler(p, regs, 0);
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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reset_current_kprobe();
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preempt_enable_no_resched();
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return 1;
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} else if (ret < 0) {
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/*
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* We don't allow kprobes on mtmsr(d)/rfi(d), etc.
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* So, we should never get here... but, its still
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* good to catch them, just in case...
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*/
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printk("Can't step on instruction %x\n", insn);
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BUG();
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} else if (ret == 0)
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/* This instruction can't be boosted */
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p->ainsn.boostable = -1;
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}
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prepare_singlestep(p, regs);
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kcb->kprobe_status = KPROBE_HIT_SS;
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return 1;
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no_kprobe:
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preempt_enable_no_resched();
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return ret;
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}
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/*
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* Function return probe trampoline:
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* - init_kprobes() establishes a probepoint here
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* - When the probed function returns, this probe
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* causes the handlers to fire
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*/
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static void __used kretprobe_trampoline_holder(void)
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{
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asm volatile(".global kretprobe_trampoline\n"
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"kretprobe_trampoline:\n"
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"nop\n");
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}
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/*
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* Called when the probe at kretprobe trampoline is hit
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*/
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static int __kprobes trampoline_probe_handler(struct kprobe *p,
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struct pt_regs *regs)
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{
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struct kretprobe_instance *ri = NULL;
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struct hlist_head *head, empty_rp;
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struct hlist_node *tmp;
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unsigned long flags, orig_ret_address = 0;
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unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
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INIT_HLIST_HEAD(&empty_rp);
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kretprobe_hash_lock(current, &head, &flags);
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/*
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* It is possible to have multiple instances associated with a given
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* task either because an multiple functions in the call path
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* have a return probe installed on them, and/or more than one return
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* return probe was registered for a target function.
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*
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* We can handle this because:
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* - instances are always inserted at the head of the list
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* - when multiple return probes are registered for the same
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* function, the first instance's ret_addr will point to the
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* real return address, and all the rest will point to
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* kretprobe_trampoline
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*/
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hlist_for_each_entry_safe(ri, tmp, head, hlist) {
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if (ri->task != current)
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/* another task is sharing our hash bucket */
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continue;
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if (ri->rp && ri->rp->handler)
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ri->rp->handler(ri, regs);
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orig_ret_address = (unsigned long)ri->ret_addr;
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recycle_rp_inst(ri, &empty_rp);
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if (orig_ret_address != trampoline_address)
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/*
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* This is the real return address. Any other
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* instances associated with this task are for
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* other calls deeper on the call stack
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*/
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break;
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}
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kretprobe_assert(ri, orig_ret_address, trampoline_address);
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regs->nip = orig_ret_address;
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reset_current_kprobe();
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kretprobe_hash_unlock(current, &flags);
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preempt_enable_no_resched();
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hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
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hlist_del(&ri->hlist);
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kfree(ri);
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}
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/*
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* By returning a non-zero value, we are telling
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* kprobe_handler() that we don't want the post_handler
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* to run (and have re-enabled preemption)
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*/
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return 1;
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}
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/*
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* Called after single-stepping. p->addr is the address of the
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* instruction whose first byte has been replaced by the "breakpoint"
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* instruction. To avoid the SMP problems that can occur when we
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* temporarily put back the original opcode to single-step, we
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* single-stepped a copy of the instruction. The address of this
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* copy is p->ainsn.insn.
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*/
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static int __kprobes post_kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *cur = kprobe_running();
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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if (!cur)
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return 0;
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/* make sure we got here for instruction we have a kprobe on */
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if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
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return 0;
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if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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cur->post_handler(cur, regs, 0);
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}
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/* Adjust nip to after the single-stepped instruction */
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regs->nip = (unsigned long)cur->addr + 4;
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regs->msr |= kcb->kprobe_saved_msr;
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/*Restore back the original saved kprobes variables and continue. */
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if (kcb->kprobe_status == KPROBE_REENTER) {
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restore_previous_kprobe(kcb);
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goto out;
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}
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reset_current_kprobe();
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out:
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preempt_enable_no_resched();
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/*
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* if somebody else is singlestepping across a probe point, msr
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* will have DE/SE set, in which case, continue the remaining processing
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* of do_debug, as if this is not a probe hit.
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*/
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if (regs->msr & MSR_SINGLESTEP)
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return 0;
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return 1;
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}
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int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
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{
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struct kprobe *cur = kprobe_running();
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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const struct exception_table_entry *entry;
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switch(kcb->kprobe_status) {
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case KPROBE_HIT_SS:
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case KPROBE_REENTER:
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/*
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* We are here because the instruction being single
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* stepped caused a page fault. We reset the current
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* kprobe and the nip points back to the probe address
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* and allow the page fault handler to continue as a
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* normal page fault.
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*/
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regs->nip = (unsigned long)cur->addr;
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regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
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regs->msr |= kcb->kprobe_saved_msr;
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if (kcb->kprobe_status == KPROBE_REENTER)
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restore_previous_kprobe(kcb);
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else
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reset_current_kprobe();
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preempt_enable_no_resched();
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break;
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case KPROBE_HIT_ACTIVE:
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case KPROBE_HIT_SSDONE:
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/*
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* We increment the nmissed count for accounting,
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* we can also use npre/npostfault count for accounting
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* these specific fault cases.
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*/
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kprobes_inc_nmissed_count(cur);
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/*
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* We come here because instructions in the pre/post
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* handler caused the page_fault, this could happen
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* if handler tries to access user space by
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* copy_from_user(), get_user() etc. Let the
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* user-specified handler try to fix it first.
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*/
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if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
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return 1;
|
|
|
|
/*
|
|
* In case the user-specified fault handler returned
|
|
* zero, try to fix up.
|
|
*/
|
|
if ((entry = search_exception_tables(regs->nip)) != NULL) {
|
|
regs->nip = entry->fixup;
|
|
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_BPT:
|
|
if (kprobe_handler(args->regs))
|
|
ret = NOTIFY_STOP;
|
|
break;
|
|
case DIE_SSTEP:
|
|
if (post_kprobe_handler(args->regs))
|
|
ret = NOTIFY_STOP;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
unsigned long arch_deref_entry_point(void *entry)
|
|
{
|
|
return ppc_global_function_entry(entry);
|
|
}
|
|
|
|
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(struct pt_regs));
|
|
|
|
/* setup return addr to the jprobe handler routine */
|
|
regs->nip = arch_deref_entry_point(jp->entry);
|
|
#ifdef CONFIG_PPC64
|
|
#if defined(_CALL_ELF) && _CALL_ELF == 2
|
|
regs->gpr[12] = (unsigned long)jp->entry;
|
|
#else
|
|
regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
|
|
#endif
|
|
#endif
|
|
|
|
return 1;
|
|
}
|
|
|
|
void __used __kprobes jprobe_return(void)
|
|
{
|
|
asm volatile("trap" ::: "memory");
|
|
}
|
|
|
|
static void __used __kprobes jprobe_return_end(void)
|
|
{
|
|
};
|
|
|
|
int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
|
|
{
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
/*
|
|
* FIXME - we should ideally be validating that we got here 'cos
|
|
* of the "trap" in jprobe_return() above, before restoring the
|
|
* saved regs...
|
|
*/
|
|
memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
|
|
preempt_enable_no_resched();
|
|
return 1;
|
|
}
|
|
|
|
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;
|
|
}
|