diff options
Diffstat (limited to 'arch/powerpc/kernel/uprobes.c')
| -rw-r--r-- | arch/powerpc/kernel/uprobes.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c new file mode 100644 index 0000000000..95a41ae9df --- /dev/null +++ b/arch/powerpc/kernel/uprobes.c @@ -0,0 +1,217 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * User-space Probes (UProbes) for powerpc + * + * Copyright IBM Corporation, 2007-2012 + * + * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@in.ibm.com> + */ +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/ptrace.h> +#include <linux/uprobes.h> +#include <linux/uaccess.h> +#include <linux/kdebug.h> + +#include <asm/sstep.h> +#include <asm/inst.h> + +#define UPROBE_TRAP_NR UINT_MAX + +/** + * is_trap_insn - check if the instruction is a trap variant + * @insn: instruction to be checked. + * Returns true if @insn is a trap variant. + */ +bool is_trap_insn(uprobe_opcode_t *insn) +{ + return (is_trap(*insn)); +} + +/** + * arch_uprobe_analyze_insn + * @mm: the probed address space. + * @arch_uprobe: the probepoint information. + * @addr: vaddr to probe. + * Return 0 on success or a -ve number on error. + */ +int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, + struct mm_struct *mm, unsigned long addr) +{ + if (addr & 0x03) + return -EINVAL; + + if (cpu_has_feature(CPU_FTR_ARCH_31) && + ppc_inst_prefixed(ppc_inst_read(auprobe->insn)) && + (addr & 0x3f) == 60) { + pr_info_ratelimited("Cannot register a uprobe on 64 byte unaligned prefixed instruction\n"); + return -EINVAL; + } + + if (!can_single_step(ppc_inst_val(ppc_inst_read(auprobe->insn)))) { + pr_info_ratelimited("Cannot register a uprobe on instructions that can't be single stepped\n"); + return -ENOTSUPP; + } + + return 0; +} + +/* + * arch_uprobe_pre_xol - prepare to execute out of line. + * @auprobe: the probepoint information. + * @regs: reflects the saved user state of current task. + */ +int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) +{ + struct arch_uprobe_task *autask = ¤t->utask->autask; + + autask->saved_trap_nr = current->thread.trap_nr; + current->thread.trap_nr = UPROBE_TRAP_NR; + regs_set_return_ip(regs, current->utask->xol_vaddr); + + user_enable_single_step(current); + return 0; +} + +/** + * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs + * @regs: Reflects the saved state of the task after it has hit a breakpoint + * instruction. + * Return the address of the breakpoint instruction. + */ +unsigned long uprobe_get_swbp_addr(struct pt_regs *regs) +{ + return instruction_pointer(regs); +} + +/* + * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc), + * then detect the case where a singlestepped instruction jumps back to its + * own address. It is assumed that anything like do_page_fault/do_trap/etc + * sets thread.trap_nr != UINT_MAX. + * + * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr, + * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to + * UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol(). + */ +bool arch_uprobe_xol_was_trapped(struct task_struct *t) +{ + if (t->thread.trap_nr != UPROBE_TRAP_NR) + return true; + + return false; +} + +/* + * Called after single-stepping. 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. + * + * This function prepares to resume execution after the single-step. + */ +int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) +{ + struct uprobe_task *utask = current->utask; + + WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR); + + current->thread.trap_nr = utask->autask.saved_trap_nr; + + /* + * On powerpc, except for loads and stores, most instructions + * including ones that alter code flow (branches, calls, returns) + * are emulated in the kernel. We get here only if the emulation + * support doesn't exist and have to fix-up the next instruction + * to be executed. + */ + regs_set_return_ip(regs, (unsigned long)ppc_inst_next((void *)utask->vaddr, auprobe->insn)); + + user_disable_single_step(current); + return 0; +} + +/* callback routine for handling exceptions. */ +int arch_uprobe_exception_notify(struct notifier_block *self, + unsigned long val, void *data) +{ + struct die_args *args = data; + struct pt_regs *regs = args->regs; + + /* regs == NULL is a kernel bug */ + if (WARN_ON(!regs)) + return NOTIFY_DONE; + + /* We are only interested in userspace traps */ + if (!user_mode(regs)) + return NOTIFY_DONE; + + switch (val) { + case DIE_BPT: + if (uprobe_pre_sstep_notifier(regs)) + return NOTIFY_STOP; + break; + case DIE_SSTEP: + if (uprobe_post_sstep_notifier(regs)) + return NOTIFY_STOP; + break; + default: + break; + } + return NOTIFY_DONE; +} + +/* + * This function gets called when XOL instruction either gets trapped or + * the thread has a fatal signal, so reset the instruction pointer to its + * probed address. + */ +void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) +{ + struct uprobe_task *utask = current->utask; + + current->thread.trap_nr = utask->autask.saved_trap_nr; + instruction_pointer_set(regs, utask->vaddr); + + user_disable_single_step(current); +} + +/* + * See if the instruction can be emulated. + * Returns true if instruction was emulated, false otherwise. + */ +bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) +{ + int ret; + + /* + * emulate_step() returns 1 if the insn was successfully emulated. + * For all other cases, we need to single-step in hardware. + */ + ret = emulate_step(regs, ppc_inst_read(auprobe->insn)); + if (ret > 0) + return true; + + return false; +} + +unsigned long +arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) +{ + unsigned long orig_ret_vaddr; + + orig_ret_vaddr = regs->link; + + /* Replace the return addr with trampoline addr */ + regs->link = trampoline_vaddr; + + return orig_ret_vaddr; +} + +bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, + struct pt_regs *regs) +{ + if (ctx == RP_CHECK_CHAIN_CALL) + return regs->gpr[1] <= ret->stack; + else + return regs->gpr[1] < ret->stack; +} |