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1// SPDX-License-Identifier: GPL-2.02#include <linux/ptrace.h>3#include <linux/sched.h>4#include <linux/sched/task_stack.h>5#include <linux/export.h>6#include <asm/syscall.h>7 8static int collect_syscall(struct task_struct *target, struct syscall_info *info)9{10 unsigned long args[6] = { };11 struct pt_regs *regs;12 13 if (!try_get_task_stack(target)) {14 /* Task has no stack, so the task isn't in a syscall. */15 memset(info, 0, sizeof(*info));16 info->data.nr = -1;17 return 0;18 }19 20 regs = task_pt_regs(target);21 if (unlikely(!regs)) {22 put_task_stack(target);23 return -EAGAIN;24 }25 26 info->sp = user_stack_pointer(regs);27 info->data.instruction_pointer = instruction_pointer(regs);28 29 info->data.nr = syscall_get_nr(target, regs);30 if (info->data.nr != -1L)31 syscall_get_arguments(target, regs, args);32 33 info->data.args[0] = args[0];34 info->data.args[1] = args[1];35 info->data.args[2] = args[2];36 info->data.args[3] = args[3];37 info->data.args[4] = args[4];38 info->data.args[5] = args[5];39 40 put_task_stack(target);41 return 0;42}43 44/**45 * task_current_syscall - Discover what a blocked task is doing.46 * @target: thread to examine47 * @info: structure with the following fields:48 * .sp - filled with user stack pointer49 * .data.nr - filled with system call number or -150 * .data.args - filled with @maxargs system call arguments51 * .data.instruction_pointer - filled with user PC52 *53 * If @target is blocked in a system call, returns zero with @info.data.nr54 * set to the call's number and @info.data.args filled in with its55 * arguments. Registers not used for system call arguments may not be available56 * and it is not kosher to use &struct user_regset calls while the system57 * call is still in progress. Note we may get this result if @target58 * has finished its system call but not yet returned to user mode, such59 * as when it's stopped for signal handling or syscall exit tracing.60 *61 * If @target is blocked in the kernel during a fault or exception,62 * returns zero with *@info.data.nr set to -1 and does not fill in63 * @info.data.args. If so, it's now safe to examine @target using64 * &struct user_regset get() calls as long as we're sure @target won't return65 * to user mode.66 *67 * Returns -%EAGAIN if @target does not remain blocked.68 */69int task_current_syscall(struct task_struct *target, struct syscall_info *info)70{71 unsigned long ncsw;72 unsigned int state;73 74 if (target == current)75 return collect_syscall(target, info);76 77 state = READ_ONCE(target->__state);78 if (unlikely(!state))79 return -EAGAIN;80 81 ncsw = wait_task_inactive(target, state);82 if (unlikely(!ncsw) ||83 unlikely(collect_syscall(target, info)) ||84 unlikely(wait_task_inactive(target, state) != ncsw))85 return -EAGAIN;86 87 return 0;88}89