projects / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
| bbc69863 RM |
2 | #include <linux/ptrace.h> |
| 3 | #include <linux/sched.h> | |
| 68db0cf1 | 4 | #include <linux/sched/task_stack.h> |
| 8bc3bcc9 | 5 | #include <linux/export.h> |
| bbc69863 RM |
6 | #include <asm/syscall.h> |
| 7 | ||
| 8 | static int collect_syscall(struct task_struct *target, long *callno, | |
| 9 | unsigned long args[6], unsigned int maxargs, | |
| 10 | unsigned long *sp, unsigned long *pc) | |
| 11 | { | |
| aa1f1a63 AL |
12 | struct pt_regs *regs; |
| 13 | ||
| 14 | if (!try_get_task_stack(target)) { | |
| 15 | /* Task has no stack, so the task isn't in a syscall. */ | |
| 854fbd6e | 16 | *sp = *pc = 0; |
| aa1f1a63 AL |
17 | *callno = -1; |
| 18 | return 0; | |
| 19 | } | |
| 20 | ||
| 21 | regs = task_pt_regs(target); | |
| 22 | if (unlikely(!regs)) { | |
| 23 | put_task_stack(target); | |
| bbc69863 | 24 | return -EAGAIN; |
| aa1f1a63 | 25 | } |
| bbc69863 RM |
26 | |
| 27 | *sp = user_stack_pointer(regs); | |
| 28 | *pc = instruction_pointer(regs); | |
| 29 | ||
| 30 | *callno = syscall_get_nr(target, regs); | |
| 31 | if (*callno != -1L && maxargs > 0) | |
| 32 | syscall_get_arguments(target, regs, 0, maxargs, args); | |
| 33 | ||
| aa1f1a63 | 34 | put_task_stack(target); |
| bbc69863 RM |
35 | return 0; |
| 36 | } | |
| 37 | ||
| 38 | /** | |
| 39 | * task_current_syscall - Discover what a blocked task is doing. | |
| 40 | * @target: thread to examine | |
| 41 | * @callno: filled with system call number or -1 | |
| 42 | * @args: filled with @maxargs system call arguments | |
| 43 | * @maxargs: number of elements in @args to fill | |
| 44 | * @sp: filled with user stack pointer | |
| 45 | * @pc: filled with user PC | |
| 46 | * | |
| 47 | * If @target is blocked in a system call, returns zero with *@callno | |
| 48 | * set to the the call's number and @args filled in with its arguments. | |
| 49 | * Registers not used for system call arguments may not be available and | |
| 50 | * it is not kosher to use &struct user_regset calls while the system | |
| 51 | * call is still in progress. Note we may get this result if @target | |
| 52 | * has finished its system call but not yet returned to user mode, such | |
| 53 | * as when it's stopped for signal handling or syscall exit tracing. | |
| 54 | * | |
| 55 | * If @target is blocked in the kernel during a fault or exception, | |
| 56 | * returns zero with *@callno set to -1 and does not fill in @args. | |
| 57 | * If so, it's now safe to examine @target using &struct user_regset | |
| 58 | * get() calls as long as we're sure @target won't return to user mode. | |
| 59 | * | |
| 60 | * Returns -%EAGAIN if @target does not remain blocked. | |
| 61 | * | |
| 62 | * Returns -%EINVAL if @maxargs is too large (maximum is six). | |
| 63 | */ | |
| 64 | int task_current_syscall(struct task_struct *target, long *callno, | |
| 65 | unsigned long args[6], unsigned int maxargs, | |
| 66 | unsigned long *sp, unsigned long *pc) | |
| 67 | { | |
| 68 | long state; | |
| 69 | unsigned long ncsw; | |
| 70 | ||
| 71 | if (unlikely(maxargs > 6)) | |
| 72 | return -EINVAL; | |
| 73 | ||
| 74 | if (target == current) | |
| 75 | return collect_syscall(target, callno, args, maxargs, sp, pc); | |
| 76 | ||
| 77 | state = 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, callno, args, maxargs, sp, pc)) || | |
| 84 | unlikely(wait_task_inactive(target, state) != ncsw)) | |
| 85 | return -EAGAIN; | |
| 86 | ||
| 87 | return 0; | |
| 88 | } |