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lib/syscall.c
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// SPDX-License-Identifier: GPL-2.0 |
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#include <linux/ptrace.h> #include <linux/sched.h> |
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#include <linux/sched/task_stack.h> |
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#include <linux/export.h> |
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#include <asm/syscall.h> |
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static int collect_syscall(struct task_struct *target, struct syscall_info *info) |
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{ |
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unsigned long args[6] = { }; |
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struct pt_regs *regs; if (!try_get_task_stack(target)) { /* Task has no stack, so the task isn't in a syscall. */ |
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memset(info, 0, sizeof(*info)); info->data.nr = -1; |
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return 0; } regs = task_pt_regs(target); if (unlikely(!regs)) { put_task_stack(target); |
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return -EAGAIN; |
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} |
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info->sp = user_stack_pointer(regs); info->data.instruction_pointer = instruction_pointer(regs); |
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info->data.nr = syscall_get_nr(target, regs); if (info->data.nr != -1L) |
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syscall_get_arguments(target, regs, args); info->data.args[0] = args[0]; info->data.args[1] = args[1]; info->data.args[2] = args[2]; info->data.args[3] = args[3]; info->data.args[4] = args[4]; info->data.args[5] = args[5]; |
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put_task_stack(target); |
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return 0; } /** * task_current_syscall - Discover what a blocked task is doing. * @target: thread to examine |
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* @info: structure with the following fields: * .sp - filled with user stack pointer * .data.nr - filled with system call number or -1 * .data.args - filled with @maxargs system call arguments * .data.instruction_pointer - filled with user PC |
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* |
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* If @target is blocked in a system call, returns zero with @info.data.nr |
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* set to the call's number and @info.data.args filled in with its |
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* arguments. Registers not used for system call arguments may not be available * and it is not kosher to use &struct user_regset calls while the system |
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* call is still in progress. Note we may get this result if @target * has finished its system call but not yet returned to user mode, such * as when it's stopped for signal handling or syscall exit tracing. * * If @target is blocked in the kernel during a fault or exception, |
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* returns zero with *@info.data.nr set to -1 and does not fill in * @info.data.args. If so, it's now safe to examine @target using * &struct user_regset get() calls as long as we're sure @target won't return * to user mode. |
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* * Returns -%EAGAIN if @target does not remain blocked. |
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*/ |
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int task_current_syscall(struct task_struct *target, struct syscall_info *info) |
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{ long state; unsigned long ncsw; |
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if (target == current) |
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return collect_syscall(target, info); |
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state = target->state; if (unlikely(!state)) return -EAGAIN; ncsw = wait_task_inactive(target, state); if (unlikely(!ncsw) || |
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unlikely(collect_syscall(target, info)) || |
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unlikely(wait_task_inactive(target, state) != ncsw)) return -EAGAIN; return 0; } |