cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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syscall.c (2744B)

      1// SPDX-License-Identifier: GPL-2.0
      2#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 examine
     47 * @info:		structure with the following fields:
     48 *			 .sp        - filled with user stack pointer
     49 *			 .data.nr   - filled with system call number or -1
     50 *			 .data.args - filled with @maxargs system call arguments
     51 *			 .data.instruction_pointer - filled with user PC
     52 *
     53 * If @target is blocked in a system call, returns zero with @info.data.nr
     54 * set to the call's number and @info.data.args filled in with its
     55 * arguments. Registers not used for system call arguments may not be available
     56 * and it is not kosher to use &struct user_regset calls while the system
     57 * call is still in progress.  Note we may get this result if @target
     58 * has finished its system call but not yet returned to user mode, such
     59 * 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 in
     63 * @info.data.args. If so, it's now safe to examine @target using
     64 * &struct user_regset get() calls as long as we're sure @target won't return
     65 * 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}