text: #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/perf_event.h>
  #include <linux/bug.h>
  #include <linux/stddef.h>
  #include <asm/perf_regs.h>
  #include <asm/ptrace.h>
  
  #ifdef CONFIG_X86_32
  #define PERF_REG_X86_MAX PERF_REG_X86_32_MAX
  #else
  #define PERF_REG_X86_MAX PERF_REG_X86_64_MAX
  #endif
  
  #define PT_REGS_OFFSET(id, r) [id] = offsetof(struct pt_regs, r)
  
  static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {
  	PT_REGS_OFFSET(PERF_REG_X86_AX, ax),
  	PT_REGS_OFFSET(PERF_REG_X86_BX, bx),
  	PT_REGS_OFFSET(PERF_REG_X86_CX, cx),
  	PT_REGS_OFFSET(PERF_REG_X86_DX, dx),
  	PT_REGS_OFFSET(PERF_REG_X86_SI, si),
  	PT_REGS_OFFSET(PERF_REG_X86_DI, di),
  	PT_REGS_OFFSET(PERF_REG_X86_BP, bp),
  	PT_REGS_OFFSET(PERF_REG_X86_SP, sp),
  	PT_REGS_OFFSET(PERF_REG_X86_IP, ip),
  	PT_REGS_OFFSET(PERF_REG_X86_FLAGS, flags),
  	PT_REGS_OFFSET(PERF_REG_X86_CS, cs),
  	PT_REGS_OFFSET(PERF_REG_X86_SS, ss),
  #ifdef CONFIG_X86_32
  	PT_REGS_OFFSET(PERF_REG_X86_DS, ds),
  	PT_REGS_OFFSET(PERF_REG_X86_ES, es),
  	PT_REGS_OFFSET(PERF_REG_X86_FS, fs),
  	PT_REGS_OFFSET(PERF_REG_X86_GS, gs),
  #else
  	/*
  	 * The pt_regs struct does not store
  	 * ds, es, fs, gs in 64 bit mode.
  	 */
  	(unsigned int) -1,
  	(unsigned int) -1,
  	(unsigned int) -1,
  	(unsigned int) -1,
  #endif
  #ifdef CONFIG_X86_64
  	PT_REGS_OFFSET(PERF_REG_X86_R8, r8),
  	PT_REGS_OFFSET(PERF_REG_X86_R9, r9),
  	PT_REGS_OFFSET(PERF_REG_X86_R10, r10),
  	PT_REGS_OFFSET(PERF_REG_X86_R11, r11),
  	PT_REGS_OFFSET(PERF_REG_X86_R12, r12),
  	PT_REGS_OFFSET(PERF_REG_X86_R13, r13),
  	PT_REGS_OFFSET(PERF_REG_X86_R14, r14),
  	PT_REGS_OFFSET(PERF_REG_X86_R15, r15),
  #endif
  };
  
  u64 perf_reg_value(struct pt_regs *regs, int idx)
  {
  	if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset)))
  		return 0;
  
  	return regs_get_register(regs, pt_regs_offset[idx]);
  }
  
  #define REG_RESERVED (~((1ULL << PERF_REG_X86_MAX) - 1ULL))
  
  #ifdef CONFIG_X86_32
  int perf_reg_validate(u64 mask)
  {
  	if (!mask || mask & REG_RESERVED)
  		return -EINVAL;
  
  	return 0;
  }
  
  u64 perf_reg_abi(struct task_struct *task)
  {
  	return PERF_SAMPLE_REGS_ABI_32;
  }
  
  void perf_get_regs_user(struct perf_regs *regs_user,
  			struct pt_regs *regs,
  			struct pt_regs *regs_user_copy)
  {
  	regs_user->regs = task_pt_regs(current);
  	regs_user->abi = perf_reg_abi(current);
  }
  #else /* CONFIG_X86_64 */
  #define REG_NOSUPPORT ((1ULL << PERF_REG_X86_DS) | \
  		       (1ULL << PERF_REG_X86_ES) | \
  		       (1ULL << PERF_REG_X86_FS) | \
  		       (1ULL << PERF_REG_X86_GS))
  
  int perf_reg_validate(u64 mask)
  {
  	if (!mask || mask & REG_RESERVED)
  		return -EINVAL;
  
  	if (mask & REG_NOSUPPORT)
  		return -EINVAL;
  
  	return 0;
  }
  
  u64 perf_reg_abi(struct task_struct *task)
  {
  	if (test_tsk_thread_flag(task, TIF_IA32))
  		return PERF_SAMPLE_REGS_ABI_32;
  	else
  		return PERF_SAMPLE_REGS_ABI_64;
  }
  
  void perf_get_regs_user(struct perf_regs *regs_user,
  			struct pt_regs *regs,
  			struct pt_regs *regs_user_copy)
  {
  	struct pt_regs *user_regs = task_pt_regs(current);
  
  	/*
  	 * If we're in an NMI that interrupted task_pt_regs setup, then
  	 * we can't sample user regs at all.  This check isn't really
  	 * sufficient, though, as we could be in an NMI inside an interrupt
  	 * that happened during task_pt_regs setup.
  	 */
  	if (regs->sp > (unsigned long)&user_regs->r11 &&
  	    regs->sp <= (unsigned long)(user_regs + 1)) {
  		regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;
  		regs_user->regs = NULL;
  		return;
  	}
  
  	/*
  	 * RIP, flags, and the argument registers are usually saved.
  	 * orig_ax is probably okay, too.
  	 */
  	regs_user_copy->ip = user_regs->ip;
  	regs_user_copy->cx = user_regs->cx;
  	regs_user_copy->dx = user_regs->dx;
  	regs_user_copy->si = user_regs->si;
  	regs_user_copy->di = user_regs->di;
  	regs_user_copy->r8 = user_regs->r8;
  	regs_user_copy->r9 = user_regs->r9;
  	regs_user_copy->r10 = user_regs->r10;
  	regs_user_copy->r11 = user_regs->r11;
  	regs_user_copy->orig_ax = user_regs->orig_ax;
  	regs_user_copy->flags = user_regs->flags;
  
  	/*
  	 * Don't even try to report the "rest" regs.
  	 */
  	regs_user_copy->bx = -1;
  	regs_user_copy->bp = -1;
  	regs_user_copy->r12 = -1;
  	regs_user_copy->r13 = -1;
  	regs_user_copy->r14 = -1;
  	regs_user_copy->r15 = -1;
  
  	/*
  	 * For this to be at all useful, we need a reasonable guess for
  	 * sp and the ABI.  Be careful: we're in NMI context, and we're
  	 * considering current to be the current task, so we should
  	 * be careful not to look at any other percpu variables that might
  	 * change during context switches.
  	 */
  	if (IS_ENABLED(CONFIG_IA32_EMULATION) &&
  	    task_thread_info(current)->status & TS_COMPAT) {
  		/* Easy case: we're in a compat syscall. */
  		regs_user->abi = PERF_SAMPLE_REGS_ABI_32;
  		regs_user_copy->sp = user_regs->sp;
  		regs_user_copy->cs = user_regs->cs;
  		regs_user_copy->ss = user_regs->ss;
  	} else if (user_regs->orig_ax != -1) {
  		/*
  		 * We're probably in a 64-bit syscall.
  		 * Warning: this code is severely racy.  At least it's better
  		 * than just blindly copying user_regs.
  		 */
  		regs_user->abi = PERF_SAMPLE_REGS_ABI_64;
  		regs_user_copy->sp = this_cpu_read(old_rsp);
  		regs_user_copy->cs = __USER_CS;
  		regs_user_copy->ss = __USER_DS;
  		regs_user_copy->cx = -1;  /* usually contains garbage */
  	} else {
  		/* We're probably in an interrupt or exception. */
  		regs_user->abi = user_64bit_mode(user_regs) ?
  			PERF_SAMPLE_REGS_ABI_64 : PERF_SAMPLE_REGS_ABI_32;
  		regs_user_copy->sp = user_regs->sp;
  		regs_user_copy->cs = user_regs->cs;
  		regs_user_copy->ss = user_regs->ss;
  	}
  
  	regs_user->regs = regs_user_copy;
  }
  #endif /* CONFIG_X86_32 */
  