text: // SPDX-License-Identifier: GPL-2.0+
  /*
   * DAWR infrastructure
   *
   * Copyright 2019, Michael Neuling, IBM Corporation.
   */
  
  #include <linux/types.h>
  #include <linux/export.h>
  #include <linux/fs.h>
  #include <linux/debugfs.h>
  #include <asm/debugfs.h>
  #include <asm/machdep.h>
  #include <asm/hvcall.h>
  
  bool dawr_force_enable;
  EXPORT_SYMBOL_GPL(dawr_force_enable);
  
  int set_dawr(int nr, struct arch_hw_breakpoint *brk)
  {
  	unsigned long dawr, dawrx, mrd;
  
  	dawr = brk->address;
  
  	dawrx  = (brk->type & (HW_BRK_TYPE_READ | HW_BRK_TYPE_WRITE))
  		<< (63 - 58);
  	dawrx |= ((brk->type & (HW_BRK_TYPE_TRANSLATE)) >> 2) << (63 - 59);
  	dawrx |= (brk->type & (HW_BRK_TYPE_PRIV_ALL)) >> 3;
  	/*
  	 * DAWR length is stored in field MDR bits 48:53.  Matches range in
  	 * doublewords (64 bits) baised by -1 eg. 0b000000=1DW and
  	 * 0b111111=64DW.
  	 * brk->hw_len is in bytes.
  	 * This aligns up to double word size, shifts and does the bias.
  	 */
  	mrd = ((brk->hw_len + 7) >> 3) - 1;
  	dawrx |= (mrd & 0x3f) << (63 - 53);
  
  	if (ppc_md.set_dawr)
  		return ppc_md.set_dawr(nr, dawr, dawrx);
  
  	if (nr == 0) {
  		mtspr(SPRN_DAWR0, dawr);
  		mtspr(SPRN_DAWRX0, dawrx);
  	} else {
  		mtspr(SPRN_DAWR1, dawr);
  		mtspr(SPRN_DAWRX1, dawrx);
  	}
  
  	return 0;
  }
  
  static void disable_dawrs_cb(void *info)
  {
  	struct arch_hw_breakpoint null_brk = {0};
  	int i;
  
  	for (i = 0; i < nr_wp_slots(); i++)
  		set_dawr(i, &null_brk);
  }
  
  static ssize_t dawr_write_file_bool(struct file *file,
  				    const char __user *user_buf,
  				    size_t count, loff_t *ppos)
  {
  	struct arch_hw_breakpoint null_brk = {0};
  	size_t rc;
  
  	/* Send error to user if they hypervisor won't allow us to write DAWR */
  	if (!dawr_force_enable &&
  	    firmware_has_feature(FW_FEATURE_LPAR) &&
  	    set_dawr(0, &null_brk) != H_SUCCESS)
  		return -ENODEV;
  
  	rc = debugfs_write_file_bool(file, user_buf, count, ppos);
  	if (rc)
  		return rc;
  
  	/* If we are clearing, make sure all CPUs have the DAWR cleared */
  	if (!dawr_force_enable)
  		smp_call_function(disable_dawrs_cb, NULL, 0);
  
  	return rc;
  }
  
  static const struct file_operations dawr_enable_fops = {
  	.read =		debugfs_read_file_bool,
  	.write =	dawr_write_file_bool,
  	.open =		simple_open,
  	.llseek =	default_llseek,
  };
  
  static int __init dawr_force_setup(void)
  {
  	if (cpu_has_feature(CPU_FTR_DAWR)) {
  		/* Don't setup sysfs file for user control on P8 */
  		dawr_force_enable = true;
  		return 0;
  	}
  
  	if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {
  		/* Turn DAWR off by default, but allow admin to turn it on */
  		debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
  					   powerpc_debugfs_root,
  					   &dawr_force_enable,
  					   &dawr_enable_fops);
  	}
  	return 0;
  }
  arch_initcall(dawr_force_setup);
  