1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * DAWR infrastructure
4 *
5 * Copyright 2019, Michael Neuling, IBM Corporation.
6 */
7
8 #include <linux/types.h>
9 #include <linux/export.h>
10 #include <linux/fs.h>
11 #include <linux/debugfs.h>
12 #include <asm/machdep.h>
13 #include <asm/hvcall.h>
14
15 bool dawr_force_enable;
16 EXPORT_SYMBOL_GPL(dawr_force_enable);
17
set_dawr(int nr,struct arch_hw_breakpoint * brk)18 int set_dawr(int nr, struct arch_hw_breakpoint *brk)
19 {
20 unsigned long dawr, dawrx, mrd;
21
22 dawr = brk->address;
23
24 dawrx = (brk->type & (HW_BRK_TYPE_READ | HW_BRK_TYPE_WRITE))
25 << (63 - 58);
26 dawrx |= ((brk->type & (HW_BRK_TYPE_TRANSLATE)) >> 2) << (63 - 59);
27 dawrx |= (brk->type & (HW_BRK_TYPE_PRIV_ALL)) >> 3;
28 /*
29 * DAWR length is stored in field MDR bits 48:53. Matches range in
30 * doublewords (64 bits) biased by -1 eg. 0b000000=1DW and
31 * 0b111111=64DW.
32 * brk->hw_len is in bytes.
33 * This aligns up to double word size, shifts and does the bias.
34 */
35 mrd = ((brk->hw_len + 7) >> 3) - 1;
36 dawrx |= (mrd & 0x3f) << (63 - 53);
37
38 if (ppc_md.set_dawr)
39 return ppc_md.set_dawr(nr, dawr, dawrx);
40
41 if (nr == 0) {
42 mtspr(SPRN_DAWR0, dawr);
43 mtspr(SPRN_DAWRX0, dawrx);
44 } else {
45 mtspr(SPRN_DAWR1, dawr);
46 mtspr(SPRN_DAWRX1, dawrx);
47 }
48
49 return 0;
50 }
51
disable_dawrs_cb(void * info)52 static void disable_dawrs_cb(void *info)
53 {
54 struct arch_hw_breakpoint null_brk = {0};
55 int i;
56
57 for (i = 0; i < nr_wp_slots(); i++)
58 set_dawr(i, &null_brk);
59 }
60
dawr_write_file_bool(struct file * file,const char __user * user_buf,size_t count,loff_t * ppos)61 static ssize_t dawr_write_file_bool(struct file *file,
62 const char __user *user_buf,
63 size_t count, loff_t *ppos)
64 {
65 struct arch_hw_breakpoint null_brk = {0};
66 size_t rc;
67
68 /* Send error to user if they hypervisor won't allow us to write DAWR */
69 if (!dawr_force_enable &&
70 firmware_has_feature(FW_FEATURE_LPAR) &&
71 set_dawr(0, &null_brk) != H_SUCCESS)
72 return -ENODEV;
73
74 rc = debugfs_write_file_bool(file, user_buf, count, ppos);
75 if (rc)
76 return rc;
77
78 /* If we are clearing, make sure all CPUs have the DAWR cleared */
79 if (!dawr_force_enable)
80 smp_call_function(disable_dawrs_cb, NULL, 0);
81
82 return rc;
83 }
84
85 static const struct file_operations dawr_enable_fops = {
86 .read = debugfs_read_file_bool,
87 .write = dawr_write_file_bool,
88 .open = simple_open,
89 .llseek = default_llseek,
90 };
91
dawr_force_setup(void)92 static int __init dawr_force_setup(void)
93 {
94 if (cpu_has_feature(CPU_FTR_DAWR)) {
95 /* Don't setup sysfs file for user control on P8 */
96 dawr_force_enable = true;
97 return 0;
98 }
99
100 if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {
101 /* Turn DAWR off by default, but allow admin to turn it on */
102 debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
103 arch_debugfs_dir,
104 &dawr_force_enable,
105 &dawr_enable_fops);
106 }
107 return 0;
108 }
109 arch_initcall(dawr_force_setup);
110