1 // SPDX-License-Identifier: GPL-2.0-only
2
3 #define pr_fmt(fmt) "papr-sysparm: " fmt
4
5 #include <linux/bug.h>
6 #include <linux/init.h>
7 #include <linux/kernel.h>
8 #include <linux/printk.h>
9 #include <linux/slab.h>
10 #include <asm/rtas.h>
11 #include <asm/papr-sysparm.h>
12 #include <asm/rtas-work-area.h>
13
papr_sysparm_buf_alloc(void)14 struct papr_sysparm_buf *papr_sysparm_buf_alloc(void)
15 {
16 struct papr_sysparm_buf *buf = kzalloc(sizeof(*buf), GFP_KERNEL);
17
18 return buf;
19 }
20
papr_sysparm_buf_free(struct papr_sysparm_buf * buf)21 void papr_sysparm_buf_free(struct papr_sysparm_buf *buf)
22 {
23 kfree(buf);
24 }
25
papr_sysparm_buf_get_length(const struct papr_sysparm_buf * buf)26 static size_t papr_sysparm_buf_get_length(const struct papr_sysparm_buf *buf)
27 {
28 return be16_to_cpu(buf->len);
29 }
30
papr_sysparm_buf_set_length(struct papr_sysparm_buf * buf,size_t length)31 static void papr_sysparm_buf_set_length(struct papr_sysparm_buf *buf, size_t length)
32 {
33 WARN_ONCE(length > sizeof(buf->val),
34 "bogus length %zu, clamping to safe value", length);
35 length = min(sizeof(buf->val), length);
36 buf->len = cpu_to_be16(length);
37 }
38
39 /*
40 * For use on buffers returned from ibm,get-system-parameter before
41 * returning them to callers. Ensures the encoded length of valid data
42 * cannot overrun buf->val[].
43 */
papr_sysparm_buf_clamp_length(struct papr_sysparm_buf * buf)44 static void papr_sysparm_buf_clamp_length(struct papr_sysparm_buf *buf)
45 {
46 papr_sysparm_buf_set_length(buf, papr_sysparm_buf_get_length(buf));
47 }
48
49 /*
50 * Perform some basic diligence on the system parameter buffer before
51 * submitting it to RTAS.
52 */
papr_sysparm_buf_can_submit(const struct papr_sysparm_buf * buf)53 static bool papr_sysparm_buf_can_submit(const struct papr_sysparm_buf *buf)
54 {
55 /*
56 * Firmware ought to reject buffer lengths that exceed the
57 * maximum specified in PAPR, but there's no reason for the
58 * kernel to allow them either.
59 */
60 if (papr_sysparm_buf_get_length(buf) > sizeof(buf->val))
61 return false;
62
63 return true;
64 }
65
66 /**
67 * papr_sysparm_get() - Retrieve the value of a PAPR system parameter.
68 * @param: PAPR system parameter token as described in
69 * 7.3.16 "System Parameters Option".
70 * @buf: A &struct papr_sysparm_buf as returned from papr_sysparm_buf_alloc().
71 *
72 * Place the result of querying the specified parameter, if available,
73 * in @buf. The result includes a be16 length header followed by the
74 * value, which may be a string or binary data. See &struct papr_sysparm_buf.
75 *
76 * Since there is at least one parameter (60, OS Service Entitlement
77 * Status) where the results depend on the incoming contents of the
78 * work area, the caller-supplied buffer is copied unmodified into the
79 * work area before calling ibm,get-system-parameter.
80 *
81 * A defined parameter may not be implemented on a given system, and
82 * some implemented parameters may not be available to all partitions
83 * on a system. A parameter's disposition may change at any time due
84 * to system configuration changes or partition migration.
85 *
86 * Context: This function may sleep.
87 *
88 * Return: 0 on success, -errno otherwise. @buf is unmodified on error.
89 */
90
papr_sysparm_get(papr_sysparm_t param,struct papr_sysparm_buf * buf)91 int papr_sysparm_get(papr_sysparm_t param, struct papr_sysparm_buf *buf)
92 {
93 const s32 token = rtas_function_token(RTAS_FN_IBM_GET_SYSTEM_PARAMETER);
94 struct rtas_work_area *work_area;
95 s32 fwrc;
96 int ret;
97
98 might_sleep();
99
100 if (WARN_ON(!buf))
101 return -EFAULT;
102
103 if (token == RTAS_UNKNOWN_SERVICE)
104 return -ENOENT;
105
106 if (!papr_sysparm_buf_can_submit(buf))
107 return -EINVAL;
108
109 work_area = rtas_work_area_alloc(sizeof(*buf));
110
111 memcpy(rtas_work_area_raw_buf(work_area), buf, sizeof(*buf));
112
113 do {
114 fwrc = rtas_call(token, 3, 1, NULL, param.token,
115 rtas_work_area_phys(work_area),
116 rtas_work_area_size(work_area));
117 } while (rtas_busy_delay(fwrc));
118
119 switch (fwrc) {
120 case 0:
121 ret = 0;
122 memcpy(buf, rtas_work_area_raw_buf(work_area), sizeof(*buf));
123 papr_sysparm_buf_clamp_length(buf);
124 break;
125 case -3: /* parameter not implemented */
126 ret = -EOPNOTSUPP;
127 break;
128 case -9002: /* this partition not authorized to retrieve this parameter */
129 ret = -EPERM;
130 break;
131 case -9999: /* "parameter error" e.g. the buffer is too small */
132 ret = -EINVAL;
133 break;
134 default:
135 pr_err("unexpected ibm,get-system-parameter result %d\n", fwrc);
136 fallthrough;
137 case -1: /* Hardware/platform error */
138 ret = -EIO;
139 break;
140 }
141
142 rtas_work_area_free(work_area);
143
144 return ret;
145 }
146
papr_sysparm_set(papr_sysparm_t param,const struct papr_sysparm_buf * buf)147 int papr_sysparm_set(papr_sysparm_t param, const struct papr_sysparm_buf *buf)
148 {
149 const s32 token = rtas_function_token(RTAS_FN_IBM_SET_SYSTEM_PARAMETER);
150 struct rtas_work_area *work_area;
151 s32 fwrc;
152 int ret;
153
154 might_sleep();
155
156 if (WARN_ON(!buf))
157 return -EFAULT;
158
159 if (token == RTAS_UNKNOWN_SERVICE)
160 return -ENOENT;
161
162 if (!papr_sysparm_buf_can_submit(buf))
163 return -EINVAL;
164
165 work_area = rtas_work_area_alloc(sizeof(*buf));
166
167 memcpy(rtas_work_area_raw_buf(work_area), buf, sizeof(*buf));
168
169 do {
170 fwrc = rtas_call(token, 2, 1, NULL, param.token,
171 rtas_work_area_phys(work_area));
172 } while (rtas_busy_delay(fwrc));
173
174 switch (fwrc) {
175 case 0:
176 ret = 0;
177 break;
178 case -3: /* parameter not supported */
179 ret = -EOPNOTSUPP;
180 break;
181 case -9002: /* this partition not authorized to modify this parameter */
182 ret = -EPERM;
183 break;
184 case -9999: /* "parameter error" e.g. invalid input data */
185 ret = -EINVAL;
186 break;
187 default:
188 pr_err("unexpected ibm,set-system-parameter result %d\n", fwrc);
189 fallthrough;
190 case -1: /* Hardware/platform error */
191 ret = -EIO;
192 break;
193 }
194
195 rtas_work_area_free(work_area);
196
197 return ret;
198 }
199