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// SPDX-License-Identifier: GPL-2.0-only
#define pr_fmt(fmt) "papr-sysparm: " fmt
#include <linux/bug.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <asm/rtas.h>
#include <asm/papr-sysparm.h>
#include <asm/rtas-work-area.h>
struct papr_sysparm_buf *papr_sysparm_buf_alloc(void)
{
struct papr_sysparm_buf *buf = kzalloc(sizeof(*buf), GFP_KERNEL);
return buf;
}
void papr_sysparm_buf_free(struct papr_sysparm_buf *buf)
{
kfree(buf);
}
static size_t papr_sysparm_buf_get_length(const struct papr_sysparm_buf *buf)
{
return be16_to_cpu(buf->len);
}
static void papr_sysparm_buf_set_length(struct papr_sysparm_buf *buf, size_t length)
{
WARN_ONCE(length > sizeof(buf->val),
"bogus length %zu, clamping to safe value", length);
length = min(sizeof(buf->val), length);
buf->len = cpu_to_be16(length);
}
/*
* For use on buffers returned from ibm,get-system-parameter before
* returning them to callers. Ensures the encoded length of valid data
* cannot overrun buf->val[].
*/
static void papr_sysparm_buf_clamp_length(struct papr_sysparm_buf *buf)
{
papr_sysparm_buf_set_length(buf, papr_sysparm_buf_get_length(buf));
}
/*
* Perform some basic diligence on the system parameter buffer before
* submitting it to RTAS.
*/
static bool papr_sysparm_buf_can_submit(const struct papr_sysparm_buf *buf)
{
/*
* Firmware ought to reject buffer lengths that exceed the
* maximum specified in PAPR, but there's no reason for the
* kernel to allow them either.
*/
if (papr_sysparm_buf_get_length(buf) > sizeof(buf->val))
return false;
return true;
}
/**
* papr_sysparm_get() - Retrieve the value of a PAPR system parameter.
* @param: PAPR system parameter token as described in
* 7.3.16 "System Parameters Option".
* @buf: A &struct papr_sysparm_buf as returned from papr_sysparm_buf_alloc().
*
* Place the result of querying the specified parameter, if available,
* in @buf. The result includes a be16 length header followed by the
* value, which may be a string or binary data. See &struct papr_sysparm_buf.
*
* Since there is at least one parameter (60, OS Service Entitlement
* Status) where the results depend on the incoming contents of the
* work area, the caller-supplied buffer is copied unmodified into the
* work area before calling ibm,get-system-parameter.
*
* A defined parameter may not be implemented on a given system, and
* some implemented parameters may not be available to all partitions
* on a system. A parameter's disposition may change at any time due
* to system configuration changes or partition migration.
*
* Context: This function may sleep.
*
* Return: 0 on success, -errno otherwise. @buf is unmodified on error.
*/
int papr_sysparm_get(papr_sysparm_t param, struct papr_sysparm_buf *buf)
{
const s32 token = rtas_function_token(RTAS_FN_IBM_GET_SYSTEM_PARAMETER);
struct rtas_work_area *work_area;
s32 fwrc;
int ret;
might_sleep();
if (WARN_ON(!buf))
return -EFAULT;
if (token == RTAS_UNKNOWN_SERVICE)
return -ENOENT;
if (!papr_sysparm_buf_can_submit(buf))
return -EINVAL;
work_area = rtas_work_area_alloc(sizeof(*buf));
memcpy(rtas_work_area_raw_buf(work_area), buf, sizeof(*buf));
do {
fwrc = rtas_call(token, 3, 1, NULL, param.token,
rtas_work_area_phys(work_area),
rtas_work_area_size(work_area));
} while (rtas_busy_delay(fwrc));
switch (fwrc) {
case 0:
ret = 0;
memcpy(buf, rtas_work_area_raw_buf(work_area), sizeof(*buf));
papr_sysparm_buf_clamp_length(buf);
break;
case -3: /* parameter not implemented */
ret = -EOPNOTSUPP;
break;
case -9002: /* this partition not authorized to retrieve this parameter */
ret = -EPERM;
break;
case -9999: /* "parameter error" e.g. the buffer is too small */
ret = -EINVAL;
break;
default:
pr_err("unexpected ibm,get-system-parameter result %d\n", fwrc);
fallthrough;
case -1: /* Hardware/platform error */
ret = -EIO;
break;
}
rtas_work_area_free(work_area);
return ret;
}
int papr_sysparm_set(papr_sysparm_t param, const struct papr_sysparm_buf *buf)
{
const s32 token = rtas_function_token(RTAS_FN_IBM_SET_SYSTEM_PARAMETER);
struct rtas_work_area *work_area;
s32 fwrc;
int ret;
might_sleep();
if (WARN_ON(!buf))
return -EFAULT;
if (token == RTAS_UNKNOWN_SERVICE)
return -ENOENT;
if (!papr_sysparm_buf_can_submit(buf))
return -EINVAL;
work_area = rtas_work_area_alloc(sizeof(*buf));
memcpy(rtas_work_area_raw_buf(work_area), buf, sizeof(*buf));
do {
fwrc = rtas_call(token, 2, 1, NULL, param.token,
rtas_work_area_phys(work_area));
} while (rtas_busy_delay(fwrc));
switch (fwrc) {
case 0:
ret = 0;
break;
case -3: /* parameter not supported */
ret = -EOPNOTSUPP;
break;
case -9002: /* this partition not authorized to modify this parameter */
ret = -EPERM;
break;
case -9999: /* "parameter error" e.g. invalid input data */
ret = -EINVAL;
break;
default:
pr_err("unexpected ibm,set-system-parameter result %d\n", fwrc);
fallthrough;
case -1: /* Hardware/platform error */
ret = -EIO;
break;
}
rtas_work_area_free(work_area);
return ret;
}
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