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/* libpaf-dsc primary implementation details.
*
* Copyright IBM Corp. 2013
*
* The MIT License (MIT)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* Contributors:
* IBM Corporation, Edjunior Barbosa Machado - Initial implementation.
*/
#include <errno.h>
#include <stdio.h>
#include <ucontext.h>
#include <signal.h>
#include <pthread.h>
#include <inttypes.h>
#include <stdlib.h>
#include "config.h"
#include <paf/dsc.h>
#include "paf-common.h"
#include "hwcap.h"
/* PowerPC instruction length */
#define PPC_INSN_LEN 4
/* SPR number used for DSCR */
typedef enum {
SPRN_DSCR_USER = 0x03,
#define SPRN_DSCR_USER 0x03
SPRN_DSCR = 0x11
#define SPRN_DSCR 0x11
} dscr_sprn_t;
#define mfspr_dscr(rn) \
(rn == SPRN_DSCR_USER ? mfspr(SPRN_DSCR_USER) : mfspr(SPRN_DSCR))
#define mtspr_dscr(rn, value) \
(rn == SPRN_DSCR_USER ? mtspr(SPRN_DSCR_USER, value) : mtspr(SPRN_DSCR, value))
/* mask of DSCR features supported (0 if not supported) */
static volatile uint64_t *dscr_support_mask = NULL;
static dscr_sprn_t dscr_sprn = SPRN_DSCR_USER;
/* error control inside the thread check_dscr_insn() */
static int init_errno = 0;
static pthread_once_t check_dscr_once_control = PTHREAD_ONCE_INIT;
void static
sigill_callback(int sig, siginfo_t *si, void *ctx)
{
ucontext_t *uctx = (ucontext_t*)(ctx);
DEBUG("Caught signal %d. No DSCR support available in kernel using SPR %d", sig, dscr_sprn);
/* set dscr_support_mask as support unavailable */
*dscr_support_mask = 0;
/* manually increment PC register in order to step over the illegal insn */
uctx->uc_mcontext.regs->nip += PPC_INSN_LEN;
}
/* verify whether dscr-related insn is treated as illegal or not */
static int
check_dscr_insn(void)
{
/* set up a signal handler to check whether the DSCR instruction
(m[ft]spr) is treated as illegal or not */
struct sigaction sa, old_sa;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
sa.sa_sigaction = sigill_callback;
if (sigaction(SIGILL, &sa, &old_sa) == 0)
{
/* dscr_support_mask will be used to check if mfspr insn does not sigill.
Marking as support available initially. */
*dscr_support_mask = 1;
/* try to issue a simple get dscr using non privileged SPR */
dscr_sprn = SPRN_DSCR_USER;
mfspr(SPRN_DSCR_USER);
/* check if the previous mfspr was unsuccessful (i.e., SIGILLed) */
if (*dscr_support_mask == 0)
{
/* if unsuccessful, try using the former (privileged) SPR */
*dscr_support_mask = 1;
dscr_sprn = SPRN_DSCR;
mfspr(SPRN_DSCR);
}
/* re-sets the former sigaction */
sigaction(SIGILL, &old_sa, NULL);
/* if the insn is not illegal, check for hw supported features */
if (*dscr_support_mask != 0)
*dscr_support_mask = check_hwcap();
}
else
{
perror("Cannot set signal handler to check dscr support.\n");
*dscr_support_mask = 0;
init_errno = ENOSYS;
return -1;
}
return 0;
}
uint64_t
paf_dsc_check_support(void)
{
if (dscr_support_mask == NULL)
{
dscr_support_mask = (uint64_t *)malloc(sizeof(uint64_t));
if (pthread_once (&check_dscr_once_control,
(void (*)(void))check_dscr_insn))
{
perror("Error pthread_once(check_dscr_insn()) failed");
*dscr_support_mask = 0;
errno = ENOSYS;
return 0;
}
/* check if something went wrong when calling check_dscr_insn() and set
errno properly */
if (init_errno != 0)
{
*dscr_support_mask = 0;
errno = init_errno;
return 0;
}
}
if (*dscr_support_mask == 0)
errno = ENOSYS;
return *dscr_support_mask;
}
int
paf_dsc_get(uint64_t *dscr)
{
if (*dscr_support_mask == 0)
{
errno = ENOSYS;
return -1;
}
*dscr = mfspr_dscr(dscr_sprn);
DEBUG("get 0x%" PRIx64, *dscr);
return 0;
}
int
paf_dsc_set(uint64_t dscr)
{
/* check whether DSCR support is available */
if (*dscr_support_mask == 0)
{
errno = ENOSYS;
return -1;
}
/* check whether the value to be set in DSCR is supported in this machine */
if ((dscr | *dscr_support_mask) != *dscr_support_mask)
{
DEBUG("Cannot set dscr 0x%" PRIx64 " (supported mask 0x%" PRIx64 ")", dscr, *dscr_support_mask);
errno = EINVAL;
return -1;
}
DEBUG("set 0x%" PRIx64, dscr);
mtspr_dscr(dscr_sprn, dscr);
return 0;
}
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