probes.c

// SPDX-License-Identifier: GPL-2.0
/*
 *    Common helper functions for kprobes and uprobes
 *
 *    Copyright IBM Corp. 2014
 */

#include <linux/errno.h>
#include <asm/kprobes.h>
#include <asm/dis.h>

int probe_is_prohibited_opcode(u16 *insn)
{
	if (!is_known_insn((unsigned char *)insn))
		return -EINVAL;
	switch (insn[0] >> 8) {
	case 0x0c:	/* bassm */
	case 0x0b:	/* bsm	 */
	case 0x83:	/* diag  */
	case 0x44:	/* ex	 */
	case 0xac:	/* stnsm */
	case 0xad:	/* stosm */
		return -EINVAL;
	case 0xc6:
		switch (insn[0] & 0x0f) {
		case 0x00: /* exrl   */
			return -EINVAL;
		}
	}
	switch (insn[0]) {
	case 0x0101:	/* pr	 */
	case 0xb25a:	/* bsa	 */
	case 0xb240:	/* bakr  */
	case 0xb258:	/* bsg	 */
	case 0xb218:	/* pc	 */
	case 0xb228:	/* pt	 */
	case 0xb98d:	/* epsw	 */
	case 0xe560:	/* tbegin */
	case 0xe561:	/* tbeginc */
	case 0xb2f8:	/* tend	 */
		return -EINVAL;
	}
	return 0;
}

int probe_get_fixup_type(u16 *insn)
{
	/* default fixup method */
	int fixup = FIXUP_PSW_NORMAL;

	switch (insn[0] >> 8) {
	case 0x05:	/* balr	*/
	case 0x0d:	/* basr */
		fixup = FIXUP_RETURN_REGISTER;
		/* if r2 = 0, no branch will be taken */
		if ((insn[0] & 0x0f) == 0)
			fixup |= FIXUP_BRANCH_NOT_TAKEN;
		break;
	case 0x06:	/* bctr	*/
	case 0x07:	/* bcr	*/
		fixup = FIXUP_BRANCH_NOT_TAKEN;
		break;
	case 0x45:	/* bal	*/
	case 0x4d:	/* bas	*/
		fixup = FIXUP_RETURN_REGISTER;
		break;
	case 0x47:	/* bc	*/
	case 0x46:	/* bct	*/
	case 0x86:	/* bxh	*/
	case 0x87:	/* bxle	*/
		fixup = FIXUP_BRANCH_NOT_TAKEN;
		break;
	case 0x82:	/* lpsw	*/
		fixup = FIXUP_NOT_REQUIRED;
		break;
	case 0xb2:	/* lpswe */
		if ((insn[0] & 0xff) == 0xb2)
			fixup = FIXUP_NOT_REQUIRED;
		break;
	case 0xa7:	/* bras	*/
		if ((insn[0] & 0x0f) == 0x05)
			fixup |= FIXUP_RETURN_REGISTER;
		break;
	case 0xc0:
		if ((insn[0] & 0x0f) == 0x05)	/* brasl */
			fixup |= FIXUP_RETURN_REGISTER;
		break;
	case 0xeb:
		switch (insn[2] & 0xff) {
		case 0x44: /* bxhg  */
		case 0x45: /* bxleg */
			fixup = FIXUP_BRANCH_NOT_TAKEN;
			break;
		}
		break;
	case 0xe3:	/* bctg	*/
		if ((insn[2] & 0xff) == 0x46)
			fixup = FIXUP_BRANCH_NOT_TAKEN;
		break;
	case 0xec:
		switch (insn[2] & 0xff) {
		case 0xe5: /* clgrb */
		case 0xe6: /* cgrb  */
		case 0xf6: /* crb   */
		case 0xf7: /* clrb  */
		case 0xfc: /* cgib  */
		case 0xfd: /* cglib */
		case 0xfe: /* cib   */
		case 0xff: /* clib  */
			fixup = FIXUP_BRANCH_NOT_TAKEN;
			break;
		}
		break;
	}
	return fixup;
}

int probe_is_insn_relative_long(u16 *insn)
{
	/* Check if we have a RIL-b or RIL-c format instruction which
	 * we need to modify in order to avoid instruction emulation. */
	switch (insn[0] >> 8) {
	case 0xc0:
		if ((insn[0] & 0x0f) == 0x00) /* larl */
			return true;
		break;
	case 0xc4:
		switch (insn[0] & 0x0f) {
		case 0x02: /* llhrl  */
		case 0x04: /* lghrl  */
		case 0x05: /* lhrl   */
		case 0x06: /* llghrl */
		case 0x07: /* sthrl  */
		case 0x08: /* lgrl   */
		case 0x0b: /* stgrl  */
		case 0x0c: /* lgfrl  */
		case 0x0d: /* lrl    */
		case 0x0e: /* llgfrl */
		case 0x0f: /* strl   */
			return true;
		}
		break;
	case 0xc6:
		switch (insn[0] & 0x0f) {
		case 0x02: /* pfdrl  */
		case 0x04: /* cghrl  */
		case 0x05: /* chrl   */
		case 0x06: /* clghrl */
		case 0x07: /* clhrl  */
		case 0x08: /* cgrl   */
		case 0x0a: /* clgrl  */
		case 0x0c: /* cgfrl  */
		case 0x0d: /* crl    */
		case 0x0e: /* clgfrl */
		case 0x0f: /* clrl   */
			return true;
		}
		break;
	}
	return false;
}