/* Dwarfless register access for s390x */

@__private30 global _reg_offsets[22]

%{
#include <asm/ptrace.h>

/*
 * The following routines help with getting arguments off the s390x
 * stack. For more details see:
 *
 * "S/390 ELF Application Binary Interface Supplement"
 * <http://refspecs.linuxfoundation.org/ELF/zSeries/lzsabi0_s390/x414.html>
 */

/*
 * This is a copy of the kernel's kernel_stack_pointer(), which is
 * only available on newer kernels.
 */
static inline unsigned long _stp_kernel_stack_pointer(struct pt_regs *regs)
{
	return regs->gprs[15] & PSW_ADDR_INSN;
}

/*
 * This is a copy of the kernel's unexported regs_within_kernel_stack().
 */
static int
_stp_regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
{
        unsigned long ksp = _stp_kernel_stack_pointer(regs);

        return (addr & ~(THREAD_SIZE - 1)) == (ksp & ~(THREAD_SIZE - 1));
}
%}

/*
 * _stp_get_kernel_stack_param() - get Nth parameter from the stack
 * n:stack parameter number (starts from 0)
 *
 * _stp_get_kernel_stack_param() returns nth parameter from
 * the kernel stack. If the nth entry is NOT in the kernel stack, this
 * returns 0. 
 *
 * This is based on the kernel's (unexported)
 * regs_get_kernel_stack_nth() function.
 */
function _stp_get_kernel_stack_param:long(n:long)
%{
	__label__ deref_fault;
        unsigned long addr;
	struct pt_regs *regs;

	regs = CONTEXT->kregs;
	if (!regs) {
		CONTEXT->last_error = "No registers available in this context";
		return;
	}

        // The parameters start just after the stack frame.
        addr = (_stp_kernel_stack_pointer(regs) + sizeof(struct stack_frame)
		+ STAP_ARG_n * sizeof(long));
        if (!_stp_regs_within_kernel_stack(regs, addr)) {
		STAP_RETVALUE = 0;
                return;
	}
        STAP_RETVALUE = kread((unsigned long *)addr);
	return;

deref_fault: /* branched to from kread() */
	snprintf (CONTEXT->error_buffer, sizeof(CONTEXT->error_buffer),
		  "kernel fault at %#lx accessing stack param(%d)",
		  addr, (int)STAP_ARG_n);
	CONTEXT->last_error = CONTEXT->error_buffer;
%}

probe init {
	/* Same order as pt_regs */
	_reg_offsets["args"] = 0
	_reg_offsets["psw.mask"] = 8
	_reg_offsets["psw.addr"] = 16
	_reg_offsets["r0"] = 24
	_reg_offsets["r1"] = 32
	_reg_offsets["r2"] = 40
	_reg_offsets["r3"] = 48
	_reg_offsets["r4"] = 56
	_reg_offsets["r5"] = 64
	_reg_offsets["r6"] = 72
	_reg_offsets["r7"] = 80
	_reg_offsets["r8"] = 88
	_reg_offsets["r9"] = 96
	_reg_offsets["r10"] = 104
	_reg_offsets["r11"] = 112
	_reg_offsets["r12"] = 120
	_reg_offsets["r13"] = 128
	_reg_offsets["r14"] = 136
	_reg_offsets["r15"] = 144

	_reg_offsets["orig_gpr2"] = 152
	_reg_offsets["ilc"] = 160
	_reg_offsets["trap"] = 162

	/*
	 * If we ever need to support s390 (31-bit arch), we can
	 * get to the register offsets by using just a
	 * reg32_offset = _reg_offsets["reg"]/2
	 * or somesuch
	 */
}


/*
 * Though the flag says 31bit, asm-s390/thread_info.h comment
 * says "32bit process"
 */
function probing_32bit_app:long() %{ /* pure */
	if (CONTEXT->user_mode_p && _stp_is_compat_task())
		STAP_RETVALUE = 1;
	else
		STAP_RETVALUE = 0;
%}

function _stp_probing_kernel: long () {
	return !user_mode();
}

function arch_bytes:long() %{ /* pure */
  STAP_RETVALUE = sizeof(long);
%}

function uarch_bytes:long() {
  assert(user_mode(), "requires user mode")
  return probing_32bit_app() ? 4 : 8
}

function _stp_get_register_by_offset:long (offset:long) %{ /* pure */
	long value;
	struct pt_regs *regs;
	if (CONTEXT->sregs)
	  regs = CONTEXT->sregs;
	else
	  regs = (CONTEXT->user_mode_p ? CONTEXT->uregs : CONTEXT->kregs);
	if (!regs) {
		CONTEXT->last_error = "No registers available in this context";
		return;
	}
	if (STAP_ARG_offset < 0 || STAP_ARG_offset > sizeof(struct pt_regs) - sizeof(unsigned short)) {
		snprintf(CONTEXT->error_buffer, sizeof(CONTEXT->error_buffer),
				"Bad register offset: %lld",
				(long long)STAP_ARG_offset);
		CONTEXT->last_error = CONTEXT->error_buffer;
		return;
	}

	if (STAP_ARG_offset < sizeof(struct pt_regs) - 2 * sizeof(unsigned short))
		memcpy(&value, ((char *)regs) + STAP_ARG_offset,
				sizeof(value));
	else {
		/* ilc or trap */
		unsigned short us_value;
		memcpy(&us_value, ((char *)regs) + STAP_ARG_offset,
				sizeof(us_value));
		value = us_value;	// not sign-extended
	}
	STAP_RETVALUE = value;
%}

function _stp_sign_extend32:long (value:long) {
	if (value & 0x80000000)
		value |= (0xffffffff << 32)
	return value
}

function _stp_register:long (name:string, sign_extend:long) {
	# don't assert this: will get *regs state checked in _stp_get_register_by_offset, and better
	# assert(registers_valid(), "cannot access CPU registers in this context")
	offset = _reg_offsets[name]
	assert(offset != 0 || (name in _reg_offsets), "Unknown register: " . name)
	value = _stp_get_register_by_offset(offset)
	if (probing_32bit_app()) {
		if (sign_extend)
			value = _stp_sign_extend32(value)
		else
			value &= 0xffffffff
	}
	return value
}

/* Return the named register value as a signed value. */
function register:long (name:string) {
	return _stp_register(name, 1)
}

/*
 * Return the named register value as an unsigned value.  Specifically,
 * don't sign-extend the register value when promoting it to 64 bits.
 */
function u_register:long (name:string) {
	return _stp_register(name, 0)
}

/*
 * Return the value of function arg #argnum (1=first arg).
 * If truncate=1, mask off the top 32 bits.
 * If sign_extend=1 and (truncate=1 or the probepoint we've hit is in a
 * 32-bit app), sign-extend the 32-bit value.
 * If force64=1, return a 64-bit value even if we're in a 32-bit app.
 */
function _stp_arg:long (argnum:long, sign_extend:long, truncate:long)
{
	return _stp_arg2(argnum, sign_extend, truncate, 0)
}
function _stp_arg2:long (argnum:long, sign_extend:long, truncate:long,
			 force64:long)
{
	val = 0
  assert(!(argnum < 1 || argnum > 8), sprintf("Cannot access arg(%d)", argnum))

	/*
	 * Why not use syscall_get_arguments() here? On the s390x,
	 * syscall_get_arguments() is only defined to work on the
	 * pt_regs structure that gets intialized when a context
	 * switch from user space to kernel space happens due to a
	 * system call. This pt_regs structure is returned by
	 * 'task_pt_regs(current)'.
	 *
	 * This function is designed to get the argument of the
	 * current kernel function, which may or may not be a
	 * syscall. So, we have to roll our own.
	 */

	if (argnum == 1)
		val = u_register("r2")
	else if (argnum == 2)
		val = u_register("r3")
	else if (argnum == 3)
		val = u_register("r4")
	else if (argnum == 4)
		val = u_register("r5")
	else if (argnum == 5)
		val = u_register("r6")
	else if (argnum == 6 && %{ CONTEXT->sregs != NULL %} ) // linux syscall arg6 goes into r7
		val = u_register("r7")
	else if (argnum >= 6)
		val = _stp_get_kernel_stack_param(argnum - 6);

	if ((truncate || @__compat_task) && !force64) {
		/* High bits may be garbage. */
		val = (val & 0xffffffff)
		if (sign_extend)
			val = _stp_sign_extend32(val)
	}
	return val
}

/* Return the value of function arg #argnum (1=first arg) as a signed int. */
function int_arg:long (argnum:long) {
	return _stp_arg2(argnum, 1, 1, 0)
}

/* Return the value of function arg #argnum (1=first arg) as an unsigned int. */
function uint_arg:long (argnum:long) {
	return _stp_arg2(argnum, 0, 1, 0)
}

function long_arg:long (argnum:long) {
	return _stp_arg2(argnum, 1, 0, 0)
}

function ulong_arg:long (argnum:long) {
	return _stp_arg2(argnum, 0, 0, 0)
}

function longlong_arg:long (argnum:long) {
	if (probing_32bit_app()) {
		highbits = _stp_arg2(argnum, 0, 1, 0)
		lowbits = _stp_arg2(argnum+1, 0, 1, 0)
		return ((highbits << 32) | lowbits)
	} else
		return _stp_arg2(argnum, 0, 0, 1)
}

function ulonglong_arg:long (argnum:long) {
	return longlong_arg(argnum)
}

function pointer_arg:long (argnum:long) {
	return _stp_arg2(argnum, 0, 0, 0)
}

function s32_arg:long (argnum:long) {
	return int_arg(argnum)
}

function u32_arg:long (argnum:long) {
	return uint_arg(argnum)
}

function s64_arg:long (argnum:long) {
	return longlong_arg(argnum)
}

function u64_arg:long (argnum:long) {
	return ulonglong_arg(argnum)
}

function asmlinkage() %{ /* pure */ %}

function fastcall() %{ /* pure */ %}

function regparm(n:long) %{
	snprintf(CONTEXT->error_buffer, sizeof(CONTEXT->error_buffer),
		"regparm is invalid on s390.");
	CONTEXT->last_error = CONTEXT->error_buffer;
%}
