1// SPDX-License-Identifier: GPL-2.0
  2#include <linux/kernel.h>
  3
  4typedef unsigned int instr;
  5
  6#define MAJOR_OP	0xfc000000
  7#define LDA_OP		0x20000000
  8#define STQ_OP		0xb4000000
  9#define BR_OP		0xc0000000
 10
 11#define STK_ALLOC_1	0x23de8000 /* lda $30,-X($30) */
 12#define STK_ALLOC_1M	0xffff8000
 13#define STK_ALLOC_2	0x43c0153e /* subq $30,X,$30 */
 14#define STK_ALLOC_2M	0xffe01fff
 15
 16#define MEM_REG		0x03e00000
 17#define MEM_BASE	0x001f0000
 18#define MEM_OFF		0x0000ffff
 19#define MEM_OFF_SIGN	0x00008000
 20#define	BASE_SP		0x001e0000
 21
 22#define STK_ALLOC_MATCH(INSTR)			\
 23  (((INSTR) & STK_ALLOC_1M) == STK_ALLOC_1	\
 24   || ((INSTR) & STK_ALLOC_2M) == STK_ALLOC_2)
 25#define STK_PUSH_MATCH(INSTR) \
 26  (((INSTR) & (MAJOR_OP | MEM_BASE | MEM_OFF_SIGN)) == (STQ_OP | BASE_SP))
 27#define MEM_OP_OFFSET(INSTR) \
 28  (((long)((INSTR) & MEM_OFF) << 48) >> 48)
 29#define MEM_OP_REG(INSTR) \
 30  (((INSTR) & MEM_REG) >> 22)
 31
 32/* Branches, jumps, PAL calls, and illegal opcodes end a basic block. */
 33#define BB_END(INSTR)						\
 34  (((instr)(INSTR) >= BR_OP) | ((instr)(INSTR) < LDA_OP) |	\
 35   ((((instr)(INSTR) ^ 0x60000000) < 0x20000000) &		\
 36    (((instr)(INSTR) & 0x0c000000) != 0)))
 37
 38#define IS_KERNEL_TEXT(PC) ((unsigned long)(PC) > START_ADDR)
 39
 40static char reg_name[][4] = {
 41	"v0 ", "t0 ", "t1 ", "t2 ", "t3 ", "t4 ", "t5 ", "t6 ", "t7 ",
 42	"s0 ", "s1 ", "s2 ", "s3 ", "s4 ", "s5 ", "s6 ", "a0 ", "a1 ",
 43	"a2 ", "a3 ", "a4 ", "a5 ", "t8 ", "t9 ", "t10", "t11", "ra ",
 44	"pv ", "at ", "gp ", "sp ", "0"
 45};
 46
 47
 48static instr *
 49display_stored_regs(instr * pro_pc, unsigned char * sp)
 50{
 51	instr * ret_pc = 0;
 52	int reg;
 53	unsigned long value;
 54
 55	printk("Prologue [<%p>], Frame %p:\n", pro_pc, sp);
 56	while (!BB_END(*pro_pc))
 57		if (STK_PUSH_MATCH(*pro_pc)) {
 58			reg = (*pro_pc & MEM_REG) >> 21;
 59			value = *(unsigned long *)(sp + (*pro_pc & MEM_OFF));
 60			if (reg == 26)
 61				ret_pc = (instr *)value;
 62			printk("\t\t%s / 0x%016lx\n", reg_name[reg], value);
 63		}
 64	return ret_pc;
 65}
 66
 67static instr *
 68seek_prologue(instr * pc)
 69{
 70	while (!STK_ALLOC_MATCH(*pc))
 71		--pc;
 72	while (!BB_END(*(pc - 1)))
 73		--pc;
 74	return pc;
 75}
 76
 77static long
 78stack_increment(instr * prologue_pc)
 79{
 80	while (!STK_ALLOC_MATCH(*prologue_pc))
 81		++prologue_pc;
 82
 83	/* Count the bytes allocated. */
 84	if ((*prologue_pc & STK_ALLOC_1M) == STK_ALLOC_1M)
 85		return -(((long)(*prologue_pc) << 48) >> 48);
 86	else
 87		return (*prologue_pc >> 13) & 0xff;
 88}
 89
 90void
 91stacktrace(void)
 92{
 93	instr * ret_pc;
 94	instr * prologue = (instr *)stacktrace;
 95	register unsigned char * sp __asm__ ("$30");
 96
 97	printk("\tstack trace:\n");
 98	do {
 99		ret_pc = display_stored_regs(prologue, sp);
100		sp += stack_increment(prologue);
101		prologue = seek_prologue(ret_pc);
102	} while (IS_KERNEL_TEXT(ret_pc));
103}