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// SPDX-License-Identifier: GPL-2.0
#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <asm/ptrace.h>
#include <asm/stacktrace.h>
#include <linux/stacktrace.h>
#include <linux/kernel.h>
#include <asm/sections.h>
#include <asm/inst.h>
struct stackframe {
unsigned long sp;
unsigned long pc;
unsigned long ra;
};
static inline int get_mem(unsigned long addr, unsigned long *result)
{
unsigned long *address = (unsigned long *) addr;
if (!access_ok(address, sizeof(unsigned long)))
return -1;
if (__copy_from_user_inatomic(result, address, sizeof(unsigned long)))
return -3;
return 0;
}
/*
* These two instruction helpers were taken from process.c
*/
static inline int is_ra_save_ins(union mips_instruction *ip)
{
/* sw / sd $ra, offset($sp) */
return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op)
&& ip->i_format.rs == 29 && ip->i_format.rt == 31;
}
static inline int is_sp_move_ins(union mips_instruction *ip)
{
/* addiu/daddiu sp,sp,-imm */
if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
return 0;
if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
return 1;
return 0;
}
/*
* Looks for specific instructions that mark the end of a function.
* This usually means we ran into the code area of the previous function.
*/
static inline int is_end_of_function_marker(union mips_instruction *ip)
{
/* jr ra */
if (ip->r_format.func == jr_op && ip->r_format.rs == 31)
return 1;
/* lui gp */
if (ip->i_format.opcode == lui_op && ip->i_format.rt == 28)
return 1;
return 0;
}
/*
* TODO for userspace stack unwinding:
* - handle cases where the stack is adjusted inside a function
* (generally doesn't happen)
* - find optimal value for max_instr_check
* - try to find a better way to handle leaf functions
*/
static inline int unwind_user_frame(struct stackframe *old_frame,
const unsigned int max_instr_check)
{
struct stackframe new_frame = *old_frame;
off_t ra_offset = 0;
size_t stack_size = 0;
unsigned long addr;
if (old_frame->pc == 0 || old_frame->sp == 0 || old_frame->ra == 0)
return -9;
for (addr = new_frame.pc; (addr + max_instr_check > new_frame.pc)
&& (!ra_offset || !stack_size); --addr) {
union mips_instruction ip;
if (get_mem(addr, (unsigned long *) &ip))
return -11;
if (is_sp_move_ins(&ip)) {
int stack_adjustment = ip.i_format.simmediate;
if (stack_adjustment > 0)
/* This marks the end of the previous function,
which means we overran. */
break;
stack_size = (unsigned long) stack_adjustment;
} else if (is_ra_save_ins(&ip)) {
int ra_slot = ip.i_format.simmediate;
if (ra_slot < 0)
/* This shouldn't happen. */
break;
ra_offset = ra_slot;
} else if (is_end_of_function_marker(&ip))
break;
}
if (!ra_offset || !stack_size)
goto done;
if (ra_offset) {
new_frame.ra = old_frame->sp + ra_offset;
if (get_mem(new_frame.ra, &(new_frame.ra)))
return -13;
}
if (stack_size) {
new_frame.sp = old_frame->sp + stack_size;
if (get_mem(new_frame.sp, &(new_frame.sp)))
return -14;
}
if (new_frame.sp > old_frame->sp)
return -2;
done:
new_frame.pc = old_frame->ra;
*old_frame = new_frame;
return 0;
}
static inline void do_user_backtrace(unsigned long low_addr,
struct stackframe *frame,
unsigned int depth)
{
const unsigned int max_instr_check = 512;
const unsigned long high_addr = low_addr + THREAD_SIZE;
while (depth-- && !unwind_user_frame(frame, max_instr_check)) {
oprofile_add_trace(frame->ra);
if (frame->sp < low_addr || frame->sp > high_addr)
break;
}
}
#ifndef CONFIG_KALLSYMS
static inline void do_kernel_backtrace(unsigned long low_addr,
struct stackframe *frame,
unsigned int depth) { }
#else
static inline void do_kernel_backtrace(unsigned long low_addr,
struct stackframe *frame,
unsigned int depth)
{
while (depth-- && frame->pc) {
frame->pc = unwind_stack_by_address(low_addr,
&(frame->sp),
frame->pc,
&(frame->ra));
oprofile_add_trace(frame->ra);
}
}
#endif
void notrace op_mips_backtrace(struct pt_regs *const regs, unsigned int depth)
{
struct stackframe frame = { .sp = regs->regs[29],
.pc = regs->cp0_epc,
.ra = regs->regs[31] };
const int userspace = user_mode(regs);
const unsigned long low_addr = ALIGN(frame.sp, THREAD_SIZE);
if (userspace)
do_user_backtrace(low_addr, &frame, depth);
else
do_kernel_backtrace(low_addr, &frame, depth);
}
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