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/* -*- linux-c -*-
* arm stack tracing functions
* Copyright (C) 2007 Quentin Barnes
*
* This file is part of systemtap, and is free software. You can
* redistribute it and/or modify it under the terms of the GNU General
* Public License (GPL); either version 2, or (at your option) any
* later version.
*/
/*
* For STR and STM instructions, an ARM core may choose to use either
* a +8 or a +12 displacement from the current instruction's address.
* Whichever value is chosen for a given core, it must be the same for
* both instructions and may not change. This function measures it.
*/
static int __init find_str_pc_offset(void)
{
int addr;
int scratch;
int ret;
__asm__("sub %[ret], pc, #4 \n\t"
"str pc, %[addr] \n\t"
"ldr %[scr], %[addr] \n\t"
"sub %[ret], %[scr], %[ret] \n\t"
: [ret] "=r" (ret), [scr] "=r" (scratch), [addr] "+m" (addr) );
return ret;
}
static void __stp_stack_print (struct pt_regs *regs, int verbose, int levels,
struct task_struct *tsk, struct uretprobe_instance *ri)
{
#ifdef STP_USE_FRAME_POINTER
int pc_offset = find_str_pc_offset();
unsigned long *fp = (unsigned long *)regs->ARM_fp;
unsigned long *next_fp, *pc;
if (levels == 0)
--levels;
while (fp && levels--) {
next_fp = (unsigned long *)*(fp - 3);
pc = (unsigned long *)(*fp - pc_offset);
/* 0xe92dd8xx == stmfd sp!, { ..., fp, ip, lr, pc } */
if ((*pc & 0xffffd800) == 0xe92dd800) {
pc -= 1;
/* Varargs functions have two stmfd instructions. */
if ((*pc & 0xffff0000) == 0xe92d0000)
pc -= 1;
}
if (verbose) {
_stp_print_char(' ');
_stp_symbol_print((unsigned long)pc);
_stp_print_char('\n');
} else {
_stp_printf("%08lx ", (unsigned long)pc);
}
/* Sanity check the next_fp. */
if (next_fp && next_fp <= fp)
break;
fp = next_fp;
}
#endif /* STP_USE_FRAME_POINTER */
}
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