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/**
* @file backtrace.c
*
* @remark Copyright 2008 Tensilica Inc.
* @remark Read the file COPYING
*
*/
#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>
#include <asm/traps.h>
/* Address of common_exception_return, used to check the
* transition from kernel to user space.
*/
extern int common_exception_return;
/* A struct that maps to the part of the frame containing the a0 and
* a1 registers.
*/
struct frame_start {
unsigned long a0;
unsigned long a1;
};
static void xtensa_backtrace_user(struct pt_regs *regs, unsigned int depth)
{
unsigned long windowstart = regs->windowstart;
unsigned long windowbase = regs->windowbase;
unsigned long a0 = regs->areg[0];
unsigned long a1 = regs->areg[1];
unsigned long pc = MAKE_PC_FROM_RA(a0, regs->pc);
int index;
/* First add the current PC to the trace. */
if (pc != 0 && pc <= TASK_SIZE)
oprofile_add_trace(pc);
else
return;
/* Two steps:
*
* 1. Look through the register window for the
* previous PCs in the call trace.
*
* 2. Look on the stack.
*/
/* Step 1. */
/* Rotate WINDOWSTART to move the bit corresponding to
* the current window to the bit #0.
*/
windowstart = (windowstart << WSBITS | windowstart) >> windowbase;
/* Look for bits that are set, they correspond to
* valid windows.
*/
for (index = WSBITS - 1; (index > 0) && depth; depth--, index--)
if (windowstart & (1 << index)) {
/* Read a0 and a1 from the
* corresponding position in AREGs.
*/
a0 = regs->areg[index * 4];
a1 = regs->areg[index * 4 + 1];
/* Get the PC from a0 and a1. */
pc = MAKE_PC_FROM_RA(a0, pc);
/* Add the PC to the trace. */
if (pc != 0 && pc <= TASK_SIZE)
oprofile_add_trace(pc);
else
return;
}
/* Step 2. */
/* We are done with the register window, we need to
* look through the stack.
*/
if (depth > 0) {
/* Start from the a1 register. */
/* a1 = regs->areg[1]; */
while (a0 != 0 && depth--) {
struct frame_start frame_start;
/* Get the location for a1, a0 for the
* previous frame from the current a1.
*/
unsigned long *psp = (unsigned long *)a1;
psp -= 4;
/* Check if the region is OK to access. */
if (!access_ok(VERIFY_READ, psp, sizeof(frame_start)))
return;
/* Copy a1, a0 from user space stack frame. */
if (__copy_from_user_inatomic(&frame_start, psp,
sizeof(frame_start)))
return;
a0 = frame_start.a0;
a1 = frame_start.a1;
pc = MAKE_PC_FROM_RA(a0, pc);
if (pc != 0 && pc <= TASK_SIZE)
oprofile_add_trace(pc);
else
return;
}
}
}
static void xtensa_backtrace_kernel(struct pt_regs *regs, unsigned int depth)
{
unsigned long pc = regs->pc;
unsigned long *psp;
unsigned long sp_start, sp_end;
unsigned long a0 = regs->areg[0];
unsigned long a1 = regs->areg[1];
sp_start = a1 & ~(THREAD_SIZE-1);
sp_end = sp_start + THREAD_SIZE;
/* Spill the register window to the stack first. */
spill_registers();
/* Read the stack frames one by one and create the PC
* from the a0 and a1 registers saved there.
*/
while (a1 > sp_start && a1 < sp_end && depth--) {
pc = MAKE_PC_FROM_RA(a0, pc);
/* Add the PC to the trace. */
oprofile_add_trace(pc);
if (pc == (unsigned long) &common_exception_return) {
regs = (struct pt_regs *)a1;
if (user_mode(regs)) {
pc = regs->pc;
if (pc != 0 && pc <= TASK_SIZE)
oprofile_add_trace(pc);
else
return;
return xtensa_backtrace_user(regs, depth);
}
a0 = regs->areg[0];
a1 = regs->areg[1];
continue;
}
psp = (unsigned long *)a1;
a0 = *(psp - 4);
a1 = *(psp - 3);
if (a1 <= (unsigned long)psp)
return;
}
return;
}
void xtensa_backtrace(struct pt_regs * const regs, unsigned int depth)
{
if (user_mode(regs))
xtensa_backtrace_user(regs, depth);
else
xtensa_backtrace_kernel(regs, depth);
}
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