linux/arch/xtensa/kernel/stacktrace.c
Max Filippov 09f8a6db20 xtensa: add support for call0 ABI in userspace
Provide a Kconfig choice to select whether only the default ABI, only
call0 ABI or both are supported. The default for XEA2 is windowed, but
it may change for XEA3. Call0 only runs userspace with PS.WOE disabled.
Supporting both windowed and call0 ABIs is tricky, as there's no
indication in the ELF binaries which ABI they use. So it is done by
probing: each process is started with PS.WOE disabled, but the handler
of an illegal instruction exception taken with PS.WOE retries faulting
instruction after enabling PS.WOE. It must happen before any signal is
delivered to the process, otherwise it may be delivered incorrectly.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
2019-09-01 13:11:57 -07:00

276 lines
6.0 KiB
C

/*
* Kernel and userspace stack tracing.
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2001 - 2013 Tensilica Inc.
* Copyright (C) 2015 Cadence Design Systems Inc.
*/
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/stacktrace.h>
#include <asm/stacktrace.h>
#include <asm/traps.h>
#include <linux/uaccess.h>
#if IS_ENABLED(CONFIG_OPROFILE) || IS_ENABLED(CONFIG_PERF_EVENTS)
/* Address of common_exception_return, used to check the
* transition from kernel to user space.
*/
extern int common_exception_return;
void xtensa_backtrace_user(struct pt_regs *regs, unsigned int depth,
int (*ufn)(struct stackframe *frame, void *data),
void *data)
{
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 = regs->pc;
struct stackframe frame;
int index;
if (!depth--)
return;
frame.pc = pc;
frame.sp = a1;
if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
return;
if (IS_ENABLED(CONFIG_USER_ABI_CALL0_ONLY) ||
(IS_ENABLED(CONFIG_USER_ABI_CALL0_PROBE) &&
!(regs->ps & PS_WOE_MASK)))
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)) {
/* Get the PC from a0 and a1. */
pc = MAKE_PC_FROM_RA(a0, pc);
/* Read a0 and a1 from the
* corresponding position in AREGs.
*/
a0 = regs->areg[index * 4];
a1 = regs->areg[index * 4 + 1];
frame.pc = pc;
frame.sp = a1;
if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
return;
}
/* Step 2. */
/* We are done with the register window, we need to
* look through the stack.
*/
if (!depth)
return;
/* Start from the a1 register. */
/* a1 = regs->areg[1]; */
while (a0 != 0 && depth--) {
pc = MAKE_PC_FROM_RA(a0, pc);
/* Check if the region is OK to access. */
if (!access_ok(&SPILL_SLOT(a1, 0), 8))
return;
/* Copy a1, a0 from user space stack frame. */
if (__get_user(a0, &SPILL_SLOT(a1, 0)) ||
__get_user(a1, &SPILL_SLOT(a1, 1)))
return;
frame.pc = pc;
frame.sp = a1;
if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
return;
}
}
EXPORT_SYMBOL(xtensa_backtrace_user);
void xtensa_backtrace_kernel(struct pt_regs *regs, unsigned int depth,
int (*kfn)(struct stackframe *frame, void *data),
int (*ufn)(struct stackframe *frame, void *data),
void *data)
{
unsigned long pc = regs->depc > VALID_DOUBLE_EXCEPTION_ADDRESS ?
regs->depc : regs->pc;
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--) {
struct stackframe frame;
frame.pc = pc;
frame.sp = a1;
if (kernel_text_address(pc) && kfn(&frame, data))
return;
if (pc == (unsigned long)&common_exception_return) {
regs = (struct pt_regs *)a1;
if (user_mode(regs)) {
if (ufn == NULL)
return;
xtensa_backtrace_user(regs, depth, ufn, data);
return;
}
a0 = regs->areg[0];
a1 = regs->areg[1];
continue;
}
sp_start = a1;
pc = MAKE_PC_FROM_RA(a0, pc);
a0 = SPILL_SLOT(a1, 0);
a1 = SPILL_SLOT(a1, 1);
}
}
EXPORT_SYMBOL(xtensa_backtrace_kernel);
#endif
void walk_stackframe(unsigned long *sp,
int (*fn)(struct stackframe *frame, void *data),
void *data)
{
unsigned long a0, a1;
unsigned long sp_end;
a1 = (unsigned long)sp;
sp_end = ALIGN(a1, THREAD_SIZE);
spill_registers();
while (a1 < sp_end) {
struct stackframe frame;
sp = (unsigned long *)a1;
a0 = SPILL_SLOT(a1, 0);
a1 = SPILL_SLOT(a1, 1);
if (a1 <= (unsigned long)sp)
break;
frame.pc = MAKE_PC_FROM_RA(a0, a1);
frame.sp = a1;
if (fn(&frame, data))
return;
}
}
#ifdef CONFIG_STACKTRACE
struct stack_trace_data {
struct stack_trace *trace;
unsigned skip;
};
static int stack_trace_cb(struct stackframe *frame, void *data)
{
struct stack_trace_data *trace_data = data;
struct stack_trace *trace = trace_data->trace;
if (trace_data->skip) {
--trace_data->skip;
return 0;
}
if (!kernel_text_address(frame->pc))
return 0;
trace->entries[trace->nr_entries++] = frame->pc;
return trace->nr_entries >= trace->max_entries;
}
void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
{
struct stack_trace_data trace_data = {
.trace = trace,
.skip = trace->skip,
};
walk_stackframe(stack_pointer(task), stack_trace_cb, &trace_data);
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
void save_stack_trace(struct stack_trace *trace)
{
save_stack_trace_tsk(current, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace);
#endif
#ifdef CONFIG_FRAME_POINTER
struct return_addr_data {
unsigned long addr;
unsigned skip;
};
static int return_address_cb(struct stackframe *frame, void *data)
{
struct return_addr_data *r = data;
if (r->skip) {
--r->skip;
return 0;
}
if (!kernel_text_address(frame->pc))
return 0;
r->addr = frame->pc;
return 1;
}
/*
* level == 0 is for the return address from the caller of this function,
* not from this function itself.
*/
unsigned long return_address(unsigned level)
{
struct return_addr_data r = {
.skip = level,
};
walk_stackframe(stack_pointer(NULL), return_address_cb, &r);
return r.addr;
}
EXPORT_SYMBOL(return_address);
#endif