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|
// SPDX-License-Identifier: GPL-2.0-only
/*
* arch/arm/kernel/unwind.c
*
* Copyright (C) 2008 ARM Limited
*
* Stack unwinding support for ARM
*
* An ARM EABI version of gcc is required to generate the unwind
* tables. For information about the structure of the unwind tables,
* see "Exception Handling ABI for the ARM Architecture" at:
*
* http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
*/
#ifndef __CHECKER__
#if !defined (__ARM_EABI__)
#warning Your compiler does not have EABI support.
#warning ARM unwind is known to compile only with EABI compilers.
#warning Change compiler or disable ARM_UNWIND option.
#elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2) && !defined(__clang__)
#warning Your compiler is too buggy; it is known to not compile ARM unwind support.
#warning Change compiler or disable ARM_UNWIND option.
#endif
#endif /* __CHECKER__ */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <asm/stacktrace.h>
#include <asm/traps.h>
#include <asm/unwind.h>
/* Dummy functions to avoid linker complaints */
void __aeabi_unwind_cpp_pr0(void)
{
};
EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
void __aeabi_unwind_cpp_pr1(void)
{
};
EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
void __aeabi_unwind_cpp_pr2(void)
{
};
EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
struct unwind_ctrl_block {
unsigned long vrs[16]; /* virtual register set */
const unsigned long *insn; /* pointer to the current instructions word */
unsigned long sp_high; /* highest value of sp allowed */
/*
* 1 : check for stack overflow for each register pop.
* 0 : save overhead if there is plenty of stack remaining.
*/
int check_each_pop;
int entries; /* number of entries left to interpret */
int byte; /* current byte number in the instructions word */
};
enum regs {
#ifdef CONFIG_THUMB2_KERNEL
FP = 7,
#else
FP = 11,
#endif
SP = 13,
LR = 14,
PC = 15
};
extern const struct unwind_idx __start_unwind_idx[];
static const struct unwind_idx *__origin_unwind_idx;
extern const struct unwind_idx __stop_unwind_idx[];
static DEFINE_RAW_SPINLOCK(unwind_lock);
static LIST_HEAD(unwind_tables);
/* Convert a prel31 symbol to an absolute address */
#define prel31_to_addr(ptr) \
({ \
/* sign-extend to 32 bits */ \
long offset = (((long)*(ptr)) << 1) >> 1; \
(unsigned long)(ptr) + offset; \
})
/*
* Binary search in the unwind index. The entries are
* guaranteed to be sorted in ascending order by the linker.
*
* start = first entry
* origin = first entry with positive offset (or stop if there is no such entry)
* stop - 1 = last entry
*/
static const struct unwind_idx *search_index(unsigned long addr,
const struct unwind_idx *start,
const struct unwind_idx *origin,
const struct unwind_idx *stop)
{
unsigned long addr_prel31;
pr_debug("%s(%08lx, %p, %p, %p)\n",
__func__, addr, start, origin, stop);
/*
* only search in the section with the matching sign. This way the
* prel31 numbers can be compared as unsigned longs.
*/
if (addr < (unsigned long)start)
/* negative offsets: [start; origin) */
stop = origin;
else
/* positive offsets: [origin; stop) */
start = origin;
/* prel31 for address relavive to start */
addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;
while (start < stop - 1) {
const struct unwind_idx *mid = start + ((stop - start) >> 1);
/*
* As addr_prel31 is relative to start an offset is needed to
* make it relative to mid.
*/
if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
mid->addr_offset)
stop = mid;
else {
/* keep addr_prel31 relative to start */
addr_prel31 -= ((unsigned long)mid -
(unsigned long)start);
start = mid;
}
}
if (likely(start->addr_offset <= addr_prel31))
return start;
else {
pr_warn("unwind: Unknown symbol address %08lx\n", addr);
return NULL;
}
}
static const struct unwind_idx *unwind_find_origin(
const struct unwind_idx *start, const struct unwind_idx *stop)
{
pr_debug("%s(%p, %p)\n", __func__, start, stop);
while (start < stop) {
const struct unwind_idx *mid = start + ((stop - start) >> 1);
if (mid->addr_offset >= 0x40000000)
/* negative offset */
start = mid + 1;
else
/* positive offset */
stop = mid;
}
pr_debug("%s -> %p\n", __func__, stop);
return stop;
}
static const struct unwind_idx *unwind_find_idx(unsigned long addr)
{
const struct unwind_idx *idx = NULL;
unsigned long flags;
pr_debug("%s(%08lx)\n", __func__, addr);
if (core_kernel_text(addr)) {
if (unlikely(!__origin_unwind_idx))
__origin_unwind_idx =
unwind_find_origin(__start_unwind_idx,
__stop_unwind_idx);
/* main unwind table */
idx = search_index(addr, __start_unwind_idx,
__origin_unwind_idx,
__stop_unwind_idx);
} else {
/* module unwind tables */
struct unwind_table *table;
raw_spin_lock_irqsave(&unwind_lock, flags);
list_for_each_entry(table, &unwind_tables, list) {
if (addr >= table->begin_addr &&
addr < table->end_addr) {
idx = search_index(addr, table->start,
table->origin,
table->stop);
/* Move-to-front to exploit common traces */
list_move(&table->list, &unwind_tables);
break;
}
}
raw_spin_unlock_irqrestore(&unwind_lock, flags);
}
pr_debug("%s: idx = %p\n", __func__, idx);
return idx;
}
static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
{
unsigned long ret;
if (ctrl->entries <= 0) {
pr_warn("unwind: Corrupt unwind table\n");
return 0;
}
ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
if (ctrl->byte == 0) {
ctrl->insn++;
ctrl->entries--;
ctrl->byte = 3;
} else
ctrl->byte--;
return ret;
}
/* Before poping a register check whether it is feasible or not */
static int unwind_pop_register(struct unwind_ctrl_block *ctrl,
unsigned long **vsp, unsigned int reg)
{
if (unlikely(ctrl->check_each_pop))
if (*vsp >= (unsigned long *)ctrl->sp_high)
return -URC_FAILURE;
/* Use READ_ONCE_NOCHECK here to avoid this memory access
* from being tracked by KASAN.
*/
ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp));
(*vsp)++;
return URC_OK;
}
/* Helper functions to execute the instructions */
static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl,
unsigned long mask)
{
unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
int load_sp, reg = 4;
load_sp = mask & (1 << (13 - 4));
while (mask) {
if (mask & 1)
if (unwind_pop_register(ctrl, &vsp, reg))
return -URC_FAILURE;
mask >>= 1;
reg++;
}
if (!load_sp)
ctrl->vrs[SP] = (unsigned long)vsp;
return URC_OK;
}
static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl,
|