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linux/arch/arm/kernel/unwind.c
Dmitry Safonov e8d7b73532 arm: add loglvl to unwind_backtrace() 
Currently, the log-level of show_stack() depends on a platform
realization.  It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on a platform or
user).

Furthermore, it forces the logic decision from user to an architecture
side.  In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.  And in
result it not only may print unwanted messages from other CPUs, but also
omit printing at all in the unlucky case where the printk() was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems an easier
approach than introducing more printk buffers.  Also, it will consolidate
printings with headers.

Add log level argument to unwind_backtrace() as a preparation for
introducing show_stack_loglvl().

As a good side-effect arm_syscall() is now printing errors with the same
log level as the backtrace.

[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u

Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Link: http://lkml.kernel.org/r/20200418201944.482088-6-dima@arista.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-09 09:39:10 -07:00

540 lines
13 KiB
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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;
ctrl->vrs[reg] = *(*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,
unsigned long insn)
{
unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
int reg;
/* pop R4-R[4+bbb] */
for (reg = 4; reg <= 4 + (insn & 7); reg++)
if (unwind_pop_register(ctrl, &vsp, reg))
return -URC_FAILURE;
if (insn & 0x8)
if (unwind_pop_register(ctrl, &vsp, 14))
return -URC_FAILURE;
ctrl->vrs[SP] = (unsigned long)vsp;
return URC_OK;
}
static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl,
unsigned long mask)
{
unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
int reg = 0;
/* pop R0-R3 according to mask */
while (mask) {
if (mask & 1)
if (unwind_pop_register(ctrl, &vsp, reg))
return -URC_FAILURE;
mask >>= 1;
reg++;
}
ctrl->vrs[SP] = (unsigned long)vsp;
return URC_OK;
}
/*
* Execute the current unwind instruction.
*/
static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
{
unsigned long insn = unwind_get_byte(ctrl);
int ret = URC_OK;
pr_debug("%s: insn = %08lx\n", __func__, insn);
if ((insn & 0xc0) == 0x00)
ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
else if ((insn & 0xc0) == 0x40)
ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
else if ((insn & 0xf0) == 0x80) {
unsigned long mask;
insn = (insn << 8) | unwind_get_byte(ctrl);
mask = insn & 0x0fff;
if (mask == 0) {
pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n",
insn);
return -URC_FAILURE;
}
ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask);
if (ret)
goto error;
} else if ((insn & 0xf0) == 0x90 &&
(insn & 0x0d) != 0x0d)
ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
else if ((insn & 0xf0) == 0xa0) {
ret = unwind_exec_pop_r4_to_rN(ctrl, insn);
if (ret)
goto error;
} else if (insn == 0xb0) {
if (ctrl->vrs[PC] == 0)
ctrl->vrs[PC] = ctrl->vrs[LR];
/* no further processing */
ctrl->entries = 0;
} else if (insn == 0xb1) {
unsigned long mask = unwind_get_byte(ctrl);
if (mask == 0 || mask & 0xf0) {
pr_warn("unwind: Spare encoding %04lx\n",
(insn << 8) | mask);
return -URC_FAILURE;
}
ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask);
if (ret)
goto error;
} else if (insn == 0xb2) {
unsigned long uleb128 = unwind_get_byte(ctrl);
ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
} else {
pr_warn("unwind: Unhandled instruction %02lx\n", insn);
return -URC_FAILURE;
}
pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
error:
return ret;
}
/*
* Unwind a single frame starting with *sp for the symbol at *pc. It
* updates the *pc and *sp with the new values.
*/
int unwind_frame(struct stackframe *frame)
{
unsigned long low;
const struct unwind_idx *idx;
struct unwind_ctrl_block ctrl;
/* store the highest address on the stack to avoid crossing it*/
low = frame->sp;
ctrl.sp_high = ALIGN(low, THREAD_SIZE);
pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
frame->pc, frame->lr, frame->sp);
if (!kernel_text_address(frame->pc))
return -URC_FAILURE;
idx = unwind_find_idx(frame->pc);
if (!idx) {
pr_warn("unwind: Index not found %08lx\n", frame->pc);
return -URC_FAILURE;
}
ctrl.vrs[FP] = frame->fp;
ctrl.vrs[SP] = frame->sp;
ctrl.vrs[LR] = frame->lr;
ctrl.vrs[PC] = 0;
if (idx->insn == 1)
/* can't unwind */
return -URC_FAILURE;
else if ((idx->insn & 0x80000000) == 0)
/* prel31 to the unwind table */
ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
else if ((idx->insn & 0xff000000) == 0x80000000)
/* only personality routine 0 supported in the index */
ctrl.insn = &idx->insn;
else {
pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n",
idx->insn, idx);
return -URC_FAILURE;
}
/* check the personality routine */
if ((*ctrl.insn & 0xff000000) == 0x80000000) {
ctrl.byte = 2;
ctrl.entries = 1;
} else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
ctrl.byte = 1;
ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
} else {
pr_warn("unwind: Unsupported personality routine %08lx at %p\n",
*ctrl.insn, ctrl.insn);
return -URC_FAILURE;
}
ctrl.check_each_pop = 0;
while (ctrl.entries > 0) {
int urc;
if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs))
ctrl.check_each_pop = 1;
urc = unwind_exec_insn(&ctrl);
if (urc < 0)
return urc;
if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high)
return -URC_FAILURE;
}
if (ctrl.vrs[PC] == 0)
ctrl.vrs[PC] = ctrl.vrs[LR];
/* check for infinite loop */
if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP])
return -URC_FAILURE;
frame->fp = ctrl.vrs[FP];
frame->sp = ctrl.vrs[SP];
frame->lr = ctrl.vrs[LR];
frame->pc = ctrl.vrs[PC];
return URC_OK;
}
void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
const char *loglvl)
{
struct stackframe frame;
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
tsk = current;
if (regs) {
arm_get_current_stackframe(regs, &frame);
/* PC might be corrupted, use LR in that case. */
if (!kernel_text_address(regs->ARM_pc))
frame.pc = regs->ARM_lr;
} else if (tsk == current) {
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.sp = current_stack_pointer;
frame.lr = (unsigned long)__builtin_return_address(0);
frame.pc = (unsigned long)unwind_backtrace;
} else {
/* task blocked in __switch_to */
frame.fp = thread_saved_fp(tsk);
frame.sp = thread_saved_sp(tsk);
/*
* The function calling __switch_to cannot be a leaf function
* so LR is recovered from the stack.
*/
frame.lr = 0;
frame.pc = thread_saved_pc(tsk);
}
while (1) {
int urc;
unsigned long where = frame.pc;
urc = unwind_frame(&frame);
if (urc < 0)
break;
dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl);
}
}
struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
unsigned long text_addr,
unsigned long text_size)
{
unsigned long flags;
struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
text_addr, text_size);
if (!tab)
return tab;
tab->start = (const struct unwind_idx *)start;
tab->stop = (const struct unwind_idx *)(start + size);
tab->origin = unwind_find_origin(tab->start, tab->stop);
tab->begin_addr = text_addr;
tab->end_addr = text_addr + text_size;
raw_spin_lock_irqsave(&unwind_lock, flags);
list_add_tail(&tab->list, &unwind_tables);
raw_spin_unlock_irqrestore(&unwind_lock, flags);
return tab;
}
void unwind_table_del(struct unwind_table *tab)
{
unsigned long flags;
if (!tab)
return;
raw_spin_lock_irqsave(&unwind_lock, flags);
list_del(&tab->list);
raw_spin_unlock_irqrestore(&unwind_lock, flags);
kfree(tab);
}
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