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linux/arch/tile/kernel/traps.c
Chris Metcalf 47ad7b9bbe tile: improve stack backtrace 
This commit fixes a number of issues with the tile backtrace code.

- Don't try to identify userspace shared object or executable paths
  if we are doing a backtrace from an interrupt; it's not legal,
  and also unlikely to be interesting.  Likewise, don't try to do
  it for other address spaces, since d_path() assumes it is being
  called in "current" context.

- Move "in_backtrace" from thread_struct to thread_info.
  This way we can access it even if our stack thread_info has been
  clobbered, which makes backtracing more robust.

- Avoid using "current" directly when testing for is_sigreturn().
  Since "current" may be corrupt, we're better off using kbt->task
  explicitly to look up the vdso_base for the current task.
  Conveniently, this simplifies the internal APIs (we only need
  one is_sigreturn() function now).

- Avoid bogus "Odd fault" warning when pc/sp/ex1 are all zero,
  as is true for kernel threads above the last frame.

- Hook into Tejun Heo's dump_stack() framework in lib/dump_stack.c.

- Write last entry in save_stack_trace() as ULONG_MAX, not zero,
  since ftrace (at least) relies on finding that marker.

- Implement save_stack_trace_regs() and save_strack_trace_user(),
  and set CONFIG_USER_STACKTRACE_SUPPORT.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
2015-05-11 11:22:40 -04:00

418 lines
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C
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/*
* Copyright 2010 Tilera Corporation. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, version 2.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for
* more details.
*/
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/module.h>
#include <linux/reboot.h>
#include <linux/uaccess.h>
#include <linux/ptrace.h>
#include <linux/context_tracking.h>
#include <asm/stack.h>
#include <asm/traps.h>
#include <asm/setup.h>
#include <arch/interrupts.h>
#include <arch/spr_def.h>
#include <arch/opcode.h>
void __init trap_init(void)
{
/* Nothing needed here since we link code at .intrpt */
}
int unaligned_fixup = 1;
static int __init setup_unaligned_fixup(char *str)
{
/*
* Say "=-1" to completely disable it. If you just do "=0", we
* will still parse the instruction, then fire a SIGBUS with
* the correct address from inside the single_step code.
*/
if (kstrtoint(str, 0, &unaligned_fixup) != 0)
return 0;
pr_info("Fixups for unaligned data accesses are %s\n",
unaligned_fixup >= 0 ?
(unaligned_fixup ? "enabled" : "disabled") :
"completely disabled");
return 1;
}
__setup("unaligned_fixup=", setup_unaligned_fixup);
#if CHIP_HAS_TILE_DMA()
static int dma_disabled;
static int __init nodma(char *str)
{
pr_info("User-space DMA is disabled\n");
dma_disabled = 1;
return 1;
}
__setup("nodma", nodma);
/* How to decode SPR_GPV_REASON */
#define IRET_ERROR (1U << 31)
#define MT_ERROR (1U << 30)
#define MF_ERROR (1U << 29)
#define SPR_INDEX ((1U << 15) - 1)
#define SPR_MPL_SHIFT 9 /* starting bit position for MPL encoded in SPR */
/*
* See if this GPV is just to notify the kernel of SPR use and we can
* retry the user instruction after adjusting some MPLs suitably.
*/
static int retry_gpv(unsigned int gpv_reason)
{
int mpl;
if (gpv_reason & IRET_ERROR)
return 0;
BUG_ON((gpv_reason & (MT_ERROR|MF_ERROR)) == 0);
mpl = (gpv_reason & SPR_INDEX) >> SPR_MPL_SHIFT;
if (mpl == INT_DMA_NOTIFY && !dma_disabled) {
/* User is turning on DMA. Allow it and retry. */
printk(KERN_DEBUG "Process %d/%s is now enabled for DMA\n",
current->pid, current->comm);
BUG_ON(current->thread.tile_dma_state.enabled);
current->thread.tile_dma_state.enabled = 1;
grant_dma_mpls();
return 1;
}
return 0;
}
#endif /* CHIP_HAS_TILE_DMA() */
extern tile_bundle_bits bpt_code;
asm(".pushsection .rodata.bpt_code,\"a\";"
".align 8;"
"bpt_code: bpt;"
".size bpt_code,.-bpt_code;"
".popsection");
static int special_ill(tile_bundle_bits bundle, int *sigp, int *codep)
{
int sig, code, maxcode;
if (bundle == bpt_code) {
*sigp = SIGTRAP;
*codep = TRAP_BRKPT;
return 1;
}
/* If it's a "raise" bundle, then "ill" must be in pipe X1. */
#ifdef __tilegx__
if ((bundle & TILEGX_BUNDLE_MODE_MASK) != 0)
return 0;
if (get_Opcode_X1(bundle) != RRR_0_OPCODE_X1)
return 0;
if (get_RRROpcodeExtension_X1(bundle) != UNARY_RRR_0_OPCODE_X1)
return 0;
if (get_UnaryOpcodeExtension_X1(bundle) != ILL_UNARY_OPCODE_X1)
return 0;
#else
if (bundle & TILEPRO_BUNDLE_Y_ENCODING_MASK)
return 0;
if (get_Opcode_X1(bundle) != SHUN_0_OPCODE_X1)
return 0;
if (get_UnShOpcodeExtension_X1(bundle) != UN_0_SHUN_0_OPCODE_X1)
return 0;
if (get_UnOpcodeExtension_X1(bundle) != ILL_UN_0_SHUN_0_OPCODE_X1)
return 0;
#endif
/* Check that the magic distinguishers are set to mean "raise". */
if (get_Dest_X1(bundle) != 29 || get_SrcA_X1(bundle) != 37)
return 0;
/* There must be an "addli zero, zero, VAL" in X0. */
if (get_Opcode_X0(bundle) != ADDLI_OPCODE_X0)
return 0;
if (get_Dest_X0(bundle) != TREG_ZERO)
return 0;
if (get_SrcA_X0(bundle) != TREG_ZERO)
return 0;
/*
* Validate the proposed signal number and si_code value.
* Note that we embed these in the static instruction itself
* so that we perturb the register state as little as possible
* at the time of the actual fault; it's unlikely you'd ever
* need to dynamically choose which kind of fault to raise
* from user space.
*/
sig = get_Imm16_X0(bundle) & 0x3f;
switch (sig) {
case SIGILL:
maxcode = NSIGILL;
break;
case SIGFPE:
maxcode = NSIGFPE;
break;
case SIGSEGV:
maxcode = NSIGSEGV;
break;
case SIGBUS:
maxcode = NSIGBUS;
break;
case SIGTRAP:
maxcode = NSIGTRAP;
break;
default:
return 0;
}
code = (get_Imm16_X0(bundle) >> 6) & 0xf;
if (code <= 0 || code > maxcode)
return 0;
/* Make it the requested signal. */
*sigp = sig;
*codep = code | __SI_FAULT;
return 1;
}
static const char *const int_name[] = {
[INT_MEM_ERROR] = "Memory error",
[INT_ILL] = "Illegal instruction",
[INT_GPV] = "General protection violation",
[INT_UDN_ACCESS] = "UDN access",
[INT_IDN_ACCESS] = "IDN access",
#if CHIP_HAS_SN()
[INT_SN_ACCESS] = "SN access",
#endif
[INT_SWINT_3] = "Software interrupt 3",
[INT_SWINT_2] = "Software interrupt 2",
[INT_SWINT_0] = "Software interrupt 0",
[INT_UNALIGN_DATA] = "Unaligned data",
[INT_DOUBLE_FAULT] = "Double fault",
#ifdef __tilegx__
[INT_ILL_TRANS] = "Illegal virtual address",
#endif
};
static int do_bpt(struct pt_regs *regs)
{
unsigned long bundle, bcode, bpt;
bundle = *(unsigned long *)instruction_pointer(regs);
/*
* bpt shoule be { bpt; nop }, which is 0x286a44ae51485000ULL.
* we encode the unused least significant bits for other purpose.
*/
bpt = bundle & ~((1ULL << 12) - 1);
if (bpt != TILE_BPT_BUNDLE)
return 0;
bcode = bundle & ((1ULL << 12) - 1);
/*
* notify the kprobe handlers, if instruction is likely to
* pertain to them.
*/
switch (bcode) {
/* breakpoint_insn */
case 0:
notify_die(DIE_BREAK, "debug", regs, bundle,
INT_ILL, SIGTRAP);
break;
/* compiled_bpt */
case DIE_COMPILED_BPT:
notify_die(DIE_COMPILED_BPT, "debug", regs, bundle,
INT_ILL, SIGTRAP);
break;
/* breakpoint2_insn */
case DIE_SSTEPBP:
notify_die(DIE_SSTEPBP, "single_step", regs, bundle,
INT_ILL, SIGTRAP);
break;
default:
return 0;
}
return 1;
}
void __kprobes do_trap(struct pt_regs *regs, int fault_num,
unsigned long reason)
{
enum ctx_state prev_state = exception_enter();
siginfo_t info = { 0 };
int signo, code;
unsigned long address = 0;
tile_bundle_bits instr;
int is_kernel = !user_mode(regs);
/* Handle breakpoints, etc. */
if (is_kernel && fault_num == INT_ILL && do_bpt(regs))
goto done;
/* Re-enable interrupts, if they were previously enabled. */
if (!(regs->flags & PT_FLAGS_DISABLE_IRQ))
local_irq_enable();
/*
* If it hits in kernel mode and we can't fix it up, just exit the
* current process and hope for the best.
*/
if (is_kernel) {
const char *name;
char buf[100];
if (fixup_exception(regs)) /* ILL_TRANS or UNALIGN_DATA */
goto done;
if (fault_num >= 0 &&
fault_num < ARRAY_SIZE(int_name) &&
int_name[fault_num] != NULL)
name = int_name[fault_num];
else
name = "Unknown interrupt";
if (fault_num == INT_GPV)
snprintf(buf, sizeof(buf), "; GPV_REASON %#lx", reason);
#ifdef __tilegx__
else if (fault_num == INT_ILL_TRANS)
snprintf(buf, sizeof(buf), "; address %#lx", reason);
#endif
else
buf[0] = '\0';
pr_alert("Kernel took bad trap %d (%s) at PC %#lx%s\n",
fault_num, name, regs->pc, buf);
show_regs(regs);
do_exit(SIGKILL); /* FIXME: implement i386 die() */
}
switch (fault_num) {
case INT_MEM_ERROR:
signo = SIGBUS;
code = BUS_OBJERR;
break;
case INT_ILL:
if (copy_from_user(&instr, (void __user *)regs->pc,
sizeof(instr))) {
pr_err("Unreadable instruction for INT_ILL: %#lx\n",
regs->pc);
do_exit(SIGKILL);
}
if (!special_ill(instr, &signo, &code)) {
signo = SIGILL;
code = ILL_ILLOPC;
}
address = regs->pc;
break;
case INT_GPV:
#if CHIP_HAS_TILE_DMA()
if (retry_gpv(reason))
goto done;
#endif
/*FALLTHROUGH*/
case INT_UDN_ACCESS:
case INT_IDN_ACCESS:
#if CHIP_HAS_SN()
case INT_SN_ACCESS:
#endif
signo = SIGILL;
code = ILL_PRVREG;
address = regs->pc;
break;
case INT_SWINT_3:
case INT_SWINT_2:
case INT_SWINT_0:
signo = SIGILL;
code = ILL_ILLTRP;
address = regs->pc;
break;
case INT_UNALIGN_DATA:
#ifndef __tilegx__ /* Emulated support for single step debugging */
if (unaligned_fixup >= 0) {
struct single_step_state *state =
current_thread_info()->step_state;
if (!state ||
(void __user *)(regs->pc) != state->buffer) {
single_step_once(regs);
goto done;
}
}
#endif
signo = SIGBUS;
code = BUS_ADRALN;
address = 0;
break;
case INT_DOUBLE_FAULT:
/*
* For double fault, "reason" is actually passed as
* SYSTEM_SAVE_K_2, the hypervisor's double-fault info, so
* we can provide the original fault number rather than
* the uninteresting "INT_DOUBLE_FAULT" so the user can
* learn what actually struck while PL0 ICS was set.
*/
fault_num = reason;
signo = SIGILL;
code = ILL_DBLFLT;
address = regs->pc;
break;
#ifdef __tilegx__
case INT_ILL_TRANS: {
/* Avoid a hardware erratum with the return address stack. */
fill_ra_stack();
signo = SIGSEGV;
address = reason;
code = SEGV_MAPERR;
break;
}
#endif
default:
panic("Unexpected do_trap interrupt number %d", fault_num);
}
info.si_signo = signo;
info.si_code = code;
info.si_addr = (void __user *)address;
if (signo == SIGILL)
info.si_trapno = fault_num;
if (signo != SIGTRAP)
trace_unhandled_signal("trap", regs, address, signo);
force_sig_info(signo, &info, current);
done:
exception_exit(prev_state);
}
void do_nmi(struct pt_regs *regs, int fault_num, unsigned long reason)
{
switch (reason) {
case TILE_NMI_DUMP_STACK:
do_nmi_dump_stack(regs);
break;
default:
panic("Unexpected do_nmi type %ld", reason);
return;
}
}
/* Deprecated function currently only used here. */
extern void _dump_stack(int dummy, ulong pc, ulong lr, ulong sp, ulong r52);
void kernel_double_fault(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
{
_dump_stack(dummy, pc, lr, sp, r52);
pr_emerg("Double fault: exiting\n");
machine_halt();
}
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