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linux/arch/s390/kernel/traps.c
Heiko Carstens e1d12d70f7 s390/traps: panic() instead of die() on translation exception 
In case of a translation exception the page tables are corrupted. If the
exception handler then calls die() which again calls show_regs()
-> show_code() -> copy_from_user(), the kernel may access the same memory
location again and generates yet another translation exception. Which in turn
will lead to a deadlock on the die_lock spinlock, which the kernel tries to
grab recursively.

Given that the page tables are corrupted anyway, if we see such an exception,
let's simply panic.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2015-03-25 11:49:38 +01:00

343 lines
8.8 KiB
C
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/*
* S390 version
* Copyright IBM Corp. 1999, 2000
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
* Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
*
* Derived from "arch/i386/kernel/traps.c"
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* 'Traps.c' handles hardware traps and faults after we have saved some
* state in 'asm.s'.
*/
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <asm/switch_to.h>
#include "entry.h"
int show_unhandled_signals = 1;
static inline void __user *get_trap_ip(struct pt_regs *regs)
{
unsigned long address;
if (regs->int_code & 0x200)
address = *(unsigned long *)(current->thread.trap_tdb + 24);
else
address = regs->psw.addr;
return (void __user *)
((address - (regs->int_code >> 16)) & PSW_ADDR_INSN);
}
static inline void report_user_fault(struct pt_regs *regs, int signr)
{
if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
return;
if (!unhandled_signal(current, signr))
return;
if (!printk_ratelimit())
return;
printk("User process fault: interruption code %04x ilc:%d ",
regs->int_code & 0xffff, regs->int_code >> 17);
print_vma_addr("in ", regs->psw.addr & PSW_ADDR_INSN);
printk("\n");
show_regs(regs);
}
int is_valid_bugaddr(unsigned long addr)
{
return 1;
}
void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
{
siginfo_t info;
if (user_mode(regs)) {
info.si_signo = si_signo;
info.si_errno = 0;
info.si_code = si_code;
info.si_addr = get_trap_ip(regs);
force_sig_info(si_signo, &info, current);
report_user_fault(regs, si_signo);
} else {
const struct exception_table_entry *fixup;
fixup = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
if (fixup)
regs->psw.addr = extable_fixup(fixup) | PSW_ADDR_AMODE;
else {
enum bug_trap_type btt;
btt = report_bug(regs->psw.addr & PSW_ADDR_INSN, regs);
if (btt == BUG_TRAP_TYPE_WARN)
return;
die(regs, str);
}
}
}
static void do_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
{
if (notify_die(DIE_TRAP, str, regs, 0,
regs->int_code, si_signo) == NOTIFY_STOP)
return;
do_report_trap(regs, si_signo, si_code, str);
}
NOKPROBE_SYMBOL(do_trap);
void do_per_trap(struct pt_regs *regs)
{
siginfo_t info;
if (notify_die(DIE_SSTEP, "sstep", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
return;
if (!current->ptrace)
return;
info.si_signo = SIGTRAP;
info.si_errno = 0;
info.si_code = TRAP_HWBKPT;
info.si_addr =
(void __force __user *) current->thread.per_event.address;
force_sig_info(SIGTRAP, &info, current);
}
NOKPROBE_SYMBOL(do_per_trap);
void default_trap_handler(struct pt_regs *regs)
{
if (user_mode(regs)) {
report_user_fault(regs, SIGSEGV);
do_exit(SIGSEGV);
} else
die(regs, "Unknown program exception");
}
#define DO_ERROR_INFO(name, signr, sicode, str) \
void name(struct pt_regs *regs) \
{ \
do_trap(regs, signr, sicode, str); \
}
DO_ERROR_INFO(addressing_exception, SIGILL, ILL_ILLADR,
"addressing exception")
DO_ERROR_INFO(execute_exception, SIGILL, ILL_ILLOPN,
"execute exception")
DO_ERROR_INFO(divide_exception, SIGFPE, FPE_INTDIV,
"fixpoint divide exception")
DO_ERROR_INFO(overflow_exception, SIGFPE, FPE_INTOVF,
"fixpoint overflow exception")
DO_ERROR_INFO(hfp_overflow_exception, SIGFPE, FPE_FLTOVF,
"HFP overflow exception")
DO_ERROR_INFO(hfp_underflow_exception, SIGFPE, FPE_FLTUND,
"HFP underflow exception")
DO_ERROR_INFO(hfp_significance_exception, SIGFPE, FPE_FLTRES,
"HFP significance exception")
DO_ERROR_INFO(hfp_divide_exception, SIGFPE, FPE_FLTDIV,
"HFP divide exception")
DO_ERROR_INFO(hfp_sqrt_exception, SIGFPE, FPE_FLTINV,
"HFP square root exception")
DO_ERROR_INFO(operand_exception, SIGILL, ILL_ILLOPN,
"operand exception")
DO_ERROR_INFO(privileged_op, SIGILL, ILL_PRVOPC,
"privileged operation")
DO_ERROR_INFO(special_op_exception, SIGILL, ILL_ILLOPN,
"special operation exception")
DO_ERROR_INFO(transaction_exception, SIGILL, ILL_ILLOPN,
"transaction constraint exception")
static inline void do_fp_trap(struct pt_regs *regs, int fpc)
{
int si_code = 0;
/* FPC[2] is Data Exception Code */
if ((fpc & 0x00000300) == 0) {
/* bits 6 and 7 of DXC are 0 iff IEEE exception */
if (fpc & 0x8000) /* invalid fp operation */
si_code = FPE_FLTINV;
else if (fpc & 0x4000) /* div by 0 */
si_code = FPE_FLTDIV;
else if (fpc & 0x2000) /* overflow */
si_code = FPE_FLTOVF;
else if (fpc & 0x1000) /* underflow */
si_code = FPE_FLTUND;
else if (fpc & 0x0800) /* inexact */
si_code = FPE_FLTRES;
}
do_trap(regs, SIGFPE, si_code, "floating point exception");
}
void translation_exception(struct pt_regs *regs)
{
/* May never happen. */
panic("Translation exception");
}
void illegal_op(struct pt_regs *regs)
{
siginfo_t info;
__u8 opcode[6];
__u16 __user *location;
int is_uprobe_insn = 0;
int signal = 0;
location = get_trap_ip(regs);
if (user_mode(regs)) {
if (get_user(*((__u16 *) opcode), (__u16 __user *) location))
return;
if (*((__u16 *) opcode) == S390_BREAKPOINT_U16) {
if (current->ptrace) {
info.si_signo = SIGTRAP;
info.si_errno = 0;
info.si_code = TRAP_BRKPT;
info.si_addr = location;
force_sig_info(SIGTRAP, &info, current);
} else
signal = SIGILL;
#ifdef CONFIG_UPROBES
} else if (*((__u16 *) opcode) == UPROBE_SWBP_INSN) {
is_uprobe_insn = 1;
#endif
} else
signal = SIGILL;
}
/*
* We got either an illegal op in kernel mode, or user space trapped
* on a uprobes illegal instruction. See if kprobes or uprobes picks
* it up. If not, SIGILL.
*/
if (is_uprobe_insn || !user_mode(regs)) {
if (notify_die(DIE_BPT, "bpt", regs, 0,
3, SIGTRAP) != NOTIFY_STOP)
signal = SIGILL;
}
if (signal)
do_trap(regs, signal, ILL_ILLOPC, "illegal operation");
}
NOKPROBE_SYMBOL(illegal_op);
DO_ERROR_INFO(specification_exception, SIGILL, ILL_ILLOPN,
"specification exception");
int alloc_vector_registers(struct task_struct *tsk)
{
__vector128 *vxrs;
int i;
/* Allocate vector register save area. */
vxrs = kzalloc(sizeof(__vector128) * __NUM_VXRS,
GFP_KERNEL|__GFP_REPEAT);
if (!vxrs)
return -ENOMEM;
preempt_disable();
if (tsk == current)
save_fp_regs(tsk->thread.fp_regs.fprs);
/* Copy the 16 floating point registers */
for (i = 0; i < 16; i++)
*(freg_t *) &vxrs[i] = tsk->thread.fp_regs.fprs[i];
tsk->thread.vxrs = vxrs;
if (tsk == current) {
__ctl_set_bit(0, 17);
restore_vx_regs(vxrs);
}
preempt_enable();
return 0;
}
void vector_exception(struct pt_regs *regs)
{
int si_code, vic;
if (!MACHINE_HAS_VX) {
do_trap(regs, SIGILL, ILL_ILLOPN, "illegal operation");
return;
}
/* get vector interrupt code from fpc */
asm volatile("stfpc %0" : "=m" (current->thread.fp_regs.fpc));
vic = (current->thread.fp_regs.fpc & 0xf00) >> 8;
switch (vic) {
case 1: /* invalid vector operation */
si_code = FPE_FLTINV;
break;
case 2: /* division by zero */
si_code = FPE_FLTDIV;
break;
case 3: /* overflow */
si_code = FPE_FLTOVF;
break;
case 4: /* underflow */
si_code = FPE_FLTUND;
break;
case 5: /* inexact */
si_code = FPE_FLTRES;
break;
default: /* unknown cause */
si_code = 0;
}
do_trap(regs, SIGFPE, si_code, "vector exception");
}
static int __init disable_vector_extension(char *str)
{
S390_lowcore.machine_flags &= ~MACHINE_FLAG_VX;
return 1;
}
__setup("novx", disable_vector_extension);
void data_exception(struct pt_regs *regs)
{
__u16 __user *location;
int signal = 0;
location = get_trap_ip(regs);
asm volatile("stfpc %0" : "=m" (current->thread.fp_regs.fpc));
/* Check for vector register enablement */
if (MACHINE_HAS_VX && !current->thread.vxrs &&
(current->thread.fp_regs.fpc & FPC_DXC_MASK) == 0xfe00) {
alloc_vector_registers(current);
/* Vector data exception is suppressing, rewind psw. */
regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
clear_pt_regs_flag(regs, PIF_PER_TRAP);
return;
}
if (current->thread.fp_regs.fpc & FPC_DXC_MASK)
signal = SIGFPE;
else
signal = SIGILL;
if (signal == SIGFPE)
do_fp_trap(regs, current->thread.fp_regs.fpc);
else if (signal)
do_trap(regs, signal, ILL_ILLOPN, "data exception");
}
void space_switch_exception(struct pt_regs *regs)
{
/* Set user psw back to home space mode. */
if (user_mode(regs))
regs->psw.mask |= PSW_ASC_HOME;
/* Send SIGILL. */
do_trap(regs, SIGILL, ILL_PRVOPC, "space switch event");
}
void kernel_stack_overflow(struct pt_regs *regs)
{
bust_spinlocks(1);
printk("Kernel stack overflow.\n");
show_regs(regs);
bust_spinlocks(0);
panic("Corrupt kernel stack, can't continue.");
}
NOKPROBE_SYMBOL(kernel_stack_overflow);
void __init trap_init(void)
{
local_mcck_enable();
}
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