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linux/arch/s390/kernel/traps.c
Sven Schnelle bae1cd368c s390/entry: add support for syscall stack randomization 
This adds support for adding a random offset to the stack while handling
syscalls. The patch uses get_tod_clock_fast() as this is considered good
enough and has much less performance penalty compared to using
get_random_int(). The patch also adds randomization in pgm_check_handler()
as the sigreturn/rt_sigreturn system calls might be called from there.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Link: https://lore.kernel.org/r/20210429091451.1062594-1-svens@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2021-04-30 17:20:39 +02:00

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// SPDX-License-Identifier: GPL-2.0
/*
* 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 "asm/irqflags.h"
#include "asm/ptrace.h"
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/randomize_kstack.h>
#include <linux/extable.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/cpu.h>
#include <linux/entry-common.h>
#include <asm/fpu/api.h>
#include <asm/vtime.h>
#include "entry.h"
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));
}
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)
{
if (user_mode(regs)) {
force_sig_fault(si_signo, si_code, get_trap_ip(regs));
report_user_fault(regs, si_signo, 0);
} else {
const struct exception_table_entry *fixup;
fixup = s390_search_extables(regs->psw.addr);
if (!fixup || !ex_handle(fixup, regs))
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)
{
if (notify_die(DIE_SSTEP, "sstep", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
return;
if (!current->ptrace)
return;
force_sig_fault(SIGTRAP, TRAP_HWBKPT,
(void __force __user *) current->thread.per_event.address);
}
NOKPROBE_SYMBOL(do_per_trap);
static void default_trap_handler(struct pt_regs *regs)
{
if (user_mode(regs)) {
report_user_fault(regs, SIGSEGV, 0);
do_exit(SIGSEGV);
} else
die(regs, "Unknown program exception");
}
#define DO_ERROR_INFO(name, signr, sicode, str) \
static 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, __u32 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");
}
static void translation_exception(struct pt_regs *regs)
{
/* May never happen. */
panic("Translation exception");
}
static void illegal_op(struct pt_regs *regs)
{
__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)
force_sig_fault(SIGTRAP, TRAP_BRKPT, location);
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");
static 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 */
save_fpu_regs();
vic = (current->thread.fpu.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 void data_exception(struct pt_regs *regs)
{
save_fpu_regs();
if (current->thread.fpu.fpc & FPC_DXC_MASK)
do_fp_trap(regs, current->thread.fpu.fpc);
else
do_trap(regs, SIGILL, ILL_ILLOPN, "data exception");
}
static 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");
}
static void monitor_event_exception(struct pt_regs *regs)
{
const struct exception_table_entry *fixup;
if (user_mode(regs))
return;
switch (report_bug(regs->psw.addr - (regs->int_code >> 16), regs)) {
case BUG_TRAP_TYPE_NONE:
fixup = s390_search_extables(regs->psw.addr);
if (fixup)
ex_handle(fixup, regs);
break;
case BUG_TRAP_TYPE_WARN:
break;
case BUG_TRAP_TYPE_BUG:
die(regs, "monitor event");
break;
}
}
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);
static void __init test_monitor_call(void)
{
int val = 1;
asm volatile(
" mc 0,0\n"
"0: xgr %0,%0\n"
"1:\n"
EX_TABLE(0b,1b)
: "+d" (val));
if (!val)
panic("Monitor call doesn't work!\n");
}
void __init trap_init(void)
{
sort_extable(__start_dma_ex_table, __stop_dma_ex_table);
local_mcck_enable();
test_monitor_call();
}
static void (*pgm_check_table[128])(struct pt_regs *regs);
void noinstr __do_pgm_check(struct pt_regs *regs)
{
unsigned long last_break = S390_lowcore.breaking_event_addr;
unsigned int trapnr, syscall_redirect = 0;
irqentry_state_t state;
add_random_kstack_offset();
regs->int_code = *(u32 *)&S390_lowcore.pgm_ilc;
regs->int_parm_long = S390_lowcore.trans_exc_code;
state = irqentry_enter(regs);
if (user_mode(regs)) {
update_timer_sys();
if (last_break < 4096)
last_break = 1;
current->thread.last_break = last_break;
regs->args[0] = last_break;
}
if (S390_lowcore.pgm_code & 0x0200) {
/* transaction abort */
memcpy(&current->thread.trap_tdb, &S390_lowcore.pgm_tdb, 256);
}
if (S390_lowcore.pgm_code & PGM_INT_CODE_PER) {
if (user_mode(regs)) {
struct per_event *ev = &current->thread.per_event;
set_thread_flag(TIF_PER_TRAP);
ev->address = S390_lowcore.per_address;
ev->cause = *(u16 *)&S390_lowcore.per_code;
ev->paid = S390_lowcore.per_access_id;
} else {
/* PER event in kernel is kprobes */
__arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
do_per_trap(regs);
goto out;
}
}
if (!irqs_disabled_flags(regs->psw.mask))
trace_hardirqs_on();
__arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
trapnr = regs->int_code & PGM_INT_CODE_MASK;
if (trapnr)
pgm_check_table[trapnr](regs);
syscall_redirect = user_mode(regs) && test_pt_regs_flag(regs, PIF_SYSCALL);
out:
local_irq_disable();
irqentry_exit(regs, state);
if (syscall_redirect) {
enter_from_user_mode(regs);
local_irq_enable();
regs->orig_gpr2 = regs->gprs[2];
do_syscall(regs);
exit_to_user_mode();
}
}
/*
* The program check table contains exactly 128 (0x00-0x7f) entries. Each
* line defines the function to be called corresponding to the program check
* interruption code.
*/
static void (*pgm_check_table[128])(struct pt_regs *regs) = {
[0x00] = default_trap_handler,
[0x01] = illegal_op,
[0x02] = privileged_op,
[0x03] = execute_exception,
[0x04] = do_protection_exception,
[0x05] = addressing_exception,
[0x06] = specification_exception,
[0x07] = data_exception,
[0x08] = overflow_exception,
[0x09] = divide_exception,
[0x0a] = overflow_exception,
[0x0b] = divide_exception,
[0x0c] = hfp_overflow_exception,
[0x0d] = hfp_underflow_exception,
[0x0e] = hfp_significance_exception,
[0x0f] = hfp_divide_exception,
[0x10] = do_dat_exception,
[0x11] = do_dat_exception,
[0x12] = translation_exception,
[0x13] = special_op_exception,
[0x14] = default_trap_handler,
[0x15] = operand_exception,
[0x16] = default_trap_handler,
[0x17] = default_trap_handler,
[0x18] = transaction_exception,
[0x19] = default_trap_handler,
[0x1a] = default_trap_handler,
[0x1b] = vector_exception,
[0x1c] = space_switch_exception,
[0x1d] = hfp_sqrt_exception,
[0x1e ... 0x37] = default_trap_handler,
[0x38] = do_dat_exception,
[0x39] = do_dat_exception,
[0x3a] = do_dat_exception,
[0x3b] = do_dat_exception,
[0x3c] = default_trap_handler,
[0x3d] = do_secure_storage_access,
[0x3e] = do_non_secure_storage_access,
[0x3f] = do_secure_storage_violation,
[0x40] = monitor_event_exception,
[0x41 ... 0x7f] = default_trap_handler,
};
#define COND_TRAP(x) asm( \
".weak " __stringify(x) "\n\t" \
".set " __stringify(x) "," \
__stringify(default_trap_handler))
COND_TRAP(do_secure_storage_access);
COND_TRAP(do_non_secure_storage_access);
COND_TRAP(do_secure_storage_violation);
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