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linux/arch/openrisc/kernel/traps.c
Stafford Horne c88cfb5cea openrisc: traps: Don't send signals to kernel mode threads 
OpenRISC exception handling sends signals to user processes on floating
point exceptions and trap instructions (for debugging) among others.
There is a bug where the trap handling logic may send signals to kernel
threads, we should not send these signals to kernel threads, if that
happens we treat it as an error.

This patch adds conditions to die if the kernel receives these
exceptions in kernel mode code.

Fixes: 27267655c5 ("openrisc: Support floating point user api")
Signed-off-by: Stafford Horne <shorne@gmail.com>
2024-04-15 15:20:39 +01:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* OpenRISC traps.c
*
* Linux architectural port borrowing liberally from similar works of
* others. All original copyrights apply as per the original source
* declaration.
*
* Modifications for the OpenRISC architecture:
* Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
* Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
*
* Here we handle the break vectors not used by the system call
* mechanism, as well as some general stack/register dumping
* things.
*/
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/kernel.h>
#include <linux/extable.h>
#include <linux/kmod.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <asm/bug.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/unwinder.h>
#include <asm/sections.h>
int lwa_flag;
static unsigned long __user *lwa_addr;
asmlinkage void unhandled_exception(struct pt_regs *regs, int ea, int vector);
asmlinkage void do_trap(struct pt_regs *regs, unsigned long address);
asmlinkage void do_fpe_trap(struct pt_regs *regs, unsigned long address);
asmlinkage void do_unaligned_access(struct pt_regs *regs, unsigned long address);
asmlinkage void do_bus_fault(struct pt_regs *regs, unsigned long address);
asmlinkage void do_illegal_instruction(struct pt_regs *regs,
unsigned long address);
static void print_trace(void *data, unsigned long addr, int reliable)
{
const char *loglvl = data;
pr_info("%s[<%p>] %s%pS\n", loglvl, (void *) addr, reliable ? "" : "? ",
(void *) addr);
}
static void print_data(unsigned long base_addr, unsigned long word, int i)
{
if (i == 0)
pr_info("(%08lx:)\t%08lx", base_addr + (i * 4), word);
else
pr_info(" %08lx:\t%08lx", base_addr + (i * 4), word);
}
/* displays a short stack trace */
void show_stack(struct task_struct *task, unsigned long *esp, const char *loglvl)
{
if (esp == NULL)
esp = (unsigned long *)&esp;
pr_info("%sCall trace:\n", loglvl);
unwind_stack((void *)loglvl, esp, print_trace);
}
void show_registers(struct pt_regs *regs)
{
int i;
int in_kernel = 1;
unsigned long esp;
esp = (unsigned long)(regs->sp);
if (user_mode(regs))
in_kernel = 0;
pr_info("CPU #: %d\n"
" PC: %08lx SR: %08lx SP: %08lx FPCSR: %08lx\n",
smp_processor_id(), regs->pc, regs->sr, regs->sp,
regs->fpcsr);
pr_info("GPR00: %08lx GPR01: %08lx GPR02: %08lx GPR03: %08lx\n",
0L, regs->gpr[1], regs->gpr[2], regs->gpr[3]);
pr_info("GPR04: %08lx GPR05: %08lx GPR06: %08lx GPR07: %08lx\n",
regs->gpr[4], regs->gpr[5], regs->gpr[6], regs->gpr[7]);
pr_info("GPR08: %08lx GPR09: %08lx GPR10: %08lx GPR11: %08lx\n",
regs->gpr[8], regs->gpr[9], regs->gpr[10], regs->gpr[11]);
pr_info("GPR12: %08lx GPR13: %08lx GPR14: %08lx GPR15: %08lx\n",
regs->gpr[12], regs->gpr[13], regs->gpr[14], regs->gpr[15]);
pr_info("GPR16: %08lx GPR17: %08lx GPR18: %08lx GPR19: %08lx\n",
regs->gpr[16], regs->gpr[17], regs->gpr[18], regs->gpr[19]);
pr_info("GPR20: %08lx GPR21: %08lx GPR22: %08lx GPR23: %08lx\n",
regs->gpr[20], regs->gpr[21], regs->gpr[22], regs->gpr[23]);
pr_info("GPR24: %08lx GPR25: %08lx GPR26: %08lx GPR27: %08lx\n",
regs->gpr[24], regs->gpr[25], regs->gpr[26], regs->gpr[27]);
pr_info("GPR28: %08lx GPR29: %08lx GPR30: %08lx GPR31: %08lx\n",
regs->gpr[28], regs->gpr[29], regs->gpr[30], regs->gpr[31]);
pr_info(" RES: %08lx oGPR11: %08lx\n",
regs->gpr[11], regs->orig_gpr11);
pr_info("Process %s (pid: %d, stackpage=%08lx)\n",
current->comm, current->pid, (unsigned long)current);
/*
* When in-kernel, we also print out the stack and code at the
* time of the fault..
*/
if (in_kernel) {
pr_info("\nStack: ");
show_stack(NULL, (unsigned long *)esp, KERN_EMERG);
if (esp < PAGE_OFFSET)
goto bad_stack;
pr_info("\n");
for (i = -8; i < 24; i += 1) {
unsigned long word;
if (__get_user(word, &((unsigned long *)esp)[i])) {
bad_stack:
pr_info(" Bad Stack value.");
break;
}
print_data(esp, word, i);
}
pr_info("\nCode: ");
if (regs->pc < PAGE_OFFSET)
goto bad;
for (i = -6; i < 6; i += 1) {
unsigned long word;
if (__get_user(word, &((unsigned long *)regs->pc)[i])) {
bad:
pr_info(" Bad PC value.");
break;
}
print_data(regs->pc, word, i);
}
}
pr_info("\n");
}
/* This is normally the 'Oops' routine */
void __noreturn die(const char *str, struct pt_regs *regs, long err)
{
console_verbose();
pr_emerg("\n%s#: %04lx\n", str, err & 0xffff);
show_registers(regs);
#ifdef CONFIG_JUMP_UPON_UNHANDLED_EXCEPTION
pr_emerg("\n\nUNHANDLED_EXCEPTION: entering infinite loop\n");
/* shut down interrupts */
local_irq_disable();
__asm__ __volatile__("l.nop 1");
do {} while (1);
#endif
make_task_dead(SIGSEGV);
}
asmlinkage void unhandled_exception(struct pt_regs *regs, int ea, int vector)
{
pr_emerg("Unable to handle exception at EA =0x%x, vector 0x%x",
ea, vector);
die("Oops", regs, 9);
}
asmlinkage void do_fpe_trap(struct pt_regs *regs, unsigned long address)
{
if (user_mode(regs)) {
int code = FPE_FLTUNK;
unsigned long fpcsr = regs->fpcsr;
if (fpcsr & SPR_FPCSR_IVF)
code = FPE_FLTINV;
else if (fpcsr & SPR_FPCSR_OVF)
code = FPE_FLTOVF;
else if (fpcsr & SPR_FPCSR_UNF)
code = FPE_FLTUND;
else if (fpcsr & SPR_FPCSR_DZF)
code = FPE_FLTDIV;
else if (fpcsr & SPR_FPCSR_IXF)
code = FPE_FLTRES;
/* Clear all flags */
regs->fpcsr &= ~SPR_FPCSR_ALLF;
force_sig_fault(SIGFPE, code, (void __user *)regs->pc);
} else {
pr_emerg("KERNEL: Illegal fpe exception 0x%.8lx\n", regs->pc);
die("Die:", regs, SIGFPE);
}
}
asmlinkage void do_trap(struct pt_regs *regs, unsigned long address)
{
if (user_mode(regs)) {
force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->pc);
} else {
pr_emerg("KERNEL: Illegal trap exception 0x%.8lx\n", regs->pc);
die("Die:", regs, SIGILL);
}
}
asmlinkage void do_unaligned_access(struct pt_regs *regs, unsigned long address)
{
if (user_mode(regs)) {
/* Send a SIGBUS */
force_sig_fault(SIGBUS, BUS_ADRALN, (void __user *)address);
} else {
pr_emerg("KERNEL: Unaligned Access 0x%.8lx\n", address);
die("Die:", regs, address);
}
}
asmlinkage void do_bus_fault(struct pt_regs *regs, unsigned long address)
{
if (user_mode(regs)) {
/* Send a SIGBUS */
force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
} else { /* Kernel mode */
pr_emerg("KERNEL: Bus error (SIGBUS) 0x%.8lx\n", address);
die("Die:", regs, address);
}
}
static inline int in_delay_slot(struct pt_regs *regs)
{
#ifdef CONFIG_OPENRISC_NO_SPR_SR_DSX
/* No delay slot flag, do the old way */
unsigned int op, insn;
insn = *((unsigned int *)regs->pc);
op = insn >> 26;
switch (op) {
case 0x00: /* l.j */
case 0x01: /* l.jal */
case 0x03: /* l.bnf */
case 0x04: /* l.bf */
case 0x11: /* l.jr */
case 0x12: /* l.jalr */
return 1;
default:
return 0;
}
#else
return mfspr(SPR_SR) & SPR_SR_DSX;
#endif
}
static inline void adjust_pc(struct pt_regs *regs, unsigned long address)
{
int displacement;
unsigned int rb, op, jmp;
if (unlikely(in_delay_slot(regs))) {
/* In delay slot, instruction at pc is a branch, simulate it */
jmp = *((unsigned int *)regs->pc);
displacement = sign_extend32(((jmp) & 0x3ffffff) << 2, 27);
rb = (jmp & 0x0000ffff) >> 11;
op = jmp >> 26;
switch (op) {
case 0x00: /* l.j */
regs->pc += displacement;
return;
case 0x01: /* l.jal */
regs->pc += displacement;
regs->gpr[9] = regs->pc + 8;
return;
case 0x03: /* l.bnf */
if (regs->sr & SPR_SR_F)
regs->pc += 8;
else
regs->pc += displacement;
return;
case 0x04: /* l.bf */
if (regs->sr & SPR_SR_F)
regs->pc += displacement;
else
regs->pc += 8;
return;
case 0x11: /* l.jr */
regs->pc = regs->gpr[rb];
return;
case 0x12: /* l.jalr */
regs->pc = regs->gpr[rb];
regs->gpr[9] = regs->pc + 8;
return;
default:
break;
}
} else {
regs->pc += 4;
}
}
static inline void simulate_lwa(struct pt_regs *regs, unsigned long address,
unsigned int insn)
{
unsigned int ra, rd;
unsigned long value;
unsigned long orig_pc;
long imm;
const struct exception_table_entry *entry;
orig_pc = regs->pc;
adjust_pc(regs, address);
ra = (insn >> 16) & 0x1f;
rd = (insn >> 21) & 0x1f;
imm = (short)insn;
lwa_addr = (unsigned long __user *)(regs->gpr[ra] + imm);
if ((unsigned long)lwa_addr & 0x3) {
do_unaligned_access(regs, address);
return;
}
if (get_user(value, lwa_addr)) {
if (user_mode(regs)) {
force_sig(SIGSEGV);
return;
}
if ((entry = search_exception_tables(orig_pc))) {
regs->pc = entry->fixup;
return;
}
/* kernel access in kernel space, load it directly */
value = *((unsigned long *)lwa_addr);
}
lwa_flag = 1;
regs->gpr[rd] = value;
}
static inline void simulate_swa(struct pt_regs *regs, unsigned long address,
unsigned int insn)
{
unsigned long __user *vaddr;
unsigned long orig_pc;
unsigned int ra, rb;
long imm;
const struct exception_table_entry *entry;
orig_pc = regs->pc;
adjust_pc(regs, address);
ra = (insn >> 16) & 0x1f;
rb = (insn >> 11) & 0x1f;
imm = (short)(((insn & 0x2200000) >> 10) | (insn & 0x7ff));
vaddr = (unsigned long __user *)(regs->gpr[ra] + imm);
if (!lwa_flag || vaddr != lwa_addr) {
regs->sr &= ~SPR_SR_F;
return;
}
if ((unsigned long)vaddr & 0x3) {
do_unaligned_access(regs, address);
return;
}
if (put_user(regs->gpr[rb], vaddr)) {
if (user_mode(regs)) {
force_sig(SIGSEGV);
return;
}
if ((entry = search_exception_tables(orig_pc))) {
regs->pc = entry->fixup;
return;
}
/* kernel access in kernel space, store it directly */
*((unsigned long *)vaddr) = regs->gpr[rb];
}
lwa_flag = 0;
regs->sr |= SPR_SR_F;
}
#define INSN_LWA 0x1b
#define INSN_SWA 0x33
asmlinkage void do_illegal_instruction(struct pt_regs *regs,
unsigned long address)
{
unsigned int op;
unsigned int insn = *((unsigned int *)address);
op = insn >> 26;
switch (op) {
case INSN_LWA:
simulate_lwa(regs, address, insn);
return;
case INSN_SWA:
simulate_swa(regs, address, insn);
return;
default:
break;
}
if (user_mode(regs)) {
/* Send a SIGILL */
force_sig_fault(SIGILL, ILL_ILLOPC, (void __user *)address);
} else { /* Kernel mode */
pr_emerg("KERNEL: Illegal instruction (SIGILL) 0x%.8lx\n",
address);
die("Die:", regs, address);
}
}
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