linux/arch/mips/kernel/process.c
David Daney 484889fc85 MIPS: Avoid clobbering struct pt_regs in kthreads
The resume() implementation octeon_switch.S examines the saved cp0_status
register.  We were clobbering the entire pt_regs structure in kernel
threads leading to random crashes.

When switching away from a kernel thread, the saved cp0_status is examined
and if bit 30 is set it is cleared and the CP2 state saved into the pt_regs
structure.  Since the kernel thread stack overlaid the pt_regs structure
this resulted in a corrupt stack.  When the kthread with the corrupt stack
was resumed, it could crash if it used any of the data in the stack that was
clobbered.

We fix it by moving the kernel thread stack down so it doesn't overlay
pt_regs.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2009-08-03 17:52:41 +01:00

484 lines
11 KiB
C

/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
* Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
* Copyright (C) 2004 Thiemo Seufer
*/
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/tick.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/mman.h>
#include <linux/personality.h>
#include <linux/sys.h>
#include <linux/user.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/random.h>
#include <asm/asm.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
#include <asm/dsp.h>
#include <asm/fpu.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/mipsregs.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/elf.h>
#include <asm/isadep.h>
#include <asm/inst.h>
#include <asm/stacktrace.h>
/*
* The idle thread. There's no useful work to be done, so just try to conserve
* power and have a low exit latency (ie sit in a loop waiting for somebody to
* say that they'd like to reschedule)
*/
void __noreturn cpu_idle(void)
{
int cpu;
/* CPU is going idle. */
cpu = smp_processor_id();
/* endless idle loop with no priority at all */
while (1) {
tick_nohz_stop_sched_tick(1);
while (!need_resched() && cpu_online(cpu)) {
#ifdef CONFIG_MIPS_MT_SMTC
extern void smtc_idle_loop_hook(void);
smtc_idle_loop_hook();
#endif
if (cpu_wait)
(*cpu_wait)();
}
#ifdef CONFIG_HOTPLUG_CPU
if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
(system_state == SYSTEM_RUNNING ||
system_state == SYSTEM_BOOTING))
play_dead();
#endif
tick_nohz_restart_sched_tick();
preempt_enable_no_resched();
schedule();
preempt_disable();
}
}
asmlinkage void ret_from_fork(void);
void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
{
unsigned long status;
/* New thread loses kernel privileges. */
status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
#ifdef CONFIG_64BIT
status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
#endif
status |= KU_USER;
regs->cp0_status = status;
clear_used_math();
clear_fpu_owner();
if (cpu_has_dsp)
__init_dsp();
regs->cp0_epc = pc;
regs->regs[29] = sp;
current_thread_info()->addr_limit = USER_DS;
}
void exit_thread(void)
{
}
void flush_thread(void)
{
}
int copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long unused, struct task_struct *p, struct pt_regs *regs)
{
struct thread_info *ti = task_thread_info(p);
struct pt_regs *childregs;
unsigned long childksp;
p->set_child_tid = p->clear_child_tid = NULL;
childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
preempt_disable();
if (is_fpu_owner())
save_fp(p);
if (cpu_has_dsp)
save_dsp(p);
preempt_enable();
/* set up new TSS. */
childregs = (struct pt_regs *) childksp - 1;
/* Put the stack after the struct pt_regs. */
childksp = (unsigned long) childregs;
*childregs = *regs;
childregs->regs[7] = 0; /* Clear error flag */
childregs->regs[2] = 0; /* Child gets zero as return value */
regs->regs[2] = p->pid;
if (childregs->cp0_status & ST0_CU0) {
childregs->regs[28] = (unsigned long) ti;
childregs->regs[29] = childksp;
ti->addr_limit = KERNEL_DS;
} else {
childregs->regs[29] = usp;
ti->addr_limit = USER_DS;
}
p->thread.reg29 = (unsigned long) childregs;
p->thread.reg31 = (unsigned long) ret_from_fork;
/*
* New tasks lose permission to use the fpu. This accelerates context
* switching for most programs since they don't use the fpu.
*/
p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
#ifdef CONFIG_MIPS_MT_SMTC
/*
* SMTC restores TCStatus after Status, and the CU bits
* are aliased there.
*/
childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
#endif
clear_tsk_thread_flag(p, TIF_USEDFPU);
#ifdef CONFIG_MIPS_MT_FPAFF
clear_tsk_thread_flag(p, TIF_FPUBOUND);
#endif /* CONFIG_MIPS_MT_FPAFF */
if (clone_flags & CLONE_SETTLS)
ti->tp_value = regs->regs[7];
return 0;
}
/* Fill in the fpu structure for a core dump.. */
int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
{
memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
return 1;
}
void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
{
int i;
for (i = 0; i < EF_R0; i++)
gp[i] = 0;
gp[EF_R0] = 0;
for (i = 1; i <= 31; i++)
gp[EF_R0 + i] = regs->regs[i];
gp[EF_R26] = 0;
gp[EF_R27] = 0;
gp[EF_LO] = regs->lo;
gp[EF_HI] = regs->hi;
gp[EF_CP0_EPC] = regs->cp0_epc;
gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
gp[EF_CP0_STATUS] = regs->cp0_status;
gp[EF_CP0_CAUSE] = regs->cp0_cause;
#ifdef EF_UNUSED0
gp[EF_UNUSED0] = 0;
#endif
}
int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
{
elf_dump_regs(*regs, task_pt_regs(tsk));
return 1;
}
int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
{
memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
return 1;
}
/*
* Create a kernel thread
*/
static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
{
do_exit(fn(arg));
}
long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
{
struct pt_regs regs;
memset(&regs, 0, sizeof(regs));
regs.regs[4] = (unsigned long) arg;
regs.regs[5] = (unsigned long) fn;
regs.cp0_epc = (unsigned long) kernel_thread_helper;
regs.cp0_status = read_c0_status();
#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
#else
regs.cp0_status |= ST0_EXL;
#endif
/* Ok, create the new process.. */
return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
}
/*
*
*/
struct mips_frame_info {
void *func;
unsigned long func_size;
int frame_size;
int pc_offset;
};
static inline int is_ra_save_ins(union mips_instruction *ip)
{
/* sw / sd $ra, offset($sp) */
return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
ip->i_format.rs == 29 &&
ip->i_format.rt == 31;
}
static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
{
if (ip->j_format.opcode == jal_op)
return 1;
if (ip->r_format.opcode != spec_op)
return 0;
return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
}
static inline int is_sp_move_ins(union mips_instruction *ip)
{
/* addiu/daddiu sp,sp,-imm */
if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
return 0;
if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
return 1;
return 0;
}
static int get_frame_info(struct mips_frame_info *info)
{
union mips_instruction *ip = info->func;
unsigned max_insns = info->func_size / sizeof(union mips_instruction);
unsigned i;
info->pc_offset = -1;
info->frame_size = 0;
if (!ip)
goto err;
if (max_insns == 0)
max_insns = 128U; /* unknown function size */
max_insns = min(128U, max_insns);
for (i = 0; i < max_insns; i++, ip++) {
if (is_jal_jalr_jr_ins(ip))
break;
if (!info->frame_size) {
if (is_sp_move_ins(ip))
info->frame_size = - ip->i_format.simmediate;
continue;
}
if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
info->pc_offset =
ip->i_format.simmediate / sizeof(long);
break;
}
}
if (info->frame_size && info->pc_offset >= 0) /* nested */
return 0;
if (info->pc_offset < 0) /* leaf */
return 1;
/* prologue seems boggus... */
err:
return -1;
}
static struct mips_frame_info schedule_mfi __read_mostly;
static int __init frame_info_init(void)
{
unsigned long size = 0;
#ifdef CONFIG_KALLSYMS
unsigned long ofs;
kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
#endif
schedule_mfi.func = schedule;
schedule_mfi.func_size = size;
get_frame_info(&schedule_mfi);
/*
* Without schedule() frame info, result given by
* thread_saved_pc() and get_wchan() are not reliable.
*/
if (schedule_mfi.pc_offset < 0)
printk("Can't analyze schedule() prologue at %p\n", schedule);
return 0;
}
arch_initcall(frame_info_init);
/*
* Return saved PC of a blocked thread.
*/
unsigned long thread_saved_pc(struct task_struct *tsk)
{
struct thread_struct *t = &tsk->thread;
/* New born processes are a special case */
if (t->reg31 == (unsigned long) ret_from_fork)
return t->reg31;
if (schedule_mfi.pc_offset < 0)
return 0;
return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
}
#ifdef CONFIG_KALLSYMS
/* used by show_backtrace() */
unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
unsigned long pc, unsigned long *ra)
{
unsigned long stack_page;
struct mips_frame_info info;
unsigned long size, ofs;
int leaf;
extern void ret_from_irq(void);
extern void ret_from_exception(void);
stack_page = (unsigned long)task_stack_page(task);
if (!stack_page)
return 0;
/*
* If we reached the bottom of interrupt context,
* return saved pc in pt_regs.
*/
if (pc == (unsigned long)ret_from_irq ||
pc == (unsigned long)ret_from_exception) {
struct pt_regs *regs;
if (*sp >= stack_page &&
*sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
regs = (struct pt_regs *)*sp;
pc = regs->cp0_epc;
if (__kernel_text_address(pc)) {
*sp = regs->regs[29];
*ra = regs->regs[31];
return pc;
}
}
return 0;
}
if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
return 0;
/*
* Return ra if an exception occured at the first instruction
*/
if (unlikely(ofs == 0)) {
pc = *ra;
*ra = 0;
return pc;
}
info.func = (void *)(pc - ofs);
info.func_size = ofs; /* analyze from start to ofs */
leaf = get_frame_info(&info);
if (leaf < 0)
return 0;
if (*sp < stack_page ||
*sp + info.frame_size > stack_page + THREAD_SIZE - 32)
return 0;
if (leaf)
/*
* For some extreme cases, get_frame_info() can
* consider wrongly a nested function as a leaf
* one. In that cases avoid to return always the
* same value.
*/
pc = pc != *ra ? *ra : 0;
else
pc = ((unsigned long *)(*sp))[info.pc_offset];
*sp += info.frame_size;
*ra = 0;
return __kernel_text_address(pc) ? pc : 0;
}
#endif
/*
* get_wchan - a maintenance nightmare^W^Wpain in the ass ...
*/
unsigned long get_wchan(struct task_struct *task)
{
unsigned long pc = 0;
#ifdef CONFIG_KALLSYMS
unsigned long sp;
unsigned long ra = 0;
#endif
if (!task || task == current || task->state == TASK_RUNNING)
goto out;
if (!task_stack_page(task))
goto out;
pc = thread_saved_pc(task);
#ifdef CONFIG_KALLSYMS
sp = task->thread.reg29 + schedule_mfi.frame_size;
while (in_sched_functions(pc))
pc = unwind_stack(task, &sp, pc, &ra);
#endif
out:
return pc;
}
/*
* Don't forget that the stack pointer must be aligned on a 8 bytes
* boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
*/
unsigned long arch_align_stack(unsigned long sp)
{
if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
sp -= get_random_int() & ~PAGE_MASK;
return sp & ALMASK;
}