/*
* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/hardirq.h>
#include <asm/current.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include "arch.h"
#include "as-layout.h"
#include "kern_util.h"
#include "os.h"
#include "skas.h"
#include "sysdep/sigcontext.h"
/*
* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by
* segv().
*/
int handle_page_fault(unsigned long address, unsigned long ip,
int is_write, int is_user, int *code_out)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
int err = -EFAULT;
*code_out = SEGV_MAPERR;
/*
* If the fault was during atomic operation, don't take the fault, just
* fail.
*/
if (in_atomic())
goto out_nosemaphore;
down_read(&mm->mmap_sem);
vma = find_vma(mm, address);
if (!vma)
goto out;
else if (vma->vm_start <= address)
goto good_area;
else if (!(vma->vm_flags & VM_GROWSDOWN))
goto out;
else if (is_user && !ARCH_IS_STACKGROW(address))
goto out;
else if (expand_stack(vma, address))
goto out;
good_area:
*code_out = SEGV_ACCERR;
if (is_write && !(vma->vm_flags & VM_WRITE))
goto out;
/* Don't require VM_READ|VM_EXEC for write faults! */
if (!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
goto out;
do {
int fault;
survive:
fault = handle_mm_fault(mm, vma, address, is_write);
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM) {
err = -ENOMEM;
goto out_of_memory;
} else if (fault & VM_FAULT_SIGBUS) {
err = -EACCES;
goto out;
}
BUG();
}
if (fault & VM_FAULT_MAJOR)
current->maj_flt++;
else
current->min_flt++;
pgd = pgd_offset(mm, address);
pud = pud_offset(pgd, address);
pmd = pmd_offset(pud, address);
pte = pte_offset_kernel(pmd, address);
} while (!pte_present(*pte));
err = 0;
/*
* The below warning was added in place of
* pte_mkyoung(); if (is_write) pte_mkdirty();
* If it's triggered, we'd see normally a hang here (a clean pte is
* marked read-only to emulate the dirty bit).
* However, the generic code can mark a PTE writable but clean on a
* concurrent read fault, triggering this harmlessly. So comment it out.
*/
#if 0
WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
#endif
flush_tlb_page(vma, address);
out:
up_read(&mm->mmap_sem);
out_nosemaphore:
return err;
/*
* We ran out of memory, or some other thing happened to us that made
* us unable to handle the page fault gracefully.
*/
out_of_memory:
if (is_global_init(current)) {
up_read(&mm->mmap_sem);
yield();
down_read(&mm->mmap_sem);
goto survive;
}
goto out;
}
static void bad_segv(struct faultinfo fi, unsigned long ip)
{
struct siginfo si;
si.si_signo = SIGSEGV;
si.si_code = SEGV_ACCERR;
si.si_addr = (void __user *) FAULT_ADDRESS(fi);
current->thread.arch.faultinfo = fi;
force_sig_info(SIGSEGV, &si, current);
}
void fatal_sigsegv(void)
{
force_sigsegv(SIGSEGV, current);
do_signal();
/*
* This is to tell gcc that we're not returning - do_signal
* can, in general, return, but in this case, it's not, since
* we just got a fatal SIGSEGV queued.
*/
os_dump_core();
}
void segv_handler(int sig, struct uml_pt_regs *regs)
{
struct faultinfo * fi = UPT_FAULTINFO(regs);
if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
bad_segv(*fi, UPT_IP(regs));
return;
}
segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
}
/*
* We give a *copy* of the faultinfo in the regs to segv.
* This must be done, since nesting SEGVs could overwrite
* the info in the regs. A pointer to the info then would
* give us bad data!
*/
unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
struct uml_pt_regs *regs)
{
struct siginfo si;
jmp_buf *catcher;
int err;
int is_write = FAULT_WRITE(fi);
unsigned long address = FAULT_ADDRESS(fi);
if (!is_user && (address >= start_vm) && (address < end_vm)) {
flush_tlb_kernel_vm();
return 0;
}
else if (current->mm == NULL) {
show_regs(container_of(regs, struct pt_regs, regs));
panic("Segfault with no mm");
}
if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
err = handle_page_fault(address, ip, is_write, is_user,
&si.si_code);
else {
err = -EFAULT;
/*
* A thread accessed NULL, we get a fault, but CR2 is invalid.
* This code is used in __do_copy_from_user() of TT mode.
* XXX tt mode is gone, so maybe this isn't needed any more
*/
address = 0;
}
catcher = current->thread.fault_catcher;
if (!err)
return 0;
else if (catcher != NULL) {
current->thread.fault_addr = (void *) address;
UML_LONGJMP(catcher, 1);
}
else if (current->thread.fault_addr != NULL)
panic("fault_addr set but no fault catcher");
else if (!is_user && arch_fixup(ip, regs))
return 0;
if (!is_user) {
show_regs(container_of(regs, struct pt_regs, regs));
panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
address, ip);
}
if (err == -EACCES) {
si.si_signo = SIGBUS;
si.si_errno = 0;
si.si_code = BUS_ADRERR;
si.si_addr = (void __user *)address;
current->thread.arch.faultinfo = fi;
force_sig_info(SIGBUS, &si, current);
} else if (err == -ENOMEM) {
printk(KERN_INFO "VM: killing process %s\n", current->comm);
do_exit(SIGKILL);
} else {
BUG_ON(err != -EFAULT);
si.si_signo = SIGSEGV;
si.si_addr = (void __user *) address;
current->thread.arch.faultinfo = fi;
force_sig_info(SIGSEGV, &si, current);
}
return 0;
}
void relay_signal(int sig, struct uml_pt_regs *regs)
{
if (!UPT_IS_USER(regs)) {
if (sig == SIGBUS)
printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
"mount likely just ran out of space\n");
panic("Kernel mode signal %d", sig);
}
arch_examine_signal(sig, regs);
current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
force_sig(sig, current);
}
void bus_handler(int sig, struct uml_pt_regs *regs)
{
if (current->thread.fault_catcher != NULL)
UML_LONGJMP(current->thread.fault_catcher, 1);
else relay_signal(sig, regs);
}
void winch(int sig, struct uml_pt_regs *regs)
{
do_IRQ(WINCH_IRQ, regs);
}
void trap_init(void)
{
}
