v4.19.13 snapshot.
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
new file mode 100644
index 0000000..cced829
--- /dev/null
+++ b/arch/um/kernel/trap.c
@@ -0,0 +1,331 @@
+/*
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/mm.h>
+#include <linux/sched/signal.h>
+#include <linux/hardirq.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/sched/debug.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>
+
+/*
+ * 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;
+ unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+
+ *code_out = SEGV_MAPERR;
+
+ /*
+ * If the fault was with pagefaults disabled, don't take the fault, just
+ * fail.
+ */
+ if (faulthandler_disabled())
+ goto out_nosemaphore;
+
+ if (is_user)
+ flags |= FAULT_FLAG_USER;
+retry:
+ 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) {
+ if (!(vma->vm_flags & VM_WRITE))
+ goto out;
+ flags |= FAULT_FLAG_WRITE;
+ } else {
+ /* Don't require VM_READ|VM_EXEC for write faults! */
+ if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
+ goto out;
+ }
+
+ do {
+ vm_fault_t fault;
+
+ fault = handle_mm_fault(vma, address, flags);
+
+ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+ goto out_nosemaphore;
+
+ if (unlikely(fault & VM_FAULT_ERROR)) {
+ if (fault & VM_FAULT_OOM) {
+ goto out_of_memory;
+ } else if (fault & VM_FAULT_SIGSEGV) {
+ goto out;
+ } else if (fault & VM_FAULT_SIGBUS) {
+ err = -EACCES;
+ goto out;
+ }
+ BUG();
+ }
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ if (fault & VM_FAULT_MAJOR)
+ current->maj_flt++;
+ else
+ current->min_flt++;
+ if (fault & VM_FAULT_RETRY) {
+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ flags |= FAULT_FLAG_TRIED;
+
+ goto retry;
+ }
+ }
+
+ 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;
+
+out_of_memory:
+ /*
+ * We ran out of memory, call the OOM killer, and return the userspace
+ * (which will retry the fault, or kill us if we got oom-killed).
+ */
+ up_read(&mm->mmap_sem);
+ if (!is_user)
+ goto out_nosemaphore;
+ pagefault_out_of_memory();
+ return 0;
+}
+EXPORT_SYMBOL(handle_page_fault);
+
+static void show_segv_info(struct uml_pt_regs *regs)
+{
+ struct task_struct *tsk = current;
+ struct faultinfo *fi = UPT_FAULTINFO(regs);
+
+ if (!unhandled_signal(tsk, SIGSEGV))
+ return;
+
+ if (!printk_ratelimit())
+ return;
+
+ printk("%s%s[%d]: segfault at %lx ip %px sp %px error %x",
+ task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
+ tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
+ (void *)UPT_IP(regs), (void *)UPT_SP(regs),
+ fi->error_code);
+
+ print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
+ printk(KERN_CONT "\n");
+}
+
+static void bad_segv(struct faultinfo fi, unsigned long ip)
+{
+ current->thread.arch.faultinfo = fi;
+ force_sig_fault(SIGSEGV, SEGV_ACCERR, (void __user *) FAULT_ADDRESS(fi),
+ current);
+}
+
+void fatal_sigsegv(void)
+{
+ force_sigsegv(SIGSEGV, current);
+ do_signal(¤t->thread.regs);
+ /*
+ * 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();
+}
+
+/**
+ * segv_handler() - the SIGSEGV handler
+ * @sig: the signal number
+ * @unused_si: the signal info struct; unused in this handler
+ * @regs: the ptrace register information
+ *
+ * The handler first extracts the faultinfo from the UML ptrace regs struct.
+ * If the userfault did not happen in an UML userspace process, bad_segv is called.
+ * Otherwise the signal did happen in a cloned userspace process, handle it.
+ */
+void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
+{
+ struct faultinfo * fi = UPT_FAULTINFO(regs);
+
+ if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
+ show_segv_info(regs);
+ 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)
+{
+ jmp_buf *catcher;
+ int si_code;
+ int err;
+ int is_write = FAULT_WRITE(fi);
+ unsigned long address = FAULT_ADDRESS(fi);
+
+ if (!is_user && regs)
+ current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
+
+ if (!is_user && (address >= start_vm) && (address < end_vm)) {
+ flush_tlb_kernel_vm();
+ goto out;
+ }
+ else if (current->mm == NULL) {
+ show_regs(container_of(regs, struct pt_regs, regs));
+ panic("Segfault with no mm");
+ }
+ else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
+ show_regs(container_of(regs, struct pt_regs, regs));
+ panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx",
+ address, ip);
+ }
+
+ if (SEGV_IS_FIXABLE(&fi))
+ err = handle_page_fault(address, ip, is_write, is_user,
+ &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)
+ goto out;
+ 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))
+ goto out;
+
+ 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);
+ }
+
+ show_segv_info(regs);
+
+ if (err == -EACCES) {
+ current->thread.arch.faultinfo = fi;
+ force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address,
+ current);
+ } else {
+ BUG_ON(err != -EFAULT);
+ current->thread.arch.faultinfo = fi;
+ force_sig_fault(SIGSEGV, si_code, (void __user *) address,
+ current);
+ }
+
+out:
+ if (regs)
+ current->thread.segv_regs = NULL;
+
+ return 0;
+}
+
+void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
+{
+ int code, err;
+ 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);
+
+ /* Is the signal layout for the signal known?
+ * Signal data must be scrubbed to prevent information leaks.
+ */
+ code = si->si_code;
+ err = si->si_errno;
+ if ((err == 0) && (siginfo_layout(sig, code) == SIL_FAULT)) {
+ struct faultinfo *fi = UPT_FAULTINFO(regs);
+ current->thread.arch.faultinfo = *fi;
+ force_sig_fault(sig, code, (void __user *)FAULT_ADDRESS(*fi),
+ current);
+ } else {
+ printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d) with errno %d\n",
+ sig, code, err);
+ force_sig(sig, current);
+ }
+}
+
+void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
+{
+ if (current->thread.fault_catcher != NULL)
+ UML_LONGJMP(current->thread.fault_catcher, 1);
+ else
+ relay_signal(sig, si, regs);
+}
+
+void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
+{
+ do_IRQ(WINCH_IRQ, regs);
+}
+
+void trap_init(void)
+{
+}