// SPDX-License-Identifier: GPL-2.0/* * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) */ #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/tlbflush.h>#include <arch.h>#include <as-layout.h>#include <kern_util.h>#include <os.h>#include <skas.h> /* * NOTE: UML does not have exception tables. As such, this is almost a copy * of the code in mm/memory.c, only adjusting the logic to simply check whether * we are coming from the kernel instead of doing an additional lookup in the * exception table. * We can do this simplification because we never get here if the exception was * fixable. */static inline bool get_mmap_lock_carefully(struct mm_struct *mm, bool is_user){ if (likely(mmap_read_trylock(mm))) return true; if (!is_user) return false; return !mmap_read_lock_killable(mm);} static inline bool mmap_upgrade_trylock(struct mm_struct *mm){ /* * We don't have this operation yet. * * It should be easy enough to do: it's basically a * atomic_long_try_cmpxchg_acquire() * from RWSEM_READER_BIAS -> RWSEM_WRITER_LOCKED, but * it also needs the proper lockdep magic etc. */ return false;} static inline bool upgrade_mmap_lock_carefully(struct mm_struct *mm, bool is_user){ mmap_read_unlock(mm); if (!is_user) return false; return !mmap_write_lock_killable(mm);} /* * Helper for page fault handling. * * This is kind of equivalend to "mmap_read_lock()" followed * by "find_extend_vma()", except it's a lot more careful about * the locking (and will drop the lock on failure). * * For example, if we have a kernel bug that causes a page * fault, we don't want to just use mmap_read_lock() to get * the mm lock, because that would deadlock if the bug were * to happen while we're holding the mm lock for writing. * * So this checks the exception tables on kernel faults in * order to only do this all for instructions that are actually * expected to fault. * * We can also actually take the mm lock for writing if we * need to extend the vma, which helps the VM layer a lot. */static struct vm_area_struct *um_lock_mm_and_find_vma(struct mm_struct *mm, unsigned long addr, bool is_user){ struct vm_area_struct *vma; if (!get_mmap_lock_carefully(mm, is_user)) return NULL; vma = find_vma(mm, addr); if (likely(vma && (vma->vm_start <= addr))) return vma; /* * Well, dang. We might still be successful, but only * if we can extend a vma to do so. */ if (!vma || !(vma->vm_flags & VM_GROWSDOWN)) { mmap_read_unlock(mm); return NULL; } /* * We can try to upgrade the mmap lock atomically, * in which case we can continue to use the vma * we already looked up. * * Otherwise we'll have to drop the mmap lock and * re-take it, and also look up the vma again, * re-checking it. */ if (!mmap_upgrade_trylock(mm)) { if (!upgrade_mmap_lock_carefully(mm, is_user)) return NULL; vma = find_vma(mm, addr); if (!vma) goto fail; if (vma->vm_start <= addr) goto success; if (!(vma->vm_flags & VM_GROWSDOWN)) goto fail; } if (expand_stack_locked(vma, addr)) goto fail; success: mmap_write_downgrade(mm); return vma; fail: mmap_write_unlock(mm); return NULL;} /* * Note this is constrained to return 0, -EFAULT, -EACCES, -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; pmd_t *pmd; pte_t *pte; int err = -EFAULT; unsigned int flags = FAULT_FLAG_DEFAULT; *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: vma = um_lock_mm_and_find_vma(mm, address, is_user); if (!vma) goto out_nosemaphore; *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, NULL); if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) goto out_nosemaphore; /* The fault is fully completed (including releasing mmap lock) */ if (fault & VM_FAULT_COMPLETED) return 0; 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 (fault & VM_FAULT_RETRY) { flags |= FAULT_FLAG_TRIED; goto retry; } pmd = pmd_off(mm, 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 out: mmap_read_unlock(mm);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). */ mmap_read_unlock(mm); if (!is_user) goto out_nosemaphore; pagefault_out_of_memory(); return 0;} 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));} void fatal_sigsegv(void){ force_fatal_sig(SIGSEGV); 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 * @mc: the mcontext of the signal * * 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, void *mc){ 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, mc);} /* * 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, void *mc){ 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) { /* * Kernel has pending updates from set_ptes that were not * flushed yet. Syncing them should fix the pagefault (if not * we'll get here again and panic). */ err = um_tlb_sync(&init_mm); if (err == -ENOMEM) report_enomem(); if (err) panic("Failed to sync kernel TLBs: %d", err); goto out; } else if (current->pagefault_disabled) { if (!mc) { show_regs(container_of(regs, struct pt_regs, regs)); panic("Segfault with pagefaults disabled but no mcontext"); } if (!current->thread.segv_continue) { show_regs(container_of(regs, struct pt_regs, regs)); panic("Segfault without recovery target"); } mc_set_rip(mc, current->thread.segv_continue); current->thread.segv_continue = NULL; 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; } if (!err) goto out; 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); } else { BUG_ON(err != -EFAULT); current->thread.arch.faultinfo = fi; force_sig_fault(SIGSEGV, si_code, (void __user *) address); } out: if (regs) current->thread.segv_regs = NULL; return 0;} void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs, void *mc){ 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)); } else { printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d) with errno %d\n", sig, code, err); force_sig(sig); }} void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs, void *mc){ do_IRQ(WINCH_IRQ, regs);}
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
*/
#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/tlbflush.h>
#include <arch.h>
#include <as-layout.h>
#include <kern_util.h>
#include <os.h>
#include <skas.h>
/*
* NOTE: UML does not have exception tables. As such, this is almost a copy
* of the code in mm/memory.c, only adjusting the logic to simply check whether
* we are coming from the kernel instead of doing an additional lookup in the
* exception table.
* We can do this simplification because we never get here if the exception was
* fixable.
*/
static inline bool get_mmap_lock_carefully(struct mm_struct *mm, bool is_user)
{
if (likely(mmap_read_trylock(mm)))
return true;
if (!is_user)
return false;
return !mmap_read_lock_killable(mm);
}
static inline bool mmap_upgrade_trylock(struct mm_struct *mm)
{
/*
* We don't have this operation yet.
*
* It should be easy enough to do: it's basically a
* atomic_long_try_cmpxchg_acquire()
* from RWSEM_READER_BIAS -> RWSEM_WRITER_LOCKED, but
* it also needs the proper lockdep magic etc.
*/
return false;
}
static inline bool upgrade_mmap_lock_carefully(struct mm_struct *mm, bool is_user)
{
mmap_read_unlock(mm);
if (!is_user)
return false;
return !mmap_write_lock_killable(mm);
}
/*
* Helper for page fault handling.
*
* This is kind of equivalend to "mmap_read_lock()" followed
* by "find_extend_vma()", except it's a lot more careful about
* the locking (and will drop the lock on failure).
*
* For example, if we have a kernel bug that causes a page
* fault, we don't want to just use mmap_read_lock() to get
* the mm lock, because that would deadlock if the bug were
* to happen while we're holding the mm lock for writing.
*
* So this checks the exception tables on kernel faults in
* order to only do this all for instructions that are actually
* expected to fault.
*
* We can also actually take the mm lock for writing if we
* need to extend the vma, which helps the VM layer a lot.
*/
static struct vm_area_struct *
um_lock_mm_and_find_vma(struct mm_struct *mm,
unsigned long addr, bool is_user)
{
struct vm_area_struct *vma;
if (!get_mmap_lock_carefully(mm, is_user))
return NULL;
vma = find_vma(mm, addr);
if (likely(vma && (vma->vm_start <= addr)))
return vma;
/*
* Well, dang. We might still be successful, but only
* if we can extend a vma to do so.
*/
if (!vma || !(vma->vm_flags & VM_GROWSDOWN)) {
mmap_read_unlock(mm);
return NULL;
}
/*
* We can try to upgrade the mmap lock atomically,
* in which case we can continue to use the vma
* we already looked up.
*
* Otherwise we'll have to drop the mmap lock and
* re-take it, and also look up the vma again,
* re-checking it.
*/
if (!mmap_upgrade_trylock(mm)) {
if (!upgrade_mmap_lock_carefully(mm, is_user))
return NULL;
vma = find_vma(mm, addr);
if (!vma)
goto fail;
if (vma->vm_start <= addr)
goto success;
if (!(vma->vm_flags & VM_GROWSDOWN))
goto fail;
}
if (expand_stack_locked(vma, addr))
goto fail;
success:
mmap_write_downgrade(mm);
return vma;
fail:
mmap_write_unlock(mm);
return NULL;
}
/*
* Note this is constrained to return 0, -EFAULT, -EACCES, -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;
pmd_t *pmd;
pte_t *pte;
int err = -EFAULT;
unsigned int flags = FAULT_FLAG_DEFAULT;
*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:
vma = um_lock_mm_and_find_vma(mm, address, is_user);
if (!vma)
goto out_nosemaphore;
*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, NULL);
if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
goto out_nosemaphore;
/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED)
return 0;
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 (fault & VM_FAULT_RETRY) {
flags |= FAULT_FLAG_TRIED;
goto retry;
}
pmd = pmd_off(mm, 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
out:
mmap_read_unlock(mm);
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).
*/
mmap_read_unlock(mm);
if (!is_user)
goto out_nosemaphore;
pagefault_out_of_memory();
return 0;
}
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));
}
void fatal_sigsegv(void)
{
force_fatal_sig(SIGSEGV);
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
* @mc: the mcontext of the signal
*
* 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,
void *mc)
{
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, mc);
}
/*
* 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, void *mc)
{
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) {
/*
* Kernel has pending updates from set_ptes that were not
* flushed yet. Syncing them should fix the pagefault (if not
* we'll get here again and panic).
*/
err = um_tlb_sync(&init_mm);
if (err == -ENOMEM)
report_enomem();
if (err)
panic("Failed to sync kernel TLBs: %d", err);
goto out;
}
else if (current->pagefault_disabled) {
if (!mc) {
show_regs(container_of(regs, struct pt_regs, regs));
panic("Segfault with pagefaults disabled but no mcontext");
}
if (!current->thread.segv_continue) {
show_regs(container_of(regs, struct pt_regs, regs));
panic("Segfault without recovery target");
}
mc_set_rip(mc, current->thread.segv_continue);
current->thread.segv_continue = NULL;
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;
}
if (!err)
goto out;
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);
} else {
BUG_ON(err != -EFAULT);
current->thread.arch.faultinfo = fi;
force_sig_fault(SIGSEGV, si_code, (void __user *) address);
}
out:
if (regs)
current->thread.segv_regs = NULL;
return 0;
}
void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs,
void *mc)
{
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));
} else {
printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d) with errno %d\n",
sig, code, err);
force_sig(sig);
}
}
void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs,
void *mc)
{
do_IRQ(WINCH_IRQ, regs);
}