/*      $NetBSD: asan.h,v 1.12 2022/09/13 09:39:49 riastradh Exp $      */

/*
* Copyright (c) 2018-2020 Maxime Villard, m00nbsd.net
* All rights reserved.
*
* This code is part of the KASAN subsystem of the NetBSD kernel.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#ifndef _AMD64_ASAN_H_
#define _AMD64_ASAN_H_

#include <sys/ksyms.h>

#include <uvm/uvm.h>

#include <amd64/pmap.h>
#include <amd64/vmparam.h>

#include <x86/bootspace.h>

#include <machine/pmap_private.h>

#ifdef __HAVE_PCPU_AREA
#error "PCPU area not allowed with KASAN"
#endif
#ifdef __HAVE_DIRECT_MAP
#error "DMAP not allowed with KASAN"
#endif

#define __MD_VIRTUAL_SHIFT      47      /* 48bit address space, cut half */
#define __MD_KERNMEM_BASE       0xFFFF800000000000 /* kern mem base address */

#define __MD_SHADOW_SIZE        (1ULL << (__MD_VIRTUAL_SHIFT - KASAN_SHADOW_SCALE_SHIFT))
#define KASAN_MD_SHADOW_START   (VA_SIGN_NEG((L4_SLOT_KASAN * NBPD_L4)))
#define KASAN_MD_SHADOW_END     (KASAN_MD_SHADOW_START + __MD_SHADOW_SIZE)

/* -------------------------------------------------------------------------- */

/*
* Early mapping, used to map just the stack at boot time. We rely on the fact
* that VA = PA + KERNBASE.
*/

static bool __md_early __read_mostly = true;
static uint8_t __md_earlypages[8 * PAGE_SIZE] __aligned(PAGE_SIZE);
static size_t __md_earlytaken = 0;

static paddr_t
__md_early_palloc(void)
{
       paddr_t ret;

       KASSERT(__md_earlytaken < 8);

       ret = (paddr_t)(&__md_earlypages[0] + __md_earlytaken * PAGE_SIZE);
       __md_earlytaken++;

       ret -= KERNBASE;

       return ret;
}

static void
__md_early_shadow_map_page(vaddr_t va)
{
       extern struct bootspace bootspace;
       const pt_entry_t pteflags = PTE_W | pmap_pg_nx | PTE_P;
       pt_entry_t *pdir = (pt_entry_t *)bootspace.pdir;
       paddr_t pa;

       if (!pmap_valid_entry(pdir[pl4_pi(va)])) {
               pa = __md_early_palloc();
               pdir[pl4_pi(va)] = pa | pteflags;
       }
       pdir = (pt_entry_t *)((pdir[pl4_pi(va)] & PTE_FRAME) + KERNBASE);

       if (!pmap_valid_entry(pdir[pl3_pi(va)])) {
               pa = __md_early_palloc();
               pdir[pl3_pi(va)] = pa | pteflags;
       }
       pdir = (pt_entry_t *)((pdir[pl3_pi(va)] & PTE_FRAME) + KERNBASE);

       if (!pmap_valid_entry(pdir[pl2_pi(va)])) {
               pa = __md_early_palloc();
               pdir[pl2_pi(va)] = pa | pteflags;
       }
       pdir = (pt_entry_t *)((pdir[pl2_pi(va)] & PTE_FRAME) + KERNBASE);

       if (!pmap_valid_entry(pdir[pl1_pi(va)])) {
               pa = __md_early_palloc();
               pdir[pl1_pi(va)] = pa | pteflags | pmap_pg_g;
       }
}

/* -------------------------------------------------------------------------- */

static inline int8_t *
kasan_md_addr_to_shad(const void *addr)
{
       vaddr_t va = (vaddr_t)addr;
       return (int8_t *)(KASAN_MD_SHADOW_START +
           ((va - __MD_KERNMEM_BASE) >> KASAN_SHADOW_SCALE_SHIFT));
}

static inline bool
kasan_md_unsupported(vaddr_t addr)
{
       return (addr >= (vaddr_t)PTE_BASE &&
           addr < ((vaddr_t)PTE_BASE + NBPD_L4));
}

static paddr_t
__md_palloc(void)
{
       /* The page is zeroed. */
       return pmap_get_physpage();
}

static inline paddr_t
__md_palloc_large(void)
{
       struct pglist pglist;
       int ret;

       if (!uvm.page_init_done)
               return 0;

       ret = uvm_pglistalloc(NBPD_L2, 0, ~0UL, NBPD_L2, 0,
           &pglist, 1, 0);
       if (ret != 0)
               return 0;

       /* The page may not be zeroed. */
       return VM_PAGE_TO_PHYS(TAILQ_FIRST(&pglist));
}

static void
kasan_md_shadow_map_page(vaddr_t va)
{
       const pt_entry_t pteflags = PTE_W | pmap_pg_nx | PTE_P;
       paddr_t pa;

       if (__predict_false(__md_early)) {
               __md_early_shadow_map_page(va);
               return;
       }

       if (!pmap_valid_entry(L4_BASE[pl4_i(va)])) {
               pa = __md_palloc();
               L4_BASE[pl4_i(va)] = pa | pteflags;
       }
       if (!pmap_valid_entry(L3_BASE[pl3_i(va)])) {
               pa = __md_palloc();
               L3_BASE[pl3_i(va)] = pa | pteflags;
       }
       if (!pmap_valid_entry(L2_BASE[pl2_i(va)])) {
               if ((pa = __md_palloc_large()) != 0) {
                       L2_BASE[pl2_i(va)] = pa | pteflags | PTE_PS |
                           pmap_pg_g;
                       __insn_barrier();
                       __builtin_memset((void *)va, 0, NBPD_L2);
                       return;
               }
               pa = __md_palloc();
               L2_BASE[pl2_i(va)] = pa | pteflags;
       } else if (L2_BASE[pl2_i(va)] & PTE_PS) {
               return;
       }
       if (!pmap_valid_entry(L1_BASE[pl1_i(va)])) {
               pa = __md_palloc();
               L1_BASE[pl1_i(va)] = pa | pteflags | pmap_pg_g;
       }
}

/*
* Map only the current stack. We will map the rest in kasan_init.
*/
static void
kasan_md_early_init(void *stack)
{
       kasan_shadow_map(stack, USPACE);
       __md_early = false;
}

/*
* Create the shadow mapping. We don't create the 'User' area, because we
* exclude it from the monitoring. The 'Main' area is created dynamically
* in pmap_growkernel.
*/
static void
kasan_md_init(void)
{
       extern struct bootspace bootspace;
       size_t i;

       CTASSERT((__MD_SHADOW_SIZE / NBPD_L4) == NL4_SLOT_KASAN);

       /* Kernel. */
       for (i = 0; i < BTSPACE_NSEGS; i++) {
               if (bootspace.segs[i].type == BTSEG_NONE) {
                       continue;
               }
               kasan_shadow_map((void *)bootspace.segs[i].va,
                   bootspace.segs[i].sz);
       }

       /* Boot region. */
       kasan_shadow_map((void *)bootspace.boot.va, bootspace.boot.sz);

       /* Module map. */
       kasan_shadow_map((void *)bootspace.smodule,
           (size_t)(bootspace.emodule - bootspace.smodule));

       /* The bootstrap spare va. */
       kasan_shadow_map((void *)bootspace.spareva, PAGE_SIZE);
}

static inline bool
__md_unwind_end(const char *name)
{
       if (!strcmp(name, "syscall") ||
           !strcmp(name, "alltraps") ||
           !strcmp(name, "handle_syscall") ||
           !strncmp(name, "Xtrap", 5) ||
           !strncmp(name, "Xintr", 5) ||
           !strncmp(name, "Xhandle", 7) ||
           !strncmp(name, "Xresume", 7) ||
           !strncmp(name, "Xstray", 6) ||
           !strncmp(name, "Xhold", 5) ||
           !strncmp(name, "Xrecurse", 8) ||
           !strcmp(name, "Xdoreti") ||
           !strncmp(name, "Xsoft", 5)) {
               return true;
       }

       return false;
}

static void
kasan_md_unwind(void)
{
       uint64_t *rbp, rip;
       const char *mod;
       const char *sym;
       size_t nsym;
       int error;

       rbp = (uint64_t *)__builtin_frame_address(0);
       nsym = 0;

       while (1) {
               /* 8(%rbp) contains the saved %rip. */
               rip = *(rbp + 1);

               if (rip < KERNBASE) {
                       break;
               }
               error = ksyms_getname(&mod, &sym, (vaddr_t)rip, KSYMS_PROC);
               if (error) {
                       break;
               }
               printf("#%zu %p in %s <%s>\n", nsym, (void *)rip, sym, mod);
               if (__md_unwind_end(sym)) {
                       break;
               }

               rbp = (uint64_t *)*(rbp);
               if (rbp == 0) {
                       break;
               }
               nsym++;

               if (nsym >= 15) {
                       break;
               }
       }
}

#endif  /* _AMD64_ASAN_H_ */

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