zircon/kernel/syscalls/system.cpp

// Copyright 2017 The Fuchsia Authors
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#include <arch/arch_ops.h>
#include <arch/mp.h>
#include <debug.h>
#include <dev/interrupt.h>
#include <kernel/cmdline.h>
#include <kernel/mp.h>
#include <kernel/range_check.h>
#include <kernel/thread.h>
#include <lib/debuglog.h>
#include <libzbi/zbi-cpp.h>
#include <mexec.h>
#include <object/process_dispatcher.h>
#include <object/resource.h>
#include <object/vm_object_dispatcher.h>
#include <platform.h>
#include <string.h>
#include <trace.h>
#include <vm/physmap.h>
#include <vm/pmm.h>
#include <vm/vm.h>
#include <vm/vm_aspace.h>
#include <zircon/boot/image.h>
#include <zircon/compiler.h>
#include <zircon/syscalls/resource.h>
#include <zircon/syscalls/system.h>
#include <zircon/types.h>

#include "system_priv.h"

#define LOCAL_TRACE 0

// Allocate this many extra bytes at the end of the bootdata for the platform
// to fill in with platform specific boot structures.
const size_t kBootdataPlatformExtraBytes = PAGE_SIZE * 4;

__BEGIN_CDECLS
extern void mexec_asm(void);
extern void mexec_asm_end(void);
__END_CDECLS

/* Allocates a page of memory that has the same physical and virtual addresses.
 */
static zx_status_t identity_page_allocate(fbl::RefPtr<VmAspace>* new_aspace,
                                          void** result_addr) {
    zx_status_t result;

    // Start by obtaining an unused physical page. This address will eventually
    // be the physical/virtual address of our identity mapped page.
    paddr_t pa;
    result = pmm_alloc_page(0, &pa);
    if (result != ZX_OK) {
        return ZX_ERR_NO_MEMORY;
    }

    // The kernel address space may be in high memory which cannot be identity
    // mapped since all Kernel Virtual Addresses might be out of range of the
    // physical address space. For this reason, we need to make a new address
    // space.
    fbl::RefPtr<VmAspace> identity_aspace =
        VmAspace::Create(VmAspace::TYPE_LOW_KERNEL, "mexec identity");
    if (!identity_aspace)
        return ZX_ERR_INTERNAL;

    // Create a new allocation in the new address space that identity maps the
    // target page.
    const uint perm_flags_rwx = ARCH_MMU_FLAG_PERM_READ |
                                ARCH_MMU_FLAG_PERM_WRITE |
                                ARCH_MMU_FLAG_PERM_EXECUTE;
    void* identity_address = (void*)pa;
    result = identity_aspace->AllocPhysical("identity mapping", PAGE_SIZE,
                                            &identity_address, 0, pa,
                                            VmAspace::VMM_FLAG_VALLOC_SPECIFIC,
                                            perm_flags_rwx);
    if (result != ZX_OK)
        return result;

    *new_aspace = ktl::move(identity_aspace);
    *result_addr = identity_address;

    return ZX_OK;
}

/* Takes all the pages in a VMO and creates a copy of them where all the pages
 * occupy a physically contiguous region of physical memory.
 * TODO(gkalsi): Don't coalesce pages into a physically contiguous region and
 *               just pass a vectored I/O list to the mexec assembly.
 */
static zx_status_t vmo_coalesce_pages(zx_handle_t vmo_hdl, const size_t extra_bytes,
                                      paddr_t* addr, uint8_t** vaddr, size_t* size) {
    DEBUG_ASSERT(addr);
    if (!addr) {
        return ZX_ERR_INVALID_ARGS;
    }

    DEBUG_ASSERT(size);
    if (!size) {
        return ZX_ERR_INVALID_ARGS;
    }

    auto up = ProcessDispatcher::GetCurrent();
    fbl::RefPtr<VmObjectDispatcher> vmo_dispatcher;
    zx_status_t st =
        up->GetDispatcherWithRights(vmo_hdl, ZX_RIGHT_READ, &vmo_dispatcher);
    if (st != ZX_OK)
        return st;

    fbl::RefPtr<VmObject> vmo = vmo_dispatcher->vmo();

    const size_t vmo_size = vmo->size();

    const size_t num_pages = ROUNDUP(vmo_size + extra_bytes, PAGE_SIZE) / PAGE_SIZE;

    paddr_t base_addr;
    list_node list = LIST_INITIAL_VALUE(list);
    st = pmm_alloc_contiguous(num_pages, PMM_ALLOC_FLAG_ANY, 0, &base_addr, &list);
    if (st != ZX_OK) {
        // TODO(gkalsi): Free pages allocated by pmm_alloc_contiguous pages
        //               and return an error.
        panic("Failed to allocate contiguous memory");
    }

    uint8_t* dst_addr = (uint8_t*)paddr_to_physmap(base_addr);

    st = vmo->Read(dst_addr, 0, vmo_size);
    if (st != ZX_OK) {
        // TODO(gkalsi): Free pages allocated by pmm_alloc_contiguous pages
        //               and return an error.
        panic("Failed to read to contiguous vmo");
    }

    arch_clean_invalidate_cache_range((addr_t)dst_addr, vmo_size);

    *size = num_pages * PAGE_SIZE;
    *addr = base_addr;
    if (vaddr)
        *vaddr = dst_addr;

    return ZX_OK;
}

static fbl::RefPtr<VmObject> stashed_crashlog;
void mexec_stash_crashlog(fbl::RefPtr<VmObject> vmo) {
    stashed_crashlog = ktl::move(vmo);
}

// zx_status_t zx_system_mexec_payload_get
zx_status_t sys_system_mexec_payload_get(zx_handle_t resource,
                                         user_out_ptr<void> user_buffer,
                                         size_t buffer_size) {
    // Highly privilidged, only root resource should have access.
    zx_status_t result = validate_resource(resource, ZX_RSRC_KIND_ROOT);
    if (result != ZX_OK) {
        return result;
    }

    // Limit the size of the result that we can return to userspace.
    if (buffer_size > kBootdataPlatformExtraBytes) {
        return ZX_ERR_INVALID_ARGS;
    }

    fbl::AllocChecker ac;
    ktl::unique_ptr<uint8_t[]> buffer;
    buffer.reset(new (&ac) uint8_t[buffer_size]);
    if (!ac.check()) {
        return ZX_ERR_NO_MEMORY;
    }
    memset(buffer.get(), 0, buffer_size);

    // Create a zero length ZBI in the buffer.
    zbi::Zbi image(buffer.get(), buffer_size);
    zbi_result_t zbi_result = image.Reset();
    if (zbi_result != ZBI_RESULT_OK) {
        return ZX_ERR_INTERNAL;
    }

    result = platform_mexec_patch_zbi(buffer.get(), buffer_size);
    if (result != ZX_OK) {
        return result;
    }

    if (stashed_crashlog && stashed_crashlog->size() <= UINT32_MAX) {
        size_t crashlog_len = stashed_crashlog->size();
        uint8_t* bootdata_section;

        zbi_result_t res = image.CreateSection(static_cast<uint32_t>(crashlog_len),
                                               ZBI_TYPE_CRASHLOG, 0, 0,
                                               reinterpret_cast<void**>(&bootdata_section));

        if (res != ZBI_RESULT_OK) {
            printf("mexec: could not append crashlog\n");
            return ZX_ERR_INTERNAL;
        }

        result = stashed_crashlog->Read(bootdata_section, 0, crashlog_len);
        if (result != ZX_OK) {
            return result;
        }
    }

    return user_buffer.copy_array_to_user(buffer.get(), buffer_size);
}

// zx_status_t zx_system_mexec
zx_status_t sys_system_mexec(zx_handle_t resource, zx_handle_t kernel_vmo, zx_handle_t bootimage_vmo) {
    // TODO(ZX-971): finer grained validation
    zx_status_t result = validate_resource(resource, ZX_RSRC_KIND_ROOT);
    if (result != ZX_OK)
        return result;

    paddr_t new_kernel_addr;
    size_t new_kernel_len;
    result = vmo_coalesce_pages(kernel_vmo, 0, &new_kernel_addr, NULL,
                                &new_kernel_len);
    if (result != ZX_OK) {
        return result;
    }

    // for kernels that are bootdata based (eg, x86-64), the location
    // to find the entrypoint depends on the bootdata format
    paddr_t entry64_addr = (get_kernel_base_phys() +
                            sizeof(zbi_header_t) + // ZBI_TYPE_CONTAINER header
                            sizeof(zbi_header_t) + // ZBI_TYPE_KERNEL header
                            offsetof(zbi_kernel_t, entry));

    paddr_t new_bootimage_addr;
    uint8_t* bootimage_buffer;
    size_t new_bootimage_len;
    result = vmo_coalesce_pages(bootimage_vmo, kBootdataPlatformExtraBytes,
                                &new_bootimage_addr, &bootimage_buffer,
                                &new_bootimage_len);
    if (result != ZX_OK) {
        return result;
    }

    void* id_page_addr = 0x0;
    fbl::RefPtr<VmAspace> aspace;
    result = identity_page_allocate(&aspace, &id_page_addr);
    if (result != ZX_OK) {
        return result;
    }

    LTRACEF("zx_system_mexec allocated identity mapped page at %p\n",
            id_page_addr);

    thread_migrate_to_cpu(BOOT_CPU_ID);

    // We assume that when the system starts, only one CPU is running. We denote
    // this as the boot CPU.
    // We want to make sure that this is the CPU that eventually branches into
    // the new kernel so we attempt to migrate this thread to that cpu.
    platform_halt_secondary_cpus();

    platform_mexec_prep(new_bootimage_addr, new_bootimage_len);

    arch_disable_ints();

    // WARNING
    // It is unsafe to return from this function beyond this point.
    // This is because we have swapped out the user address space and halted the
    // secondary cores and there is no trivial way to bring both of these back.
    vmm_set_active_aspace(reinterpret_cast<vmm_aspace_t*>(aspace.get()));

    // We're going to copy this into our identity page, make sure it's not
    // longer than a single page.
    size_t mexec_asm_length = (uintptr_t)mexec_asm_end - (uintptr_t)mexec_asm;
    DEBUG_ASSERT(mexec_asm_length <= PAGE_SIZE);

    memcpy(id_page_addr, (const void*)mexec_asm, mexec_asm_length);
    arch_sync_cache_range((addr_t)id_page_addr, mexec_asm_length);

    // We must pass in an arg that represents a list of memory regions to
    // shuffle around. We put this args list immediately after the mexec
    // assembly.
    uintptr_t ops_ptr = ((((uintptr_t)id_page_addr) + mexec_asm_length + 8) | 0x7) + 1;
    memmov_ops_t* ops = (memmov_ops_t*)(ops_ptr);

    const size_t num_ops = 2;
    // Make sure that we can also pack the arguments in the same page as the
    // final mexec assembly shutdown code.
    DEBUG_ASSERT(((sizeof(*ops) * num_ops + ops_ptr) - (uintptr_t)id_page_addr) < PAGE_SIZE);

    // Op to move the new kernel into place.
    ops[0].src = (void*)new_kernel_addr;
    ops[0].dst = (void*)get_kernel_base_phys();
    ops[0].len = new_kernel_len;

    // Null terminated list.
    ops[1] = {0, 0, 0};

    // Make sure that the kernel, when copied, will not overwrite the bootdata.
    DEBUG_ASSERT(!Intersects(reinterpret_cast<uintptr_t>(ops[0].dst),
                             ops[0].len,
                             reinterpret_cast<uintptr_t>(new_bootimage_addr),
                             new_bootimage_len));

    // Sync because there is code in here that we intend to run.
    arch_sync_cache_range((addr_t)id_page_addr, PAGE_SIZE);

    // Clean because we're going to turn the MMU/caches off and we want to make
    // sure that things are still available afterwards.
    arch_clean_cache_range((addr_t)id_page_addr, PAGE_SIZE);

    shutdown_interrupts();

    // Ask the platform to mexec into the next kernel.
    mexec_asm_func mexec_assembly = (mexec_asm_func)id_page_addr;
    platform_mexec(mexec_assembly, ops, new_bootimage_addr, new_bootimage_len, entry64_addr);

    panic("Execution should never reach here\n");
    return ZX_OK;
}

// Gracefully halt and perform |action|.
static void platform_graceful_halt(platform_halt_action action) {
    thread_migrate_to_cpu(BOOT_CPU_ID);
    platform_halt_secondary_cpus();

    // Delay shutdown of debuglog to ensure log messages emitted by above calls will be written.
    dlog_shutdown();

    platform_halt(action, HALT_REASON_SW_RESET);
    panic("ERROR: failed to halt the platform\n");
}

// zx_status_t zx_system_powerctl
zx_status_t sys_system_powerctl(zx_handle_t root_rsrc, uint32_t cmd,
                                user_in_ptr<const zx_system_powerctl_arg_t> raw_arg) {

    zx_status_t status;
    if ((status = validate_resource(root_rsrc, ZX_RSRC_KIND_ROOT)) < 0) {
        return status;
    }

    switch (cmd) {
    case ZX_SYSTEM_POWERCTL_ENABLE_ALL_CPUS: {
        cpu_mask_t all_cpus = ((cpu_mask_t)1u << arch_max_num_cpus()) - 1;
        return mp_hotplug_cpu_mask(~mp_get_online_mask() & all_cpus);
    }
    case ZX_SYSTEM_POWERCTL_DISABLE_ALL_CPUS_BUT_PRIMARY: {
        cpu_mask_t primary = cpu_num_to_mask(0);
        return mp_unplug_cpu_mask(mp_get_online_mask() & ~primary);
    }
    case ZX_SYSTEM_POWERCTL_ACPI_TRANSITION_S_STATE:
    case ZX_SYSTEM_POWERCTL_X86_SET_PKG_PL1: {
        zx_system_powerctl_arg_t arg;
        status = raw_arg.copy_from_user(&arg);
        if (status != ZX_OK) {
            return status;
        }

        return arch_system_powerctl(cmd, &arg);
    }
    case ZX_SYSTEM_POWERCTL_REBOOT:
        platform_graceful_halt(HALT_ACTION_REBOOT);
        break;
    case ZX_SYSTEM_POWERCTL_REBOOT_BOOTLOADER:
        platform_graceful_halt(HALT_ACTION_REBOOT_BOOTLOADER);
        break;
    case ZX_SYSTEM_POWERCTL_REBOOT_RECOVERY:
        platform_graceful_halt(HALT_ACTION_REBOOT_RECOVERY);
        break;
    case ZX_SYSTEM_POWERCTL_SHUTDOWN:
        platform_graceful_halt(HALT_ACTION_SHUTDOWN);
        break;
    default:
        return ZX_ERR_INVALID_ARGS;
    }
    return ZX_OK;
}