system/utest/vdso/vdso.cpp

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <elfload/elfload.h>
#include <fbl/array.h>
#include <lib/zx/process.h>
#include <lib/zx/vmar.h>
#include <lib/zx/vmo.h>
#include <limits.h>
#include <new>
#include <string.h>
#include <unittest/unittest.h>
#include <zircon/process.h>
#include <zircon/processargs.h>
#include <zircon/syscalls.h>

static const zx::vmo vdso_vmo{zx_take_startup_handle(PA_HND(PA_VMO_VDSO, 0))};

class ScratchPad {
public:
    ScratchPad() = delete;
    ScratchPad(const char* name) {
        EXPECT_EQ(zx_process_create(
                      zx_job_default(),
                      name, static_cast<uint32_t>(strlen(name)), 0,
                      process_.reset_and_get_address(),
                      root_vmar_.reset_and_get_address()),
                  ZX_OK, "zx_process_create");
    }

    const zx::vmar& root_vmar() const { return root_vmar_; }
    uintptr_t vdso_base() const { return vdso_base_; }
    uintptr_t vdso_code_offset() const { return vdso_code_offset_; }
    uintptr_t vdso_code_size() const { return vdso_code_size_; }
    uintptr_t vdso_code_address() const {
        return vdso_base_ + vdso_code_offset_;
    }
    uintptr_t vdso_total_size() const {
        return vdso_code_offset_ + vdso_code_size_;
    }

    zx_status_t load_vdso(zx::vmar* segments_vmar = nullptr,
                          bool really_load = true) {
        elf_load_header_t header;
        uintptr_t phoff;
        zx_status_t status = elf_load_prepare(vdso_vmo.get(), nullptr, 0,
                                              &header, &phoff);
        if (status == ZX_OK) {
            fbl::Array<elf_phdr_t> phdrs(new elf_phdr_t[header.e_phnum],
                                          header.e_phnum);
            status = elf_load_read_phdrs(vdso_vmo.get(), phdrs.get(), phoff,
                                         header.e_phnum);
            if (status == ZX_OK) {
                for (const auto& ph : phdrs) {
                    if (ph.p_type == PT_LOAD && (ph.p_type & PF_X)) {
                        vdso_code_offset_ = ph.p_vaddr;
                        vdso_code_size_ = ph.p_memsz;
                    }
                }
                if (really_load) {
                    status = elf_load_map_segments(
                        root_vmar_.get(), &header, phdrs.get(), vdso_vmo.get(),
                        segments_vmar ? segments_vmar->reset_and_get_address() : nullptr,
                        &vdso_base_, nullptr);
                }
            }
        }
        return status;
    }

    zx_status_t compute_vdso_sizes() {
        return load_vdso(nullptr, false);
    }

private:
    zx::process process_;
    zx::vmar root_vmar_;
    uintptr_t vdso_base_ = 0;
    uintptr_t vdso_code_offset_ = 0;
    uintptr_t vdso_code_size_ = 0;
};

bool vdso_map_twice_test() {
    BEGIN_TEST;

    ScratchPad scratch(__func__);

    // Load the vDSO once.  That's on me.
    EXPECT_EQ(scratch.load_vdso(), ZX_OK, "load vDSO into empty process");

    // Load the vDSO twice.  Can't get loaded again.
    EXPECT_EQ(scratch.load_vdso(), ZX_ERR_ACCESS_DENIED, "load vDSO second time");

    END_TEST;
}

bool vdso_map_change_test() {
    BEGIN_TEST;

    ScratchPad scratch(__func__);

    // Load the vDSO and hold onto the sub-VMAR.
    zx::vmar vdso_vmar;
    EXPECT_EQ(scratch.load_vdso(&vdso_vmar), ZX_OK, "load vDSO");

    // Changing protections on the code pages is forbidden.
    EXPECT_EQ(vdso_vmar.protect(scratch.vdso_code_address(),
                                scratch.vdso_code_size(),
                                ZX_VM_PERM_READ),
              ZX_ERR_ACCESS_DENIED, "zx_vmar_protect on vDSO code");

    zx::vmo vmo;
    ASSERT_EQ(zx::vmo::create(scratch.vdso_total_size(), 0, &vmo),
              ZX_OK, "zx_vmo_create");

    // Implicit unmapping by overwriting the mapping is forbidden.
    uintptr_t addr = 0;
    EXPECT_EQ(vdso_vmar.map(0, vmo, 0, scratch.vdso_total_size(),
                            ZX_VM_PERM_READ |
                            ZX_VM_SPECIFIC_OVERWRITE,
                            &addr),
              ZX_ERR_ACCESS_DENIED, "zx_vmar_map to overmap vDSO");
    EXPECT_EQ(addr, 0, "zx_vmar_map to overmap vDSO");

    // Also forbidden if done from a parent VMAR.
    zx_info_vmar_t root_vmar_info;
    ASSERT_EQ(scratch.root_vmar().get_info(ZX_INFO_VMAR, &root_vmar_info,
                                           sizeof(root_vmar_info),
                                           nullptr, nullptr),
              ZX_OK, "zx_object_get_info on root VMAR");
    EXPECT_EQ(scratch.root_vmar().
              map(scratch.vdso_base() - root_vmar_info.base, vmo,
                  0, scratch.vdso_total_size(),
                  ZX_VM_PERM_READ | ZX_VM_SPECIFIC_OVERWRITE,
                  &addr),
              ZX_ERR_ACCESS_DENIED, "zx_vmar_map to overmap vDSO from root");
    EXPECT_EQ(addr, 0, "zx_vmar_map to overmap vDSO from root");

    // Explicit unmapping covering the vDSO code region is forbidden.
    EXPECT_EQ(scratch.root_vmar().unmap(scratch.vdso_base(),
                                        scratch.vdso_total_size()),
              ZX_ERR_ACCESS_DENIED, "zx_vmar_unmap to unmap vDSO");

    // Implicit unmapping by destroying a containing VMAR is forbidden.
    EXPECT_EQ(vdso_vmar.destroy(),
              ZX_ERR_ACCESS_DENIED, "zx_vmar_destroy to unmap vDSO");
    EXPECT_EQ(scratch.root_vmar().destroy(),
              ZX_ERR_ACCESS_DENIED, "zx_vmar_destroy on root to unmap vDSO");

    END_TEST;
}

bool vdso_map_code_wrong_test() {
    BEGIN_TEST;

    ScratchPad scratch(__func__);

    ASSERT_EQ(scratch.compute_vdso_sizes(), ZX_OK,
              "cannot read vDSO program headers");

    // Try to map the first page, which is not the code, as executable.
    uintptr_t addr;
    EXPECT_EQ(scratch.root_vmar().
              map(0, vdso_vmo, 0, PAGE_SIZE,
                  ZX_VM_PERM_READ | ZX_VM_PERM_EXECUTE, &addr),
              ZX_ERR_ACCESS_DENIED, "executable mapping of wrong part of vDSO");

    // Try to map only part of the code, not the whole code segment.
    ASSERT_GE(scratch.vdso_code_size(), PAGE_SIZE, "vDSO code < page??");
    if (scratch.vdso_code_size() > PAGE_SIZE) {
        ASSERT_EQ(scratch.vdso_code_size() % PAGE_SIZE, 0);
        EXPECT_EQ(scratch.root_vmar().
                  map(0, vdso_vmo, scratch.vdso_code_offset(), PAGE_SIZE,
                      ZX_VM_PERM_READ | ZX_VM_PERM_EXECUTE, &addr),
                  ZX_ERR_ACCESS_DENIED,
                  "executable mapping of subset of vDSO code");
    }

    END_TEST;
}

BEGIN_TEST_CASE(vdso_tests)
RUN_TEST(vdso_map_twice_test);
RUN_TEST(vdso_map_code_wrong_test);
RUN_TEST(vdso_map_change_test);
END_TEST_CASE(vdso_tests)

int main(int argc, char** argv) {
    return unittest_run_all_tests(argc, argv) ? 0 : -1;
}