Magisk/native/jni/magiskboot/dtb.cpp

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#include <unistd.h>
#include <sys/mman.h>
#include <bitset>
#include <vector>
#include <map>
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#include <utils.hpp>
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#include "magiskboot.hpp"
#include "dtb.hpp"
extern "C" {
#include <libfdt.h>
}
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using namespace std;
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constexpr int MAX_DEPTH = 32;
static bitset<MAX_DEPTH> depth_set;
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static void pretty_node(int depth) {
if (depth == 0)
return;
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for (int i = 0; i < depth - 1; ++i)
printf(depth_set[i] ? "" : " ");
printf(depth_set[depth - 1] ? "├── " : "└── ");
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}
static void pretty_prop(int depth) {
for (int i = 0; i < depth; ++i)
printf(depth_set[i] ? "" : " ");
printf(depth_set[depth] ? "" : " ");
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}
static void print_node(const void *fdt, int node = 0, int depth = 0) {
// Print node itself
pretty_node(depth);
printf("#%d: %s\n", node, fdt_get_name(fdt, node, nullptr));
// Print properties
depth_set[depth] = fdt_first_subnode(fdt, node) >= 0;
int prop;
fdt_for_each_property_offset(prop, fdt, node) {
pretty_prop(depth);
int size;
const char *name;
auto value = static_cast<const char *>(fdt_getprop_by_offset(fdt, prop, &name, &size));
bool is_str = !(size > 1 && value[0] == 0);
if (is_str) {
// Scan through value to see if printable
for (int i = 0; i < size; ++i) {
char c = value[i];
if (i == size - 1) {
// Make sure null terminate
is_str = c == '\0';
} else if ((c > 0 && c < 32) || c >= 127) {
is_str = false;
break;
}
}
}
if (is_str) {
printf("[%s]: [%s]\n", name, value);
} else {
printf("[%s]: <bytes>(%d)\n", name, size);
}
}
// Recursive
if (depth_set[depth]) {
int child;
int prev = -1;
fdt_for_each_subnode(child, fdt, node) {
if (prev >= 0)
print_node(fdt, prev, depth + 1);
prev = child;
}
depth_set[depth] = false;
print_node(fdt, prev, depth + 1);
}
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}
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static int find_fstab(const void *fdt, int node = 0) {
if (fdt_get_name(fdt, node, nullptr) == "fstab"sv)
return node;
int child;
fdt_for_each_subnode(child, fdt, node) {
int fstab = find_fstab(fdt, child);
if (fstab >= 0)
return fstab;
}
return -1;
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}
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static void dtb_print(const char *file, bool fstab) {
size_t size;
uint8_t *dtb;
fprintf(stderr, "Loading dtbs from [%s]\n", file);
mmap_ro(file, dtb, size);
// Loop through all the dtbs
int dtb_num = 0;
for (int i = 0; i < size; ++i) {
if (memcmp(dtb + i, FDT_MAGIC_STR, 4) == 0) {
auto fdt = dtb + i;
if (fstab) {
int node = find_fstab(fdt);
if (node >= 0) {
fprintf(stderr, "Found fstab in dtb.%04d\n", dtb_num);
print_node(fdt, node);
}
} else {
fprintf(stderr, "Printing dtb.%04d\n", dtb_num);
print_node(fdt);
}
++dtb_num;
i += fdt_totalsize(fdt) - 1;
}
}
fprintf(stderr, "\n");
munmap(dtb, size);
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}
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[[maybe_unused]]
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static bool dtb_patch_rebuild(uint8_t *dtb, size_t dtb_sz, const char *file);
static bool dtb_patch(const char *file) {
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bool keep_verity = check_env("KEEPVERITY");
size_t size;
uint8_t *dtb;
fprintf(stderr, "Loading dtbs from [%s]\n", file);
mmap_rw(file, dtb, size);
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bool patched = false;
for (int i = 0; i < size; ++i) {
if (memcmp(dtb + i, FDT_MAGIC_STR, 4) == 0) {
auto fdt = dtb + i;
if (int fstab = find_fstab(fdt); fstab >= 0) {
int node;
fdt_for_each_subnode(node, fdt, fstab) {
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if (!keep_verity) {
int len;
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char *value = (char *) fdt_getprop(fdt, node, "fsmgr_flags", &len);
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patched |= patch_verity(value, len) != len;
}
}
}
i += fdt_totalsize(fdt) - 1;
}
}
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munmap(dtb, size);
return patched;
}
int dtb_commands(int argc, char *argv[]) {
char *dtb = argv[0];
++argv;
--argc;
if (argv[0] == "print"sv) {
dtb_print(dtb, argc > 1 && argv[1] == "-f"sv);
return 0;
} else if (argv[0] == "patch"sv) {
if (!dtb_patch(dtb))
exit(1);
return 0;
} else {
return 1;
}
}
namespace {
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struct fdt_blob {
void *fdt;
uint32_t offset;
uint32_t len;
};
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}
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static bool fdt_patch(void *fdt) {
int fstab = find_fstab(fdt);
if (fstab < 0)
return false;
bool modified = false;
int node;
fdt_for_each_subnode(node, fdt, fstab) {
const char *name = fdt_get_name(fdt, node, nullptr);
// Force remove AVB for 2SI since it may bootloop some devices
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int len;
auto value = (const char *) fdt_getprop(fdt, node, "fsmgr_flags", &len);
string copy(value, len);
uint32_t new_len = patch_verity(copy.data(), len);
if (new_len != len) {
modified = true;
fdt_setprop(fdt, node, "fsmgr_flags", copy.data(), new_len);
}
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if (name == "system"sv) {
fprintf(stderr, "Setting [mnt_point] to [/system_root]\n");
fdt_setprop_string(fdt, node, "mnt_point", "/system_root");
modified = true;
}
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}
return modified;
}
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#define MAX_FDT_GROWTH 256
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template <class Table, class Header>
static bool dt_table_patch(const Header *hdr, const char *out) {
map<uint32_t, fdt_blob> dtb_map;
auto buf = reinterpret_cast<const uint8_t *>(hdr);
auto tables = reinterpret_cast<const Table *>(buf + sizeof(Header));
constexpr bool is_aosp = std::is_same_v<Header, dt_table_header>;
// AOSP DTB store ints in big endian
using endian_conv = uint32_t (*)(uint32_t);
endian_conv be_to_le;
endian_conv le_to_be;
if constexpr (is_aosp) {
be_to_le = fdt32_to_cpu;
le_to_be = cpu_to_fdt32;
} else {
be_to_le = le_to_be = [](uint32_t x) { return x; };
}
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// Collect all dtbs
auto num_dtb = be_to_le(hdr->num_dtbs);
for (int i = 0; i < num_dtb; ++i) {
auto offset = be_to_le(tables[i].offset);
if (dtb_map.count(offset) == 0) {
auto blob = buf + offset;
uint32_t size = fdt_totalsize(blob);
auto fdt = xmalloc(size + MAX_FDT_GROWTH);
memcpy(fdt, blob, size);
fdt_open_into(fdt, fdt, size + MAX_FDT_GROWTH);
dtb_map[offset] = { fdt, offset };
}
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}
if (dtb_map.empty())
return false;
// Patch fdt
bool modified = false;
for (auto &[_, blob] : dtb_map)
modified |= fdt_patch(blob.fdt);
if (!modified)
return false;
unlink(out);
int fd = xopen(out, O_RDWR | O_CREAT | O_CLOEXEC, 0644);
// This value is only used if AOSP DTB
uint32_t total_size = 0;
// Copy headers and tables
total_size += xwrite(fd, buf, dtb_map.begin()->first);
// mmap rw to patch table values retroactively
auto mmap_sz = lseek(fd, 0, SEEK_CUR);
auto addr = (uint8_t *) xmmap(nullptr, mmap_sz, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
// Guess alignment using gcd
uint32_t align = 1;
if constexpr (!is_aosp) {
auto it = dtb_map.begin();
align = (it++)->first;
for (; it != dtb_map.end(); ++it)
align = binary_gcd(align, it->first);
}
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// Write dtbs
for (auto &val : dtb_map) {
val.second.offset = lseek(fd, 0, SEEK_CUR);
auto fdt = val.second.fdt;
fdt_pack(fdt);
auto size = fdt_totalsize(fdt);
total_size += xwrite(fd, fdt, size);
if constexpr (!is_aosp) {
val.second.len = do_align(size, align);
write_zero(fd, align_off(lseek(fd, 0, SEEK_CUR), align));
}
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free(fdt);
}
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// Patch headers
if constexpr (is_aosp) {
auto hdr_rw = reinterpret_cast<Header *>(addr);
hdr_rw->total_size = le_to_be(total_size);
}
auto tables_rw = reinterpret_cast<Table *>(addr + sizeof(Header));
for (int i = 0; i < num_dtb; ++i) {
auto &blob = dtb_map[be_to_le(tables_rw[i].offset)];
tables_rw[i].offset = le_to_be(blob.offset);
tables_rw[i].len = le_to_be(blob.len);
}
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munmap(addr, mmap_sz);
close(fd);
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return true;
}
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static bool blob_patch(uint8_t *dtb, size_t dtb_sz, const char *out) {
vector<uint8_t *> fdt_list;
vector<uint32_t> padding_list;
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for (int i = 0; i < dtb_sz; ++i) {
if (memcmp(dtb + i, FDT_MAGIC_STR, 4) == 0) {
auto len = fdt_totalsize(dtb + i);
auto fdt = static_cast<uint8_t *>(xmalloc(len + MAX_FDT_GROWTH));
memcpy(fdt, dtb + i, len);
fdt_pack(fdt);
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uint32_t padding = len - fdt_totalsize(fdt);
padding_list.push_back(padding);
fdt_open_into(fdt, fdt, len + MAX_FDT_GROWTH);
fdt_list.push_back(fdt);
i += len - 1;
}
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}
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bool modified = false;
for (auto fdt : fdt_list)
modified |= fdt_patch(fdt);
if (!modified)
return false;
unlink(out);
int fd = xopen(out, O_WRONLY | O_CREAT | O_CLOEXEC, 0644);
for (int i = 0; i < fdt_list.size(); ++i) {
auto fdt = fdt_list[i];
fdt_pack(fdt);
// Only add padding back if it is anything meaningful
if (padding_list[i] > 4) {
auto len = fdt_totalsize(fdt);
fdt_set_totalsize(fdt, len + padding_list[i]);
}
xwrite(fd, fdt, fdt_totalsize(fdt));
free(fdt);
}
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close(fd);
return true;
}
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#define MATCH(s) (memcmp(dtb, s, sizeof(s) - 1) == 0)
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static bool dtb_patch_rebuild(uint8_t *dtb, size_t dtb_sz, const char *file) {
if (MATCH(QCDT_MAGIC)) {
auto hdr = reinterpret_cast<qcdt_hdr*>(dtb);
switch (hdr->version) {
case 1:
fprintf(stderr, "QCDT v1\n");
return dt_table_patch<qctable_v1>(hdr, file);
case 2:
fprintf(stderr, "QCDT v2\n");
return dt_table_patch<qctable_v2>(hdr, file);
case 3:
fprintf(stderr, "QCDT v3\n");
return dt_table_patch<qctable_v3>(hdr, file);
default:
return false;
}
} else if (MATCH(DTBH_MAGIC)) {
auto hdr = reinterpret_cast<dtbh_hdr *>(dtb);
switch (hdr->version) {
case 2:
fprintf(stderr, "DTBH v2\n");
return dt_table_patch<bhtable_v2>(hdr, file);
default:
return false;
}
} else if (MATCH(PXADT_MAGIC)) {
auto hdr = reinterpret_cast<pxadt_hdr *>(dtb);
switch (hdr->version) {
case 1:
fprintf(stderr, "PXA-DT v1\n");
return dt_table_patch<pxatable_v1>(hdr, file);
default:
return false;
}
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} else if (MATCH(PXA19xx_MAGIC)) {
auto hdr = reinterpret_cast<pxa19xx_hdr *>(dtb);
switch (hdr->version) {
case 1:
fprintf(stderr, "PXA-19xx v1\n");
return dt_table_patch<pxatable_v1>(hdr, file);
default:
return false;
}
} else if (MATCH(SPRD_MAGIC)) {
auto hdr = reinterpret_cast<sprd_hdr *>(dtb);
switch (hdr->version) {
case 1:
fprintf(stderr, "SPRD v1\n");
return dt_table_patch<sprdtable_v1>(hdr, file);
default:
return false;
}
} else if (MATCH(DT_TABLE_MAGIC)) {
auto hdr = reinterpret_cast<dt_table_header *>(dtb);
switch (hdr->version) {
case 0:
fprintf(stderr, "DT_TABLE v0\n");
return dt_table_patch<dt_table_entry>(hdr, file);
default:
return false;
}
} else {
return blob_patch(dtb, dtb_sz, file);
}
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}