Magisk/native/jni/magiskboot/dtb.cpp

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#include <unistd.h>
#include <sys/mman.h>
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extern "C" {
#include <libfdt.h>
}
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#include <utils.h>
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#include <bitset>
#include <vector>
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#include "magiskboot.h"
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#include "format.h"
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using namespace std;
constexpr int MAX_DEPTH = 32;
static bitset<MAX_DEPTH> depth_set;
static void pretty_node(int depth) {
if (depth == 0)
return;
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;
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int prop;
fdt_for_each_property_offset(prop, fdt, node) {
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pretty_prop(depth);
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int size;
const char *name;
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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);
}
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}
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// 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)
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return fstab;
}
return -1;
}
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static void dtb_print(const char *file, bool fstab) {
size_t size;
uint8_t *dtb;
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fprintf(stderr, "Loading dtbs from [%s]\n", file);
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mmap_ro(file, dtb, size);
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// Loop through all the dtbs
int dtb_num = 0;
for (int i = 0; i < size; ++i) {
if (memcmp(dtb + i, DTB_MAGIC, 4) == 0) {
auto fdt = dtb + i;
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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;
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}
}
fprintf(stderr, "\n");
munmap(dtb, size);
exit(0);
}
static void dtb_patch(const char *in, const char *out) {
bool keepverity = check_env("KEEPVERITY");
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bool redirect = check_env("TWOSTAGEINIT");
vector<uint8_t *> fdt_list;
size_t dtb_sz ;
uint8_t *dtb;
fprintf(stderr, "Loading dtbs from [%s]\n", in);
mmap_ro(in, dtb, dtb_sz);
bool modified = false;
for (int i = 0; i < dtb_sz; ++i) {
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if (memcmp(dtb + i, DTB_MAGIC, 4) == 0) {
int len = fdt_totalsize(dtb + i);
auto fdt = static_cast<uint8_t *>(xmalloc(redirect ? len + 256 : len));
memcpy(fdt, dtb + i, len);
if (redirect)
fdt_open_into(fdt, fdt, len + 256);
int fstab = find_fstab(fdt);
if (fstab < 0)
continue;
fprintf(stderr, "Found fstab in dtb.%04d\n", fdt_list.size());
int block;
fdt_for_each_subnode(block, fdt, fstab) {
const char *name = fdt_get_name(fdt, block, nullptr);
fprintf(stderr, "Found entry [%s] in fstab\n", name);
if (!keepverity) {
uint32_t size;
auto value = static_cast<const char *>(
fdt_getprop(fdt, block, "fsmgr_flags", reinterpret_cast<int *>(&size)));
char *pval = patch_verity(value, size);
if (pval) {
modified = true;
fdt_setprop_string(fdt, block, "fsmgr_flags", pval);
}
}
if (redirect && name == "system"sv) {
modified = true;
fprintf(stderr, "Changing mnt_point to /system_root\n");
fdt_setprop_string(fdt, block, "mnt_point", "/system_root");
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}
}
fdt_list.push_back(fdt);
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}
}
munmap(dtb, dtb_sz);
if (modified) {
if (!out)
out = in;
int fd = xopen(out, O_WRONLY | O_CREAT | O_CLOEXEC);
for (auto fdt : fdt_list) {
fdt_pack(fdt);
xwrite(fd, fdt, fdt_totalsize(fdt));
}
close(fd);
}
exit(!modified);
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}
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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);
} else if (argv[0] == "patch"sv) {
dtb_patch(dtb, argv[1]);
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} else {
return 1;
}
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return 0;
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}