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Preserve fdt paddings

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Some Motorola devices (Qualcomm kernel with CONFIG_MMI_DEVICE_DTBS
configuration enabled) need 1k of padding to the DTBs to allow for
environment variables to be runtime added by the bootloader.
Those extra paddings will be removed during the process of dtb patch,
devices won’t be able to boot-up and return to fastboot mode immediately
after flashed the flawed boot.img.

Credits to @shakalaca, close #2273
This commit is contained in:
topjohnwu 2020-02-01 00:48:21 +08:00
parent 290624844b
commit 5c988510b3
1 changed files with 13 additions and 2 deletions
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15
native/jni/magiskboot/dtb.cpp
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@ -283,24 +283,35 @@ static int dt_table_patch(const Header *hdr, const char *out) {
static int blob_patch(uint8_t *dtb, size_t dtb_sz, const char *out) {
vector<uint8_t *> fdt_list;
vector<uint32_t> padding_list;
for (int i = 0; i < dtb_sz; ++i) {
if (memcmp(dtb + i, FDT_MAGIC_STR, 4) == 0) {
int len = fdt_totalsize(dtb + i);
auto len = fdt_totalsize(dtb + i);
auto fdt = static_cast<uint8_t *>(xmalloc(len + 256));
memcpy(fdt, dtb + i, len);
fdt_pack(fdt);
uint32_t padding = len - fdt_totalsize(fdt);
padding_list.push_back(padding);
fdt_open_into(fdt, fdt, len + 256);
fdt_list.push_back(fdt);
i += len - 1;
}
}
if (!fdt_patch(fdt_list.begin(), fdt_list.end()))
return 1;
unlink(out);
int fd = xopen(out, O_WRONLY | O_CREAT | O_CLOEXEC, 0644);
for (auto fdt : fdt_list) {
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);
}