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eboot: .RODATA, upstream uzlib, move CRC, save 112 bytes (#7844)

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RODATA can be copied automatically by the bootrom, so no reason not to
allow its use for strings and constants in eboot.c

Revert to pfalcon's original uzlib since the single patch to remove
RODATA is not required.

Rationalize eboot.ld linker script, clean up BSS and init it in code.

Saves 112 bytes of space in the bootloader sector by removing the
extra code associated with literal loads.

* Move CRC out of bootload sector

We added protection to only erase the bootload sector when flashing an
image when the new sector != the old sector.  This was intended to
minimize the chance of bricking (i.e. if there was a powerfail during
flashing of the boot sector the chip would be dead).

Unfortunately, by placing the CRC inside the eboot sector *every*
application will have a unique eboot sector (due to the crc/len), so
this protection doesn't work.

Move the CRC into the first 8 bytes of IROM itself.  This frees up extra
space in the boot sector and ensures that eboot won't be reflashed
unless there really is an eboot change.
This commit is contained in:
Earle F. Philhower, III
2021-02-07 16:32:56 -08:00
committed by GitHub
parent 6c564c269c
commit 07b4c09b90
9 changed files with 68 additions and 109 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
cores/esp8266/Esp.cpp
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@ -444,22 +444,24 @@ bool EspClass::checkFlashConfig(bool needsEquals) {
return false;
}
// These are defined in the linker script, and filled in by the elf2bin.py util
extern "C" uint32_t __crc_len;
extern "C" uint32_t __crc_val;
bool EspClass::checkFlashCRC() {
// The CRC and total length are placed in extra space at the end of the 4K chunk
// of flash occupied by the bootloader. If the bootloader grows to >4K-8 bytes,
// we'll need to adjust this.
uint32_t flashsize = *((uint32_t*)(0x40200000 + 4088)); // Start of PROGMEM plus 4K-8
uint32_t flashcrc = *((uint32_t*)(0x40200000 + 4092)); // Start of PROGMEM plus 4K-4
// Dummy CRC fill
uint32_t z[2];
z[0] = z[1] = 0;
uint32_t firstPart = (uintptr_t)&__crc_len - 0x40200000; // How many bytes to check before the 1st CRC val
// Start the checksum
uint32_t crc = crc32((const void*)0x40200000, 4096-8, 0xffffffff);
uint32_t crc = crc32((const void*)0x40200000, firstPart, 0xffffffff);
// Pretend the 2 words of crc/len are zero to be idempotent
crc = crc32(z, 8, crc);
// Finish the CRC calculation over the rest of flash
crc = crc32((const void*)0x40201000, flashsize-4096, crc);
return crc == flashcrc;
crc = crc32((const void*)(0x40200000 + firstPart + 8), __crc_len - (firstPart + 8), crc);
return crc == __crc_val;
}