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| author | Jacques Comeaux <jacquesrcomeaux@protonmail.com> | 2024-07-01 12:16:02 -0500 |
|---|---|---|
| committer | Jacques Comeaux <jacquesrcomeaux@protonmail.com> | 2024-07-01 12:16:02 -0500 |
| commit | 83aef192e447c800cba6f4dbde8a450a4f8581a5 (patch) | |
| tree | c5b21bb6238d9117057f3433d4122d66f4add9f8 /misc | |
| parent | 4e018fc5bdd4ff9ee6065a5167fa291404e20576 (diff) | |
Use in-house CRC32 computation for boot sector
Diffstat (limited to 'misc')
| -rw-r--r-- | misc/crc.s | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/misc/crc.s b/misc/crc.s new file mode 100644 index 0000000..03c0ce2 --- /dev/null +++ b/misc/crc.s @@ -0,0 +1,24 @@ +.syntax unified +.cpu cortex-m0plus +.thumb + +.type CRC32, %function +.global CRC32 + +// R0 = input addr +// R1 = length +CRC32: LDR R5, =0x04C11DB7 + LDR R4, =0xFFFFFFFF +10: LDR R2, [R0] + REV R2, R2; + EORS R4, R2 + MOVS R3, 32 +20: LSLS R4, 1 + BCC 30f + EORS R4, R5 +30: SUBS R3, 1 + BNE 20b + ADDS R0, 4 + SUBS R1, 1 + BNE 10b + BX LR |