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wasm: implement relocations to set memory layout

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Brian Carroll 2022-05-29 12:17:13 +02:00
parent 73f0a7c96c
commit 9b47dada6a
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5 changed files with 127 additions and 80 deletions
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87
compiler/gen_wasm/src/wasm_module/serialize.rs
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@ -121,19 +121,23 @@ macro_rules! write_unencoded {
};
}
macro_rules! encode_padded_sleb128 {
($name: ident, $ty: ty) => {
/// write a maximally-padded SLEB128 integer (only used in relocations)
fn $name(&mut self, value: $ty) {
let mut x = value;
let size = (std::mem::size_of::<$ty>() / 4) * MAX_SIZE_ENCODED_U32;
for _ in 0..(size - 1) {
self.append_u8(0x80 | (x & 0x7f) as u8);
x >>= 7;
}
self.append_u8((x & 0x7f) as u8);
}
};
/// For relocations
pub fn overwrite_padded_i32(buffer: &mut [u8], offset: usize, value: i32) {
let mut x = value;
for byte in buffer.iter_mut().skip(offset).take(4) {
*byte = 0x80 | ((x & 0x7f) as u8);
x >>= 7;
}
buffer[4] = (x & 0x7f) as u8;
}
fn overwrite_padded_u32_help(buffer: &mut [u8], value: u32) {
let mut x = value;
for byte in buffer.iter_mut().take(4) {
*byte = 0x80 | ((x & 0x7f) as u8);
x >>= 7;
}
buffer[4] = x as u8;
}
pub trait SerialBuffer: Debug {
@ -163,17 +167,6 @@ pub trait SerialBuffer: Debug {
// methods for relocations
write_unencoded!(write_unencoded_u32, u32);
write_unencoded!(write_unencoded_u64, u64);
encode_padded_sleb128!(encode_padded_i32, i32);
encode_padded_sleb128!(encode_padded_i64, i64);
}
fn overwrite_padded_u32_help(buffer: &mut [u8], value: u32) {
let mut x = value;
for byte in buffer.iter_mut().take(4) {
*byte = 0x80 | ((x & 0x7f) as u8);
x >>= 7;
}
buffer[4] = x as u8;
}
impl SerialBuffer for std::vec::Vec<u8> {
@ -367,48 +360,18 @@ mod tests {
assert_eq!(buffer, &[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff]);
}
fn help_pad_i32(val: i32) -> std::vec::Vec<u8> {
let mut buffer = std::vec::Vec::with_capacity(MAX_SIZE_ENCODED_U32);
buffer.encode_padded_i32(val);
fn help_pad_i32(val: i32) -> [u8; MAX_SIZE_ENCODED_U32] {
let mut buffer = [0; MAX_SIZE_ENCODED_U32];
overwrite_padded_i32(&mut buffer, 0, val);
buffer
}
#[test]
fn test_encode_padded_i32() {
assert_eq!(help_pad_i32(0), &[0x80, 0x80, 0x80, 0x80, 0x00]);
assert_eq!(help_pad_i32(1), &[0x81, 0x80, 0x80, 0x80, 0x00]);
assert_eq!(help_pad_i32(-1), &[0xff, 0xff, 0xff, 0xff, 0x7f]);
assert_eq!(help_pad_i32(i32::MAX), &[0xff, 0xff, 0xff, 0xff, 0x07]);
assert_eq!(help_pad_i32(i32::MIN), &[0x80, 0x80, 0x80, 0x80, 0x78]);
}
fn help_pad_i64(val: i64) -> std::vec::Vec<u8> {
let mut buffer = std::vec::Vec::with_capacity(10);
buffer.encode_padded_i64(val);
buffer
}
#[test]
fn test_encode_padded_i64() {
assert_eq!(
help_pad_i64(0),
&[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x00]
);
assert_eq!(
help_pad_i64(1),
&[0x81, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x00]
);
assert_eq!(
help_pad_i64(-1),
&[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f]
);
assert_eq!(
help_pad_i64(i64::MAX),
&[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00],
);
assert_eq!(
help_pad_i64(i64::MIN),
&[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x7f],
);
assert_eq!(help_pad_i32(0), [0x80, 0x80, 0x80, 0x80, 0x00]);
assert_eq!(help_pad_i32(1), [0x81, 0x80, 0x80, 0x80, 0x00]);
assert_eq!(help_pad_i32(-1), [0xff, 0xff, 0xff, 0xff, 0x7f]);
assert_eq!(help_pad_i32(i32::MAX), [0xff, 0xff, 0xff, 0xff, 0x07]);
assert_eq!(help_pad_i32(i32::MIN), [0x80, 0x80, 0x80, 0x80, 0x78]);
}
}