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Implemented position independent addresses for x86

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This commit is contained in:
Eduard Urbach 2025-03-07 11:39:13 +01:00
parent 014f161633
commit 0765351891
Signed by: eduard
GPG key ID: 49226B848C78F6C8
3 changed files with 68 additions and 13 deletions
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13
src/x86/LoadAddress.go Normal file
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package x86
import (
"encoding/binary"
"git.urbach.dev/cli/q/src/cpu"
)
// LoadAddress calculates the address with the RIP-relative offset and writes the result to the destination register.
func LoadAddress(code []byte, destination cpu.Register, offset int) []byte {
code = encode(code, AddressMemory, destination, 0b101, 8, 0x8D)
return binary.LittleEndian.AppendUint32(code, uint32(offset))
}

40
src/x86/LoadAddress_test.go Normal file
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package x86_test
import (
"testing"
"git.urbach.dev/cli/q/src/cpu"
"git.urbach.dev/cli/q/src/x86"
"git.urbach.dev/go/assert"
)
func TestLoadAddress(t *testing.T) {
usagePatterns := []struct {
Destination cpu.Register
Offset int
Code []byte
}{
{x86.RAX, 0, []byte{0x48, 0x8D, 0x05, 0x00, 0x00, 0x00, 0x00}},
{x86.RCX, 0, []byte{0x48, 0x8D, 0x0D, 0x00, 0x00, 0x00, 0x00}},
{x86.RDX, 0, []byte{0x48, 0x8D, 0x15, 0x00, 0x00, 0x00, 0x00}},
{x86.RBX, 0, []byte{0x48, 0x8D, 0x1D, 0x00, 0x00, 0x00, 0x00}},
{x86.RSP, 0, []byte{0x48, 0x8D, 0x25, 0x00, 0x00, 0x00, 0x00}},
{x86.RBP, 0, []byte{0x48, 0x8D, 0x2D, 0x00, 0x00, 0x00, 0x00}},
{x86.RSI, 0, []byte{0x48, 0x8D, 0x35, 0x00, 0x00, 0x00, 0x00}},
{x86.RDI, 0, []byte{0x48, 0x8D, 0x3D, 0x00, 0x00, 0x00, 0x00}},
{x86.R8, 0, []byte{0x4C, 0x8D, 0x05, 0x00, 0x00, 0x00, 0x00}},
{x86.R9, 0, []byte{0x4C, 0x8D, 0x0D, 0x00, 0x00, 0x00, 0x00}},
{x86.R10, 0, []byte{0x4C, 0x8D, 0x15, 0x00, 0x00, 0x00, 0x00}},
{x86.R11, 0, []byte{0x4C, 0x8D, 0x1D, 0x00, 0x00, 0x00, 0x00}},
{x86.R12, 0, []byte{0x4C, 0x8D, 0x25, 0x00, 0x00, 0x00, 0x00}},
{x86.R13, 0, []byte{0x4C, 0x8D, 0x2D, 0x00, 0x00, 0x00, 0x00}},
{x86.R14, 0, []byte{0x4C, 0x8D, 0x35, 0x00, 0x00, 0x00, 0x00}},
{x86.R15, 0, []byte{0x4C, 0x8D, 0x3D, 0x00, 0x00, 0x00, 0x00}},
}
for _, pattern := range usagePatterns {
t.Logf("lea %s, [rip+%d]", pattern.Destination, pattern.Offset)
code := x86.LoadAddress(nil, pattern.Destination, pattern.Offset)
assert.DeepEqual(t, code, pattern.Code)
}
}