From bb0515bf11e2e197cefb307eed55e3db5ca04355 Mon Sep 17 00:00:00 2001
From: Mrmaxmeier <Mrmaxmeier@gmail.com>
Date: Mon, 20 Nov 2023 15:19:43 +0000
Subject: [PATCH] cranelift-jit: implement GOT relocations for aarch64

---
 cranelift/codegen/src/binemit/mod.rs |  2 +-
 cranelift/jit/src/compiled_blob.rs   | 29 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/cranelift/codegen/src/binemit/mod.rs b/cranelift/codegen/src/binemit/mod.rs
index 9eed2905c4cd..14509736e8b7 100644
--- a/cranelift/codegen/src/binemit/mod.rs
+++ b/cranelift/codegen/src/binemit/mod.rs
@@ -81,7 +81,7 @@ pub enum Reloc {
     Aarch64TlsDescCall,
 
     /// AArch64 GOT Page
-    /// Set the immediate value of an ADRP to bits 32:12 of X; check that –232 <= X < 232
+    /// Set the immediate value of an ADRP to bits 32:12 of X; check that –2^32 <= X < 2^32
     /// This is equivalent to `R_AARCH64_ADR_GOT_PAGE` (311) in the  [aaelf64](https://github.com/ARM-software/abi-aa/blob/2bcab1e3b22d55170c563c3c7940134089176746/aaelf64/aaelf64.rst#static-aarch64-relocations)
     Aarch64AdrGotPage21,
 
diff --git a/cranelift/jit/src/compiled_blob.rs b/cranelift/jit/src/compiled_blob.rs
index f4f134023ea2..904cb79ae6a4 100644
--- a/cranelift/jit/src/compiled_blob.rs
+++ b/cranelift/jit/src/compiled_blob.rs
@@ -93,6 +93,35 @@ impl CompiledBlob {
                     let imm26 = (diff as u32) << chop >> chop;
                     unsafe { modify_inst32(iptr, |inst| inst | imm26) };
                 }
+                Reloc::Aarch64AdrGotPage21 => {
+                    // Set the immediate value of an ADRP to bits [32:12] of X; check that –2^32 <= X < 2^32
+                    assert_eq!(addend, 0, "addend affects the address looked up in get_got_entry, which is currently only called with a symbol");
+                    let what = get_got_entry(name);
+                    let what_page = (what as usize) & !0xfff;
+                    let at_page = (at as usize) & !0xfff;
+                    let pcrel = (what_page as isize).checked_sub(at_page as isize).unwrap();
+                    assert!(
+                        (-1 << 32) <= pcrel && pcrel < (1 << 32),
+                        "can't reach GOT page with ±4GB `adrp` instruction"
+                    );
+                    let val = pcrel >> 12;
+
+                    let immlo = ((val as u32) & 0b11) << 29;
+                    let immhi = (((val as u32) >> 2) & &0x7ffff) << 5;
+                    let mask = !((0x7ffff << 5) | (0b11 << 29));
+                    unsafe { modify_inst32(at as *mut u32, |adrp| (adrp & mask) | immlo | immhi) };
+                }
+                Reloc::Aarch64Ld64GotLo12Nc => {
+                    // Set the LD/ST immediate field to bits 11:3 of X. No overflow check; check that X&7 = 0
+                    assert_eq!(addend, 0);
+                    let base = get_got_entry(name);
+                    let what = base as u32;
+                    assert_eq!(what & 0b111, 0);
+                    let val = what >> 3;
+                    let imm9 = (val & 0x1ff) << 10;
+                    let mask = !(0x1ff << 10);
+                    unsafe { modify_inst32(at as *mut u32, |ldr| (ldr & mask) | imm9) };
+                }
                 Reloc::RiscvCallPlt => {
                     // A R_RISCV_CALL_PLT relocation expects auipc+jalr instruction pair.
                     // It is the equivalent of two relocations: