From ddce5e03c21bae4c628d46b37938c9f511c1f435 Mon Sep 17 00:00:00 2001
From: Simon Wanner <simon+git@skyrising.xyz>
Date: Sun, 29 Oct 2023 02:24:51 +0200
Subject: [PATCH] LibJS/JIT: Clear unwind context handler on usage

This clears the handler pointer of the current unwind context
before jumping to it. This is necessary to not loop infinitely
when an exception is thrown from the handler.
In that case control flow should go to the finalizer instead.

This mirrors how unwind_context.handler_called is used in the
Bytecode::Interpreter.

`try { throw 1 } catch (e) { throw 2 } finally {}` now runs
without looping infinitely in the catch block.
---
 Userland/Libraries/LibJS/JIT/Compiler.cpp | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/Userland/Libraries/LibJS/JIT/Compiler.cpp b/Userland/Libraries/LibJS/JIT/Compiler.cpp
index 10a9507982..c22c3eb43b 100644
--- a/Userland/Libraries/LibJS/JIT/Compiler.cpp
+++ b/Userland/Libraries/LibJS/JIT/Compiler.cpp
@@ -346,10 +346,6 @@ void Compiler::handle_exception()
     handle_exception.link(m_assembler);
 
     // if (unwind_context.handler) {
-    //     accumulator = exception;
-    //     exception = Value();
-    //     goto handler;
-    // }
     Assembler::Label no_handler {};
     m_assembler.mov(
         Assembler::Operand::Register(GPR0),
@@ -358,13 +354,24 @@ void Compiler::handle_exception()
         Assembler::Operand::Register(GPR0),
         Assembler::Operand::Imm(0),
         no_handler);
+    //     accumulator = exception;
     load_vm_register(GPR1, Bytecode::Register::exception());
     store_vm_register(Bytecode::Register::accumulator(), GPR1);
+    //     exception = Value();
     m_assembler.mov(
         Assembler::Operand::Register(GPR1),
         Assembler::Operand::Imm(Value().encoded()));
     store_vm_register(Bytecode::Register::exception(), GPR1);
+    //     unwind_context.handler = nullptr;
+    m_assembler.mov(
+        Assembler::Operand::Register(GPR1),
+        Assembler::Operand::Imm(0));
+    m_assembler.mov(
+        Assembler::Operand::Mem64BaseAndOffset(UNWIND_CONTEXT_BASE, 8),
+        Assembler::Operand::Register(GPR1));
+    //     goto handler;
     m_assembler.jump(Assembler::Operand::Register(GPR0));
+    // }
 
     // no_handler:
     no_handler.link(m_assembler);