From: Dimitris Panokostas <midwan@gmail.com>
Date: Tue, 19 May 2026 21:56:20 +0000 (+0200)
Subject: Include ModRM byte in x64 RIP range check
X-Git-Url: https://git.unchartedbackwaters.co.uk/w/?a=commitdiff_plain;h=19e2abc2f762c85d2bb831a9baac6dbc5a7459ee;p=francis%2Fwinuae.git

Include ModRM byte in x64 RIP range check
---

diff --git a/jit/codegen_x86.h b/jit/codegen_x86.h
index 49f76f6c..43b783f6 100644
--- a/jit/codegen_x86.h
+++ b/jit/codegen_x86.h
@@ -423,11 +423,11 @@ static inline int x86_RIP_addressing_possible(uintptr addr, uintptr offset)
 #if X86_TARGET_64BIT
 	/*
 	 * address of the next instruction.
-	 * The opcode has already been emitted,
-	 * so this is the size of a 32-bit displacement +
+	 * The opcode has already been emitted, but the ModR/M byte has not,
+	 * so this is the size of the ModR/M byte + a 32-bit displacement +
 	 * the size of any immediate value that is part of the instruction (offset),
 	 */
-	uintptr next = (uintptr)get_target() + 4 + offset;
+	uintptr next = (uintptr)get_target() + 1 + 4 + offset;
 	if (addr >= next) {
 		return addr - next <= 0x7fffffffULL;
 	}