From c876bf9346f1afb5471947a65fb1e105caeff433 Mon Sep 17 00:00:00 2001 From: Cherry Mui Date: Thu, 29 Feb 2024 14:27:57 -0500 Subject: [PATCH] cmd/internal/obj/wasm: use 64-bit instructions for indirect calls Currently, on Wasm, an indirect call is compiled to // function index = PC>>16, PC is already on stack I32WrapI64 I32Const $16 ShrU // set PC_B to 0 ... // actual call CallIndirect Specifically, the function index is extracted from bits 16-31 of the "PC". When there are more than 65536 functions, this will overflow and wrap around, causing wrong function being called. This CL changes it to use 64-bit operations to extract the function index from the "PC", so there are enough bits to for it. For #64856. Change-Id: I83c11db4b78cf66250e88ac02a82bd13730a8914 Reviewed-on: https://go-review.googlesource.com/c/go/+/567896 LUCI-TryBot-Result: Go LUCI Reviewed-by: Than McIntosh Reviewed-by: Dmitri Shuralyov --- src/cmd/internal/obj/wasm/wasmobj.go | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/src/cmd/internal/obj/wasm/wasmobj.go b/src/cmd/internal/obj/wasm/wasmobj.go index 9a3520f319..e8bf927a82 100644 --- a/src/cmd/internal/obj/wasm/wasmobj.go +++ b/src/cmd/internal/obj/wasm/wasmobj.go @@ -465,9 +465,9 @@ func preprocess(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) { case obj.TYPE_NONE: // (target PC is on stack) + p = appendp(p, AI64Const, constAddr(16)) // only needs PC_F bits (16-63), PC_B bits (0-15) are zero + p = appendp(p, AI64ShrU) p = appendp(p, AI32WrapI64) - p = appendp(p, AI32Const, constAddr(16)) // only needs PC_F bits (16-31), PC_B bits (0-15) are zero - p = appendp(p, AI32ShrU) // Set PC_B parameter to function entry. // We need to push this before pushing the target PC_F, @@ -521,9 +521,9 @@ func preprocess(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) { case obj.TYPE_NONE: // (target PC is on stack) + p = appendp(p, AI64Const, constAddr(16)) // only needs PC_F bits (16-63), PC_B bits (0-15) are zero + p = appendp(p, AI64ShrU) p = appendp(p, AI32WrapI64) - p = appendp(p, AI32Const, constAddr(16)) // only needs PC_F bits (16-31), PC_B bits (0-15) are zero - p = appendp(p, AI32ShrU) // Set PC_B parameter to function entry. // We need to push this before pushing the target PC_F, -- 2.50.0