[release-branch.go1.16] cmd/link: increase reserved space for passing env on wasm

On wasm, the wasm_exec.js helper passes the command line arguments and
environment variables via a reserved space in the wasm linear memory.
Increase this reserved space from 4096 to 8192 bytes so more environment
variables can fit into the limit.

Later, after https://golang.org/cl/350737 landed, we can switch to the
WASI interface for getting the arguments and environment. This would
remove the limit entirely.

Updates #49011.
Fixes #49153.

Change-Id: I48a6e952a97d33404ed692c98e9b49c5cd6b269b
Reviewed-on: https://go-review.googlesource.com/c/go/+/358194
Trust: Richard Musiol <neelance@gmail.com>
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
(cherry picked from commit 252324e879e32f948d885f787decf8af06f82be9)
Reviewed-on: https://go-review.googlesource.com/c/go/+/359400
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>

diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index a0a264278b1b1d2a7e7232d111a3009241a01f77..48164c3a4be655330ce63a1f8f46b56de3ca2520 100644 (file)
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -566,9 +566,9 @@
 
                        // The linker guarantees global data starts from at least wasmMinDataAddr.
                        // Keep in sync with cmd/link/internal/ld/data.go:wasmMinDataAddr.
-                       const wasmMinDataAddr = 4096 + 4096;
+                       const wasmMinDataAddr = 4096 + 8192;
                        if (offset >= wasmMinDataAddr) {
-                               throw new Error("command line too long");
+                               throw new Error("total length of command line and environment variables exceeds limit");
                        }
 
                        this._inst.exports.run(argc, argv);

diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index 54a1d188cdb955d8e35c3d9ce009424e7cd4907a..7028b85cac99a8790f28309f11fc0cab55c8d257 100644 (file)
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -2330,10 +2330,11 @@ func assignAddress(ctxt *Link, sect *sym.Section, n int, s loader.Sym, va uint64
        return sect, n, va
 }
 
-// On Wasm, we reserve 4096 bytes for zero page, then 4096 bytes for wasm_exec.js
-// to store command line args. Data sections starts from at least address 8192.
+// On Wasm, we reserve 4096 bytes for zero page, then 8192 bytes for wasm_exec.js
+// to store command line args and environment variables.
+// Data sections starts from at least address 12288.
 // Keep in sync with wasm_exec.js.
-const wasmMinDataAddr = 4096 + 4096
+const wasmMinDataAddr = 4096 + 8192
 
 // address assigns virtual addresses to all segments and sections and
 // returns all segments in file order.