go-patches: add exception search fix, CL340070

https://go-review.googlesource.com/c/go/+/340070

Also, move to using `git format-patch --no-numbered --zero-commit` so
that there's less churn when adding patches.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

2 files changed, 48 insertions, 1 deletions

diff --git a/go-patches/0001-runtime-allow-builtin-write-function-to-be-redirecte.patch b/go-patches/0001-runtime-allow-builtin-write-function-to-be-redirecte.patch
index d6a1ac65..c2a5dd52 100644
--- a/go-patches/0001-runtime-allow-builtin-write-function-to-be-redirecte.patch
+++ b/go-patches/0001-runtime-allow-builtin-write-function-to-be-redirecte.patch
@@ -1,4 +1,4 @@
-From 1c566ea2420f0503c8494e361bccb943d83c135c Mon Sep 17 00:00:00 2001
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
 From: "Jason A. Donenfeld" <Jason@zx2c4.com>
 Date: Thu, 3 Dec 2020 13:29:58 +0100
 Subject: [PATCH] runtime: allow builtin write function to be redirected with
diff --git a/go-patches/0002-runtime-allow-arm64-SEH-to-be-called-if-illegal-inst.patch b/go-patches/0002-runtime-allow-arm64-SEH-to-be-called-if-illegal-inst.patch
new file mode 100644
index 00000000..3537f493
--- /dev/null
+++ b/go-patches/0002-runtime-allow-arm64-SEH-to-be-called-if-illegal-inst.patch
@@ -0,0 +1,47 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: "Jason A. Donenfeld" <Jason@zx2c4.com>
+Date: Thu, 5 Aug 2021 13:37:29 +0200
+Subject: [PATCH] runtime: allow arm64 SEH to be called if illegal instruction
+
+DLLs built with recent Microsoft toolchains for ARM64 test for ARMv8.1
+atomics by potentially calling an illegal instruction, and then trapping
+the exception to disable use of them by way of a structured exception
+handler. However, vectored exception handlers are always called before
+structured exception handlers. When LoadLibrary-ing DLLs that do this
+probing during initialization, our lastcontinuehandler winds up being
+called, and then crashing, but actually it should give execution back to
+the library to handle the exception and fix up the state. So special
+case this for arm64 with illegal instructions, and hope that we're not
+masking other things in external DLLs that might more fatally trigger an
+illegal instruction exception.
+
+Change-Id: I341ab99cd8d513ae999b75596749d49779072022
+---
+ src/runtime/signal_windows.go | 11 +++++++++++
+ 1 file changed, 11 insertions(+)
+
+diff --git a/src/runtime/signal_windows.go b/src/runtime/signal_windows.go
+index f2ce24d735..b720ddcf16 100644
+--- a/src/runtime/signal_windows.go
++++ b/src/runtime/signal_windows.go
+@@ -183,6 +183,17 @@ func lastcontinuehandler(info *exceptionrecord, r *context, gp *g) int32 {
+ 		return _EXCEPTION_CONTINUE_SEARCH
+ 	}
+ 
++	// VEH is called before SEH, but arm64 MSVC DLLs use SEH to trap
++	// illegal instructions during runtime initialization to determine
++	// CPU features, so if we make it to the last handler and we're
++	// arm64 and it's an illegal instruction and this is coming from
++	// non-Go code, then assume it's this runtime probing happen, and
++	// pass that onward to SEH.
++	if GOARCH == "arm64" && info.exceptioncode == _EXCEPTION_ILLEGAL_INSTRUCTION &&
++		(r.ip() < firstmoduledata.text || firstmoduledata.etext < r.ip()) {
++		return _EXCEPTION_CONTINUE_SEARCH
++	}
++
+ 	winthrow(info, r, gp)
+ 	return 0 // not reached
+ }
+-- 
+2.32.0
+