From f63bc569fab1450def4c817f100e580dddb425c5 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Mon, 11 Sep 2023 13:33:27 +0200
Subject: [PATCH] Windows/ARM64: Fix exception unwinding.

Thanks to Peter Cawley. #593
---
 src/host/buildvm_peobj.c | 14 +++++++-------
 src/lj_err.c             | 10 ++++++----
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/host/buildvm_peobj.c b/src/host/buildvm_peobj.c
index fc3ef71a..cdbb79b6 100644
--- a/src/host/buildvm_peobj.c
+++ b/src/host/buildvm_peobj.c
@@ -354,7 +354,7 @@ void emit_peobj(BuildCtx *ctx)
 #define CBE16(x)	(*p = ((x) >> 8) & 0xff, p[1] = (x) & 0xff, p += 2)
 #define CALLOC_S(s)	(*p++ = ((s) >> 4))  /* s < 512 */
 #define CSAVE_FPLR(o)	(*p++ = 0x40 | ((o) >> 3))  /* o <= 504 */
-#define CSAVE_REGP(r,o)	CBE16(0xc800 | (((r)-19)<< 6) | ((o) >> 3))
+#define CSAVE_REGP(r,o)	CBE16(0xc800 | (((r) - 19) << 6) | ((o) >> 3))
 #define CSAVE_REGS(r1,r2,o1) do { \
   int r, o; for (r = r1, o = o1; r <= r2; r += 2, o -= 16) CSAVE_REGP(r, o); \
 } while (0)
@@ -362,6 +362,7 @@ void emit_peobj(BuildCtx *ctx)
 #define CSAVE_FREGS(r1,r2,o1) do { \
   int r, o; for (r = r1, o = o1; r <= r2; r += 2, o -= 16) CSAVE_FREGP(r, o); \
 } while (0)
+#define CSAVE_REG(r,o)	CBE16(0xd000 | (((r) - 19) << 6) | (~(o) >> 3))
 #define CSAVE_REGX(r,o)	CBE16(0xd400 | (((r) - 19) << 5) | (~(o) >> 3))
 #define CADD_FP(s)	CBE16(0xe200 | ((s) >> 3))  /* s < 8*256 */
 #define CODE_NOP	0xe3
@@ -373,12 +374,11 @@ void emit_peobj(BuildCtx *ctx)
 
     /* Unwind codes for .text section with handler. */
     p = uwc;
-    CALLOC_S(208);		/* +1 */
-    CSAVE_FPLR(192);		/* +1 */
-    CADD_FP(192);		/* +2 */
     CSAVE_REGS(19, 28, 184);	/* +5*2 */
     CSAVE_FREGS(8, 15, 104);	/* +4*2 */
-    CEND_ALIGN;			/* +1 +1 -> 24 */
+    CSAVE_FPLR(192);		/* +1 */
+    CALLOC_S(208);		/* +1 */
+    CEND_ALIGN;			/* +1 +3 -> 24 */
 
     u32 = ((24u >> 2) << 27) | (1u << 20) | (fcofs >> 2);
     owrite(ctx, &u32, 4);
@@ -389,9 +389,9 @@ void emit_peobj(BuildCtx *ctx)
 
     /* Unwind codes for vm_ffi_call without handler. */
     p = uwc;
-    CSAVE_FPLR(16);		/* +1 */
     CADD_FP(16);		/* +2 */
-    CSAVE_REGX(19, -24);	/* +2 */
+    CSAVE_FPLR(16);		/* +1 */
+    CSAVE_REG(19, 8);		/* +2 */
     CSAVE_REGX(20, -32);	/* +2 */
     CEND_ALIGN;			/* +1 +0 -> 8 */
 
diff --git a/src/lj_err.c b/src/lj_err.c
index 6e50cbee..8ef51bf2 100644
--- a/src/lj_err.c
+++ b/src/lj_err.c
@@ -261,6 +261,8 @@ LJ_FUNCA int lj_err_unwind_win(EXCEPTION_RECORD *rec,
 {
 #if LJ_TARGET_X86
   void *cf = (char *)f - CFRAME_OFS_SEH;
+#elif LJ_TARGET_ARM64
+  void *cf = (char *)f - CFRAME_SIZE;
 #else
   void *cf = f;
 #endif
@@ -297,11 +299,11 @@ LJ_FUNCA int lj_err_unwind_win(EXCEPTION_RECORD *rec,
 #else
       /* Unwind the stack and call all handlers for all lower C frames
       ** (including ourselves) again with EH_UNWINDING set. Then set
-      ** stack pointer = cf, result = errcode and jump to the specified target.
+      ** stack pointer = f, result = errcode and jump to the specified target.
       */
-      RtlUnwindEx(cf, (void *)((cframe_unwind_ff(cf2) && errcode != LUA_YIELD) ?
-			       lj_vm_unwind_ff_eh :
-			       lj_vm_unwind_c_eh),
+      RtlUnwindEx(f, (void *)((cframe_unwind_ff(cf2) && errcode != LUA_YIELD) ?
+			      lj_vm_unwind_ff_eh :
+			      lj_vm_unwind_c_eh),
 		  rec, (void *)(uintptr_t)errcode, ctx, dispatch->HistoryTable);
       /* RtlUnwindEx should never return. */
 #endif