From eac35edfd1101e8f7c34dbdd7b595fdac8f0ad4c Mon Sep 17 00:00:00 2001
From: Yuta Saito <kateinoigakukun@gmail.com>
Date: Tue, 18 Feb 2025 16:06:36 +0000
Subject: [PATCH] [wasm] Stop using mprotect(PROT_NONE) on WASI

we had been using a stub weak definition of `mprotect` in wasm/missing.c
so far, but wasi-sdk 23 added mprotect emulation to wasi-libc[^1], so the
emulation is now linked instead. However, the emulation doesn't support
PROT_NONE and fails with ENOSYS, so we need to avoid calling mprotect
completely on WASI.

[^1]: https://github.com/WebAssembly/wasi-libc/commit/7528b13170462c82e367d91ae0ecead84e470ceb
---
 cont.c               | 3 +++
 gc/default/default.c | 4 ++++
 wasm/missing.c       | 7 -------
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/cont.c b/cont.c
index 929bbd06c1..072ae4562f 100644
--- a/cont.c
+++ b/cont.c
@@ -551,6 +551,9 @@ fiber_pool_expand(struct fiber_pool * fiber_pool, size_t count)
             VirtualFree(allocation->base, 0, MEM_RELEASE);
             rb_raise(rb_eFiberError, "can't set a guard page: %s", ERRNOMSG);
         }
+#elif defined(__wasi__)
+        // wasi-libc's mprotect emulation doesn't support PROT_NONE.
+        (void)page;
 #else
         if (mprotect(page, RB_PAGE_SIZE, PROT_NONE) < 0) {
             munmap(allocation->base, count*stride);
diff --git a/gc/default/default.c b/gc/default/default.c
index 7e0049bb4f..4cf39a0331 100644
--- a/gc/default/default.c
+++ b/gc/default/default.c
@@ -3199,6 +3199,10 @@ protect_page_body(struct heap_page_body *body, DWORD protect)
     DWORD old_protect;
     return VirtualProtect(body, HEAP_PAGE_SIZE, protect, &old_protect) != 0;
 }
+#elif defined(__wasi__)
+// wasi-libc's mprotect emulation does not support PROT_NONE
+enum {HEAP_PAGE_LOCK, HEAP_PAGE_UNLOCK};
+#define protect_page_body(body, protect) 1
 #else
 enum {HEAP_PAGE_LOCK = PROT_NONE, HEAP_PAGE_UNLOCK = PROT_READ | PROT_WRITE};
 #define protect_page_body(body, protect) !mprotect((body), HEAP_PAGE_SIZE, (protect))
diff --git a/wasm/missing.c b/wasm/missing.c
index 5bbf988642..b9ecf520fd 100644
--- a/wasm/missing.c
+++ b/wasm/missing.c
@@ -119,13 +119,6 @@ umask(rb_mode_t mask)
     return 0;
 }
 
-WASM_MISSING_LIBC_FUNC
-int
-mprotect(const void *addr, size_t len, int prot)
-{
-    return 0;
-}
-
 WASM_MISSING_LIBC_FUNC
 int
 pclose(FILE *stream)