Merge pull request #2 from fedimint/om/sdallocx

fix: Android SIGSEGV caused by weak sdallocx symbol in aws-lc-sys

Author: MrImmortal09

fedimint-client-uniffi/Cargo.lock

@@ -19,6 +19,10 @@ path = "uniffi-bindgen.rs"
 
 [dependencies]
 anyhow = "1.0.98"
+# Pin aws-lc-rs to 1.15.1 / aws-lc-sys to 0.34.0 (same as Fedi).
+# aws-lc-sys v0.35.0 introduced a jitter entropy init bug: SIGSEGV on
+# aarch64-android via aws_lc_0_35_0_tree_jitter_initialize → pthread_once → [anon:.bss]
+aws-lc-rs = { version = "=1.15.1" }
 fedimint-client-rpc = { version = "0.10.0" }
 fedimint-connectors = { version = "0.10.0" }
 fedimint-core = { version = "0.10.0" }
@@ -32,6 +36,7 @@ tokio = "1.48.0"
 uniffi = { version = "0.29", features = ["cli"] }
 
 [build-dependencies]
+cc = "1"
 fedimint-build = { version= "0.10.0" }
 uniffi = { version = "0.29", features = ["build"] }
 

fedimint-client-uniffi/Cargo.toml

@@ -1,3 +1,15 @@
 fn main() {
     fedimint_build::set_code_version();
+
+    // On Android, aws-lc declares `sdallocx` as a weak symbol and checks
+    // `if (sdallocx)` before calling it. Android's linker resolves the GLOB_DAT
+    // entry for weak undefined symbols to the PLT stub (non-NULL) while the
+    // JUMP_SLOT remains 0, causing a SIGSEGV. Provide a strong stub that
+    // delegates to free() so both GOT entries resolve correctly.
+    let target_os = std::env::var("CARGO_CFG_TARGET_OS").unwrap_or_default();
+    if target_os == "android" {
+        cc::Build::new()
+            .file("sdallocx_stub.c")
+            .compile("sdallocx_stub");
+    }
 }

fedimint-client-uniffi/build.rs

@@ -0,0 +1,19 @@
+// Stub for sdallocx to fix Android weak symbol resolution bug.
+//
+// aws-lc declares sdallocx as a weak symbol and checks `if (sdallocx)` before
+// calling it. On Android's linker, weak undefined symbols can have their
+// GLOB_DAT GOT entry resolved to the PLT stub (non-NULL) while the JUMP_SLOT
+// still resolves to 0. This causes the NULL check to pass but the actual call
+// to jump to address 0 (in .bss) → SIGSEGV "trying to execute non-executable
+// memory".
+//
+// Providing a strong definition of sdallocx that delegates to free() fixes this
+// by ensuring both the GOT and PLT entries resolve to a valid function.
+
+#include <stdlib.h>
+
+void sdallocx(void *ptr, size_t size, int flags) {
+    (void)size;
+    (void)flags;
+    free(ptr);
+}

fedimint-client-uniffi/sdallocx_stub.c

@@ -4,9 +4,22 @@ use fedimint_client_rpc::{RpcGlobalState, RpcRequest, RpcResponse, RpcResponseHa
 use fedimint_connectors::ConnectorRegistry;
 use fedimint_core::db::Database;
 
+// Force the linker to pull in our strong sdallocx stub from sdallocx_stub.c.
+// On Android, aws-lc declares sdallocx as a weak symbol. The Android linker
+// resolves weak GLOB_DAT entries to the PLT stub (non-NULL) while JUMP_SLOT
+// stays 0 → SIGSEGV. Our stub provides a strong definition that delegates to free().
+#[cfg(target_os = "android")]
+extern "C" {
+    fn sdallocx(ptr: *mut std::ffi::c_void, size: usize, flags: i32);
+}
+
+#[cfg(target_os = "android")]
+#[used]
+static FORCE_SDALLOCX: unsafe extern "C" fn(*mut std::ffi::c_void, usize, i32) = sdallocx;
+
 uniffi::setup_scaffolding!();
 
-const DB_FILE_NAME: &str = "fedimint.redb";
+const DB_DIR_NAME: &str = "fedimint_db";
 
 #[derive(Debug, thiserror::Error, uniffi::Error)]
 pub enum FedimintError {
@@ -93,7 +106,7 @@ impl RpcResponseHandler for CallbackWrapper {
 async fn create_database(path: &str) -> anyhow::Result<Database> {
     tokio::fs::create_dir_all(path).await?;
 
-    let db_path = std::path::Path::new(path).join(DB_FILE_NAME);
+    let db_path = std::path::Path::new(path).join(DB_DIR_NAME);
     let db = fedimint_rocksdb::RocksDb::build(db_path).open().await?;
 
     Ok(Database::new(db, Default::default()))