From 5c7f2ab011f9c1cd522ab76a674d0acc5f397041 Mon Sep 17 00:00:00 2001
From: Kenta Iwasaki <kenta@lithdew.net>
Date: Mon, 20 Dec 2021 00:30:49 +0900
Subject: [PATCH] stage1: deal with BPF not supporting @returnAddress()

Make `@returnAddress()` return for the BPF target, as the BPF target for
the time being does not support probing for the return address. Stack
traces for the general purpose allocator for the BPF target is also set
to not be captured.
---
 lib/std/heap/general_purpose_allocator.zig | 5 +++++
 src/stage1/codegen.cpp                     | 2 +-
 src/stage1/target.cpp                      | 4 ++++
 src/stage1/target.hpp                      | 1 +
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/std/heap/general_purpose_allocator.zig b/lib/std/heap/general_purpose_allocator.zig
index 9900823d5b..dfef8016d5 100644
--- a/lib/std/heap/general_purpose_allocator.zig
+++ b/lib/std/heap/general_purpose_allocator.zig
@@ -118,6 +118,11 @@ const sys_can_stack_trace = switch (builtin.cpu.arch) {
     .wasm64,
     => builtin.os.tag == .emscripten,
 
+    // `@returnAddress()` is unsupported in LLVM 13.
+    .bpfel,
+    .bpfeb,
+    => false,
+
     else => true,
 };
 const default_test_stack_trace_frames: usize = if (builtin.is_test) 8 else 4;
diff --git a/src/stage1/codegen.cpp b/src/stage1/codegen.cpp
index ff4d44113e..335af423a8 100644
--- a/src/stage1/codegen.cpp
+++ b/src/stage1/codegen.cpp
@@ -6208,7 +6208,7 @@ static LLVMValueRef ir_render_breakpoint(CodeGen *g, Stage1Air *executable, Stag
 static LLVMValueRef ir_render_return_address(CodeGen *g, Stage1Air *executable,
         Stage1AirInstReturnAddress *instruction)
 {
-    if (target_is_wasm(g->zig_target) && g->zig_target->os != OsEmscripten) {
+    if ((target_is_wasm(g->zig_target) && g->zig_target->os != OsEmscripten) || target_is_bpf(g->zig_target)) {
         // I got this error from LLVM 10:
         // "Non-Emscripten WebAssembly hasn't implemented __builtin_return_address"
         return LLVMConstNull(get_llvm_type(g, instruction->base.value->type));
diff --git a/src/stage1/target.cpp b/src/stage1/target.cpp
index 106c77854d..feb2c7f143 100644
--- a/src/stage1/target.cpp
+++ b/src/stage1/target.cpp
@@ -940,6 +940,10 @@ bool target_is_wasm(const ZigTarget *target) {
     return target->arch == ZigLLVM_wasm32 || target->arch == ZigLLVM_wasm64;
 }
 
+bool target_is_bpf(const ZigTarget *target) {
+    return target->arch == ZigLLVM_bpfel || target->arch == ZigLLVM_bpfeb;
+}
+
 ZigLLVM_EnvironmentType target_default_abi(ZigLLVM_ArchType arch, Os os) {
     if (arch == ZigLLVM_wasm32 || arch == ZigLLVM_wasm64) {
         return ZigLLVM_Musl;
diff --git a/src/stage1/target.hpp b/src/stage1/target.hpp
index cbd86071af..6851d88618 100644
--- a/src/stage1/target.hpp
+++ b/src/stage1/target.hpp
@@ -75,6 +75,7 @@ bool target_allows_addr_zero(const ZigTarget *target);
 bool target_has_valgrind_support(const ZigTarget *target);
 bool target_os_is_darwin(Os os);
 bool target_is_wasm(const ZigTarget *target);
+bool target_is_bpf(const ZigTarget *target);
 bool target_is_riscv(const ZigTarget *target);
 bool target_is_sparc(const ZigTarget *target);
 bool target_is_android(const ZigTarget *target);