aya-ebpf: introduce `panic_handler` macro

All eBPF crates need to define a panic-handler.
To deduplicate that code, we introduce a macro for it.

ebpf/aya-ebpf/src/lib.rs

@@ -133,6 +133,24 @@ pub fn check_bounds_signed(value: i64, lower: i64, upper: i64) -> bool {
     }
 }
 
+#[macro_export]
+macro_rules! panic_handler {
+    () => {
+        /// Defines the panic handler when compiling for eBPF.
+        ///
+        /// eBPF programs don't support the concept of a panic and therefore, compiling a program that includes panics should fail at link time.
+        ///
+        /// Yet, as part of compiling for `no_std`, we need to define a panic handler.
+        /// The eBPF verifier enforces that programs terminate and will thus reject unbounded loops.
+        /// By using an endless loop within our panic handler, we can ensure that if this panic handler were somehow linked into the program, the eBPF verifier would reject it.
+        #[cfg(not(test))]
+        #[panic_handler]
+        fn panic(_info: &core::panic::PanicInfo) -> ! {
+            loop {}
+        }
+    };
+}
+
 #[inline]
 fn insert<K, V>(
     def: *mut bindings::bpf_map_def,

test/integration-ebpf/src/bpf_probe_read.rs

@@ -72,8 +72,4 @@ pub fn test_bpf_probe_read_kernel_str_bytes(ctx: ProbeContext) {
     );
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/log.rs

@@ -82,8 +82,4 @@ pub fn test_log(ctx: ProbeContext) {
     }
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/map_test.rs

@@ -36,8 +36,4 @@ pub fn simple_prog(_ctx: SkBuffContext) -> i64 {
     0
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/memmove_test.rs

@@ -54,8 +54,4 @@ fn try_do_dnat(ctx: XdpContext) -> Result<u32, ()> {
     Ok(xdp_action::XDP_PASS)
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/name_test.rs

@@ -15,8 +15,4 @@ unsafe fn try_pass(_ctx: XdpContext) -> Result<u32, u32> {
     Ok(xdp_action::XDP_PASS)
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/pass.rs

@@ -17,8 +17,4 @@ unsafe fn try_pass(_ctx: XdpContext) -> Result<u32, u32> {
     Ok(xdp_action::XDP_PASS)
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/raw_tracepoint.rs

@@ -26,8 +26,4 @@ pub fn sys_enter(ctx: RawTracePointContext) -> i32 {
     0
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/redirect.rs

@@ -75,8 +75,4 @@ fn inc_hit(index: u32) {
     }
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/relocations.rs

@@ -39,8 +39,4 @@ fn set_result_backward(index: u32, value: u64) {
     set_result(index, value);
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/ring_buf.rs

@@ -46,8 +46,4 @@ pub fn ring_buf_test(ctx: ProbeContext) {
     }
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/simple_prog.rs

@@ -12,8 +12,4 @@ pub fn simple_prog(_ctx: SkBuffContext) -> i64 {
     0
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/strncmp.rs

@@ -27,8 +27,4 @@ pub fn test_bpf_strncmp(ctx: ProbeContext) -> Result<(), c_long> {
     Ok(())
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/tcx.rs

@@ -8,8 +8,4 @@ pub fn tcx_next(_ctx: TcContext) -> i32 {
     TCX_NEXT
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/test.rs

@@ -53,8 +53,4 @@ pub fn test_flow(_ctx: FlowDissectorContext) -> u32 {
     bpf_ret_code::BPF_FLOW_DISSECTOR_CONTINUE
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/two_progs.rs

@@ -14,8 +14,4 @@ pub fn test_tracepoint_two(_ctx: TracePointContext) -> u32 {
     0
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/uprobe_cookie.rs

@@ -18,8 +18,4 @@ pub fn uprobe_cookie(ctx: ProbeContext) {
     let _res = RING_BUF.output(&cookie_bytes, 0);
 }
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

test/integration-ebpf/src/xdp_sec.rs

@@ -19,8 +19,4 @@ probe!(xdp_devmap, (map = "devmap"));
 probe!(xdp_frags_cpumap, (frags, map = "cpumap"));
 probe!(xdp_frags_devmap, (frags, map = "devmap"));
 
-#[cfg(not(test))]
+aya_ebpf::panic_handler!();
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}

xtask/public-api/aya-ebpf.txt

@@ -2728,6 +2728,7 @@ pub fn aya_ebpf::programs::xdp::XdpContext::borrow_mut(&mut self) -> &mut T
 impl<T> core::convert::From<T> for aya_ebpf::programs::xdp::XdpContext
 pub fn aya_ebpf::programs::xdp::XdpContext::from(t: T) -> T
 pub macro aya_ebpf::bpf_printk!
+pub macro aya_ebpf::panic_handler!
 pub struct aya_ebpf::PtRegs
 impl aya_ebpf::PtRegs
 pub fn aya_ebpf::PtRegs::arg<T: aya_ebpf::args::FromPtRegs>(&self, n: usize) -> core::option::Option<T>