Merge branch 'main' into unwind_debug

.github/workflows/vmtests.yml

@@ -0,0 +1,34 @@
+name: vmtests
+on:
+    pull_request:
+    push:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  vmtests:
+    runs-on: ubuntu-22.04
+    permissions:
+        id-token: write
+        contents: read
+
+    steps:
+    - uses: actions/checkout@main
+    - uses: DeterminateSystems/nix-installer-action@main
+    - uses: DeterminateSystems/magic-nix-cache-action@main
+
+    - name: Install system dependencies
+      run: |
+        export DEBIAN_FRONTEND=noninteractive
+        sudo apt-get -y install --no-install-recommends qemu-system-x86 qemu-guest-agent
+
+    - name: Set up nix dev env
+      run: nix develop --command echo 0
+
+    - name: Build `lightswitch`
+      run: nix develop --ignore-environment --command bash -c 'cargo build'
+
+    - name: Run kernel tests
+      run: nix develop --command 'vmtest'

.gitignore

@@ -1,3 +1,4 @@
 /target
 flame.svg
 src/bpf/*_skel.rs
+.vmtest.log

flake.nix

@@ -53,6 +53,13 @@
               # snapshot testing plugin binary
               cargo-insta
               # ocamlPackages.magic-trace
+              (import ./vm.nix { inherit pkgs; }).vmtest
+              (import ./vm.nix { inherit pkgs; }).kernel_5_15
+              (import ./vm.nix { inherit pkgs; }).kernel_6_0
+              (import ./vm.nix { inherit pkgs; }).kernel_6_2
+              (import ./vm.nix { inherit pkgs; }).kernel_6_6
+              (import ./vm.nix { inherit pkgs; }).kernel_6_8_7
+              (import ./vm.nix { inherit pkgs; }).kernel_6_9_rc5
             ];
 
             LIBCLANG_PATH = lib.makeLibraryPath [ llvmPackages_16.libclang ];

src/bpf/profiler.bpf.c

@@ -71,29 +71,19 @@ struct {
 } rate_limits SEC(".maps");
 
 
-// On arm64 running 6.8.4-200.fc39.aarch64 the verifier fails with argument list too long. This
-// did not use to happen before and it's probably due to a regression in the way the verifier
-// accounts for the explored paths. I have tried many other things, such as two mid variables
-// but that did not do it. The theory of why this works is that perhaps it's making the verifier
-// reset the state it had about the program exploration so the branches its exploring per iteration
-// do not grow as much.
-#ifdef __TARGET_ARCH_arm64
-static u32 __attribute__((optnone)) verifier_workaround(u32 value) {
-    return value;
-}
-#endif
-#ifdef __TARGET_ARCH_x86
-static __always_inline u32 verifier_workaround(u32 value) {
-    return value;
-}
-#endif
-
 // Binary search the unwind table to find the row index containing the unwind
 // information for a given program counter (pc) relative to the object file.
 static __always_inline u64 find_offset_for_pc(stack_unwind_table_t *table, u64 pc, u64 left,
                               u64 right) {
   u64 found = BINARY_SEARCH_DEFAULT;
 
+
+  // On kernels ~6.8 and greater the verifier fails with argument list too long. This did not use to
+  // happen before and it's probably due to a regression in the way the verifier accounts for the explored
+  // paths. I have tried many other things, such as two mid variables but that did not do it.
+  // Perhaps unrolling the loop works is that the verifier doesn't have as many states to explore
+  // per iteration.
+  #pragma unroll
   for (int i = 0; i < MAX_BINARY_SEARCH_DEPTH; i++) {
     // TODO(javierhonduco): ensure that this condition is right as we use
     // unsigned values...
@@ -102,7 +92,7 @@ static __always_inline u64 find_offset_for_pc(stack_unwind_table_t *table, u64 p
       return found;
     }
 
-    u32 mid = verifier_workaround((left + right) / 2);
+    u32 mid = (left + right) / 2;
     // Appease the verifier.
     if (mid < 0 || mid >= MAX_UNWIND_TABLE_SIZE) {
       LOG("\t.should never happen, mid: %lu, max: %lu", mid,
@@ -229,7 +219,7 @@ static __always_inline bool retrieve_task_registers(u64 *ip, u64 *sp, u64 *bp) {
   }
 
   void *ptr = stack + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
-  struct pt_regs *regs = ((struct pt_regs *)ptr) - 1;
+  bpf_user_pt_regs_t *regs = ((bpf_user_pt_regs_t *)ptr) - 1;
 
   *ip = PT_REGS_IP_CORE(regs);
   *sp = PT_REGS_SP_CORE(regs);
@@ -350,7 +340,7 @@ int dwarf_unwind(struct bpf_perf_event_data *ctx) {
     }
 
     if (mapping->type == 2) {
-      LOG("JIT section, stopping");
+      LOG("vDSO section, stopping");
       return 1;
     }
 
@@ -570,7 +560,7 @@ int dwarf_unwind(struct bpf_perf_event_data *ctx) {
 }
 
 // Set up the initial unwinding state.
-static __always_inline bool set_initial_state(unwind_state_t *unwind_state, struct pt_regs *regs) {
+static __always_inline bool set_initial_state(unwind_state_t *unwind_state, bpf_user_pt_regs_t *regs) {
   unwind_state->stack.len = 0;
   unwind_state->tail_calls = 0;
 

src/bpf/profiler_bindings.rs

@@ -16,9 +16,17 @@ unsafe impl Plain for exec_mappings_key {}
 unsafe impl Plain for mapping_t {}
 
 impl exec_mappings_key {
-    pub fn new(pid: u32, address: u64, prefix: u32) -> Self {
+    pub fn new(pid: u32, address: u64, prefix_len: u32) -> Self {
+        let key_size_bits = std::mem::size_of::<Self>() * 8;
+        assert!(
+            prefix_len <= key_size_bits.try_into().unwrap(),
+            "prefix_len {} should be <= than the size of exec_mappings_key {}",
+            prefix_len,
+            key_size_bits
+        );
+
         Self {
-            prefix_len: 32 + prefix,
+            prefix_len,
             pid: pid.to_be(),
             data: address.to_be(),
         }

src/main.rs

@@ -20,7 +20,10 @@ use tracing_subscriber::FmtSubscriber;
 use lightswitch::collector::Collector;
 use lightswitch::object::ObjectFile;
 use lightswitch::profiler::Profiler;
-use lightswitch::unwind_info::{compact_printing_callback, UnwindInfoBuilder};
+use lightswitch::unwind_info::in_memory_unwind_info;
+use lightswitch::unwind_info::remove_redundant;
+use lightswitch::unwind_info::remove_unnecesary_markers;
+use lightswitch::unwind_info::UnwindInfoBuilder;
 
 const SAMPLE_FREQ_RANGE: RangeInclusive<usize> = 1..=1009;
 
@@ -125,6 +128,25 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     let args = Cli::parse();
 
+    if let Some(path) = args.show_unwind_info {
+        let mut unwind_info = in_memory_unwind_info(&path).unwrap();
+        remove_unnecesary_markers(&mut unwind_info);
+        remove_redundant(&mut unwind_info);
+
+        for compact_row in unwind_info {
+            let pc = compact_row.pc;
+            let cfa_type = compact_row.cfa_type;
+            let rbp_type = compact_row.rbp_type;
+            let cfa_offset = compact_row.cfa_offset;
+            let rbp_offset = compact_row.rbp_offset;
+            println!(
+                "pc: {:x} cfa_type: {:<2} rbp_type: {:<2} cfa_offset: {:<4} rbp_offset: {:<4}",
+                pc, cfa_type, rbp_type, cfa_offset, rbp_offset
+            );
+        }
+        return Ok(());
+    }
+
     let subscriber = FmtSubscriber::builder()
         .with_max_level(if args.filter_logs {
             Level::TRACE
@@ -137,11 +159,6 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     tracing::subscriber::set_global_default(subscriber).expect("setting default subscriber failed");
 
-    if let Some(path) = args.show_unwind_info {
-        UnwindInfoBuilder::with_callback(&path, compact_printing_callback)?.process()?;
-        return Ok(());
-    }
-
     if let Some(path) = args.show_info {
         let objet_file = ObjectFile::new(&PathBuf::from(path.clone())).unwrap();
         println!("build id {:?}", objet_file.build_id());

src/profiler.rs

@@ -809,17 +809,9 @@ impl Profiler<'_> {
             }
             span.exit();
 
-            let span: span::EnteredSpan = span!(Level::DEBUG, "sort unwind info").entered();
-            found_unwind_info.sort_by(|a, b| {
-                let a_pc = a.pc;
-                let b_pc = b.pc;
-                a_pc.cmp(&b_pc)
-            });
-            span.exit();
-
             let span: span::EnteredSpan = span!(Level::DEBUG, "optimize unwind info").entered();
-            let found_unwind_info = remove_unnecesary_markers(&found_unwind_info);
-            let found_unwind_info = remove_redundant(&found_unwind_info);
+            remove_unnecesary_markers(&mut found_unwind_info);
+            remove_redundant(&mut found_unwind_info);
             span.exit();
 
             debug!(
@@ -981,7 +973,7 @@ impl Profiler<'_> {
                     let key = exec_mappings_key::new(
                         pid.try_into().unwrap(),
                         address_range.addr,
-                        address_range.range,
+                        32 + address_range.prefix_len,
                     );
 
                     self.add_bpf_mapping(&key, &mapping).unwrap();