Skip function prologue for uprobes

bpftrace · Mar 30, 2024 · b82fd29 · b82fd29
1 parent 81ea7bd
commit b82fd29
Show file tree

Hide file tree

Showing 5 changed files with 28 additions and 5 deletions.
diff --git a/src/arch/x86_64.cpp b/src/arch/x86_64.cpp
@@ -3,8 +3,8 @@
 #include <algorithm>
 #include <array>
 
-// SP + 8 points to the first argument that is passed on the stack
-#define ARG0_STACK 8
+// SP + 16 points to the first argument that is passed on the stack
+#define ARG0_STACK 16
 
 namespace bpftrace {
 namespace arch {

diff --git a/src/bpftrace.cpp b/src/bpftrace.cpp
@@ -332,6 +332,12 @@ int BPFtrace::add_probe(ast::Probe &p)
             generateWatchpointSetupProbe(func_id, *attach_point, p));
 
         resources.watchpoint_probes.emplace_back(std::move(probe));
+      } else if (probetype(attach_point->provider) == ProbeType::uprobe) {
+        if (auto *dwarf = get_dwarf(target))
+          probe.func_offset = std::max(probe.func_offset,
+                                       dwarf->get_prologue_size(func_id));
+
+        resources.probes.push_back(probe);
       } else {
         resources.probes.push_back(probe);
       }

diff --git a/src/dwarf_parser.cpp b/src/dwarf_parser.cpp
@@ -50,6 +50,17 @@ std::unique_ptr<Dwarf> Dwarf::GetFromBinary(BPFtrace *bpftrace,
   }
 }
 
+uint64_t Dwarf::get_prologue_size(const std::string &function)
+{
+  auto functions = target_.FindFunctions(function.c_str());
+  // The given function name MUST identify a unique function!
+  if (functions.GetSize() != 1)
+    return 0;
+
+  auto fn = functions.GetContextAtIndex(0).GetFunction();
+  return fn.GetPrologueByteSize();
+}
+
 std::string Dwarf::get_type_name(lldb::SBType type)
 {
   std::string type_name = type.GetDisplayTypeName() ?: "<anonymous type>";

diff --git a/src/dwarf_parser.h b/src/dwarf_parser.h
@@ -23,6 +23,7 @@ class Dwarf {
   static std::unique_ptr<Dwarf> GetFromBinary(BPFtrace *bpftrace,
                                               std::string file_path);
 
+  uint64_t get_prologue_size(const std::string &function);
   std::vector<std::string> get_function_params(const std::string &function);
   Struct resolve_args(const std::string &function);
 
@@ -70,6 +71,11 @@ class Dwarf {
     return nullptr;
   }
 
+  uint64_t get_prologue_size(const std::string &function __attribute((unused)))
+  {
+    return 0;
+  }
+
   std::vector<std::string> get_function_params(const std::string &function
                                                __attribute__((unused)))
   {

diff --git a/tests/runtime/call b/tests/runtime/call
@@ -229,7 +229,7 @@ AFTER ./testprogs/syscall nanosleep  1e8
 NAME ustack_stack_mode_env_bpftrace
 PROG u:./testprogs/uprobe_loop:uprobeFunction1 { printf("%s\n", ustack(1)); exit(); }
 ENV BPFTRACE_STACK_MODE=bpftrace
-EXPECT uprobeFunction1+0
+EXPECT_REGEX uprobeFunction1\+[1-9][0-9]*
 TIMEOUT 5
 AFTER ./testprogs/uprobe_loop
 # This was debugged as far down as std::cout having badbit [0] set after a
@@ -249,7 +249,7 @@ SKIP_IF_ENV_HAS CI=true
 NAME ustack_stack_mode_env_perf
 PROG u:./testprogs/uprobe_loop:uprobeFunction1 { printf("%s\n", ustack(1)); exit(); }
 ENV BPFTRACE_STACK_MODE=perf
-EXPECT_REGEX \d+ uprobeFunction1\+0 \(.*/uprobe_loop\)
+EXPECT_REGEX [0-9a-f]+ uprobeFunction1\+[1-9][0-9]* \(.*/uprobe_loop\)
 TIMEOUT 5
 AFTER ./testprogs/uprobe_loop
 # See https://github.com/bpftrace/bpftrace/issues/3080
@@ -276,7 +276,7 @@ SKIP_IF_ENV_HAS CI=true
 NAME ustack_elf_symtable
 ENV BPFTRACE_CACHE_USER_SYMBOLS=PER_PROGRAM
 PROG uprobe:./testprogs/uprobe_symres_exited_process:test { print(ustack); exit(); }
-EXPECT_REGEX ^\s+test\+0\s+main\+[1-9][0-9]*
+EXPECT_REGEX ^\s+test\+[1-9][0-9]*\s+test2\+[1-9][0-9]*\s+main\+[1-9][0-9]*
 AFTER ./testprogs/disable_aslr ./testprogs/uprobe_symres_exited_process
 ARCH x86_64
 TIMEOUT 5