Debugging Gas Usage - Stack Trace

[kroggen]

This is for the record of how to get stack trace of LuaJIT inside of Aergo

This is the changes I am using for the lua_gasuse function:

~/aergo/libtool/src/luajit/src# git diff
diff --git a/src/Makefile b/src/Makefile
index 7839ffb..489f2eb 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -36,7 +36,7 @@ CC= $(DEFAULT_CC)
 # to slow down the C part by not omitting it. Debugging, tracebacks and
 # unwinding are not affected -- the assembler part has frame unwind
 # information and GCC emits it where needed (x64) or with -g (see CCDEBUG).
-CCOPT= -O2 -fomit-frame-pointer
+#CCOPT= -O2 -fomit-frame-pointer
 # Use this if you want to generate a smaller binary (but it's slower):
 #CCOPT= -Os -fomit-frame-pointer
 # Note: it's no longer recommended to use -O3 with GCC 4.x.
@@ -54,9 +54,9 @@ CCOPT_arm64=
 CCOPT_ppc=
 CCOPT_mips=
 #
-CCDEBUG=
+#CCDEBUG=
 # Uncomment the next line to generate debug information:
-#CCDEBUG= -g
+CCDEBUG= -g -rdynamic
 #
 CCWARN= -Wall
 # Uncomment the next line to enable more warnings:
diff --git a/src/lj_gas.c b/src/lj_gas.c
index 4fee114..3e14a9f 100644
--- a/src/lj_gas.c
+++ b/src/lj_gas.c
@@ -2,6 +2,30 @@
 #include "lj_err.h"
 #include "lj_dispatch.h"
 
+#include <stdio.h>
+#include <execinfo.h>
+
+void print_stack_trace(unsigned long long gas) {
+    void* trace[13];
+    int traceSize = backtrace(trace, 12);
+    char** messages = backtrace_symbols(trace, traceSize);
+
+    FILE *file;
+    file = fopen("/root/aergo/output.log", "a+");
+
+    fprintf(file, "------------------------------------------------------\n");
+    fprintf(file, "lua_gasuse: %llu\n", gas);
+
+    for (int i=0; i<traceSize; i++) {
+        char *ptr = strrchr(messages[i], '/'); // search for the last `/`
+        if (ptr==NULL) ptr = messages[i];
+        fprintf(file, "[%d] %s\n", i+1, ptr);
+    }
+
+    fclose(file);
+    free(messages);
+}
+
 static unsigned long long lj_gas_mul_no_ovt(unsigned long long a, unsigned long long b)
 {
   unsigned long long r;
@@ -23,6 +47,7 @@ LUA_API void lua_gasuse(lua_State *L, unsigned long long sz)
   if (gg->total_gas < sz) {
     lj_err_gas(L);
   }
+  print_stack_trace(sz);
   gg->total_gas -= sz;
 }

Then compile aergo:

make clean
rm -rf build
go clean --cache
make

It may be interesting to remove the static keyword from some functions

Also make sure that the symbols are not being "stripped" from the binary (the build should not run the strip tool)

[kroggen]

⚠️ IMPORTANT ⚠️

The above does NOT work with golang 1.21

[kroggen]

There is a workaround. Check #307

[kroggen]

It is possible to use brick, like this:

~/aergo3/contract/vm_dummy/test_files# ../../../bin/brick 
0> inject me 100000000000
  INF inject an account successfully cmd=inject module=brick
1> deploy me 0 cc gas_per_function.lua
  INF deploy a smart contract successfully cmd=deploy events=[] gas=285097 module=brick
2> hardfork 3
  INF hardfork set successfully cmd=hardfork module=brick
2> call me 0 cc run_test `["unary_ops"]`
  INF success cmd=call events=[] gas=134849 module=brick
3> hardfork 4
  INF hardfork set successfully cmd=hardfork module=brick
3> call me 0 cc run_test `["unary_ops"]`
  INF success cmd=call events=[] gas=270241 module=brick

It is also possible to build a binary from the vm tests, with:

cd contract/vm_dummy
go test -c -gcflags "all=-N -l" -o output_test .

And then run it

Or use gdb:

make clean
export CGO_CFLAGS="-g"
make debug
cd contract/vm_dummy
go test -c -gcflags "all=-N -l" -o output_test .
gdb output_test
break lj_cf_abi_register
run -test.run TestTypeOP