bcc/filelife and bpftrace/segfault patch

Posted 2022-12-13 rtoax

 

2022-11-13

================================================================================

```

libbpf-tools: filelife: update arguments and add vfs_open()

I already open a PR for `tools/filelife.py`, i think two PR better than

single one. After all, `libbpf-tools/filelife` is compiled separately,

and `tools/filelife.py` is the python script.

Since kernel commit 6521f8917082("namei: prepare for idmapped mounts"),

the vfs_unlink() function add argument 'struct user_namespace'. And

add vfs_open() probe if 'f_mode = FMODE_CREATED'.

Link: https://github.com/iovisor/bcc/pull/4339

```

```

Attaching 3 probes...

d_alloc: 0xffff9ad511a05900

d_alloc: 0xffff9ad511a05900

d_alloc: 0xffff9ad5977e7000

d_alloc: 0xffff9ad5977e76c0

d_alloc: 0xffff9ad5977e7d80

d_alloc: 0xffff9ad5977e7240

vfs_open: comm touch, dentry 0xffff9ad5f6d6e300, (nil), 809346181

unlink: 0xffff9ad316f7ad00, 1051722

d_alloc: 0xffff9ad511a05900

d_alloc: 0xffff9ad511b16a80

d_alloc: 0xffff9ad5d7125d80

d_alloc: 0xffff9ad5d71256c0

d_alloc: 0xffff9ad422729b40

d_alloc: 0xffff9ad422729d80

d_alloc: 0xffff9ad422729840

d_alloc: 0xffff9ad422729cc0

d_alloc: 0xffff9ad422729cc0

d_alloc: 0xffff9ad422729840

d_alloc: 0xffff9ad422729d80

d_alloc: 0xffff9ad422729b40

d_alloc: 0xffff9ad5d71256c0

d_alloc: 0xffff9ad5d7125d80

d_alloc: 0xffff9ad511b16a80

d_alloc: 0xffff9ad422726840

d_alloc: 0xffff9ad422728a80

d_alloc: 0xffff9ad422728000

d_alloc: 0xffff9ad422728900

d_alloc: 0xffff9ad422728600

d_alloc: 0xffff9ad5f76be480

d_alloc: 0xffff9ad5f76be3c0

d_alloc: 0xffff9ad5f76be0c0

d_alloc: 0xffff9ad5f76becc0

d_alloc: 0xffff9ad5f76be900

d_alloc: 0xffff9ad5f76be240

d_alloc: 0xffff9ad5f76be600

d_alloc: 0xffff9ad5f76bee40

vfs_open: comm touch, dentry 0xffff9ad5f6d6e300, (nil), 809346181

unlink: 0xffff9ad316f7ad00, 1051722

d_alloc: 0xffff9ad511a05e40

vfs_open: comm touch, dentry 0xffff9ad5f6d6e300, (nil), 809346181

unlink: 0xffff9ad316f7ad00, 1051722

d_alloc: 0xffff9ad511a05e40

```

 

2022-11-13

================================================================================

https://github.com/iovisor/bpftrace/pull/2423

# 段错误

Fix segfault for invalid AssignVarStatement visit

When CodegenLLVM::visit calls CreateStore() with NULL expr_ as parameter,

segfault is generated, for example:

#include <linux/fs.h>

kprobe:vfs_open

$file = (struct file *)

printf("Hello\\n");

Acctually, we want to '$file = (struct file *)arg1;' here. When writing

incorrectly '$file = (struct file *)', printf() make expr_ == nullptr,

when call CreateStore(NULL, ...), segfault has occurred, and the stack

backtrace is as follows:

(gdb) bt

#0 0x00000000007098c6 in llvm::Value::getType (this=0x0) at /usr/include/llvm/IR/Value.h:255

#1 0x000000000070cc76 in llvm::IRBuilderBase::CreateAlignedStore (this=0x7fffffffbe40, Val=0x0,

Ptr=0x15e2340, Align=..., isVolatile=false) at /usr/include/llvm/IR/IRBuilder.h:1689

#2 0x000000000070cab3 in llvm::IRBuilderBase::CreateStore (this=0x7fffffffbe40, Val=0x0, Ptr=0x15e2340,

isVolatile=false) at /usr/include/llvm/IR/IRBuilder.h:1663

#3 0x00000000006f6948 in bpftrace::ast::CodegenLLVM::visit (this=0x7fffffffbe10, assignment=...)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:2140

#4 0x0000000000751258 in bpftrace::ast::AssignVarStatement::accept (this=0x7fffe99b9a30, v=...)

at /home/rongtao/Git/bpftrace/src/ast/ast.cpp:35

#5 0x00000000006ff6ea in bpftrace::ast::CodegenLLVM::accept (this=0x7fffffffbe10, node=0x7fffe99b9a30)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:3360

We should prompt the user for some useful information, like:

$ sudo ./sample.bt

./t3-call.bt:4:9-10: FATAL: Invalid expression for "$file"

$file = (struct file *)

~

Aborted

We can't solve this problem semantic_analyser because the syntax is

correct. Maybe in the future we can solve it by modifying parser.yy,

but this modification is not considered because it is more complicated.

In any case, the CreateStore() parameter should not be NULL during the

codegen phase.

LLVM/Clang Version: 15.0.1

 

(gdb) bt

#0 0x00000000007098c6 in llvm::Value::getType (this=0x0) at /usr/include/llvm/IR/Value.h:255

#1 0x000000000070cc76 in llvm::IRBuilderBase::CreateAlignedStore (this=0x7fffffffbe40, Val=0x0,

Ptr=0x15e2340, Align=..., isVolatile=false) at /usr/include/llvm/IR/IRBuilder.h:1689

#2 0x000000000070cab3 in llvm::IRBuilderBase::CreateStore (this=0x7fffffffbe40, Val=0x0, Ptr=0x15e2340,

isVolatile=false) at /usr/include/llvm/IR/IRBuilder.h:1663

#3 0x00000000006f6948 in bpftrace::ast::CodegenLLVM::visit (this=0x7fffffffbe10, assignment=...)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:2140

#4 0x0000000000751258 in bpftrace::ast::AssignVarStatement::accept (this=0x7fffe99b9a30, v=...)

at /home/rongtao/Git/bpftrace/src/ast/ast.cpp:35

#5 0x00000000006ff6ea in bpftrace::ast::CodegenLLVM::accept (this=0x7fffffffbe10, node=0x7fffe99b9a30)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:3360

#6 0x00000000006f7aef in bpftrace::ast::CodegenLLVM::generateProbe (this=0x7fffffffbe10, probe=...,

full_func_id="kprobe:vfs_open", section_name="kprobe:vfs_open", func_type=0x15766c0, expansion=false,

usdt_location_index=std::optional<int> [no contained value], dummy=false)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:2361

#7 0x00000000006f7f92 in bpftrace::ast::CodegenLLVM::visit (this=0x7fffffffbe10, probe=...)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:2447

#8 0x00000000007513b6 in bpftrace::ast::Probe::accept (this=0x7fffe804acf0, v=...)

at /home/rongtao/Git/bpftrace/src/ast/ast.cpp:42

#9 0x00000000006ff6ea in bpftrace::ast::CodegenLLVM::accept (this=0x7fffffffbe10, node=0x7fffe804acf0)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:3360

#10 0x00000000006f8dc8 in bpftrace::ast::CodegenLLVM::visit (this=0x7fffffffbe10, program=...)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:2580

#11 0x00000000007513e8 in bpftrace::ast::Program::accept (this=0x7fffe804aa60, v=...)

at /home/rongtao/Git/bpftrace/src/ast/ast.cpp:43

#12 0x00000000006ff6ea in bpftrace::ast::CodegenLLVM::accept (this=0x7fffffffbe10, node=0x7fffe804aa60)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:3360

#13 0x00000000006fed1a in bpftrace::ast::CodegenLLVM::generate_ir (this=0x7fffffffbe10)

at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:3216

#14 0x000000000041df47 in main (argc=3, argv=0x7fffffffe508) at /home/rongtao/Git/bpftrace/src/main.cpp:896

 

================================================================================

```

warning: sdist: manifest template 'MANIFEST.in' does not exist (using default file list)

warning: sdist: standard file not found: should have one of README, README.txt, README.rst

writing manifest file 'MANIFEST'

```