Fix segfault for invalid AssignVarStatement visit #2423
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I'd say that the actual problem is that typecast gets an invalid expression (one with |
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@viktormalik You are right, thanks a lot, i just update this PR. $ cat sample.bt #include <linux/fs.h>
kprobe:vfs_open {
$file = (struct file *)
printf("Hello\n");
} |
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viktormalik
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Nov 14, 2022
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The change now fixes an invalid typecast rather than variable assignment.
When CodegenLLVM::visit calls CreateStore() with NULL expr_ as parameter,
segfault is generated, for example:
$ cat sample.bt
#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
bpftrace#1 0x000000000070cc76 in llvm::IRBuilderBase::CreateAlignedStore (this=0x7fffffffbe40, Val=0x0,
Ptr=0x15e2340, Align=..., isVolatile=false) at /usr/include/llvm/IR/IRBuilder.h:1689
bpftrace#2 0x000000000070cab3 in llvm::IRBuilderBase::CreateStore (this=0x7fffffffbe40, Val=0x0, Ptr=0x15e2340,
isVolatile=false) at /usr/include/llvm/IR/IRBuilder.h:1663
bpftrace#3 0x00000000006f6948 in bpftrace::ast::CodegenLLVM::visit (this=0x7fffffffbe10, assignment=...)
at /home/rongtao/Git/bpftrace/src/ast/passes/codegen_llvm.cpp:2140
bpftrace#4 0x0000000000751258 in bpftrace::ast::AssignVarStatement::accept (this=0x7fffe99b9a30, v=...)
at /home/rongtao/Git/bpftrace/src/ast/ast.cpp:35
bpftrace#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
./sample.bt:4:11-26: ERROR: Cannot cast from "none" type
$file = (struct file *)
~~~~~~~~~~~~~~~
LLVM/Clang Version: 15.0.1
Signed-off-by: Rong Tao <[email protected]>
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Done to update the CHANGELOG, thanks. |
viktormalik
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Nov 15, 2022
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When CodegenLLVM::visit calls CreateStore() with NULL expr_ as parameter, segfault is generated, for example:
Acctually, we want to '
$file = (struct file *)arg1;' here. When writing incorrectly '$file = (struct file *)', printf() makeexpr_ == nullptr, when call CreateStore(NULL, ...), segfault has occurred, and the stack backtrace is as follows:We should prompt the user for some useful information, like:
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