dareen khalid via llvm-dev
2019-Apr-16 19:44 UTC
[llvm-dev] "compiler-rt" - DataFlowSanitizer
Hi all, I have some questions about "DataFlowSanitizer" from "compiler-rt". I want to know how I can test the "DataFlowSanitizer"? Can I configure it to label only some values, i.e, the return values from specific functions? Also, how can I print these labels? Thanks, Dareen -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20190416/7f83438c/attachment.html>
Sam Kerner via llvm-dev
2019-Apr-17 17:56 UTC
[llvm-dev] "compiler-rt" - DataFlowSanitizer
On Tue, Apr 16, 2019 at 3:44 PM dareen khalid via llvm-dev <llvm-dev at lists.llvm.org> wrote:> > Hi all, > > I have some questions about "DataFlowSanitizer" from "compiler-rt". > I want to know how I can test the "DataFlowSanitizer"?This document is a good reference for DataFlowSanitizer: https://clang.llvm.org/docs/DataFlowSanitizer.html> Can I configure it to label only some values,The section named "Example" in the document above shows a simple program that sets and tests for labels. dfsan_create_label() creates a label. dfsan_set_label() applies a label to the memory holding a variable.> i.e, the return values from specific functions?To label the return value of a function, add a call to dfsan_set_label() on the return value of the function: // Outside the function: dfsan_label return_label = dfsan_create_label("return_label", 0); // An example function: int MyFunction(int a, int b) { ... int result = ...; // Set a label on the returned value: dfsan_set_label(return_label, &result, sizeof(result)); return result; }> Also, how can I print these labels?To discover the label on a variable, you can test for it and print the result: int var = ...; // Does 'var' have label 'return_label'? dfsan_label var_label = dfsan_get_label(var); if (dfsan_has_label(var_label, return_label)) { printf("'var' has the label ''return_label"); } To see the state of all labels at the time the program exits set, set the shell variable DFSAN_OPTIONS to "dump_labels_at_exit=<file path>". For example, suppose the example program in the document is in a file named "dfsan.c". Here are the commands I ran to see the state of all labels when it exits: # Compile dfsan.c into a binary named "dfsan": $ clang -g -fsanitize=dataflow dfsan.c -o dfsan # Run it. There is no output because all assertions pass: $ ./dfsan # Run it again with shell variable DFSAN_OPTIONS set to export label state to standard out on exit: $ env DFSAN_OPTIONS=dump_labels_at_exit=/dev/stdout ./dfsan ==21994==INFO: DataFlowSanitizer: dumping labels to /dev/stdout 1 0 0 i 2 0 0 j 3 0 0 k 4 1 2 5 3 4 If you tell us more about what you are trying to accomplish with DataFlowSanitizer, we may be able to give more specific advice.> > Thanks, > Dareen > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
dareen khalid via llvm-dev
2019-Apr-18 14:00 UTC
[llvm-dev] "compiler-rt" - DataFlowSanitizer
I'm new to llvm passes. I wonder if I can use the pass to dynamically
analyze a program.
Let me explain what I want to do in the following example .
//"Result" is an object that doesn't have a fixed length like int
and float.
//The program is as follows.
Result retrieve_data_fun (){
//the function retrieves some sensitive data from files/DB
return result_info;
}
void main(){
...
Result var1, var2, var3l
var1 = retrieve_data_fun();
...
Result var2 = retrieve_data_fun();
printf (var1);
var3 = var2+'xxx';
print (var3);
}
My goal is to track all the returned data from "retrieve_data_fun" and
monitor actions on them.
So, whenever the data is used (e.g., printed) , I want to detect that; maybe by
printing a statement or anything.
Could you please help me to do that ?
Thanks,
Daren
________________________________
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Sam
Kerner via llvm-dev <llvm-dev at lists.llvm.org>
Sent: Wednesday, April 17, 2019 5:56 PM
To: llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] "compiler-rt" - DataFlowSanitizer
On Tue, Apr 16, 2019 at 3:44 PM dareen khalid via llvm-dev
<llvm-dev at lists.llvm.org> wrote:>
> Hi all,
>
> I have some questions about "DataFlowSanitizer" from
"compiler-rt".
> I want to know how I can test the "DataFlowSanitizer"?
This document is a good reference for DataFlowSanitizer:
https://clang.llvm.org/docs/DataFlowSanitizer.html
> Can I configure it to label only some values,
The section named "Example" in the document above shows a simple
program that sets and tests for labels.
dfsan_create_label() creates a label.
dfsan_set_label() applies a label to the memory holding a variable.
> i.e, the return values from specific functions?
To label the return value of a function, add a call to
dfsan_set_label() on the return value of the function:
// Outside the function:
dfsan_label return_label = dfsan_create_label("return_label", 0);
// An example function:
int MyFunction(int a, int b) {
...
int result = ...;
// Set a label on the returned value:
dfsan_set_label(return_label, &result, sizeof(result));
return result;
}
> Also, how can I print these labels?
To discover the label on a variable, you can test for it and print the result:
int var = ...;
// Does 'var' have label 'return_label'?
dfsan_label var_label = dfsan_get_label(var);
if (dfsan_has_label(var_label, return_label)) {
printf("'var' has the label ''return_label");
}
To see the state of all labels at the time the program exits set, set
the shell variable DFSAN_OPTIONS to "dump_labels_at_exit=<file
path>".
For example, suppose the example program in the document is in a file
named "dfsan.c". Here are the commands I ran to see the state of all
labels when it exits:
# Compile dfsan.c into a binary named "dfsan":
$ clang -g -fsanitize=dataflow dfsan.c -o dfsan
# Run it. There is no output because all assertions pass:
$ ./dfsan
# Run it again with shell variable DFSAN_OPTIONS set to export label
state to standard out on exit:
$ env DFSAN_OPTIONS=dump_labels_at_exit=/dev/stdout ./dfsan
==21994==INFO: DataFlowSanitizer: dumping labels to /dev/stdout
1 0 0 i
2 0 0 j
3 0 0 k
4 1 2
5 3 4
If you tell us more about what you are trying to accomplish with
DataFlowSanitizer, we may be able to give more specific advice.
>
> Thanks,
> Dareen
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
_______________________________________________
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