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Fixing a flaky Linux exploitability unittest.

Browse Source 
BUG=https://code.google.com/p/chromium/issues/detail?id=584174
R=mmandlis@chromium.org

Review URL: https://codereview.chromium.org/1697963002 .
This commit is contained in:
Ivan Penkov 2016-02-16 11:46:04 -08:00
parent e5adfac03b
commit 12bd7fc52b
3 changed files with 82 additions and 16 deletions
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44
src/processor/exploitability_linux.cc
View File

@ -231,21 +231,10 @@ bool ExploitabilityLinux::EndedOnIllegalWrite(uint64_t instruction_ptr) {
MAX_OBJDUMP_BUFFER_LEN,
objdump_output_buffer);
// Put buffer data into stream to output line-by-line.
std::stringstream objdump_stream;
objdump_stream.str(string(objdump_output_buffer));
string line;
// Pipe each output line into the string until the string contains
// the first instruction from objdump.
// Loop until the line shows the first instruction or there are no lines left.
do {
if (!getline(objdump_stream, line)) {
BPLOG(INFO) << "Objdump instructions not found";
return false;
}
} while (line.find("0:") == string::npos);
// This first instruction contains the above substring.
if (!GetObjdumpInstructionLine(objdump_output_buffer, &line)) {
return false;
}
// Convert objdump instruction line into the operation and operands.
string instruction = "";
@ -399,6 +388,33 @@ bool ExploitabilityLinux::CalculateAddress(const string &address_expression,
return true;
}
// static
bool ExploitabilityLinux::GetObjdumpInstructionLine(
const char *objdump_output_buffer,
string *instruction_line) {
// Put buffer data into stream to output line-by-line.
std::stringstream objdump_stream;
objdump_stream.str(string(objdump_output_buffer));
// Pipe each output line into the string until the string contains the first
// instruction from objdump. All lines before the "<.data>:" section are
// skipped. Loop until the line shows the first instruction or there are no
// lines left.
bool data_section_seen = false;
do {
if (!getline(objdump_stream, *instruction_line)) {
BPLOG(INFO) << "Objdump instructions not found";
return false;
}
if (instruction_line->find("<.data>:") != string::npos) {
data_section_seen = true;
}
} while (!data_section_seen || instruction_line->find("0:") == string::npos);
// This first instruction contains the above substring.
return true;
}
bool ExploitabilityLinux::TokenizeObjdumpInstruction(const string &line,
string *operation,
string *dest,

7
src/processor/exploitability_linux.h
View File

@ -86,6 +86,13 @@ class ExploitabilityLinux : public Exploitability {
const unsigned int MAX_OBJDUMP_BUFFER_LEN,
char *objdump_output_buffer);
// Parses the objdump output given in |objdump_output_buffer| and extracts
// the line of the first instruction into |instruction_line|. Returns true
// when the instruction line is successfully extracted.
static bool GetObjdumpInstructionLine(
const char *objdump_output_buffer,
string *instruction_line);
// Tokenizes out the operation and operands from a line of instruction
// disassembled by objdump. This method modifies the pointers to match the
// tokens of the instruction, and returns if the tokenizing was a success.

47
src/processor/exploitability_unittest.cc
View File

@ -47,9 +47,10 @@ namespace google_breakpad {
class ExploitabilityLinuxTest : public ExploitabilityLinux {
public:
using ExploitabilityLinux::DisassembleBytes;
using ExploitabilityLinux::TokenizeObjdumpInstruction;
using ExploitabilityLinux::CalculateAddress;
using ExploitabilityLinux::DisassembleBytes;
using ExploitabilityLinux::GetObjdumpInstructionLine;
using ExploitabilityLinux::TokenizeObjdumpInstruction;
};
class ExploitabilityLinuxTestMinidumpContext : public MinidumpContext {
@ -200,6 +201,48 @@ TEST(ExploitabilityLinuxUtilsTest, DisassembleBytesTest) {
ASSERT_EQ(line, " 0:\tc7 00 05 00 00 00 \tmov DWORD PTR [rax],0x5");
}
TEST(ExploitabilityLinuxUtilsTest, GetObjdumpInstructionLine) {
string disassebly =
"\n"
"/tmp/breakpad_mem_region-raw_bytes-tMmMo0: file format binary\n"
"// Trying to confuse the parser 0:\n"
"\n"
"Disassembly of section .data:\n"
"\n"
"0000000000000000 <.data>:\n"
" 0:\tc7 00 01 00 00 00 \tmov DWORD PTR [rax],0x1\n"
" 6:\t5d \tpop rbp\n"
" 7:\tc3 \tret \n"
" 8:\t55 \tpush rbp\n"
" 9:\t48 89 e5 \tmov rbp,rsp\n"
" c:\t53 \tpush rbx\n"
" d:\t48 \trex.W\n"
" e:\t81 \t.byte 0x81\n";
string line;
EXPECT_TRUE(ExploitabilityLinuxTest::GetObjdumpInstructionLine(
disassebly.c_str(), &line));
EXPECT_EQ(" 0:\tc7 00 01 00 00 00 \tmov DWORD PTR [rax],0x1", line);
// There is no "0:" after "<.data>:". Expected to return false.
disassebly =
"\n"
"/tmp/breakpad_mem_region-raw_bytes-tMmMo0: file format binary\n"
"// Trying to confuse the parser 0:\n"
"\n"
"Disassembly of section .data:\n"
"\n"
" 0:\tc7 00 01 00 00 00 \tmov DWORD PTR [rax],0x1\n"
" 6:\t5d \tpop rbp\n"
" 7:\tc3 \tret \n"
" 8:\t55 \tpush rbp\n"
" 9:\t48 89 e5 \tmov rbp,rsp\n"
" d:\t48 \trex.W\n"
"0000000000000000 <.data>:\n"
" c:\t53 \tpush rbx\n";
EXPECT_FALSE(ExploitabilityLinuxTest::GetObjdumpInstructionLine(
disassebly.c_str(), &line));
}
TEST(ExploitabilityLinuxUtilsTest, TokenizeObjdumpInstructionTest) {
ASSERT_FALSE(ExploitabilityLinuxTest::TokenizeObjdumpInstruction("",
NULL,