213 Recitation Exam 2 review Elie Krevat and Jiri Simsa Exam coverage Lectures 8 17 Buf lab Shell lab Buffer overflow Main Memory and Caches Exceptions Logical control flow Sys level I O Virtual Memory Malloc Disk Storage What s NOT covered Linking Garbage Collection not in depth VM access permissions not in depth 2 level Page Tables Buffer overflow Understand layout of a stack frame Be able to read assembly code Frame ptr stack ptr instruction ptr Given unsafe code in C and assembly Output exploit string that calls a function Buffer overflow push rbp mov rsp rbp sub 0x10 rsp lea 0xfffffffffffffff0 rbp rdi mov 0x0 eax callq 4003a8 gets plt mov 0x0 eax leaveq retq Caches Understand operation of caches Bits for tag set index block offset Direct mapped fully associative or N way set associative Coding for locality replacement policies Given Cache description and sequence of memory accesses Output Identify hits and misses Caches char sum matrix char matrix 3 3 int row col char sum 0 for col 0 col 3 col for row 0 row 3 row sum matrix row col return sum chars are 8 bits cache is direct mapped with 4 sets of 4 bytes Control flow signals Know fork wait kill signal Given C source code with printf Output All possible outputs Control flow signals void handler int sig printf Whoops n exit 0 int main int pid signal SIGUSR1 handler if pid fork printf Hi n kill pid SIGUSR1 printf Peace n Sys level I O File descriptors I O redirection Descriptor table per process Open file vnode table all processes Know open dup2 fork Given C sources with printf Output Correct output File descriptors int main int fd1 fd2 char c int fd1 open test txt RD ONLY fd2 dup fd1 read fd2 c 1 printf 1 c n c fork read fd1 c 1 printf 2 c n c test txt contains 15213 rocks Virtual memory How memory request is handled Translation look aside buffer Virtual vs physical address Page table Page hit vs Page miss Given VM description and requests Output Sequence of events Virtual memory See exam 2 fall 06 problem 4 Malloc Know malloc Implicit explicit list free blocks Types of errors e g mem leaks wrong allocation amounts Initialization Input C code Output Identify error Malloc int p p malloc N sizeof int for i 0 i N i p i malloc M sizeof int Disk Storage Know physical construction of disk Disk heads platters etc How data is read Speed and performance characteristics Questions Good luck
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