commit for once

1 files changed, 52 insertions, 0 deletions

diff --git a/3/10_control_and_data/48_stack_protection.c b/3/10_control_and_data/48_stack_protection.c
new file mode 100644
index 0000000..08cb4e8
--- /dev/null
+++ b/3/10_control_and_data/48_stack_protection.c
@@ -0,0 +1,52 @@
+int len(char *s) {
+    return strlen(s);
+}
+
+void iptoa(char *s, long *p) {
+    long val = *p;
+    sprintf(s, "%ld", val);
+}
+
+// int inlen(long x)
+// x in %rdi
+// without canary
+//
+// intlen:
+//      subq        $40, %rsp           allocate 5*8 bytes
+//      movq        %rdi, 24(%rsp)      put x on the stack
+//      leaq        24(%rsp), %rsi      set &v = &x to the second argument
+//      movq        %rsp, %rdi          set buf[12] to %rsp
+//      call        iptoa
+//
+//  0<rsp+32    <-?
+//  0<rsp+24    <-v
+//  0<rsp+16    <-?
+//  0<rsp+8     <-buf[12]
+//  0<rsp       <-buf[12]
+//
+// with canary
+//
+// intlen:
+//      subq        $56, %rsp
+//      movq        %fs:40, %rax
+//      movq        %rax, 40(%rsp)
+//      xorl        %eax, %eax
+//      movq        %rdi, 8(%rsp)
+//      leaq        8(%rsp), %rsi
+//      leaq        16(%rsp), %rdi
+//      call        iptoa
+//
+//  0<rsp+48    <-
+//  0<rsp+40    <-canary
+//  0<rsp+32    <-
+//  0<rsp+24    <-
+//  0<rsp+16    <-buf[12]
+//  0<rsp+8     <-v
+//  0<rsp       <-
+int intlen(long x) {
+    long v;
+    char buf[12];
+    v = x;
+    iptoa(buf, &v);
+    return len(buf);
+}