From 9df3a40bd9c71e9fee6346a36be1aa1b445d4f50 Mon Sep 17 00:00:00 2001
From: Nelson Elhage <nelhage@nelhage.com>
Date: Sun, 16 Jan 2011 18:17:20 -0500
Subject: [PATCH] Add initial setup for injected stub.

---
 .gitignore |  1 +
 Makefile   |  7 +++-
 stub.c     | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 104 insertions(+), 1 deletion(-)
 create mode 100644 stub.c

diff --git a/.gitignore b/.gitignore
index c6086ef..aa36f89 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 reptyr
+*.o
diff --git a/Makefile b/Makefile
index eee922d..b7c8143 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,8 @@
 CFLAGS=-Wall -Werror
+STUB_CFLAGS=$(CFLAGS) -nostdlib -Wl,-r -fomit-frame-pointer
 
-all: reptyr
+all: reptyr stub.o
+
+stub.o: stub.c
+	$(CC) -c $(STUB_CFLAGS) -o $@ $^
+	! nm $@ | grep ' U '
diff --git a/stub.c b/stub.c
new file mode 100644
index 0000000..e927bd0
--- /dev/null
+++ b/stub.c
@@ -0,0 +1,97 @@
+#define _GNU_SOURCE
+
+#include <sys/syscall.h>
+#define _FCNTL_H
+#include <bits/fcntl.h>
+
+static inline unsigned long __syscall(unsigned long sysno,
+                                      unsigned long p0, unsigned long p1,
+                                      unsigned long p2, unsigned long p3,
+                                      unsigned long p4, unsigned long p5) {
+    unsigned long rv;
+#ifdef __amd64__
+    register unsigned long _p3 asm("r10") = p3;
+    register unsigned long _p4 asm("r8")  = p4;
+    register unsigned long _p5 asm("r9")  = p5;
+    asm("syscall" : "=a" (rv) : "a" (sysno),
+        "rdi" (p0), "rsi" (p1), "rdx" (p2), "r"   (_p3), "r"  (_p4), "r"   (_p5)
+        : "memory", "cc");
+#else
+    register unsigned long _p0 asm("ebx") = p0;
+    register unsigned long _p1 asm("ecx") = p1;
+    register unsigned long _p2 asm("edx") = p2;
+    register unsigned long _p3 asm("esi") = p3;
+    register unsigned long _p4 asm("edi") = p4;
+    register unsigned long _p5 asm("ebp") = p5;
+    asm("int $0x80" : "=a" (rv) : "a" (sysno),
+        "r" (_p0), "r" (_p1), "r" (_p2), "r" (_p3), "r" (_p4), "r" (_p5)
+        : "memory", "cc");
+#endif
+    return rv;
+}
+
+#define syscall1(name, t0, p0) \
+    unsigned long name(t0 p0) {                                 \
+        return __syscall(__NR_##name,                           \
+                         (unsigned long)p0,                     \
+                         0, 0, 0, 0, 0);                        \
+    }
+
+#define syscall2(name, t0, p0, t1, p1)                          \
+    unsigned long name(t0 p0, t1 p1) {                          \
+        return __syscall(__NR_##name,                           \
+                         (unsigned long)p0,                     \
+                         (unsigned long)p1,                     \
+                         0, 0, 0, 0);                           \
+    }
+
+#define syscall3(name, t0, p0, t1, p1, t2, p2)                  \
+    unsigned long name(t0 p0, t1 p1, t2 p2) {                   \
+        return __syscall(__NR_##name,                           \
+                         (unsigned long)p0,                     \
+                         (unsigned long)p1,                     \
+                         (unsigned long)p2,                     \
+                         0, 0, 0);                              \
+    }
+
+#define syscall4(name, t0, p0, t1, p1, t2, p2, t3, p3)          \
+    unsigned long name(t0 p0, t1 p1, t2 p2, t3 p3) {            \
+        return __syscall(__NR_##name,                           \
+                         (unsigned long)p0,                     \
+                         (unsigned long)p1,                     \
+                         (unsigned long)p2,                     \
+                         (unsigned long)p3,                     \
+                         0, 0);                                 \
+    }
+
+#define syscall5(name, t0, p0, t1, p1, t2, p2, t3, p3, t4, p4)  \
+    unsigned long name(t0 p0, t1 p1, t2 p2, t3 p3, t4 p4) {     \
+        return __syscall(__NR_##name,                           \
+                         (unsigned long)p0,                     \
+                         (unsigned long)p1,                     \
+                         (unsigned long)p2,                     \
+                         (unsigned long)p3,                     \
+                         (unsigned long)p4,                     \
+                         0);                                    \
+    }
+
+#define syscall6(name, t0, p0, t1, p1, t2, p2, t3, p3, t4, p4,  \
+                 t5, p5)                                        \
+    unsigned long name(t0 p0, t1 p1, t2 p2, t3 p3, t4 p4,       \
+                       t5 p5) {                                 \
+        return __syscall(__NR_##name,                           \
+                         (unsigned long)p0,                     \
+                         (unsigned long)p1,                     \
+                         (unsigned long)p2,                     \
+                         (unsigned long)p3,                     \
+                         (unsigned long)p4,                     \
+                         (unsigned long)p5);                    \
+    }
+
+syscall1(close, int, fd);
+syscall2(open, const char*, path, int, mode);
+
+void stub_entry() {
+}
+
+void _start(void) __attribute__((alias("stub_entry")));