Box: Generalize decoding of syscall arguments and implement amd64 version

diff --git a/box/Makefile b/box/Makefile
index 7f7150115554cd12e89ea89254bf8ef3d8bf6a03..11f8931b93bcf04c695926538398774921f8b503 100644 (file)
--- a/box/Makefile
+++ b/box/Makefile
@@ -8,6 +8,8 @@ BOX_CFLAGS=-m64 -DCONFIG_BOX_AMD64
 
 $(o)/box/box: $(o)/box/box.o
 $(o)/box/box.o: $(o)/box/syscall-table.h
+
+$(o)/box/box: LDFLAGS+=$(BOX_CFLAGS)
 $(o)/box/box.o: CFLAGS+=$(BOX_CFLAGS)
 
 $(o)/box/syscall-table.h: $(s)/box/mk-syscall-table

diff --git a/box/box.c b/box/box.c
index 4a096e49a9a3039f1e44e7471f5915c73490fe8f..b44d11a6217e57a3d9de5470f0d38fc7ab4ca7fa 100644 (file)
--- a/box/box.c
+++ b/box/box.c
@@ -13,6 +13,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
+#include <stdint.h>
 #include <unistd.h>
 #include <getopt.h>
 #include <time.h>
@@ -594,10 +595,75 @@ setup_environment(void)
   return env;
 }
 
+/*** Low-level parsing of syscalls ***/
+
+#ifdef CONFIG_BOX_AMD64
+typedef uint64_t arg_t;
+#else
+typedef uint32_t arg_t;
+#endif
+
+struct syscall_args {
+  arg_t sys;
+  arg_t arg1, arg2, arg3;
+  arg_t result;
+  struct user user;
+};
+
+#ifdef CONFIG_BOX_AMD64
+
+static void
+get_syscall_args(struct syscall_args *a)
+{
+  if (ptrace(PTRACE_GETREGS, box_pid, NULL, &a->user) < 0)
+    die("ptrace(PTRACE_GETREGS): %m");
+  a->sys = a->user.regs.orig_rax;
+  a->arg1 = a->user.regs.rdi;
+  a->arg2 = a->user.regs.rsi;
+  a->arg3 = a->user.regs.rdx;
+  a->result = a->user.regs.rax;
+
+  // FIXME: Check that it's really a 64-bit syscall
+}
+
+static void
+set_syscall_nr(struct syscall_args *a, arg_t sys)
+{
+  a->sys = sys;
+  a->user.regs.orig_rax = sys;
+  if (ptrace(PTRACE_SETREGS, box_pid, NULL, &a->user) < 0)
+    die("ptrace(PTRACE_SETREGS): %m");
+}
+
+#else
+
+static void
+get_syscall_args(struct syscall_args *a)
+{
+  if (ptrace(PTRACE_GETREGS, box_pid, NULL, &a->user) < 0)
+    die("ptrace(PTRACE_GETREGS): %m");
+  a->sys = a->user.regs.orig_eax;
+  a->arg1 = a->user.regs.ebx;
+  a->arg2 = a->user.regs.ecx;
+  a->arg3 = a->user.regs.edx;
+  a->result = a->user.regs.eax;
+}
+
+static void
+set_syscall_nr(struct syscall_args *a, arg_t sys)
+{
+  a->sys = sys;
+  a->user.regs.orig_eax = sys;
+  if (ptrace(PTRACE_SETREGS, box_pid, NULL, &a->user) < 0)
+    die("ptrace(PTRACE_SETREGS): %m");
+}
+
+#endif
+
 /*** Syscall checks ***/
 
 static void
-valid_filename(unsigned long addr)
+valid_filename(arg_t addr)
 {
   char namebuf[4096], *p, *end;
   static int mem_fd;
@@ -666,9 +732,9 @@ valid_filename(unsigned long addr)
 
 // Check syscall. If invalid, return -1, otherwise return the action mask.
 static int
-valid_syscall(struct user *u)
+valid_syscall(struct syscall_args *a)
 {
-  unsigned int sys = u->regs.orig_eax;
+  unsigned int sys = a->sys;
   unsigned int act = (sys < NUM_ACTIONS) ? syscall_action[sys] : A_DEFAULT;
 
   if (act & A_LIBERAL)
@@ -684,7 +750,7 @@ valid_syscall(struct user *u)
     case A_NO:
       return -1;
     case A_FILENAME:
-      valid_filename(u->regs.ebx);
+      valid_filename(a->arg1);
       return act;
     default: ;
     }
@@ -692,17 +758,17 @@ valid_syscall(struct user *u)
   switch (sys)
     {
     case __NR_kill:
-      if (u->regs.ebx == box_pid)
+      if (a->arg1 == (arg_t) box_pid)
        {
-         meta_printf("exitsig:%d\n", (int)u->regs.ecx);
-         err("SG: Committed suicide by signal %d", (int)u->regs.ecx);
+         meta_printf("exitsig:%d\n", (int) a->arg2);
+         err("SG: Committed suicide by signal %d", (int) a->arg2);
        }
       return -1;
     case __NR_tgkill:
-      if (u->regs.ebx == box_pid && u->regs.ecx == box_pid)
+      if (a->arg1 == (arg_t) box_pid && a->arg2 == (arg_t) box_pid)
        {
-         meta_printf("exitsig:%d\n", (int)u->regs.edx);
-         err("SG: Committed suicide by signal %d", (int)u->regs.edx);
+         meta_printf("exitsig:%d\n", (int) a->arg3);
+         err("SG: Committed suicide by signal %d", (int) a->arg3);
        }
       return -1;
     default:
@@ -931,23 +997,23 @@ boxkeeper(void)
            {
              if (verbose > 2)
                msg("[ptrace status %08x] ", stat);
-             struct user u;
-             static unsigned int sys_tick, last_sys, last_act;
-             if (ptrace(PTRACE_GETREGS, box_pid, NULL, &u) < 0)
-               die("ptrace(PTRACE_GETREGS): %m");
-             unsigned int sys = u.regs.orig_eax;
+             struct syscall_args a;
+             static unsigned int sys_tick, last_act;
+             static arg_t last_sys;
+             get_syscall_args(&a);
+             arg_t sys = a.sys;
              if (++sys_tick & 1)               /* Syscall entry */
                {
                  char namebuf[32];
                  int act;
-                 msg(">> Syscall %-12s (%08lx,%08lx,%08lx) ", syscall_name(sys, namebuf), u.regs.ebx, u.regs.ecx, u.regs.edx);
+                 msg(">> Syscall %-12s (%08jx,%08jx,%08jx) ", syscall_name(sys, namebuf), (intmax_t) a.arg1, (intmax_t) a.arg2, (intmax_t) a.arg3);
                  if (!exec_seen)
                    {
                      msg("[master] ");
                      if (sys == __NR_execve)
                        exec_seen = 1;
                    }
-                 else if ((act = valid_syscall(&u)) >= 0)
+                 else if ((act = valid_syscall(&a)) >= 0)
                    {
                      last_act = act;
                      syscall_count++;
@@ -961,16 +1027,14 @@ boxkeeper(void)
                       * so we have to change it to something harmless (e.g., an undefined
                       * syscall) and make the program continue.
                       */
-                     u.regs.orig_eax = 0xffffffff;
-                     if (ptrace(PTRACE_SETREGS, box_pid, NULL, &u) < 0)
-                       die("ptrace(PTRACE_SETREGS): %m");
+                     set_syscall_nr(&a, ~(arg_t)0);
                      err("FO: Forbidden syscall %s", syscall_name(sys, namebuf));
                    }
                  last_sys = sys;
                }
              else                                      /* Syscall return */
                {
-                 if (sys == 0xffffffff)
+                 if (sys == ~(arg_t)0)
                    {
                      /* Some syscalls (sigreturn et al.) do not return a value */
                      if (!(last_act & A_NO_RETVAL))
@@ -984,7 +1048,7 @@ boxkeeper(void)
                  if (last_act & A_NO_RETVAL)
                    msg("= ?\n");
                  else
-                   msg("= %ld\n", u.regs.eax);
+                   msg("= %jd\n", (intmax_t) a.result);
                }
              ptrace(PTRACE_SYSCALL, box_pid, 0, 0);
            }