mckernel overlay: replace mcoverlayfs with a soft userspace overlay

mcoverlayfs has a high maintenance burden and does not work on rhel8's 4.18
kernel (while it works on vanilla 4.18...); instead of debugging this further
time is better spent making it independent from overlayfs.

Change-Id: I7454ae95b0fbb3373c256aa2fd83cdfec466c009

configure

@@ -3766,7 +3766,7 @@ fi
 if test "${enable_mcoverlayfs+set}" = set; then :
   enableval=$enable_mcoverlayfs; ENABLE_MCOVERLAYFS=$enableval
 else
-  ENABLE_MCOVERLAYFS=yes
+  ENABLE_MCOVERLAYFS=no
 fi
 
 

configure.ac

@@ -193,7 +193,7 @@ AC_ARG_ENABLE([mcoverlayfs],
 	      AC_HELP_STRING([--enable-mcoverlayfs],
 			     [enable mcoverlayfs implementation]),
 	      [ENABLE_MCOVERLAYFS=$enableval],
-	      [ENABLE_MCOVERLAYFS=yes])
+	      [ENABLE_MCOVERLAYFS=no])
 
 AC_ARG_ENABLE([rusage],
 	      AC_HELP_STRING([--enable-rusage],

executer/user/arch/arm64/Makefile.in

@@ -10,15 +10,12 @@ LIBS=@LIBS@
 
 all: $(TARGET)
 
-../../libmcexec.a: archdep.o arch_syscall.o
+../../libmcexec.a: archdep.o
-	$(AR) cr ../../libmcexec.a archdep.o arch_syscall.o
+	$(AR) cr ../../libmcexec.a archdep.o
 
 archdep.o: archdep.c archdep.S
 	$(CC) -c -I${KDIR} $(CFLAGS) $(EXTRA_CFLAGS) -fPIE -pie -pthread $^
 
-arch_syscall.o: arch_syscall.c
-	$(CC) -c -I${KDIR} $(CFLAGS) $(EXTRA_CFLAGS) -fPIE -pie -pthread $<
-
 clean:
 	$(RM) $(TARGET) *.o
 

executer/user/arch/arm64/arch_syscall.c

@@ -1,7 +0,0 @@
-struct syscall_wait_desc;
-
-int
-archdep_syscall(struct syscall_wait_desc *w, long *ret)
-{
-	return -1;
-}

executer/user/arch/x86_64/Makefile.in

@@ -10,15 +10,12 @@ LIBS=@LIBS@
 
 all: $(TARGET)
 
-../../libmcexec.a: archdep.o arch_syscall.o
+../../libmcexec.a: archdep.o
-	$(AR) cr ../../libmcexec.a archdep.o arch_syscall.o
+	$(AR) cr ../../libmcexec.a archdep.o
 
 archdep.o: archdep.S
 	$(CC) -c -I${KDIR} $(CFLAGS) $(EXTRA_CFLAGS) -fPIE -pie -pthread $<
 
-arch_syscall.o: arch_syscall.c
-	$(CC) -c -I${KDIR} $(CFLAGS) $(EXTRA_CFLAGS) -fPIE -pie -pthread $<
-
 ../../libsyscall_intercept_arch.a: archdep_c.o
 	$(AR) cr ../../libsyscall_intercept_arch.a archdep_c.o
 

executer/user/arch/x86_64/arch_syscall.c

@@ -1,63 +0,0 @@
-#define _GNU_SOURCE
-#include <stdio.h>
-#include <stdlib.h>
-#include <errno.h>
-#include <unistd.h>
-#include <fcntl.h>
-#include <string.h>
-#include <sys/resource.h>
-#include <sys/syscall.h>
-#include <elf.h>
-#include <dirent.h>
-#include "../../../include/uprotocol.h"
-#include "../../archdep.h"
-
-//#define DEBUG
-#ifndef DEBUG
-#define __dprint(msg, ...)
-#define __dprintf(arg, ...)
-#define __eprint(msg, ...)
-#define __eprintf(format, ...)
-#else
-#define __dprint(msg, ...)  {printf("%s: " msg, __FUNCTION__);fflush(stdout);}
-#define __dprintf(format, ...)  {printf("%s: " format, __FUNCTION__, \
-					__VA_ARGS__);fflush(stdout);}
-#define __eprint(msg, ...)  {fprintf(stderr, "%s: " msg, __FUNCTION__);\
-					fflush(stderr);}
-#define __eprintf(format, ...)  {fprintf(stderr, "%s: " format, __FUNCTION__, \
-					__VA_ARGS__);fflush(stderr);}
-#endif
-
-extern char *chgpath(char *, char *);
-extern long do_strncpy_from_user(int, void *, void *, unsigned long);
-extern int fd;
-
-#define SET_ERR(ret) if (ret == -1) ret = -errno
-
-int
-archdep_syscall(struct syscall_wait_desc *w, long *ret)
-{
-	char *fn;
-	char pathbuf[PATH_MAX];
-	char tmpbuf[PATH_MAX];
-
-	switch (w->sr.number) {
-		case __NR_open:
-			*ret = do_strncpy_from_user(fd, pathbuf,
-			                       (void *)w->sr.args[0], PATH_MAX);
-			if (*ret >= PATH_MAX) {
-				*ret = -ENAMETOOLONG;
-			}
-			if (*ret < 0) {
-				return 0;
-			}
-			__dprintf("open: %s\n", pathbuf);
-
-			fn = chgpath(pathbuf, tmpbuf);
-
-			*ret = open(fn, w->sr.args[1], w->sr.args[2]);
-			SET_ERR(*ret);
-			return 0;
-	}
-	return -1;
-}

lib/include/list.h

@@ -1,7 +1,9 @@
 #ifndef _LINUX_LIST_H
 #define _LINUX_LIST_H
 
+#ifndef offsetof
 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
+#endif
 /**
  * container_of - cast a member of a structure out to the containing structure
  * @ptr:        the pointer to the member.