exec() cleanup, generalization, improvement

. make exec() callers (i.e. vfs and rs) determine the
	  memory layout by explicitly reserving regions using
	  mmap() calls on behalf of the exec()ing process,
	  i.e. handling all of the exec logic, thereby eliminating
	  all special exec() knowledge from VM.
	. the new procedure is: clear the exec()ing process
	  first, then call third-party mmap()s to reserve memory, then
	  copy the executable file section contents in, all using callbacks
	  tailored to the caller's way of starting an executable
	. i.e. no more explicit EXEC_NEWMEM-style calls in PM or VM
	  as with rigid 2-section arguments
	. this naturally allows generalizing exec() by simply loading
	  all ELF sections
	. drop/merge of lots of duplicate exec() code into libexec
	. not copying the code sections to vfs and into the executable
	  again is a measurable performance improvement (about 3.3% faster
	  for 'make' in src/servers/)

include/arch/i386/include/vmparam.h

@@ -49,4 +49,9 @@
 #define	PAGE_SIZE	(1 << PAGE_SHIFT)
 #define	PAGE_MASK	(PAGE_SIZE - 1)
 
+/* As visible from the user space process, where is the top of the
+ * stack (first non-stack byte), when in paged mode?
+ */
+#define VM_STACKTOP     0x80000000
+
 #endif /* _I386_VMPARAM_H_ */

include/minix/callnr.h

@@ -97,9 +97,7 @@
 #define CPROF             99    /* to PM */
 
 /* Calls provided by PM and FS that are not part of the API */
-#define EXEC_NEWMEM	100	/* from VFS or RS to PM: new memory map for
-				 * exec
-				 */
+#define PM_NEWEXEC	100	/* from VFS or RS to PM: new exec */
 #define SRV_FORK  	101	/* to PM: special fork call for RS */
 #define EXEC_RESTART	102	/* to PM: final part of exec for RS */
 #define GETPROCNR	104	/* to PM */

include/minix/sys_config.h

@@ -54,4 +54,7 @@ error "_MINIX_MACHINE has incorrect value (0)"
 
 #define _KMESS_BUF_SIZE  10000
 
+/* Default stack size (limit) */
+#define DEFAULT_STACK_LIMIT (64 * 1024 * 1024)
+
 #endif /* _MINIX_SYS_CONFIG_H */

include/minix/type.h

@@ -166,26 +166,6 @@ struct mem_range
 	phys_bytes mr_limit;	/* Highest memory address in range */
 };
 
-/* For EXEC_NEWMEM */
-struct exec_newmem
-{
-	vir_bytes text_addr;	/* Starting address of text section */
-	vir_bytes text_bytes;	/* Length of text section (in bytes) */
-	vir_bytes data_addr;	/* Starting address of data section */
-	vir_bytes data_bytes;	/* Length of data section (in bytes) */
-	vir_bytes tot_bytes;	/* Minimum stack region size (in bytes) */
-	vir_bytes args_bytes;	/* Arguments/environ size on stack (in bytes) */
-	int sep_id;		/* Separate I&D?  */
-	int is_elf;		/* Is ELF exe? */
-	dev_t st_dev;		/* Device holding executable file */
-	ino_t st_ino;		/* Inode of executable file */
-	time_t enst_ctime;	/* Last changed time of executable file */
-	uid_t new_uid;		/* Process UID after exec */
-	gid_t new_gid;		/* Process GID after exec */
-	int setugid;		/* Process is setuid or setgid */
-	char progname[16];	/* Should be at least PROC_NAME_LEN */
-};
-
 /* Memory chunks. */
 struct memory {
 	phys_bytes	base;

include/minix/vm.h

@@ -9,8 +9,6 @@
 int vm_exit(endpoint_t ep);
 int vm_fork(endpoint_t ep, int slotno, endpoint_t *child_ep);
 int vm_brk(endpoint_t ep, char *newaddr);
-int vm_exec_newmem(endpoint_t ep, struct exec_newmem *args, int
-	args_bytes, char **ret_stack_top, int *ret_flags);
 int vm_push_sig(endpoint_t ep, vir_bytes *old_sp);
 int vm_willexit(endpoint_t ep);
 int vm_adddma(endpoint_t proc_e, phys_bytes start, phys_bytes size);