/* This file handles the EXEC system call. It performs the work as follows: * - see if the permissions allow the file to be executed * - read the header and extract the sizes * - fetch the initial args and environment from the user space * - allocate the memory for the new process * - copy the initial stack from PM to the process * - read in the text and data segments and copy to the process * - take care of setuid and setgid bits * - fix up 'mproc' table * - tell kernel about EXEC * - save offset to initial argc (for ps) * * The entry points into this file are: * pm_exec: perform the EXEC system call */ #include "fs.h" #include #include #include #include #include #include #include #include #include #include #include #include #include "fproc.h" #include "path.h" #include "param.h" #include "vnode.h" #include "file.h" #include #include #include #include #define _KERNEL /* for ELF_AUX_ENTRIES */ #include /* fields only used by elf and in VFS */ struct vfs_exec_info { struct exec_info args; /* libexec exec args */ struct vnode *vp; /* Exec file's vnode */ struct vmnt *vmp; /* Exec file's vmnt */ struct stat sb; /* Exec file's stat structure */ int userflags; /* exec() flags from userland */ int is_dyn; /* Dynamically linked executable */ int elf_main_fd; /* Dyn: FD of main program execuatble */ char execname[PATH_MAX]; /* Full executable invocation */ int vmfd; int vmfd_used; }; static void lock_exec(void); static void unlock_exec(void); static int patch_stack(struct vnode *vp, char stack[ARG_MAX], size_t *stk_bytes, char path[PATH_MAX]); static int is_script(struct vfs_exec_info *execi); static int insert_arg(char stack[ARG_MAX], size_t *stk_bytes, char *arg, int replace); static void clo_exec(struct fproc *rfp); static int stack_prepare_elf(struct vfs_exec_info *execi, char *curstack, size_t *frame_len, vir_bytes *vsp, int *extrabase); static int map_header(struct vfs_exec_info *execi); static int read_seg(struct exec_info *execi, off_t off, off_t seg_addr, size_t seg_bytes); #define PTRSIZE sizeof(char *) /* Size of pointers in argv[] and envp[]. */ /* Array of loaders for different object file formats */ typedef int (*exechook_t)(struct vfs_exec_info *execpackage); typedef int (*stackhook_t)(struct vfs_exec_info *execi, char *curstack, size_t *frame_len, vir_bytes *, int *extrabase); struct exec_loaders { libexec_exec_loadfunc_t load_object; /* load executable into memory */ stackhook_t setup_stack; /* prepare stack before argc and argv push */ }; static const struct exec_loaders exec_loaders[] = { { libexec_load_elf, stack_prepare_elf }, { NULL, NULL } }; /*===========================================================================* * lock_exec * *===========================================================================*/ static void lock_exec(void) { struct fproc *org_fp; struct worker_thread *org_self; /* First try to get it right off the bat */ if (mutex_trylock(&exec_lock) == 0) return; org_fp = fp; org_self = self; if (mutex_lock(&exec_lock) != 0) panic("Could not obtain lock on exec"); fp = org_fp; self = org_self; } /*===========================================================================* * unlock_exec * *===========================================================================*/ static void unlock_exec(void) { if (mutex_unlock(&exec_lock) != 0) panic("Could not release lock on exec"); } /*===========================================================================* * get_read_vp * *===========================================================================*/ static int get_read_vp(struct vfs_exec_info *execi, char *fullpath, int copyprogname, int sugid, struct lookup *resolve, struct fproc *fp) { /* Make the executable that we want to exec() into the binary pointed * to by 'fullpath.' This function fills in necessary details in the execi * structure, such as opened vnode. It unlocks and releases the vnode if * it was already there. This makes it easy to change the executable * during the exec(), which is often necessary, by calling this function * more than once. This is specifically necessary when we discover the * executable is actually a script or a dynamically linked executable. */ int r; /* Caller wants to switch vp to the file in 'fullpath.' * unlock and put it first if there is any there. */ if(execi->vp) { unlock_vnode(execi->vp); put_vnode(execi->vp); execi->vp = NULL; } /* Remember/overwrite the executable name if requested. */ if(copyprogname) { char *cp = strrchr(fullpath, '/'); if(cp) cp++; else cp = fullpath; strlcpy(execi->args.progname, cp, sizeof(execi->args.progname)); execi->args.progname[sizeof(execi->args.progname)-1] = '\0'; } /* Open executable */ if ((execi->vp = eat_path(resolve, fp)) == NULL) return err_code; unlock_vmnt(execi->vmp); if (!S_ISREG(execi->vp->v_mode)) return ENOEXEC; else if ((r = forbidden(fp, execi->vp, X_BIT)) != OK) return r; else r = req_stat(execi->vp->v_fs_e, execi->vp->v_inode_nr, VFS_PROC_NR, (vir_bytes) &(execi->sb)); if (r != OK) return r; /* If caller wants us to, honour suid/guid mode bits. */ if (sugid) { /* Deal with setuid/setgid executables */ if (execi->vp->v_mode & I_SET_UID_BIT) { execi->args.new_uid = execi->vp->v_uid; execi->args.allow_setuid = 1; } if (execi->vp->v_mode & I_SET_GID_BIT) { execi->args.new_gid = execi->vp->v_gid; execi->args.allow_setuid = 1; } } /* Read in first chunk of file. */ if((r=map_header(execi)) != OK) return r; return OK; } #define FAILCHECK(expr) if((r=(expr)) != OK) { goto pm_execfinal; } while(0) #define Get_read_vp(e,f,p,s,rs,fp) do { \ r=get_read_vp(&e,f,p,s,rs,fp); if(r != OK) { FAILCHECK(r); } \ } while(0) static int vfs_memmap(struct exec_info *execi, vir_bytes vaddr, vir_bytes len, vir_bytes foffset, u16_t clearend, int protflags) { struct vfs_exec_info *vi = (struct vfs_exec_info *) execi->opaque; struct vnode *vp = ((struct vfs_exec_info *) execi->opaque)->vp; int r; u16_t flags = 0; if(protflags & PROT_WRITE) flags |= MVM_WRITABLE; r = minix_vfs_mmap(execi->proc_e, foffset, len, vp->v_dev, vp->v_inode_nr, vi->vmfd, vaddr, clearend, flags); if(r == OK) { vi->vmfd_used = 1; } return r; } /*===========================================================================* * pm_exec * *===========================================================================*/ int pm_exec(endpoint_t proc_e, vir_bytes path, size_t path_len, vir_bytes frame, size_t frame_len, vir_bytes *pc, vir_bytes *newsp, int user_exec_flags) { /* Perform the execve(name, argv, envp) call. The user library builds a * complete stack image, including pointers, args, environ, etc. The stack * is copied to a buffer inside VFS, and then to the new core image. */ int r, slot; vir_bytes vsp; struct fproc *rfp; int extrabase = 0; static char mbuf[ARG_MAX]; /* buffer for stack and zeroes */ struct vfs_exec_info execi; int i; static char fullpath[PATH_MAX], elf_interpreter[PATH_MAX], firstexec[PATH_MAX], finalexec[PATH_MAX]; struct lookup resolve; struct fproc *vmfp = &fproc[VM_PROC_NR]; stackhook_t makestack = NULL; static int n; n++; struct filp *newfilp = NULL; lock_exec(); lock_proc(vmfp, 0); /* unset execi values are 0. */ memset(&execi, 0, sizeof(execi)); execi.vmfd = -1; /* passed from exec() libc code */ execi.userflags = user_exec_flags; execi.args.stack_high = kinfo.user_sp; execi.args.stack_size = DEFAULT_STACK_LIMIT; okendpt(proc_e, &slot); rfp = fp = &fproc[slot]; rfp->text_size = 0; rfp->data_size = 0; lookup_init(&resolve, fullpath, PATH_NOFLAGS, &execi.vmp, &execi.vp); resolve.l_vmnt_lock = VMNT_READ; resolve.l_vnode_lock = VNODE_READ; /* Fetch the stack from the user before destroying the old core image. */ if (frame_len > ARG_MAX) FAILCHECK(ENOMEM); /* stack too big */ r = sys_datacopy(proc_e, (vir_bytes) frame, SELF, (vir_bytes) mbuf, (size_t) frame_len); if (r != OK) { /* can't fetch stack (e.g. bad virtual addr) */ printf("VFS: pm_exec: sys_datacopy failed\n"); FAILCHECK(r); } /* The default is to keep the original user and group IDs */ execi.args.new_uid = rfp->fp_effuid; execi.args.new_gid = rfp->fp_effgid; /* Get the exec file name. */ FAILCHECK(fetch_name(path, path_len, fullpath)); strlcpy(finalexec, fullpath, PATH_MAX); strlcpy(firstexec, fullpath, PATH_MAX); /* Get_read_vp will return an opened vn in execi. * if necessary it releases the existing vp so we can * switch after we find out what's inside the file. * It reads the start of the file. */ Get_read_vp(execi, fullpath, 1, 1, &resolve, fp); /* If this is a script (i.e. has a #!/interpreter line), * retrieve the name of the interpreter and open that * executable instead. */ if(is_script(&execi)) { /* patch_stack will add interpreter name and * args to stack and retrieve the new binary * name into fullpath. */ FAILCHECK(fetch_name(path, path_len, fullpath)); FAILCHECK(patch_stack(execi.vp, mbuf, &frame_len, fullpath)); strlcpy(finalexec, fullpath, PATH_MAX); strlcpy(firstexec, fullpath, PATH_MAX); Get_read_vp(execi, fullpath, 1, 0, &resolve, fp); } /* If this is a dynamically linked executable, retrieve * the name of that interpreter in elf_interpreter and open that * executable instead. But open the current executable in an * fd for the current process. */ if(elf_has_interpreter(execi.args.hdr, execi.args.hdr_len, elf_interpreter, sizeof(elf_interpreter))) { /* Switch the executable vnode to the interpreter */ execi.is_dyn = 1; /* The interpreter (loader) needs an fd to the main program, * which is currently in finalexec */ if((r = execi.elf_main_fd = common_open(finalexec, O_RDONLY, 0)) < 0) { printf("VFS: exec: dynamic: open main exec failed %s (%d)\n", fullpath, r); FAILCHECK(r); } /* ld.so is linked at 0, but it can relocate itself; we * want it higher to trap NULL pointer dereferences. */ execi.args.load_offset = 0x10000; /* Remember it */ strlcpy(execi.execname, finalexec, PATH_MAX); /* The executable we need to execute first (loader) * is in elf_interpreter, and has to be in fullpath to * be looked up */ strlcpy(fullpath, elf_interpreter, PATH_MAX); strlcpy(firstexec, elf_interpreter, PATH_MAX); Get_read_vp(execi, fullpath, 0, 0, &resolve, fp); } /* We also want an FD for VM to mmap() the process in if possible. */ { struct vnode *vp = execi.vp; assert(vp); if(vp->v_vmnt->m_haspeek && major(vp->v_dev) != MEMORY_MAJOR) { int newfd = -1; if(get_fd(vmfp, 0, R_BIT, &newfd, &newfilp) == OK) { assert(newfd >= 0 && newfd < OPEN_MAX); assert(!vmfp->fp_filp[newfd]); newfilp->filp_count = 1; newfilp->filp_vno = vp; newfilp->filp_flags = O_RDONLY; FD_SET(newfd, &vmfp->fp_filp_inuse); vmfp->fp_filp[newfd] = newfilp; /* dup_vnode(vp); */ execi.vmfd = newfd; execi.args.memmap = vfs_memmap; } } } /* callback functions and data */ execi.args.copymem = read_seg; execi.args.clearproc = libexec_clearproc_vm_procctl; execi.args.clearmem = libexec_clear_sys_memset; execi.args.allocmem_prealloc_cleared = libexec_alloc_mmap_prealloc_cleared; execi.args.allocmem_prealloc_junk = libexec_alloc_mmap_prealloc_junk; execi.args.allocmem_ondemand = libexec_alloc_mmap_ondemand; execi.args.opaque = &execi; execi.args.proc_e = proc_e; execi.args.frame_len = frame_len; execi.args.filesize = execi.vp->v_size; for (i = 0; exec_loaders[i].load_object != NULL; i++) { r = (*exec_loaders[i].load_object)(&execi.args); /* Loaded successfully, so no need to try other loaders */ if (r == OK) { makestack = exec_loaders[i].setup_stack; break; } } FAILCHECK(r); /* Inform PM */ FAILCHECK(libexec_pm_newexec(proc_e, &execi.args)); /* Save off PC */ *pc = execi.args.pc; /* call a stack-setup function if this executable type wants it */ vsp = execi.args.stack_high - frame_len; if(makestack) FAILCHECK(makestack(&execi, mbuf, &frame_len, &vsp, &extrabase)); /* Patch up stack and copy it from VFS to new core image. */ libexec_patch_ptr(mbuf, vsp + extrabase); FAILCHECK(sys_datacopy(SELF, (vir_bytes) mbuf, proc_e, (vir_bytes) vsp, (phys_bytes)frame_len)); /* Return new stack pointer to caller */ *newsp = vsp; clo_exec(rfp); if (execi.args.allow_setuid) { /* If after loading the image we're still allowed to run with * setuid or setgid, change credentials now */ rfp->fp_effuid = execi.args.new_uid; rfp->fp_effgid = execi.args.new_gid; } /* Remember the new name of the process */ strlcpy(rfp->fp_name, execi.args.progname, PROC_NAME_LEN); rfp->text_size = execi.args.text_size; rfp->data_size = execi.args.data_size; pm_execfinal: if(newfilp) unlock_filp(newfilp); else if (execi.vp != NULL) { unlock_vnode(execi.vp); put_vnode(execi.vp); } if(execi.vmfd >= 0 && !execi.vmfd_used) { if(OK != close_fd(vmfp, execi.vmfd)) { printf("VFS: unexpected close fail of vm fd\n"); } } unlock_proc(vmfp); unlock_exec(); return(r); } static int stack_prepare_elf(struct vfs_exec_info *execi, char *frame, size_t *framelen, vir_bytes *newsp, int *extrabase) { AuxInfo *a, *term; Elf_Ehdr *elf_header; int nulls; char **mysp = (char **) frame, **mysp_end = (char **) ((char *)frame + *framelen); if(!execi->is_dyn) return OK; assert(execi->args.hdr_len >= sizeof(*elf_header)); elf_header = (Elf_Ehdr *) execi->args.hdr; /* exec() promises stack space. Now find it. */ mysp++; /* skip argc */ /* find a terminating NULL entry twice: one for argv[], one for envp[]. */ for(nulls = 0; nulls < 2; nulls++) { assert(mysp < mysp_end); while(*mysp && mysp < mysp_end) mysp++; /* find terminating NULL */ if(mysp >= mysp_end) { printf("VFS: malformed stack for exec()\n"); return ENOEXEC; } assert(!*mysp); mysp++; } /* Userland provides a fully filled stack frame, with argc, argv, envp * and then all the argv and envp strings; consistent with ELF ABI, except * for a list of Aux vectors that should be between envp points and the * start of the strings. * * It would take some very unpleasant hackery to insert the aux vectors before * the strings, and correct all the pointers, so the exec code in libc makes * space for us first and indicates the fact it did this with this flag. */ if(!(execi->userflags & PMEF_AUXVECTORSPACE)) { char *f = (char *) mysp; int remain; vir_bytes extrabytes = sizeof(*a) * PMEF_AUXVECTORS; /* Create extrabytes more space */ remain = *framelen - (int)(f - frame); if(*framelen + extrabytes >= ARG_MAX) return ENOMEM; *framelen += extrabytes; *newsp -= extrabytes; *extrabase += extrabytes; memmove(f+extrabytes, f, remain); memset(f, 0, extrabytes); } /* Ok, what mysp points to now we can use for the aux vectors. */ a = (AuxInfo *) mysp; #define AUXINFO(type, value) \ { assert((char *) a < (char *) mysp_end); a->a_type = type; a->a_v = value; a++; } #if 0 AUXINFO(AT_PHENT, elf_header->e_phentsize); AUXINFO(AT_PHNUM, elf_header->e_phnum); #endif AUXINFO(AT_BASE, execi->args.load_base); AUXINFO(AT_ENTRY, execi->args.pc); AUXINFO(AT_PAGESZ, PAGE_SIZE); AUXINFO(AT_EXECFD, execi->elf_main_fd); /* This is where we add the AT_NULL */ term = a; /* Always terminate with AT_NULL */ AUXINFO(AT_NULL, 0); /* Empty space starts here, if any. */ if((execi->userflags & PMEF_EXECNAMESPACE1) && strlen(execi->execname) < PMEF_EXECNAMELEN1) { char *spacestart; vir_bytes userp; /* Make space for the real closing AT_NULL entry. */ AUXINFO(AT_NULL, 0); /* Empty space starts here; we can put the name here. */ spacestart = (char *) a; strlcpy(spacestart, execi->execname, PATH_MAX); /* What will the address of the string for the user be */ userp = *newsp + (spacestart-frame); /* Move back to where the AT_NULL is */ a = term; AUXINFO(AT_SUN_EXECNAME, userp); AUXINFO(AT_NULL, 0); } return OK; } /*===========================================================================* * is_script * *===========================================================================*/ static int is_script(struct vfs_exec_info *execi) { /* Is Interpreted script? */ assert(execi->args.hdr != NULL); return(execi->args.hdr[0] == '#' && execi->args.hdr[1] == '!' && execi->args.hdr_len >= 2); } /*===========================================================================* * patch_stack * *===========================================================================*/ static int patch_stack(vp, stack, stk_bytes, path) struct vnode *vp; /* pointer for open script file */ char stack[ARG_MAX]; /* pointer to stack image within VFS */ size_t *stk_bytes; /* size of initial stack */ char path[PATH_MAX]; /* path to script file */ { /* Patch the argument vector to include the path name of the script to be * interpreted, and all strings on the #! line. Returns the path name of * the interpreter. */ enum { INSERT=FALSE, REPLACE=TRUE }; int n, r; off_t pos; char *sp, *interp = NULL; u64_t new_pos; unsigned int cum_io; char buf[_MAX_BLOCK_SIZE]; /* Make 'path' the new argv[0]. */ if (!insert_arg(stack, stk_bytes, path, REPLACE)) return(ENOMEM); pos = 0; /* Read from the start of the file */ /* Issue request */ r = req_readwrite(vp->v_fs_e, vp->v_inode_nr, ((u64_t)(pos)), READING, VFS_PROC_NR, buf, _MAX_BLOCK_SIZE, &new_pos, &cum_io); if (r != OK) return(r); n = vp->v_size; if (n > _MAX_BLOCK_SIZE) n = _MAX_BLOCK_SIZE; if (n < 2) return ENOEXEC; sp = &(buf[2]); /* just behind the #! */ n -= 2; if (n > PATH_MAX) n = PATH_MAX; /* Use the 'path' variable for temporary storage */ memcpy(path, sp, n); if ((sp = memchr(path, '\n', n)) == NULL) /* must be a proper line */ return(ENOEXEC); /* Move sp backwards through script[], prepending each string to stack. */ for (;;) { /* skip spaces behind argument. */ while (sp > path && (*--sp == ' ' || *sp == '\t')) {} if (sp == path) break; sp[1] = 0; /* Move to the start of the argument. */ while (sp > path && sp[-1] != ' ' && sp[-1] != '\t') --sp; interp = sp; if (!insert_arg(stack, stk_bytes, sp, INSERT)) { printf("VFS: patch_stack: insert_arg failed\n"); return(ENOMEM); } } if(!interp) return ENOEXEC; /* Round *stk_bytes up to the size of a pointer for alignment contraints. */ *stk_bytes= ((*stk_bytes + PTRSIZE - 1) / PTRSIZE) * PTRSIZE; if (interp != path) memmove(path, interp, strlen(interp)+1); return(OK); } /*===========================================================================* * insert_arg * *===========================================================================*/ static int insert_arg( char stack[ARG_MAX], /* pointer to stack image within PM */ size_t *stk_bytes, /* size of initial stack */ char *arg, /* argument to prepend/replace as new argv[0] */ int replace ) { /* Patch the stack so that arg will become argv[0]. Be careful, the stack may * be filled with garbage, although it normally looks like this: * nargs argv[0] ... argv[nargs-1] NULL envp[0] ... NULL * followed by the strings "pointed" to by the argv[i] and the envp[i]. The * pointers are really offsets from the start of stack. * Return true iff the operation succeeded. */ int offset; vir_bytes a0, a1; size_t old_bytes = *stk_bytes; /* Prepending arg adds at least one string and a zero byte. */ offset = strlen(arg) + 1; a0 = (int) ((char **) stack)[1]; /* argv[0] */ if (a0 < 4 * PTRSIZE || a0 >= old_bytes) return(FALSE); a1 = a0; /* a1 will point to the strings to be moved */ if (replace) { /* Move a1 to the end of argv[0][] (argv[1] if nargs > 1). */ do { if (a1 == old_bytes) return(FALSE); --offset; } while (stack[a1++] != 0); } else { offset += PTRSIZE; /* new argv[0] needs new pointer in argv[] */ a0 += PTRSIZE; /* location of new argv[0][]. */ } /* stack will grow by offset bytes (or shrink by -offset bytes) */ if ((*stk_bytes += offset) > ARG_MAX) return(FALSE); /* Reposition the strings by offset bytes */ memmove(stack + a1 + offset, stack + a1, old_bytes - a1); strlcpy(stack + a0, arg, PATH_MAX); /* Put arg in the new space. */ if (!replace) { /* Make space for a new argv[0]. */ memmove(stack + 2 * PTRSIZE, stack + 1 * PTRSIZE, a0 - 2 * PTRSIZE); ((char **) stack)[0]++; /* nargs++; */ } /* Now patch up argv[] and envp[] by offset. */ libexec_patch_ptr(stack, (vir_bytes) offset); ((char **) stack)[1] = (char *) a0; /* set argv[0] correctly */ return(TRUE); } /*===========================================================================* * read_seg * *===========================================================================*/ static int read_seg(struct exec_info *execi, off_t off, off_t seg_addr, size_t seg_bytes) { /* * The byte count on read is usually smaller than the segment count, because * a segment is padded out to a click multiple, and the data segment is only * partially initialized. */ int r; u64_t new_pos; unsigned int cum_io; struct vnode *vp = ((struct vfs_exec_info *) execi->opaque)->vp; /* Make sure that the file is big enough */ if (off + seg_bytes > LONG_MAX) return(EIO); if ((unsigned long) vp->v_size < off+seg_bytes) return(EIO); if ((r = req_readwrite(vp->v_fs_e, vp->v_inode_nr, ((u64_t)(off)), READING, execi->proc_e, (char*)seg_addr, seg_bytes, &new_pos, &cum_io)) != OK) { printf("VFS: read_seg: req_readwrite failed (data)\n"); return(r); } if (r == OK && cum_io != seg_bytes) printf("VFS: read_seg segment has not been read properly\n"); return(r); } /*===========================================================================* * clo_exec * *===========================================================================*/ static void clo_exec(struct fproc *rfp) { /* Files can be marked with the FD_CLOEXEC bit (in fp->fp_cloexec). */ int i; /* Check the file desriptors one by one for presence of FD_CLOEXEC. */ for (i = 0; i < OPEN_MAX; i++) if ( FD_ISSET(i, &rfp->fp_cloexec_set)) (void) close_fd(rfp, i); } /*===========================================================================* * map_header * *===========================================================================*/ static int map_header(struct vfs_exec_info *execi) { int r; u64_t new_pos; unsigned int cum_io; off_t pos; static char hdr[PAGE_SIZE]; /* Assume that header is not larger than a page */ pos = 0; /* Read from the start of the file */ /* How much is sensible to read */ execi->args.hdr_len = MIN(execi->vp->v_size, sizeof(hdr)); execi->args.hdr = hdr; r = req_readwrite(execi->vp->v_fs_e, execi->vp->v_inode_nr, ((u64_t)(pos)), READING, VFS_PROC_NR, hdr, execi->args.hdr_len, &new_pos, &cum_io); if (r != OK) { printf("VFS: exec: map_header: req_readwrite failed\n"); return(r); } return(OK); }