head 1.1;A access ; symbols ; locks ; strict; comment @ * @; 1.1 date 85.03.31.18.11.42; author bbanerje; state Exp; branches ; next ; desc @@ 1.1 log @Initial revision @ text @/* * unexec.c - Convert a running program into an a.out file. * * Author: Spencer W. Thomas * Computer Science Dept. * University of Utah * Date: Tue Mar 2 1982 * Copyright (c) 1982 Spencer W. Thomas * * Synopsis: * unexec( new_name, a_name, data_start, bss_start ) * char *new_name, *a_name; * unsigned data_start, bss_start; * * Takes a snapshot of the program and makes an a.out format file in the * file named by the string argument new_name. * If a_name is non-NULL, the symbol table will be taken from the given file. * * The boundaries within the a.out file may be adjusted with the data_start * and bss_start arguments. Either or both may be given as 0 for defaults. * * Data_start gives the boundary between the text segment and the data * segment of the program. The text segment can contain shared, read-only * program code and literal data, while the data segment is always unshared * and unprotected. Data_start gives the lowest unprotected address. Since * the granularity of write-protection is on 1k page boundaries on the VAX, a * given data_start value which is not on a page boundary is rounded down to * the beginning of the page it is on. The default when 0 is given leaves the * number of protected pages the same as it was before. * * Bss_start indicates how much of the data segment is to be saved in the * a.out file and restored when the program is executed. It gives the lowest * unsaved address, and is rounded up to a page boundary. The default when 0 * is given assumes that the entire data segment is to be stored, including * the previous data and bss as well as any additional storage allocated with * break (2). * * This routine is expected to only work on a VAX running 4.1 bsd UNIX and * will probably require substantial conversion effort for other systems. * In particular, it depends on the fact that a process' _u structure is * accessible directly from the user program. * * If you make improvements I'd like to get them too. * harpo!utah-cs!thomas, thomas@@Utah-20 * */ #include #include #include #include #include #include /* #include */ #if !defined(vax) && !defined(m68000) /* this is ridiculous, it */ /* won''t work anywhere else */ #define N_BADMAG(x) ((x.a_magic != A_MAGIC1) && (x.a_magic != A_MAGIC2) &&\ (x.a_magic != A_MAGIC3) && (x.a_magic != A_MAGIC4) &&\ (x.a_magic != A_MAGIC5) && (x.a_magic != A_MAGIC6) ) #define N_TXTOFF(hdr) (sizeof hdr) #define OMAGIC A_MAGIC1 /* Magic number of Writeable text file */ #define UPAGES 020 #endif #ifdef vax #define UADDR (0x80000000 - ctob(UPAGES)) /* where _u starts */ #define PSIZE 10240 #endif #ifdef m68000 #define UADDR (0x1000000 - ctob(UPAGES)) #define PSIZE 8192 #endif #ifndef emacs #include #define PERROR perror #define ERROR fprintf #define ERRORF stderr, #else #define PERROR(file) error ("Failure operating on %s", file) #define ERROR error #define ERRORF #endif static struct user u; static struct exec hdr, ohdr; /* **************************************************************** * unexec * * driving logic. */ unexec( new_name, a_name, data_start, bss_start ) char *new_name, *a_name; unsigned data_start, bss_start; { int new, a_out = -1; if ( a_name && (a_out = open( a_name, 0 )) < 0 ) { PERROR( a_name ); return -1; } if ( (new = creat (new_name, 0666)) < 0) { PERROR( new_name ); return -1; } read_u(); if (make_hdr( new, a_out, data_start, bss_start ) < 0 || copy_text_and_data( new ) < 0 || copy_sym( new, a_out ) < 0) { close( new ); /* unlink( new_name ); /* Failed, unlink new a.out */ return -1; } close( new ); if ( a_out >= 0 ) close( a_out ); mark_x( new_name ); return 0; } /* **************************************************************** * read_u * * Get the u structure (from memory.) */ static read_u() { u = *(struct user *)UADDR; /* Simple, when it's in core... */ } /* **************************************************************** * make_hdr * * Make the header in the new a.out from the header in core. * Modify the text and data sizes. */ static int make_hdr( new, a_out, data_start, bss_start ) int new, a_out; unsigned data_start, bss_start; { /* Get symbol table info from header of a.out file if given one. */ if ( a_out >= 0 ) { if ( read( a_out, &hdr, sizeof hdr ) != sizeof hdr ) { PERROR( "Couldn't read header from a.out file" ); return -1; } if N_BADMAG( hdr ) { ERROR( ERRORF "a.out file doesn't have legal magic number\n" ); return -1; } /* Check for agreement between a.out file and program. */ /* This is not valid when the symbol table can come from * an oload incremental load file... */ # ifdef CHECK_A_OUT if ( hdr.a_magic != u.u_exdata.ux_mag || ( (hdr.a_magic != OMAGIC) && (hdr.a_text != u.u_exdata.ux_tsize || hdr.a_data != u.u_exdata.ux_dsize) ) || ( (hdr.a_magic == OMAGIC) && (hdr.a_data + hdr.a_text != u.u_exdata.ux_dsize) ) || hdr.a_entry != u.u_exdata.ux_entloc ) { ERROR( ERRORF "unexec: Program didn't come from given a.out\n" ); return -1; } # endif CHECK_A_OUT } else hdr.a_syms = 0; /* No a.out, so no symbol info. */ /* Construct header from user structure. */ hdr.a_magic = u.u_exdata.ux_mag; if(N_BADMAG(hdr)) { ERROR(ERRORF "unexec: bad magic number %d. Check u. layout\n"); return -1; } hdr.a_text = u.u_exdata.ux_tsize; hdr.a_data = u.u_exdata.ux_dsize; hdr.a_bss = u.u_exdata.ux_bsize; /* hdr.a_syms is set above. */ hdr.a_entry = u.u_exdata.ux_entloc; hdr.a_trsize = 0; hdr.a_drsize = 0; /* Save hdr before adjustments, for msgs. */ ohdr = hdr; /* Adjust data/bss boundary. */ if ( bss_start != 0 ) { bss_start = (bss_start+01777) & ~01777; /* (Up) to page bdry. */ if ( bss_start > ctob( u.u_dsize ) + ctob( u.u_tsize ) ) { ERROR( ERRORF "unexec: Specified bss_start( %u ) is past end of program.\n", bss_start ); return -1; } hdr.a_data = bss_start - hdr.a_text; /* Data between text and bss. */ hdr.a_bss = ctob( u.u_dsize ) - hdr.a_data; /* Remainder is bss. */ } else /* Default - All data is inited now! */ { hdr.a_data = ctob( u.u_dsize ); hdr.a_bss = 0; bss_start = ctob( u.u_dsize ) + ctob( u.u_tsize ); /* At end. */ } /* Adjust text/data boundary. */ if ( data_start != 0 ) { data_start = data_start & ~01777; /* (Down) to page boundary. */ hdr.a_text = data_start; /* Size of text segment. */ hdr.a_data = bss_start - hdr.a_text; /* Data between text and bss. */ } else { data_start = hdr.a_text; } /* Chatty... */ #ifndef emacs printf( "Text/Data boundary was %u, is now %u\n", ohdr.a_text, hdr.a_text ); printf( "Data/Bss boundary was %u, is now %u\n", ohdr.a_text + ohdr.a_data, hdr.a_text + hdr.a_data ); #endif if ( data_start > bss_start ) /* Can't have negative data size. */ { ERROR( ERRORF "unexec: data_start(%u) can't be greater than bss_start( %u ).\n", data_start, bss_start ); return -1; } #ifndef emacs printf( "Data segment size (excluding bss) was %u, is now %u\n", ohdr.a_data, hdr.a_data ); #endif if ( write( new, &hdr, sizeof hdr ) != sizeof hdr ) { PERROR( "Couldn't write header to new a.out file" ); return -1; } return 0; } /* **************************************************************** * copy_text_and_data * * Copy the text and data segments from memory to the new a.out */ static int copy_text_and_data( new ) int new; { int ret; char buf[80]; lseek( new, (long)N_TXTOFF(hdr), 0 ); ret = write (new, 0, hdr.a_text + hdr.a_data); if (ret != hdr.a_text + hdr.a_data) { sprintf(buf, "Write failure in unexec: \ ret %d s.b. %u mgc %d txt %u dta %u", ret, hdr.a_text + hdr.a_data, hdr.a_magic, hdr.a_text, hdr.a_data); PERROR(buf); return -1; } return 0; } /* **************************************************************** * copy_sym * * Copy the relocation information and symbol table from the a.out to the new */ static int copy_sym( new, a_out ) int new, a_out; { char page[PSIZE]; int n; if ( a_out < 0 ) return 0; lseek( a_out, (long)N_SYMOFF(ohdr), 0 ); /* Position a.out to symtab.*/ while ( (n = read( a_out, page, PSIZE )) > 0 ) { if ( write( new, page, n ) != n ) { PERROR( "Error writing symbol table to new a.out" ); ERROR( ERRORF "new a.out should be ok otherwise\n" ); return 0; } } if ( n < 0 ) { PERROR( "Error reading symbol table from a.out,\n" ); ERROR( ERRORF "new a.out should be ok otherwise\n" ); } return 0; } /* **************************************************************** * mark_x * * After succesfully building the new a.out, mark it executable */ static mark_x( name ) char *name; { struct stat sbuf; int um; um = umask( 777 ); umask( um ); if ( stat( name, &sbuf ) == -1 ) { PERROR ( "Can't stat new a.out" ); ERROR( ERRORF "Setting protection to %o\n", 0777 & ~um ); sbuf.st_mode = 0777; } sbuf.st_mode |= 0111 & ~um; if ( chmod( name, sbuf.st_mode ) == -1 ) PERROR( "Couldn't change mode of new a.out to executable" ); } @