ref: a2ad59b340bf3339dbba105310002474b98d0184
dir: /sys/src/libmach/executable.c/
#include <u.h> #include <libc.h> #include <bio.h> #include <bootexec.h> #include <mach.h> #include "elf.h" /* * All a.out header types. The dummy entry allows canonical * processing of the union as a sequence of longs */ typedef struct { union{ struct { Exec; /* a.out.h */ uvlong hdr[1]; }; Ehdr; /* elf.h */ E64hdr; struct mipsexec; /* bootexec.h */ struct mips4kexec; /* bootexec.h */ struct sparcexec; /* bootexec.h */ struct nextexec; /* bootexec.h */ } e; long dummy; /* padding to ensure extra long */ } ExecHdr; static int nextboot(int, Fhdr*, ExecHdr*); static int sparcboot(int, Fhdr*, ExecHdr*); static int mipsboot(int, Fhdr*, ExecHdr*); static int mips4kboot(int, Fhdr*, ExecHdr*); static int common(int, Fhdr*, ExecHdr*); static int commonllp64(int, Fhdr*, ExecHdr*); static int adotout(int, Fhdr*, ExecHdr*); static int elfdotout(int, Fhdr*, ExecHdr*); static int armdotout(int, Fhdr*, ExecHdr*); static void setsym(Fhdr*, long, long, long, vlong); static void setdata(Fhdr*, uvlong, long, vlong, long); static void settext(Fhdr*, uvlong, uvlong, long, vlong); static void hswal(void*, int, ulong(*)(ulong)); static uvlong _round(uvlong, ulong); /* * definition of per-executable file type structures */ typedef struct Exectable{ long magic; /* big-endian magic number of file */ char *name; /* executable identifier */ char *dlmname; /* dynamically loadable module identifier */ uchar type; /* Internal code */ uchar _magic; /* _MAGIC() magic */ Mach *mach; /* Per-machine data */ long hsize; /* header size */ ulong (*swal)(ulong); /* beswal or leswal */ int (*hparse)(int, Fhdr*, ExecHdr*); } ExecTable; extern Mach mmips; extern Mach mmips2le; extern Mach mmips2be; extern Mach msparc; extern Mach msparc64; extern Mach m68020; extern Mach mi386; extern Mach mamd64; extern Mach marm; extern Mach mthumb; extern Mach marm64; extern Mach mpower; extern Mach mpower64; extern Mach mloong; ExecTable exectab[] = { { V_MAGIC, /* Mips v.out */ "mips plan 9 executable BE", "mips plan 9 dlm BE", FMIPS, 1, &mmips, sizeof(Exec), beswal, adotout }, { P_MAGIC, /* Mips 0.out (r3k le) */ "mips plan 9 executable LE", "mips plan 9 dlm LE", FMIPSLE, 1, &mmips, sizeof(Exec), beswal, adotout }, { M_MAGIC, /* Mips 4.out */ "mips 4k plan 9 executable BE", "mips 4k plan 9 dlm BE", FMIPS2BE, 1, &mmips2be, sizeof(Exec), beswal, adotout }, { N_MAGIC, /* Mips 0.out */ "mips 4k plan 9 executable LE", "mips 4k plan 9 dlm LE", FMIPS2LE, 1, &mmips2le, sizeof(Exec), beswal, adotout }, { 0x160<<16, /* Mips boot image */ "mips plan 9 boot image", nil, FMIPSB, 0, &mmips, sizeof(struct mipsexec), beswal, mipsboot }, { (0x160<<16)|3, /* Mips boot image */ "mips 4k plan 9 boot image", nil, FMIPSB, 0, &mmips2be, sizeof(struct mips4kexec), beswal, mips4kboot }, { K_MAGIC, /* Sparc k.out */ "sparc plan 9 executable", "sparc plan 9 dlm", FSPARC, 1, &msparc, sizeof(Exec), beswal, adotout }, { 0x01030107, /* Sparc boot image */ "sparc plan 9 boot image", nil, FSPARCB, 0, &msparc, sizeof(struct sparcexec), beswal, sparcboot }, { U_MAGIC, /* Sparc64 u.out */ "sparc64 plan 9 executable", "sparc64 plan 9 dlm", FSPARC64, 1, &msparc64, sizeof(Exec), beswal, adotout }, { A_MAGIC, /* 68020 2.out & boot image */ "68020 plan 9 executable", "68020 plan 9 dlm", F68020, 1, &m68020, sizeof(Exec), beswal, common }, { 0xFEEDFACE, /* Next boot image */ "next plan 9 boot image", nil, FNEXTB, 0, &m68020, sizeof(struct nextexec), beswal, nextboot }, { I_MAGIC, /* I386 8.out & boot image */ "386 plan 9 executable", "386 plan 9 dlm", FI386, 1, &mi386, sizeof(Exec), beswal, common }, { S_MAGIC, /* amd64 6.out & boot image */ "amd64 plan 9 executable", "amd64 plan 9 dlm", FAMD64, 1, &mamd64, sizeof(Exec)+8, nil, commonllp64 }, { Q_MAGIC, /* PowerPC q.out & boot image */ "power plan 9 executable", "power plan 9 dlm", FPOWER, 1, &mpower, sizeof(Exec), beswal, common }, { T_MAGIC, /* power64 9.out & boot image */ "power64 plan 9 executable", "power64 plan 9 dlm", FPOWER64, 1, &mpower64, sizeof(Exec)+8, nil, commonllp64 }, { ELF_MAG, /* any ELF */ "elf executable", nil, FNONE, 0, &mi386, sizeof(Ehdr), nil, elfdotout }, { E_MAGIC, /* Arm 5.out and boot image */ "arm plan 9 executable", "arm plan 9 dlm", FARM, 1, &marm, sizeof(Exec), beswal, common }, { (143<<16)|0413, /* (Free|Net)BSD Arm */ "arm *bsd executable", nil, FARM, 0, &marm, sizeof(Exec), leswal, armdotout }, { R_MAGIC, /* Arm64 7.out and boot image */ "arm64 plan 9 executable", "arm64 plan 9 dlm", FARM64, 1, &marm64, sizeof(Exec)+8, nil, commonllp64 }, { Z_MAGIC, /* LoongArch z.out and boot image */ "loong plan 9 executable", "loong plan 9 dlm", FLOONG, 1, &mloong, sizeof(Exec)+8, nil, commonllp64 }, { 0 }, }; Mach *mach = &mi386; /* Global current machine table */ int crackhdr(int fd, Fhdr *fp) { ExecTable *mp; ExecHdr d; int nb, ret; ulong magic; fp->type = FNONE; nb = read(fd, (char *)&d.e, sizeof(d.e)); if (nb <= 0) return 0; ret = 0; magic = beswal(d.e.magic); /* big-endian */ for (mp = exectab; mp->magic; mp++) { if (nb < mp->hsize) continue; /* * The magic number has morphed into something * with fields (the straw was DYN_MAGIC) so now * a flag is needed in Fhdr to distinguish _MAGIC() * magic numbers from foreign magic numbers. * * This code is creaking a bit and if it has to * be modified/extended much more it's probably * time to step back and redo it all. */ if(mp->_magic){ if(mp->magic != (magic & ~DYN_MAGIC)) continue; if ((magic & DYN_MAGIC) && mp->dlmname != nil) fp->name = mp->dlmname; else fp->name = mp->name; } else{ if(mp->magic != magic) continue; fp->name = mp->name; } fp->type = mp->type; fp->hdrsz = mp->hsize; /* will be zero on bootables */ fp->_magic = mp->_magic; fp->magic = magic; mach = mp->mach; if(mp->swal != nil) hswal(&d, sizeof(d.e)/sizeof(ulong), mp->swal); ret = mp->hparse(fd, fp, &d); seek(fd, mp->hsize, 0); /* seek to end of header */ break; } switch(mp->magic){ case E_MAGIC: thumbpctab(fd, fp); break; case 0: werrstr("unknown header type"); break; } return ret; } /* * Convert header to canonical form */ static void hswal(void *v, int n, ulong (*swap)(ulong)) { ulong *ulp; for(ulp = v; n--; ulp++) *ulp = (*swap)(*ulp); } /* * Crack a normal a.out-type header */ static int adotout(int fd, Fhdr *fp, ExecHdr *hp) { long pgsize; USED(fd); pgsize = mach->pgsize; settext(fp, hp->e.entry, pgsize+sizeof(Exec), hp->e.text, sizeof(Exec)); setdata(fp, _round(pgsize+fp->txtsz+sizeof(Exec), pgsize), hp->e.data, fp->txtsz+sizeof(Exec), hp->e.bss); setsym(fp, hp->e.syms, hp->e.spsz, hp->e.pcsz, fp->datoff+fp->datsz); return 1; } static void commonboot(Fhdr *fp) { /* arm needs to check for both arm and thumb */ if(fp->type == FARM && (fp->entry & mthumb.ktmask)) goto FTHUM; if (!(fp->entry & mach->ktmask)) return; switch(fp->type) { /* boot image */ case F68020: fp->type = F68020B; fp->name = "68020 plan 9 boot image"; break; case FI386: fp->type = FI386B; fp->txtaddr = (u32int)fp->entry; fp->name = "386 plan 9 boot image"; fp->dataddr = _round(fp->txtaddr+fp->txtsz, mach->pgsize); break; FTHUM: case FARM: fp->type = FARMB; fp->txtaddr = (u32int)fp->entry; fp->name = "ARM plan 9 boot image"; fp->dataddr = _round(fp->txtaddr+fp->txtsz, mach->pgsize); return; case FARM64: fp->type = FARM64B; fp->txtaddr = fp->entry; fp->name = "arm64 plan 9 boot image"; fp->dataddr = _round(fp->txtaddr+fp->txtsz, mach->pgsize); return; case FLOONG: fp->type = FLOONGB; fp->txtaddr = fp->entry; fp->name = "loong plan 9 boot image"; fp->dataddr = _round(fp->txtaddr+fp->txtsz, mach->pgsize); return; case FPOWER: fp->type = FPOWERB; fp->txtaddr = (u32int)fp->entry; fp->name = "power plan 9 boot image"; fp->dataddr = fp->txtaddr+fp->txtsz; break; case FAMD64: fp->type = FAMD64B; fp->txtaddr = fp->entry; fp->name = "amd64 plan 9 boot image"; fp->dataddr = _round(fp->txtaddr+fp->txtsz, 4096); break; case FPOWER64: fp->type = FPOWER64B; fp->txtaddr = fp->entry; fp->name = "power64 plan 9 boot image"; fp->dataddr = fp->txtaddr+fp->txtsz; break; default: return; } fp->hdrsz = 0; /* header stripped */ } /* * _MAGIC() style headers and * alpha plan9-style bootable images for axp "headerless" boot * */ static int common(int fd, Fhdr *fp, ExecHdr *hp) { adotout(fd, fp, hp); if(hp->e.magic & DYN_MAGIC) { fp->txtaddr = 0; fp->dataddr = fp->txtsz; return 1; } commonboot(fp); return 1; } static int commonllp64(int, Fhdr *fp, ExecHdr *hp) { long pgsize; uvlong entry; hswal(&hp->e, sizeof(Exec)/sizeof(long), beswal); if(!(hp->e.magic & HDR_MAGIC)) return 0; /* * There can be more magic here if the * header ever needs more expansion. * For now just catch use of any of the * unused bits. */ if((hp->e.magic & ~DYN_MAGIC)>>16) return 0; entry = beswav(hp->e.hdr[0]); pgsize = mach->pgsize; settext(fp, entry, pgsize+fp->hdrsz, hp->e.text, fp->hdrsz); setdata(fp, _round(pgsize+fp->txtsz+fp->hdrsz, pgsize), hp->e.data, fp->txtsz+fp->hdrsz, hp->e.bss); setsym(fp, hp->e.syms, hp->e.spsz, hp->e.pcsz, fp->datoff+fp->datsz); if(hp->e.magic & DYN_MAGIC) { fp->txtaddr = 0; fp->dataddr = fp->txtsz; return 1; } commonboot(fp); return 1; } /* * mips bootable image. */ static int mipsboot(int fd, Fhdr *fp, ExecHdr *hp) { USED(fd); fp->type = FMIPSB; switch(hp->e.amagic) { default: case 0407: /* some kind of mips */ settext(fp, (u32int)hp->e.mentry, (u32int)hp->e.text_start, hp->e.tsize, sizeof(struct mipsexec)+4); setdata(fp, (u32int)hp->e.data_start, hp->e.dsize, fp->txtoff+hp->e.tsize, hp->e.bsize); break; case 0413: /* some kind of mips */ settext(fp, (u32int)hp->e.mentry, (u32int)hp->e.text_start, hp->e.tsize, 0); setdata(fp, (u32int)hp->e.data_start, hp->e.dsize, hp->e.tsize, hp->e.bsize); break; } setsym(fp, hp->e.nsyms, 0, hp->e.pcsize, hp->e.symptr); fp->hdrsz = 0; /* header stripped */ return 1; } /* * mips4k bootable image. */ static int mips4kboot(int fd, Fhdr *fp, ExecHdr *hp) { USED(fd); fp->type = FMIPSB; switch(hp->e.h.amagic) { default: case 0407: /* some kind of mips */ settext(fp, (u32int)hp->e.h.mentry, (u32int)hp->e.h.text_start, hp->e.h.tsize, sizeof(struct mips4kexec)); setdata(fp, (u32int)hp->e.h.data_start, hp->e.h.dsize, fp->txtoff+hp->e.h.tsize, hp->e.h.bsize); break; case 0413: /* some kind of mips */ settext(fp, (u32int)hp->e.h.mentry, (u32int)hp->e.h.text_start, hp->e.h.tsize, 0); setdata(fp, (u32int)hp->e.h.data_start, hp->e.h.dsize, hp->e.h.tsize, hp->e.h.bsize); break; } setsym(fp, hp->e.h.nsyms, 0, hp->e.h.pcsize, hp->e.h.symptr); fp->hdrsz = 0; /* header stripped */ return 1; } /* * sparc bootable image */ static int sparcboot(int fd, Fhdr *fp, ExecHdr *hp) { USED(fd); fp->type = FSPARCB; settext(fp, hp->e.sentry, hp->e.sentry, hp->e.stext, sizeof(struct sparcexec)); setdata(fp, hp->e.sentry+hp->e.stext, hp->e.sdata, fp->txtoff+hp->e.stext, hp->e.sbss); setsym(fp, hp->e.ssyms, 0, hp->e.sdrsize, fp->datoff+hp->e.sdata); fp->hdrsz = 0; /* header stripped */ return 1; } /* * next bootable image */ static int nextboot(int fd, Fhdr *fp, ExecHdr *hp) { USED(fd); fp->type = FNEXTB; settext(fp, hp->e.textc.vmaddr, hp->e.textc.vmaddr, hp->e.texts.size, hp->e.texts.offset); setdata(fp, hp->e.datac.vmaddr, hp->e.datas.size, hp->e.datas.offset, hp->e.bsss.size); setsym(fp, hp->e.symc.nsyms, hp->e.symc.spoff, hp->e.symc.pcoff, hp->e.symc.symoff); fp->hdrsz = 0; /* header stripped */ return 1; } /* * ELF64 binaries. */ static int elf64dotout(int fd, Fhdr *fp, ExecHdr *hp) { E64hdr *ep; P64hdr *ph; ushort (*swab)(ushort); ulong (*swal)(ulong); uvlong (*swav)(uvlong); int i, it, id, is, phsz; uvlong uvl; ep = &hp->e; if(ep->ident[DATA] == ELFDATA2LSB) { swab = leswab; swal = leswal; swav = leswav; } else if(ep->ident[DATA] == ELFDATA2MSB) { swab = beswab; swal = beswal; swav = beswav; } else { werrstr("bad ELF64 encoding - not big or little endian"); return 0; } ep->type = swab(ep->type); ep->machine = swab(ep->machine); ep->version = swal(ep->version); if(ep->type != EXEC || ep->version != CURRENT) return 0; ep->elfentry = swav(ep->elfentry); ep->phoff = swav(ep->phoff); ep->shoff = swav(ep->shoff); ep->flags = swal(ep->flags); ep->ehsize = swab(ep->ehsize); ep->phentsize = swab(ep->phentsize); ep->phnum = swab(ep->phnum); ep->shentsize = swab(ep->shentsize); ep->shnum = swab(ep->shnum); ep->shstrndx = swab(ep->shstrndx); fp->magic = ELF_MAG; fp->hdrsz = (ep->ehsize+ep->phnum*ep->phentsize+16)&~15; switch(ep->machine) { default: return 0; case AMD64: mach = &mamd64; fp->type = FAMD64; fp->name = "amd64 ELF64 executable"; break; case POWER64: mach = &mpower64; fp->type = FPOWER64; fp->name = "power64 ELF64 executable"; break; } if(ep->phentsize != sizeof(P64hdr)) { werrstr("bad ELF64 header size"); return 0; } phsz = sizeof(P64hdr)*ep->phnum; ph = malloc(phsz); if(!ph) return 0; seek(fd, ep->phoff, 0); if(read(fd, ph, phsz) < 0) { free(ph); return 0; } for(i = 0; i < ep->phnum; i++) { ph[i].type = swal(ph[i].type); ph[i].flags = swal(ph[i].flags); ph[i].offset = swav(ph[i].offset); ph[i].vaddr = swav(ph[i].vaddr); ph[i].paddr = swav(ph[i].paddr); ph[i].filesz = swav(ph[i].filesz); ph[i].memsz = swav(ph[i].memsz); ph[i].align = swav(ph[i].align); } /* find text, data and symbols and install them */ it = id = is = -1; for(i = 0; i < ep->phnum; i++) { if(ph[i].type == LOAD && (ph[i].flags & (R|X)) == (R|X) && it == -1) it = i; else if(ph[i].type == LOAD && (ph[i].flags & (R|W)) == (R|W) && id == -1) id = i; else if(ph[i].type == NOPTYPE && is == -1) is = i; } if(it == -1 || id == -1) { werrstr("No ELF64 TEXT or DATA sections"); free(ph); return 0; } settext(fp, ep->elfentry, ph[it].vaddr, ph[it].memsz, ph[it].offset); /* 8c: out of fixed registers */ uvl = ph[id].memsz - ph[id].filesz; setdata(fp, ph[id].vaddr, ph[id].filesz, ph[id].offset, uvl); if(is != -1) setsym(fp, ph[is].filesz, 0, ph[is].memsz, ph[is].offset); free(ph); return 1; } /* * ELF32 binaries. */ static int elf32dotout(int fd, Fhdr *fp, ExecHdr *hp) { ulong (*swal)(ulong); ushort (*swab)(ushort); Ehdr *ep; Phdr *ph; int i, it, id, is, phsz; /* bitswap the header according to the DATA format */ ep = &hp->e; if(ep->ident[DATA] == ELFDATA2LSB) { swab = leswab; swal = leswal; } else if(ep->ident[DATA] == ELFDATA2MSB) { swab = beswab; swal = beswal; } else { werrstr("bad ELF32 encoding - not big or little endian"); return 0; } ep->type = swab(ep->type); ep->machine = swab(ep->machine); ep->version = swal(ep->version); ep->elfentry = swal(ep->elfentry); ep->phoff = swal(ep->phoff); ep->shoff = swal(ep->shoff); ep->flags = swal(ep->flags); ep->ehsize = swab(ep->ehsize); ep->phentsize = swab(ep->phentsize); ep->phnum = swab(ep->phnum); ep->shentsize = swab(ep->shentsize); ep->shnum = swab(ep->shnum); ep->shstrndx = swab(ep->shstrndx); if(ep->type != EXEC || ep->version != CURRENT) return 0; /* we could definitely support a lot more machines here */ fp->magic = ELF_MAG; fp->hdrsz = (ep->ehsize+ep->phnum*ep->phentsize+16)&~15; switch(ep->machine) { case I386: mach = &mi386; fp->type = FI386; fp->name = "386 ELF32 executable"; break; case MIPS: mach = &mmips; if(ep->ident[DATA] == ELFDATA2LSB){ fp->type = FMIPSLE; fp->name = "mips le ELF32 executable"; } else { fp->type = FMIPS; fp->name = "mips be ELF32 executable"; } break; case SPARC64: mach = &msparc64; fp->type = FSPARC64; fp->name = "sparc64 ELF32 executable"; break; case POWER: mach = &mpower; fp->type = FPOWER; fp->name = "power ELF32 executable"; break; case POWER64: mach = &mpower64; fp->type = FPOWER64; fp->name = "power64 ELF32 executable"; break; case AMD64: mach = &mamd64; fp->type = FAMD64; fp->name = "amd64 ELF32 executable"; break; case ARM: mach = &marm; fp->type = FARM; fp->name = "arm ELF32 executable"; break; default: return 0; } if(ep->phentsize != sizeof(Phdr)) { werrstr("bad ELF32 header size"); return 0; } phsz = sizeof(Phdr)*ep->phnum; ph = malloc(phsz); if(!ph) return 0; seek(fd, ep->phoff, 0); if(read(fd, ph, phsz) < 0) { free(ph); return 0; } hswal(ph, phsz/sizeof(ulong), swal); /* find text, data and symbols and install them */ it = id = is = -1; for(i = 0; i < ep->phnum; i++) { if(ph[i].type == LOAD && (ph[i].flags & (R|X)) == (R|X) && it == -1) it = i; else if(ph[i].type == LOAD && (ph[i].flags & (R|W)) == (R|W) && id == -1) id = i; else if(ph[i].type == NOPTYPE && is == -1) is = i; } if(it == -1 || id == -1) { /* * The SPARC64 boot image is something of an ELF hack. * Text+Data+BSS are represented by ph[0]. Symbols * are represented by ph[1]: * * filesz, memsz, vaddr, paddr, off * ph[0] : txtsz+datsz, txtsz+datsz+bsssz, txtaddr-KZERO, datasize, txtoff * ph[1] : symsz, lcsz, 0, 0, symoff */ if(ep->machine == SPARC64 && ep->phnum == 2) { ulong txtaddr, txtsz, dataddr, bsssz; txtaddr = ph[0].vaddr | 0x80000000; txtsz = ph[0].filesz - ph[0].paddr; dataddr = txtaddr + txtsz; bsssz = ph[0].memsz - ph[0].filesz; settext(fp, ep->elfentry | 0x80000000, txtaddr, txtsz, ph[0].offset); setdata(fp, dataddr, ph[0].paddr, ph[0].offset + txtsz, bsssz); setsym(fp, ph[1].filesz, 0, ph[1].memsz, ph[1].offset); free(ph); return 1; } werrstr("No ELF32 TEXT or DATA sections"); free(ph); return 0; } settext(fp, ep->elfentry, ph[it].vaddr, ph[it].memsz, ph[it].offset); setdata(fp, ph[id].vaddr, ph[id].filesz, ph[id].offset, ph[id].memsz - ph[id].filesz); if(is != -1) setsym(fp, ph[is].filesz, 0, ph[is].memsz, ph[is].offset); free(ph); return 1; } /* * Elf binaries. */ static int elfdotout(int fd, Fhdr *fp, ExecHdr *hp) { Ehdr *ep; /* bitswap the header according to the DATA format */ ep = &hp->e; if(ep->ident[CLASS] == ELFCLASS32) return elf32dotout(fd, fp, hp); else if(ep->ident[CLASS] == ELFCLASS64) return elf64dotout(fd, fp, hp); werrstr("bad ELF class - not 32 bit"); return 0; } /* * (Free|Net)BSD ARM header. */ static int armdotout(int fd, Fhdr *fp, ExecHdr *hp) { uvlong kbase; USED(fd); settext(fp, hp->e.entry, sizeof(Exec), hp->e.text, sizeof(Exec)); setdata(fp, fp->txtsz, hp->e.data, fp->txtsz, hp->e.bss); setsym(fp, hp->e.syms, hp->e.spsz, hp->e.pcsz, fp->datoff+fp->datsz); kbase = 0xF0000000; if ((fp->entry & kbase) == kbase) { /* Boot image */ fp->txtaddr = kbase+sizeof(Exec); fp->name = "ARM *BSD boot image"; fp->hdrsz = 0; /* header stripped */ fp->dataddr = kbase+fp->txtsz; } return 1; } static void settext(Fhdr *fp, uvlong e, uvlong a, long s, vlong off) { fp->txtaddr = a; fp->entry = e; fp->txtsz = s; fp->txtoff = off; } static void setdata(Fhdr *fp, uvlong a, long s, vlong off, long bss) { fp->dataddr = a; fp->datsz = s; fp->datoff = off; fp->bsssz = bss; } static void setsym(Fhdr *fp, long symsz, long sppcsz, long lnpcsz, vlong symoff) { fp->symsz = symsz; fp->symoff = symoff; fp->sppcsz = sppcsz; fp->sppcoff = fp->symoff+fp->symsz; fp->lnpcsz = lnpcsz; fp->lnpcoff = fp->sppcoff+fp->sppcsz; } static uvlong _round(uvlong a, ulong b) { uvlong w; w = (a/b)*b; if (a!=w) w += b; return(w); }