ref: faa625a1d5ab47ac0438b2cea5b2bde1ea747b8b
dir: /sys/src/cmd/snap/take.c/
#include <u.h> #include <libc.h> #include <bio.h> #include <mach.h> #include "snap.h" /* research 16-bit crc. good enough. */ static ulong sumr(ulong sum, void *buf, int n) { uchar *s, *send; if(buf == 0) return sum; for(s=buf, send=s+n; s<send; s++) if(sum & 1) sum = 0xffff & ((sum>>1)+*s+0x8000); else sum = 0xffff & ((sum>>1)+*s); return sum; } char zeros[Pagesize]; static ulong npage; static Page *pgtab[1<<10]; Page* datapage(char *p, long len) { Page *pg; ulong sum; if(len > Pagesize) sysfatal("datapage cannot handle pages > %d", Pagesize); sum = sumr(0, p, len) & (nelem(pgtab)-1); for(pg = pgtab[sum]; pg != nil; pg=pg->link) if(pg->len == len && memcmp(pg->data, p, len) == 0) return pg; pg = emalloc(sizeof(*pg)+len); pg->data = (char*)&pg[1]; pg->type = 0; pg->len = len; memmove(pg->data, p, len); if(sum == 0 && memcmp(zeros, p, len) == 0) { pg->type = 'z'; pg->written = 1; } pg->link = pgtab[sum]; pgtab[sum] = pg; ++npage; return pg; } static Data* readsection(long pid, char *sec) { char buf[8192]; int n, fd; int hdr, tot; Data *d = nil; snprint(buf, sizeof buf, "/proc/%ld/%s", pid, sec); if((fd = open(buf, OREAD)) < 0) return nil; tot = 0; hdr = (int)((Data*)0)->data; while((n = read(fd, buf, sizeof buf)) > 0) { d = erealloc(d, tot+n+hdr); memmove(d->data+tot, buf, n); tot += n; } close(fd); if(d == nil) return nil; d->len = tot; return d; } static Seg* readseg(int fd, uvlong off, uvlong len, char *name) { char buf[Pagesize]; ulong npg; Page **pg; Seg *s; int n; if(debug) fprint(2, "readseg %.8llux - %.8llux %s\n", off, off+len, name); s = emalloc(sizeof(*s)); s->name = estrdup(name); if(seek(fd, off, 0) < 0) { fprint(2, "seek fails\n"); goto Die; } s->offset = off; s->len = 0; pg = nil; npg = 0; while(s->len < len){ n = Pagesize; if(n > len - s->len) n = len - s->len; if((n = readn(fd, buf, n)) <= 0) break; s->len += n; if((npg & (npg-1)) == 0) pg = erealloc(pg, sizeof(*pg) * (npg==0 | npg*2)); pg[npg++] = datapage(buf, n); if(n != Pagesize) /* any short read, planned or otherwise */ break; } if(s->len==0 && len!=0){ free(pg); goto Die; } pg = erealloc(pg, sizeof(*pg) * npg); s->pg = pg; s->npg = npg; return s; Die: free(s->name); free(s); return nil; } /* discover the stack pointer of the given process */ uvlong stackptr(Proc *proc, int fd) { char *q; Fhdr f; Reglist *r; vlong textoff; int i; Data *dreg; textoff = -1; for(i=0; i<proc->nseg; i++) if(proc->seg[i] && strcmp(proc->seg[i]->name, "Text") == 0) textoff = proc->seg[i]->offset; if(textoff == -1) return 0; if(seek(fd, textoff, 0) < 0) return 0; if(crackhdr(fd, &f) == 0) return 0; machbytype(f.type); for(r=mach->reglist; r->rname; r++) if(strcmp(r->rname, mach->sp) == 0) break; if(r == nil) { fprint(2, "couldn't find stack pointer register?\n"); return 0; } if((dreg = proc->d[Pregs]) == nil) return 0; if(r->roffs+mach->szaddr > dreg->len) { fprint(2, "SP register too far into registers?\n"); return 0; } q = dreg->data+r->roffs; switch(mach->szaddr) { case 4: return machdata->swal(*(ulong*)q); case 8: return machdata->swav(*(uvlong*)q); default: fprint(2, "address size is %d bytes?\n", mach->szaddr); return 0; } } Proc* snap(long pid, int usetext) { Data *d; Proc *proc; Seg **s; char *name, *segdat, *q, *f[128+1], buf[128]; int fd, i, stacki, nf, np; uvlong off, len, stackoff, stacklen, sp; proc = emalloc(sizeof(*proc)); proc->pid = pid; np = 0; for(i=0; i<Npfile; i++) { if(proc->d[i] = readsection(pid, pfile[i])) np++; else fprint(2, "warning: can't include /proc/%ld/%s\n", pid, pfile[i]); } if(np == 0) return nil; if(usetext) { snprint(buf, sizeof buf, "/proc/%ld/text", pid); if((fd = open(buf, OREAD)) >= 0) { werrstr(""); if((proc->text = readseg(fd, 0, 1<<31, "textfile")) == nil) fprint(2, "warning: can't include %s: %r\n", buf); close(fd); } else fprint(2, "warning: can't include /proc/%ld/text\n", pid); } if((d=proc->d[Psegment]) == nil) { fprint(2, "warning: no segment table, no memory image\n"); return proc; } segdat = emalloc(d->len+1); memmove(segdat, d->data, d->len); segdat[d->len] = 0; nf = getfields(segdat, f, nelem(f), 1, "\n"); if(nf == nelem(f)) { nf--; fprint(2, "process %ld has >%d segments; only using first %d\n", pid, nf, nf); } if(nf <= 0) { fprint(2, "warning: couldn't understand segment table, no memory image\n"); free(segdat); return proc; } snprint(buf, sizeof buf, "/proc/%ld/mem", pid); if((fd = open(buf, OREAD)) < 0) { fprint(2, "warning: can't include /proc/%ld/mem\n", pid); return proc; } s = emalloc(nf*sizeof(*s)); stacklen = 0; stackoff = 0; stacki = 0; for(i=0; i<nf; i++) { if(q = strchr(f[i], ' ')) *q = 0; name = f[i]; off = strtoull(name+10, &q, 16); len = strtoull(q, &q, 16) - off; if(strcmp(name, "Stack") == 0) { stackoff = off; stacklen = len; stacki = i; } else s[i] = readseg(fd, off, len, name); } proc->nseg = nf; proc->seg = s; /* stack hack: figure sp so don't need to page in the whole segment */ if(stacklen) { sp = stackptr(proc, fd); if(debug) fprint(2, "stackseg %.8llux - %.8llux sp %.8llux\n", stackoff, stackoff+stacklen, sp); if(stackoff <= sp && sp < stackoff+stacklen) { off = sp - 8*1024; } else { /* stack pointer not in segment. thread library? */ off = stackoff + stacklen - 16*1024; } off &= ~((uvlong)Pagesize-1); if(off < stackoff) off = stackoff; len = stacklen - (off - stackoff); s[stacki] = readseg(fd, off, len, "Stack"); } return proc; }