- Local symbols could shadow globals in some instances. Fix it.
- mutex_enter() from ksyms_getval() could panic due to a change made in revision 1.40. Fix it. - Replace the p-tree with a binary search of global symbols. Saves about 250kB of wired memory on i386 and allows for faster lookups within module symbol tables.
This commit is contained in:
ad
parent
e5c4df967a
commit
9485f42356
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@ -1,4 +1,4 @@
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/* $NetBSD: kern_ksyms.c,v 1.42 2008/11/12 12:36:16 ad Exp $ */
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/* $NetBSD: kern_ksyms.c,v 1.43 2008/11/16 15:13:35 ad Exp $ */
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/*-
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* Copyright (c) 2008 The NetBSD Foundation, Inc.
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@ -67,14 +67,11 @@
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/*
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* TODO:
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*
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* Consider replacing patricia tree with simpler binary search
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* for symbol tables.
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*
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* Add support for mmap, poll.
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: kern_ksyms.c,v 1.42 2008/11/12 12:36:16 ad Exp $");
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__KERNEL_RCSID(0, "$NetBSD: kern_ksyms.c,v 1.43 2008/11/16 15:13:35 ad Exp $");
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#ifdef _KERNEL
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#include "opt_ddb.h"
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@ -134,21 +131,6 @@ TAILQ_HEAD(, ksyms_symtab) ksyms_symtabs =
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TAILQ_HEAD_INITIALIZER(ksyms_symtabs);
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static struct ksyms_symtab kernel_symtab;
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/*
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* Patricia-tree-based lookup structure for the in-kernel global symbols.
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* Based on a design by Mikael Sundstrom, msm@sm.luth.se.
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*/
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struct ptree {
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int16_t bitno;
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int16_t lr[2];
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} *symb;
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static int16_t baseidx;
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static int treex = 1;
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#define P_BIT(key, bit) ((key[bit >> 3] >> (bit & 7)) & 1)
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#define STRING(idx) (kernel_symtab.sd_symstart[idx].st_name + \
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kernel_symtab.sd_strstart)
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static int
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ksyms_verify(void *symstart, void *strstart)
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{
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@ -166,146 +148,54 @@ ksyms_verify(void *symstart, void *strstart)
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return 1;
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}
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/*
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* Walk down the tree until a terminal node is found.
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*/
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static int
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symbol_traverse(const char *key)
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{
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int16_t nb, rbit = baseidx;
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while (rbit > 0) {
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nb = symb[rbit].bitno;
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rbit = symb[rbit].lr[P_BIT(key, nb)];
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}
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return -rbit;
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}
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static int
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ptree_add(char *key, int val)
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{
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int idx;
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int nix, cix, bit, rbit, sb, lastrbit, svbit = 0, ix;
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char *m, *k;
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if (baseidx == 0) {
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baseidx = -val;
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return 0; /* First element */
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}
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/* Get string to match against */
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idx = symbol_traverse(key);
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/* Find first mismatching bit */
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m = STRING(idx);
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k = key;
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if (strcmp(m, k) == 0)
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return 1;
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for (cix = 0; *m && *k && *m == *k; m++, k++, cix += 8)
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;
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ix = ffs((int)*m ^ (int)*k) - 1;
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cix += ix;
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/* Create new node */
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nix = treex++;
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bit = P_BIT(key, cix);
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symb[nix].bitno = cix;
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symb[nix].lr[bit] = -val;
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/* Find where to insert node */
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rbit = baseidx;
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lastrbit = 0;
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for (;;) {
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if (rbit < 0)
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break;
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sb = symb[rbit].bitno;
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if (sb > cix)
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break;
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if (sb == cix)
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printf("symb[rbit].bitno == cix!!!\n");
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lastrbit = rbit;
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svbit = P_BIT(key, sb);
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rbit = symb[rbit].lr[svbit];
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}
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/* Do the actual insertion */
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if (lastrbit == 0) {
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/* first element */
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symb[nix].lr[!bit] = baseidx;
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baseidx = nix;
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} else {
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symb[nix].lr[!bit] = rbit;
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symb[lastrbit].lr[svbit] = nix;
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}
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return 0;
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}
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static int
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ptree_find(const char *key)
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{
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int idx;
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if (baseidx == 0)
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return 0;
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idx = symbol_traverse(key);
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if (strcmp(key, STRING(idx)) == 0)
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return idx;
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return 0;
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}
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static void
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ptree_gen(char *off, struct ksyms_symtab *tab)
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{
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Elf_Sym *sym;
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int i, nsym;
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if (off != NULL)
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symb = (struct ptree *)ALIGN(off);
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else
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symb = malloc((tab->sd_symsize/sizeof(Elf_Sym)) *
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sizeof(struct ptree), M_DEVBUF, M_WAITOK);
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symb--; /* sym index won't be 0 */
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sym = tab->sd_symstart;
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if ((nsym = tab->sd_symsize/sizeof(Elf_Sym)) > INT16_MAX) {
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printf("Too many symbols for tree, skipping %d symbols\n",
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nsym-INT16_MAX);
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nsym = INT16_MAX;
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}
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for (i = 1; i < nsym; i++) {
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if (ELF_ST_BIND(sym[i].st_info) != STB_GLOBAL)
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continue;
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ptree_add(tab->sd_strstart+sym[i].st_name, i);
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if (tab->sd_minsym == NULL ||
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sym[i].st_value < tab->sd_minsym->st_value)
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tab->sd_minsym = &sym[i];
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if (tab->sd_maxsym == NULL ||
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sym[i].st_value > tab->sd_maxsym->st_value)
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tab->sd_maxsym = &sym[i];
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}
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}
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/*
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* Finds a certain symbol name in a certain symbol table.
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*/
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static Elf_Sym *
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findsym(const char *name, struct ksyms_symtab *table)
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findsym(const char *name, struct ksyms_symtab *table, int type)
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{
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Elf_Sym *start = table->sd_symstart;
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int i, sz = table->sd_symsize/sizeof(Elf_Sym);
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char *np;
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char *realstart = table->sd_strstart - table->sd_usroffset;
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Elf_Sym *sym, *maxsym;
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int low, mid, high, nglob;
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char *str, *cmp;
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if (table == &kernel_symtab && (i = ptree_find(name)) != 0)
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return &start[i];
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sym = table->sd_symstart;
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str = table->sd_strstart - table->sd_usroffset;
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nglob = table->sd_nglob;
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low = 0;
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high = nglob;
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for (i = 0; i < sz; i++) {
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np = realstart + start[i].st_name;
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if (name[0] == np[0] && name[1] == np[1] &&
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strcmp(name, np) == 0)
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return &start[i];
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/*
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* Start with a binary search of all global symbols in this table.
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* Global symbols must have unique names.
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*/
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while (low < high) {
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mid = (low + high) >> 1;
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cmp = sym[mid].st_name + str;
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if (cmp[0] < name[0] || strcmp(cmp, name) < 0) {
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low = mid + 1;
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} else {
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high = mid;
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}
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}
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KASSERT(low == high);
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if (__predict_true(low < nglob &&
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strcmp(sym[low].st_name + str, name) == 0)) {
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KASSERT(ELF_ST_BIND(sym[low].st_info) == STB_GLOBAL);
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return &sym[low];
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}
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/*
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* Perform a linear search of local symbols (rare). Many local
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* symbols with the same name can exist so are not included in
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* the binary search.
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*/
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if (type != KSYMS_EXTERN) {
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maxsym = sym + table->sd_symsize / sizeof(Elf_Sym);
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for (sym += nglob; sym < maxsym; sym++) {
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if (strcmp(name, sym->st_name + str) == 0) {
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return sym;
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}
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}
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}
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return NULL;
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}
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ksymsattach(int arg)
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{
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if (baseidx == 0)
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ptree_gen(0, &kernel_symtab);
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}
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/*
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* newstart - Address to which the symbol table has to be copied during
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* shrinking. If NULL, it is not moved.
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*/
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static const char *addsymtab_strstart;
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static int
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addsymtab_compar(const void *a, const void *b)
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{
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const Elf_Sym *sa, *sb;
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sa = a;
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sb = b;
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/*
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* Split the symbol table into two, with globals at the start
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* and locals at the end.
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*/
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if (ELF_ST_BIND(sa->st_info) != ELF_ST_BIND(sb->st_info)) {
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if (ELF_ST_BIND(sa->st_info) == STB_GLOBAL) {
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return -1;
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}
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if (ELF_ST_BIND(sb->st_info) == STB_GLOBAL) {
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return 1;
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}
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}
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/* Within each band, sort by name. */
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return strcmp(sa->st_name + addsymtab_strstart,
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sb->st_name + addsymtab_strstart);
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}
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static void
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addsymtab(const char *name, void *symstart, size_t symsize,
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void *strstart, size_t strsize, struct ksyms_symtab *tab,
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void *newstart)
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{
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Elf_Sym *sym, *nsym;
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int i, j, n;
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int i, j, n, nglob;
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char *str;
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tab->sd_symstart = symstart;
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@ -362,6 +278,7 @@ addsymtab(const char *name, void *symstart, size_t symsize,
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sym = tab->sd_symstart;
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nsym = (Elf_Sym *)newstart;
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str = tab->sd_strstart;
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nglob = 0;
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for (i = n = 0; i < tab->sd_symsize/sizeof(Elf_Sym); i++) {
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/*
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* Remove useless symbols.
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@ -384,14 +301,30 @@ addsymtab(const char *name, void *symstart, size_t symsize,
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/* Save symbol. Set it as an absolute offset */
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nsym[n] = sym[i];
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nsym[n].st_shndx = SHN_ABS;
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j = strlen(nsym[n].st_name + tab->sd_strstart) + 1;
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j = strlen(nsym[n].st_name + str) + 1;
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if (j > ksyms_maxlen)
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ksyms_maxlen = j;
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n++;
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nglob += (ELF_ST_BIND(nsym[n].st_info) == STB_GLOBAL);
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/* Compute min and max symbols. */
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if (tab->sd_minsym == NULL ||
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tab->sd_minsym->st_value > nsym[n].st_value) {
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tab->sd_minsym = &nsym[n];
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}
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if (tab->sd_maxsym == NULL ||
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tab->sd_maxsym->st_value < nsym[n].st_value) {
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tab->sd_maxsym = &nsym[n];
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}
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n++;
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}
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/* Fill the rest of the record, and sort the symbols. */
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tab->sd_symstart = nsym;
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tab->sd_symsize = n * sizeof(Elf_Sym);
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tab->sd_nglob = nglob;
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addsymtab_strstart = str;
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qsort(nsym, n, sizeof(Elf_Sym), addsymtab_compar);
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/* ksymsread() is unlocked, so membar. */
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membar_producer();
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TAILQ_INSERT_TAIL(&ksyms_symtabs, tab, sd_queue);
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@ -514,9 +447,6 @@ ksyms_getval_unlocked(const char *mod, const char *sym, unsigned long *val,
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struct ksyms_symtab *st;
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Elf_Sym *es;
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if (!ksyms_initted)
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return ENOENT;
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#ifdef KSYMS_DEBUG
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if (ksyms_debug & FOLLOW_CALLS)
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printf("ksyms_getval_unlocked: mod %s sym %s valp %p\n",
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@ -524,24 +454,15 @@ ksyms_getval_unlocked(const char *mod, const char *sym, unsigned long *val,
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#endif
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TAILQ_FOREACH(st, &ksyms_symtabs, sd_queue) {
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if (st->sd_gone)
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if (__predict_false(st->sd_gone))
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continue;
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if (mod && strcmp(st->sd_name, mod))
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if (mod != NULL && strcmp(st->sd_name, mod))
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continue;
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if ((es = findsym(sym, st)) == NULL)
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continue;
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if (es->st_shndx == SHN_UNDEF)
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continue;
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/* Skip if bad binding */
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if (type == KSYMS_EXTERN &&
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ELF_ST_BIND(es->st_info) != STB_GLOBAL)
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continue;
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if (val)
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if ((es = findsym(sym, st, type)) != NULL) {
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*val = es->st_value;
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return 0;
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}
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}
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return ENOENT;
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}
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@ -550,6 +471,9 @@ ksyms_getval(const char *mod, const char *sym, unsigned long *val, int type)
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{
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int rc;
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if (!ksyms_initted)
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return ENOENT;
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mutex_enter(&ksyms_lock);
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rc = ksyms_getval_unlocked(mod, sym, val, type);
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mutex_exit(&ksyms_lock);
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@ -962,7 +886,7 @@ ksymsioctl(dev_t dev, u_long cmd, void *data, int fflag, struct lwp *l)
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TAILQ_FOREACH(st, &ksyms_symtabs, sd_queue) {
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if (st->sd_gone)
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continue;
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if ((sym = findsym(str, st)) == NULL)
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if ((sym = findsym(str, st, KSYMS_ANY)) == NULL)
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continue;
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#ifdef notdef
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/* Skip if bad binding */
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@ -1,4 +1,4 @@
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/* $NetBSD: ksyms.h,v 1.18 2008/11/12 12:36:28 ad Exp $ */
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/* $NetBSD: ksyms.h,v 1.19 2008/11/16 15:13:35 ad Exp $ */
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/*
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* Copyright (c) 2001, 2003 Anders Magnusson (ragge@ludd.luth.se).
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@ -45,6 +45,7 @@ struct ksyms_symtab {
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int sd_usroffset; /* Real address for userspace */
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int sd_symsize; /* Size in bytes of symbol table */
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int sd_strsize; /* Size of string table */
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int sd_nglob; /* Number of global symbols */
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bool sd_gone; /* dead but around for open() */
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};
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Reference in New Issue