Refine symtab sorting in libproc.
Add some rules to more closely match what illumos does when an address resolves to multiple symbols: - prefer non-local symbols - prefer symbols with fewer leading underscores and no leading '$' Add some regression tests to verify these rules.
This commit is contained in:
Mark Johnston
parent
7c72b10912
commit
1bdc41d252
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=326064
@ -1,5 +1,5 @@
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/*-
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* Copyright (c) 2016 Mark Johnston <markj@FreeBSD.org>
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* Copyright (c) 2016-2017 Mark Johnston <markj@FreeBSD.org>
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* Copyright (c) 2010 The FreeBSD Foundation
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* Copyright (c) 2008 John Birrell (jb@freebsd.org)
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* All rights reserved.
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@ -100,27 +100,59 @@ demangle(const char *symbol, char *buf, size_t len)
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strlcpy(buf, symbol, len);
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}
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static int
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symvalcomp(void *thunk, const void *a1, const void *a2)
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{
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struct symsort_thunk {
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Elf *e;
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struct symtab *symtab;
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};
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static int
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symvalcmp(void *_thunk, const void *a1, const void *a2)
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{
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GElf_Sym sym1, sym2;
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struct symsort_thunk *thunk;
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const char *s1, *s2;
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u_int i1, i2;
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int ret;
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int bind1, bind2;
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i1 = *(const u_int *)a1;
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i2 = *(const u_int *)a2;
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symtab = thunk;
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thunk = _thunk;
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(void)gelf_getsym(symtab->data, i1, &sym1);
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(void)gelf_getsym(symtab->data, i2, &sym2);
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if (sym1.st_value < sym2.st_value)
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ret = -1;
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else if (sym1.st_value == sym2.st_value)
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ret = 0;
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else
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ret = 1;
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return (ret);
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(void)gelf_getsym(thunk->symtab->data, i1, &sym1);
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(void)gelf_getsym(thunk->symtab->data, i2, &sym2);
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if (sym1.st_value != sym2.st_value)
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return (sym1.st_value < sym2.st_value ? -1 : 1);
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/* Prefer non-local symbols. */
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bind1 = GELF_ST_BIND(sym1.st_info);
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bind2 = GELF_ST_BIND(sym2.st_info);
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if (bind1 != bind2) {
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if (bind1 == STB_LOCAL && bind2 != STB_LOCAL)
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return (-1);
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if (bind1 != STB_LOCAL && bind2 == STB_LOCAL)
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return (1);
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}
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s1 = elf_strptr(thunk->e, thunk->symtab->stridx, sym1.st_name);
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s2 = elf_strptr(thunk->e, thunk->symtab->stridx, sym2.st_name);
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if (s1 != NULL && s2 != NULL) {
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/* Prefer symbols without a leading '$'. */
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if (*s1 == '$')
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return (-1);
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if (*s2 == '$')
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return (1);
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/* Prefer symbols with fewer leading underscores. */
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for (; *s1 == '_' && *s2 == '_'; s1++, s2++)
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;
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if (*s1 == '_')
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return (-1);
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if (*s2 == '_')
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return (1);
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}
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return (0);
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}
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static int
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@ -128,6 +160,7 @@ load_symtab(Elf *e, struct symtab *symtab, u_long sh_type)
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{
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GElf_Ehdr ehdr;
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GElf_Shdr shdr;
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struct symsort_thunk thunk;
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Elf_Scn *scn;
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u_int nsyms;
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@ -155,9 +188,13 @@ load_symtab(Elf *e, struct symtab *symtab, u_long sh_type)
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return (-1);
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for (u_int i = 0; i < nsyms; i++)
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symtab->index[i] = i;
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qsort_r(symtab->index, nsyms, sizeof(u_int), symtab, symvalcomp);
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symtab->nsyms = nsyms;
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symtab->stridx = shdr.sh_link;
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thunk.e = e;
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thunk.symtab = symtab;
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qsort_r(symtab->index, nsyms, sizeof(u_int), &thunk, symvalcmp);
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return (0);
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}
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@ -416,12 +453,16 @@ proc_addr2map(struct proc_handle *p, uintptr_t addr)
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* symbol and its name.
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*/
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static int
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lookup_symbol_by_addr(Elf *elf, struct symtab *symtab, uintptr_t addr,
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const char **namep, GElf_Sym *sym)
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lookup_symbol_by_addr(Elf *e, struct symtab *symtab, uintptr_t addr,
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const char **namep, GElf_Sym *symp)
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{
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GElf_Sym sym;
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Elf_Data *data;
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const char *s;
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int min, max, mid;
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u_int i, min, max, mid;
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if (symtab->nsyms == 0)
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return (ENOENT);
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data = symtab->data;
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min = 0;
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@ -429,21 +470,31 @@ lookup_symbol_by_addr(Elf *elf, struct symtab *symtab, uintptr_t addr,
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while (min <= max) {
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mid = (max + min) / 2;
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(void)gelf_getsym(data, symtab->index[mid], sym);
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if (addr >= sym->st_value &&
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addr < sym->st_value + sym->st_size) {
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s = elf_strptr(elf, symtab->stridx, sym->st_name);
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if (s != NULL && namep != NULL)
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*namep = s;
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return (0);
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}
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(void)gelf_getsym(data, symtab->index[mid], &sym);
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if (addr >= sym.st_value && addr < sym.st_value + sym.st_size)
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break;
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if (addr < sym->st_value)
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if (addr < sym.st_value)
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max = mid - 1;
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else
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min = mid + 1;
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}
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return (ENOENT);
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if (min > max)
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return (ENOENT);
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/*
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* Advance until we find the matching symbol with largest index.
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*/
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for (i = mid; i < symtab->nsyms; i++) {
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(void)gelf_getsym(data, symtab->index[i], &sym);
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if (addr < sym.st_value || addr >= sym.st_value + sym.st_size)
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break;
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}
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(void)gelf_getsym(data, symtab->index[i - 1], symp);
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s = elf_strptr(e, symtab->stridx, symp->st_name);
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if (s != NULL && namep != NULL)
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*namep = s;
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return (0);
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}
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int
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@ -1,5 +1,5 @@
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/*-
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* Copyright (c) 2014-2016 Mark Johnston <markj@FreeBSD.org>
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* Copyright (c) 2014-2017 Mark Johnston <markj@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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@ -370,6 +370,93 @@ ATF_TC_BODY(signal_forward, tc)
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proc_free(phdl);
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}
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ATF_TC(symbol_sort_local);
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ATF_TC_HEAD(symbol_sort_local, tc)
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{
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atf_tc_set_md_var(tc, "descr",
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"Ensure that proc_addr2sym() returns the non-local alias when "
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"the address resolves to multiple symbols.");
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}
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ATF_TC_BODY(symbol_sort_local, tc)
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{
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char symname[32];
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GElf_Sym bar_sym;
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struct proc_handle *phdl;
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int error;
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phdl = start_prog(tc, true);
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error = proc_name2sym(phdl, target_prog_file, "bar", &bar_sym, NULL);
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ATF_REQUIRE_MSG(error == 0, "failed to look up 'bar' in %s",
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target_prog_file);
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ATF_REQUIRE(GELF_ST_BIND(bar_sym.st_info) == STB_LOCAL);
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error = proc_addr2sym(phdl, bar_sym.st_value, symname, sizeof(symname),
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&bar_sym);
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ATF_REQUIRE_MSG(error == 0, "failed to resolve 'bar' by addr");
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ATF_REQUIRE_MSG(strcmp(symname, "baz") == 0,
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"unexpected symbol name '%s'", symname);
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ATF_REQUIRE(GELF_ST_BIND(bar_sym.st_info) == STB_GLOBAL);
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}
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ATF_TC(symbol_sort_prefix);
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ATF_TC_HEAD(symbol_sort_prefix, tc)
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{
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atf_tc_set_md_var(tc, "descr",
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"Ensure that proc_addr2sym() returns the alias whose name is not "
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"prefixed with '$' if one exists.");
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}
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ATF_TC_BODY(symbol_sort_prefix, tc)
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{
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char symname[32];
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GElf_Sym qux_sym;
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struct proc_handle *phdl;
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int error;
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phdl = start_prog(tc, true);
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error = proc_name2sym(phdl, target_prog_file, "$qux", &qux_sym, NULL);
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ATF_REQUIRE_MSG(error == 0, "failed to look up '$qux' in %s",
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target_prog_file);
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error = proc_addr2sym(phdl, qux_sym.st_value, symname, sizeof(symname),
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&qux_sym);
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ATF_REQUIRE_MSG(error == 0, "failed to resolve 'qux' by addr");
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ATF_REQUIRE_MSG(strcmp(symname, "qux") == 0,
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"unexpected symbol name '%s'", symname);
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}
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ATF_TC(symbol_sort_underscore);
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ATF_TC_HEAD(symbol_sort_underscore, tc)
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{
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atf_tc_set_md_var(tc, "descr",
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"Ensure that proc_addr2sym() returns the alias with fewest leading "
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"underscores in the name when the address resolves to multiple "
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"symbols.");
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}
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ATF_TC_BODY(symbol_sort_underscore, tc)
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{
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char symname[32];
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GElf_Sym foo_sym;
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struct proc_handle *phdl;
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int error;
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phdl = start_prog(tc, true);
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error = proc_name2sym(phdl, target_prog_file, "foo", &foo_sym, NULL);
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ATF_REQUIRE_MSG(error == 0, "failed to look up 'foo' in %s",
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target_prog_file);
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error = proc_addr2sym(phdl, foo_sym.st_value, symname, sizeof(symname),
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&foo_sym);
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ATF_REQUIRE_MSG(error == 0, "failed to resolve 'foo' by addr");
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ATF_REQUIRE_MSG(strcmp(symname, "foo") == 0,
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"unexpected symbol name '%s'", symname);
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}
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ATF_TP_ADD_TCS(tp)
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{
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@ -379,6 +466,9 @@ ATF_TP_ADD_TCS(tp)
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ATF_TP_ADD_TC(tp, symbol_lookup);
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ATF_TP_ADD_TC(tp, symbol_lookup_fail);
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ATF_TP_ADD_TC(tp, signal_forward);
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ATF_TP_ADD_TC(tp, symbol_sort_local);
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ATF_TP_ADD_TC(tp, symbol_sort_prefix);
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ATF_TP_ADD_TC(tp, symbol_sort_underscore);
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return (atf_no_error());
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}
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@ -42,10 +42,33 @@ usr1(int sig __unused)
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saw = 1;
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}
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void foo(void);
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void qux(void);
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void
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foo(void)
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{
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}
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__weak_reference(foo, _foo);
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static void
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bar(void)
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{
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}
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__strong_reference(bar, baz);
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void
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qux(void)
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{
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}
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__strong_reference(qux, $qux);
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int
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main(int argc, char **argv)
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{
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bar(); /* force the symbol to be emitted */
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if (argc == 1)
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return (EXIT_SUCCESS);
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if (argc == 2 && strcmp(argv[1], "-s") == 0) {
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