Author: markj
Date: Tue Nov 21 16:03:21 2017
New Revision: 326064
URL: https://svnweb.freebsd.org/changeset/base/326064
Log:
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.
Modified:
head/lib/libproc/proc_sym.c
head/lib/libproc/tests/proc_test.c
head/lib/libproc/tests/target_prog.c
Modified: head/lib/libproc/proc_sym.c
==============================================================================
--- head/lib/libproc/proc_sym.c Tue Nov 21 16:00:18 2017 (r326063)
+++ head/lib/libproc/proc_sym.c Tue Nov 21 16:03:21 2017 (r326064)
@@ -1,5 +1,5 @@
/*-
- * Copyright (c) 2016 Mark Johnston <ma...@freebsd.org>
+ * Copyright (c) 2016-2017 Mark Johnston <ma...@freebsd.org>
* Copyright (c) 2010 The FreeBSD Foundation
* Copyright (c) 2008 John Birrell (j...@freebsd.org)
* All rights reserved.
@@ -100,27 +100,59 @@ fail:
strlcpy(buf, symbol, len);
}
+struct symsort_thunk {
+ Elf *e;
+ struct symtab *symtab;
+};
+
static int
-symvalcomp(void *thunk, const void *a1, const void *a2)
+symvalcmp(void *_thunk, const void *a1, const void *a2)
{
- struct symtab *symtab;
GElf_Sym sym1, sym2;
+ struct symsort_thunk *thunk;
+ const char *s1, *s2;
u_int i1, i2;
- int ret;
+ int bind1, bind2;
i1 = *(const u_int *)a1;
i2 = *(const u_int *)a2;
- symtab = thunk;
+ thunk = _thunk;
- (void)gelf_getsym(symtab->data, i1, &sym1);
- (void)gelf_getsym(symtab->data, i2, &sym2);
- if (sym1.st_value < sym2.st_value)
- ret = -1;
- else if (sym1.st_value == sym2.st_value)
- ret = 0;
- else
- ret = 1;
- return (ret);
+ (void)gelf_getsym(thunk->symtab->data, i1, &sym1);
+ (void)gelf_getsym(thunk->symtab->data, i2, &sym2);
+
+ if (sym1.st_value != sym2.st_value)
+ return (sym1.st_value < sym2.st_value ? -1 : 1);
+
+ /* Prefer non-local symbols. */
+ bind1 = GELF_ST_BIND(sym1.st_info);
+ bind2 = GELF_ST_BIND(sym2.st_info);
+ if (bind1 != bind2) {
+ if (bind1 == STB_LOCAL && bind2 != STB_LOCAL)
+ return (-1);
+ if (bind1 != STB_LOCAL && bind2 == STB_LOCAL)
+ return (1);
+ }
+
+ s1 = elf_strptr(thunk->e, thunk->symtab->stridx, sym1.st_name);
+ s2 = elf_strptr(thunk->e, thunk->symtab->stridx, sym2.st_name);
+ if (s1 != NULL && s2 != NULL) {
+ /* Prefer symbols without a leading '$'. */
+ if (*s1 == '$')
+ return (-1);
+ if (*s2 == '$')
+ return (1);
+
+ /* Prefer symbols with fewer leading underscores. */
+ for (; *s1 == '_' && *s2 == '_'; s1++, s2++)
+ ;
+ if (*s1 == '_')
+ return (-1);
+ if (*s2 == '_')
+ return (1);
+ }
+
+ return (0);
}
static int
@@ -128,6 +160,7 @@ load_symtab(Elf *e, struct symtab *symtab, u_long sh_t
{
GElf_Ehdr ehdr;
GElf_Shdr shdr;
+ struct symsort_thunk thunk;
Elf_Scn *scn;
u_int nsyms;
@@ -155,9 +188,13 @@ load_symtab(Elf *e, struct symtab *symtab, u_long sh_t
return (-1);
for (u_int i = 0; i < nsyms; i++)
symtab->index[i] = i;
- qsort_r(symtab->index, nsyms, sizeof(u_int), symtab, symvalcomp);
symtab->nsyms = nsyms;
symtab->stridx = shdr.sh_link;
+
+ thunk.e = e;
+ thunk.symtab = symtab;
+ qsort_r(symtab->index, nsyms, sizeof(u_int), &thunk, symvalcmp);
+
return (0);
}
@@ -416,34 +453,48 @@ proc_addr2map(struct proc_handle *p, uintptr_t addr)
* symbol and its name.
*/
static int
-lookup_symbol_by_addr(Elf *elf, struct symtab *symtab, uintptr_t addr,
- const char **namep, GElf_Sym *sym)
+lookup_symbol_by_addr(Elf *e, struct symtab *symtab, uintptr_t addr,
+ const char **namep, GElf_Sym *symp)
{
+ GElf_Sym sym;
Elf_Data *data;
const char *s;
- int min, max, mid;
+ u_int i, min, max, mid;
+ if (symtab->nsyms == 0)
+ return (ENOENT);
+
data = symtab->data;
min = 0;
max = symtab->nsyms - 1;
while (min <= max) {
mid = (max + min) / 2;
- (void)gelf_getsym(data, symtab->index[mid], sym);
- if (addr >= sym->st_value &&
- addr < sym->st_value + sym->st_size) {
- s = elf_strptr(elf, symtab->stridx, sym->st_name);
- if (s != NULL && namep != NULL)
- *namep = s;
- return (0);
- }
+ (void)gelf_getsym(data, symtab->index[mid], &sym);
+ if (addr >= sym.st_value && addr < sym.st_value + sym.st_size)
+ break;
- if (addr < sym->st_value)
+ if (addr < sym.st_value)
max = mid - 1;
else
min = mid + 1;
}
- return (ENOENT);
+ if (min > max)
+ return (ENOENT);
+
+ /*
+ * Advance until we find the matching symbol with largest index.
+ */
+ for (i = mid; i < symtab->nsyms; i++) {
+ (void)gelf_getsym(data, symtab->index[i], &sym);
+ if (addr < sym.st_value || addr >= sym.st_value + sym.st_size)
+ break;
+ }
+ (void)gelf_getsym(data, symtab->index[i - 1], symp);
+ s = elf_strptr(e, symtab->stridx, symp->st_name);
+ if (s != NULL && namep != NULL)
+ *namep = s;
+ return (0);
}
int
Modified: head/lib/libproc/tests/proc_test.c
==============================================================================
--- head/lib/libproc/tests/proc_test.c Tue Nov 21 16:00:18 2017
(r326063)
+++ head/lib/libproc/tests/proc_test.c Tue Nov 21 16:03:21 2017
(r326064)
@@ -1,5 +1,5 @@
/*-
- * Copyright (c) 2014-2016 Mark Johnston <ma...@freebsd.org>
+ * Copyright (c) 2014-2017 Mark Johnston <ma...@freebsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -370,6 +370,93 @@ ATF_TC_BODY(signal_forward, tc)
proc_free(phdl);
}
+ATF_TC(symbol_sort_local);
+ATF_TC_HEAD(symbol_sort_local, tc)
+{
+ atf_tc_set_md_var(tc, "descr",
+ "Ensure that proc_addr2sym() returns the non-local alias when "
+ "the address resolves to multiple symbols.");
+}
+ATF_TC_BODY(symbol_sort_local, tc)
+{
+ char symname[32];
+ GElf_Sym bar_sym;
+ struct proc_handle *phdl;
+ int error;
+
+ phdl = start_prog(tc, true);
+
+ error = proc_name2sym(phdl, target_prog_file, "bar", &bar_sym, NULL);
+ ATF_REQUIRE_MSG(error == 0, "failed to look up 'bar' in %s",
+ target_prog_file);
+ ATF_REQUIRE(GELF_ST_BIND(bar_sym.st_info) == STB_LOCAL);
+
+ error = proc_addr2sym(phdl, bar_sym.st_value, symname, sizeof(symname),
+ &bar_sym);
+ ATF_REQUIRE_MSG(error == 0, "failed to resolve 'bar' by addr");
+
+ ATF_REQUIRE_MSG(strcmp(symname, "baz") == 0,
+ "unexpected symbol name '%s'", symname);
+ ATF_REQUIRE(GELF_ST_BIND(bar_sym.st_info) == STB_GLOBAL);
+}
+
+ATF_TC(symbol_sort_prefix);
+ATF_TC_HEAD(symbol_sort_prefix, tc)
+{
+ atf_tc_set_md_var(tc, "descr",
+ "Ensure that proc_addr2sym() returns the alias whose name is not "
+ "prefixed with '$' if one exists.");
+}
+ATF_TC_BODY(symbol_sort_prefix, tc)
+{
+ char symname[32];
+ GElf_Sym qux_sym;
+ struct proc_handle *phdl;
+ int error;
+
+ phdl = start_prog(tc, true);
+
+ error = proc_name2sym(phdl, target_prog_file, "$qux", &qux_sym, NULL);
+ ATF_REQUIRE_MSG(error == 0, "failed to look up '$qux' in %s",
+ target_prog_file);
+
+ error = proc_addr2sym(phdl, qux_sym.st_value, symname, sizeof(symname),
+ &qux_sym);
+ ATF_REQUIRE_MSG(error == 0, "failed to resolve 'qux' by addr");
+
+ ATF_REQUIRE_MSG(strcmp(symname, "qux") == 0,
+ "unexpected symbol name '%s'", symname);
+}
+
+ATF_TC(symbol_sort_underscore);
+ATF_TC_HEAD(symbol_sort_underscore, tc)
+{
+ atf_tc_set_md_var(tc, "descr",
+ "Ensure that proc_addr2sym() returns the alias with fewest leading "
+ "underscores in the name when the address resolves to multiple "
+ "symbols.");
+}
+ATF_TC_BODY(symbol_sort_underscore, tc)
+{
+ char symname[32];
+ GElf_Sym foo_sym;
+ struct proc_handle *phdl;
+ int error;
+
+ phdl = start_prog(tc, true);
+
+ error = proc_name2sym(phdl, target_prog_file, "foo", &foo_sym, NULL);
+ ATF_REQUIRE_MSG(error == 0, "failed to look up 'foo' in %s",
+ target_prog_file);
+
+ error = proc_addr2sym(phdl, foo_sym.st_value, symname, sizeof(symname),
+ &foo_sym);
+ ATF_REQUIRE_MSG(error == 0, "failed to resolve 'foo' by addr");
+
+ ATF_REQUIRE_MSG(strcmp(symname, "foo") == 0,
+ "unexpected symbol name '%s'", symname);
+}
+
ATF_TP_ADD_TCS(tp)
{
@@ -379,6 +466,9 @@ ATF_TP_ADD_TCS(tp)
ATF_TP_ADD_TC(tp, symbol_lookup);
ATF_TP_ADD_TC(tp, symbol_lookup_fail);
ATF_TP_ADD_TC(tp, signal_forward);
+ ATF_TP_ADD_TC(tp, symbol_sort_local);
+ ATF_TP_ADD_TC(tp, symbol_sort_prefix);
+ ATF_TP_ADD_TC(tp, symbol_sort_underscore);
return (atf_no_error());
}
Modified: head/lib/libproc/tests/target_prog.c
==============================================================================
--- head/lib/libproc/tests/target_prog.c Tue Nov 21 16:00:18 2017
(r326063)
+++ head/lib/libproc/tests/target_prog.c Tue Nov 21 16:03:21 2017
(r326064)
@@ -42,9 +42,32 @@ usr1(int sig __unused)
saw = 1;
}
+void foo(void);
+void qux(void);
+
+void
+foo(void)
+{
+}
+__weak_reference(foo, _foo);
+
+static void
+bar(void)
+{
+}
+__strong_reference(bar, baz);
+
+void
+qux(void)
+{
+}
+__strong_reference(qux, $qux);
+
int
main(int argc, char **argv)
{
+
+ bar(); /* force the symbol to be emitted */
if (argc == 1)
return (EXIT_SUCCESS);
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