module: reduce string table for loaded modules (v2)

Also remove all parts of the string table (referenced by the symbol table) that are not needed for kallsyms use (i.e. which were only referenced by symbols discarded by the previous patch, or not referenced at all for whatever reason). Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

module: reduce string table for loaded modules (v2)
Also remove all parts of the string table (referenced by the symbol table) that are not needed for kallsyms use (i.e. which were only referenced by symbols discarded by the previous patch, or not referenced at all for whatever reason). Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Jan Beulich · Rusty Russell
1 parent 4a4962263f
Showing 2 changed files with 57 additions and 13 deletions Side-by-side Diff
include/linux/module.h
kernel/module.c
@@ -315,7 +315,7 @@
 	 */
 	Elf_Sym *symtab, *core_symtab;
 	unsigned int num_symtab, core_num_syms;
-	char *strtab;
+	char *strtab, *core_strtab;
  
 	/* Section attributes */
 	struct module_sect_attrs *sect_attrs;
@@ -1886,12 +1886,17 @@
 static unsigned long layout_symtab(struct module *mod,
 				   Elf_Shdr *sechdrs,
 				   unsigned int symindex,
+				   unsigned int strindex,
 				   const Elf_Ehdr *hdr,
-				   const char *secstrings)
+				   const char *secstrings,
+				   unsigned long *pstroffs,
+				   unsigned long *strmap)
 {
 	unsigned long symoffs;
 	Elf_Shdr *symsect = sechdrs + symindex;
+	Elf_Shdr *strsect = sechdrs + strindex;
 	const Elf_Sym *src;
+	const char *strtab;
 	unsigned int i, nsrc, ndst;
  
 	/* Put symbol section at end of init part of module. */
  
  
  
@@ -1902,14 +1907,31 @@
  
 	src = (void *)hdr + symsect->sh_offset;
 	nsrc = symsect->sh_size / sizeof(*src);
+	strtab = (void *)hdr + strsect->sh_offset;
 	for (ndst = i = 1; i < nsrc; ++i, ++src)
-		if (is_core_symbol(src, sechdrs, hdr->e_shnum))
+		if (is_core_symbol(src, sechdrs, hdr->e_shnum)) {
+			unsigned int j = src->st_name;
+
+			while(!__test_and_set_bit(j, strmap) && strtab[j])
+				++j;
 			++ndst;
+		}
  
 	/* Append room for core symbols at end of core part. */
 	symoffs = ALIGN(mod->core_size, symsect->sh_addralign ?: 1);
 	mod->core_size = symoffs + ndst * sizeof(Elf_Sym);
  
+	/* Put string table section at end of init part of module. */
+	strsect->sh_flags |= SHF_ALLOC;
+	strsect->sh_entsize = get_offset(mod, &mod->init_size, strsect,
+					 strindex) | INIT_OFFSET_MASK;
+	DEBUGP("\t%s\n", secstrings + strsect->sh_name);
+
+	/* Append room for core symbols' strings at end of core part. */
+	*pstroffs = mod->core_size;
+	__set_bit(0, strmap);
+	mod->core_size += bitmap_weight(strmap, strsect->sh_size);
+
 	return symoffs;
 }
  
  
@@ -1919,11 +1941,14 @@
 			 unsigned int symindex,
 			 unsigned int strindex,
 			 unsigned long symoffs,
-			 const char *secstrings)
+			 unsigned long stroffs,
+			 const char *secstrings,
+			 unsigned long *strmap)
 {
 	unsigned int i, ndst;
 	const Elf_Sym *src;
 	Elf_Sym *dst;
+	char *s;
  
 	mod->symtab = (void *)sechdrs[symindex].sh_addr;
 	mod->num_symtab = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
  
  
  
@@ -1941,16 +1966,25 @@
 		if (!is_core_symbol(src, sechdrs, shnum))
 			continue;
 		dst[ndst] = *src;
+		dst[ndst].st_name = bitmap_weight(strmap, dst[ndst].st_name);
 		++ndst;
 	}
 	mod->core_num_syms = ndst;
+
+	mod->core_strtab = s = mod->module_core + stroffs;
+	for (*s = 0, i = 1; i < sechdrs[strindex].sh_size; ++i)
+		if (test_bit(i, strmap))
+			*++s = mod->strtab[i];
 }
 #else
 static inline unsigned long layout_symtab(struct module *mod,
 					  Elf_Shdr *sechdrs,
 					  unsigned int symindex,
+					  unsigned int strindex,
 					  const Elf_Hdr *hdr,
-					  const char *secstrings)
+					  const char *secstrings,
+					  unsigned long *pstroffs,
+					  unsigned long *strmap)
 {
 }
 static inline void add_kallsyms(struct module *mod,
@@ -1959,7 +1993,9 @@
 				unsigned int symindex,
 				unsigned int strindex,
 				unsigned long symoffs,
-				const char *secstrings)
+				unsigned long stroffs,
+				const char *secstrings,
+				const unsigned long *strmap)
 {
 }
 #endif /* CONFIG_KALLSYMS */
@@ -2035,7 +2071,7 @@
 	long err = 0;
 	void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
 #ifdef CONFIG_KALLSYMS
-	unsigned long symoffs;
+	unsigned long symoffs, stroffs, *strmap;
 #endif
 	mm_segment_t old_fs;
  
@@ -2118,10 +2154,6 @@
 	/* Don't keep modinfo and version sections. */
 	sechdrs[infoindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
 	sechdrs[versindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
-#ifdef CONFIG_KALLSYMS
-	/* Keep string table for decoding later. */
-	sechdrs[strindex].sh_flags |= SHF_ALLOC;
-#endif
  
 	/* Check module struct version now, before we try to use module. */
 	if (!check_modstruct_version(sechdrs, versindex, mod)) {
@@ -2157,6 +2189,13 @@
 		goto free_hdr;
 	}
  
+	strmap = kzalloc(BITS_TO_LONGS(sechdrs[strindex].sh_size)
+			 * sizeof(long), GFP_KERNEL);
+	if (!strmap) {
+		err = -ENOMEM;
+		goto free_mod;
+	}
+
 	if (find_module(mod->name)) {
 		err = -EEXIST;
 		goto free_mod;
@@ -2186,7 +2225,8 @@
 	   this is done generically; there doesn't appear to be any
 	   special cases for the architectures. */
 	layout_sections(mod, hdr, sechdrs, secstrings);
-	symoffs = layout_symtab(mod, sechdrs, symindex, hdr, secstrings);
+	symoffs = layout_symtab(mod, sechdrs, symindex, strindex, hdr,
+				secstrings, &stroffs, strmap);
  
 	/* Do the allocs. */
 	ptr = module_alloc_update_bounds(mod->core_size);
@@ -2392,7 +2432,9 @@
 		       sechdrs[pcpuindex].sh_size);
  
 	add_kallsyms(mod, sechdrs, hdr->e_shnum, symindex, strindex,
-		     symoffs, secstrings);
+		     symoffs, stroffs, secstrings, strmap);
+	kfree(strmap);
+	strmap = NULL;
  
 	if (!mod->taints) {
 		struct _ddebug *debug;
@@ -2481,6 +2523,7 @@
 		percpu_modfree(percpu);
  free_mod:
 	kfree(args);
+	kfree(strmap);
  free_hdr:
 	vfree(hdr);
 	return ERR_PTR(err);
@@ -2573,6 +2616,7 @@
 #ifdef CONFIG_KALLSYMS
 	mod->num_symtab = mod->core_num_syms;
 	mod->symtab = mod->core_symtab;
+	mod->strtab = mod->core_strtab;
 #endif
 	module_free(mod, mod->module_init);
 	mod->module_init = NULL;
...	...	@@ -315,7 +315,7 @@
315	315	*/
316	316	Elf_Sym symtab, core_symtab;
317	317	unsigned int num_symtab, core_num_syms;
318		- char *strtab;
	318	+ char strtab, core_strtab;
319	319
320	320	/* Section attributes */
321	321	struct module_sect_attrs *sect_attrs;
...	...	@@ -1886,12 +1886,17 @@
1886	1886	static unsigned long layout_symtab(struct module *mod,
1887	1887	Elf_Shdr *sechdrs,
1888	1888	unsigned int symindex,
	1889	+ unsigned int strindex,
1889	1890	const Elf_Ehdr *hdr,
1890		- const char *secstrings)
	1891	+ const char *secstrings,
	1892	+ unsigned long *pstroffs,
	1893	+ unsigned long *strmap)
1891	1894	{
1892	1895	unsigned long symoffs;
1893	1896	Elf_Shdr *symsect = sechdrs + symindex;
	1897	+ Elf_Shdr *strsect = sechdrs + strindex;
1894	1898	const Elf_Sym *src;
	1899	+ const char *strtab;
1895	1900	unsigned int i, nsrc, ndst;
1896	1901
1897	1902	/* Put symbol section at end of init part of module. */
1898	1903
1899	1904
1900	1905
...	...	@@ -1902,14 +1907,31 @@
1902	1907
1903	1908	src = (void *)hdr + symsect->sh_offset;
1904	1909	nsrc = symsect->sh_size / sizeof(*src);
	1910	+ strtab = (void *)hdr + strsect->sh_offset;
1905	1911	for (ndst = i = 1; i < nsrc; ++i, ++src)
1906		- if (is_core_symbol(src, sechdrs, hdr->e_shnum))
	1912	+ if (is_core_symbol(src, sechdrs, hdr->e_shnum)) {
	1913	+ unsigned int j = src->st_name;
	1914	+
	1915	+ while(!__test_and_set_bit(j, strmap) && strtab[j])
	1916	+ ++j;
1907	1917	++ndst;
	1918	+ }
1908	1919
1909	1920	/* Append room for core symbols at end of core part. */
1910	1921	symoffs = ALIGN(mod->core_size, symsect->sh_addralign ?: 1);
1911	1922	mod->core_size = symoffs + ndst * sizeof(Elf_Sym);
1912	1923
	1924	+ /* Put string table section at end of init part of module. */
	1925	+ strsect->sh_flags \|= SHF_ALLOC;
	1926	+ strsect->sh_entsize = get_offset(mod, &mod->init_size, strsect,
	1927	+ strindex) \| INIT_OFFSET_MASK;
	1928	+ DEBUGP("\t%s\n", secstrings + strsect->sh_name);
	1929	+
	1930	+ /* Append room for core symbols' strings at end of core part. */
	1931	+ *pstroffs = mod->core_size;
	1932	+ __set_bit(0, strmap);
	1933	+ mod->core_size += bitmap_weight(strmap, strsect->sh_size);
	1934	+
1913	1935	return symoffs;
1914	1936	}
1915	1937
1916	1938
...	...	@@ -1919,11 +1941,14 @@
1919	1941	unsigned int symindex,
1920	1942	unsigned int strindex,
1921	1943	unsigned long symoffs,
1922		- const char *secstrings)
	1944	+ unsigned long stroffs,
	1945	+ const char *secstrings,
	1946	+ unsigned long *strmap)
1923	1947	{
1924	1948	unsigned int i, ndst;
1925	1949	const Elf_Sym *src;
1926	1950	Elf_Sym *dst;
	1951	+ char *s;
1927	1952
1928	1953	mod->symtab = (void *)sechdrs[symindex].sh_addr;
1929	1954	mod->num_symtab = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
1930	1955
1931	1956
1932	1957
...	...	@@ -1941,16 +1966,25 @@
1941	1966	if (!is_core_symbol(src, sechdrs, shnum))
1942	1967	continue;
1943	1968	dst[ndst] = *src;
	1969	+ dst[ndst].st_name = bitmap_weight(strmap, dst[ndst].st_name);
1944	1970	++ndst;
1945	1971	}
1946	1972	mod->core_num_syms = ndst;
	1973	+
	1974	+ mod->core_strtab = s = mod->module_core + stroffs;
	1975	+ for (*s = 0, i = 1; i < sechdrs[strindex].sh_size; ++i)
	1976	+ if (test_bit(i, strmap))
	1977	+ *++s = mod->strtab[i];
1947	1978	}
1948	1979	#else
1949	1980	static inline unsigned long layout_symtab(struct module *mod,
1950	1981	Elf_Shdr *sechdrs,
1951	1982	unsigned int symindex,
	1983	+ unsigned int strindex,
1952	1984	const Elf_Hdr *hdr,
1953		- const char *secstrings)
	1985	+ const char *secstrings,
	1986	+ unsigned long *pstroffs,
	1987	+ unsigned long *strmap)
1954	1988	{
1955	1989	}
1956	1990	static inline void add_kallsyms(struct module *mod,
...	...	@@ -1959,7 +1993,9 @@
1959	1993	unsigned int symindex,
1960	1994	unsigned int strindex,
1961	1995	unsigned long symoffs,
1962		- const char *secstrings)
	1996	+ unsigned long stroffs,
	1997	+ const char *secstrings,
	1998	+ const unsigned long *strmap)
1963	1999	{
1964	2000	}
1965	2001	#endif /* CONFIG_KALLSYMS */
...	...	@@ -2035,7 +2071,7 @@
2035	2071	long err = 0;
2036	2072	void percpu = NULL, ptr = NULL; /* Stops spurious gcc warning */
2037	2073	#ifdef CONFIG_KALLSYMS
2038		- unsigned long symoffs;
	2074	+ unsigned long symoffs, stroffs, *strmap;
2039	2075	#endif
2040	2076	mm_segment_t old_fs;
2041	2077
...	...	@@ -2118,10 +2154,6 @@
2118	2154	/* Don't keep modinfo and version sections. */
2119	2155	sechdrs[infoindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
2120	2156	sechdrs[versindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
2121		-#ifdef CONFIG_KALLSYMS
2122		- /* Keep string table for decoding later. */
2123		- sechdrs[strindex].sh_flags \|= SHF_ALLOC;
2124		-#endif
2125	2157
2126	2158	/* Check module struct version now, before we try to use module. */
2127	2159	if (!check_modstruct_version(sechdrs, versindex, mod)) {
...	...	@@ -2157,6 +2189,13 @@
2157	2189	goto free_hdr;
2158	2190	}
2159	2191
	2192	+ strmap = kzalloc(BITS_TO_LONGS(sechdrs[strindex].sh_size)
	2193	+ * sizeof(long), GFP_KERNEL);
	2194	+ if (!strmap) {
	2195	+ err = -ENOMEM;
	2196	+ goto free_mod;
	2197	+ }
	2198	+
2160	2199	if (find_module(mod->name)) {
2161	2200	err = -EEXIST;
2162	2201	goto free_mod;
...	...	@@ -2186,7 +2225,8 @@
2186	2225	this is done generically; there doesn't appear to be any
2187	2226	special cases for the architectures. */
2188	2227	layout_sections(mod, hdr, sechdrs, secstrings);
2189		- symoffs = layout_symtab(mod, sechdrs, symindex, hdr, secstrings);
	2228	+ symoffs = layout_symtab(mod, sechdrs, symindex, strindex, hdr,
	2229	+ secstrings, &stroffs, strmap);
2190	2230
2191	2231	/* Do the allocs. */
2192	2232	ptr = module_alloc_update_bounds(mod->core_size);
...	...	@@ -2392,7 +2432,9 @@
2392	2432	sechdrs[pcpuindex].sh_size);
2393	2433
2394	2434	add_kallsyms(mod, sechdrs, hdr->e_shnum, symindex, strindex,
2395		- symoffs, secstrings);
	2435	+ symoffs, stroffs, secstrings, strmap);
	2436	+ kfree(strmap);
	2437	+ strmap = NULL;
2396	2438
2397	2439	if (!mod->taints) {
2398	2440	struct _ddebug *debug;
...	...	@@ -2481,6 +2523,7 @@
2481	2523	percpu_modfree(percpu);
2482	2524	free_mod:
2483	2525	kfree(args);
	2526	+ kfree(strmap);
2484	2527	free_hdr:
2485	2528	vfree(hdr);
2486	2529	return ERR_PTR(err);
...	...	@@ -2573,6 +2616,7 @@
2573	2616	#ifdef CONFIG_KALLSYMS
2574	2617	mod->num_symtab = mod->core_num_syms;
2575	2618	mod->symtab = mod->core_symtab;
	2619	+ mod->strtab = mod->core_strtab;
2576	2620	#endif
2577	2621	module_free(mod, mod->module_init);
2578	2622	mod->module_init = NULL;