Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 vdso updates from Ingo Molnar:
 "Further simplifications and improvements to the VDSO code, by Andy
  Lutomirski"

* 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86_64/vsyscall: Fix warn_bad_vsyscall log output
  x86/vdso: Set VM_MAYREAD for the vvar vma
  x86, vdso: Get rid of the fake section mechanism
  x86, vdso: Move the vvar area before the vdso text

1 files changed, 41 insertions, 186 deletions

diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h
index 11b65d4..fd57829 100644
--- a/arch/x86/vdso/vdso2c.h
+++ b/arch/x86/vdso/vdso2c.h
@@ -4,139 +4,23 @@
  * are built for 32-bit userspace.
  */
 
-/*
- * We're writing a section table for a few reasons:
- *
- * The Go runtime had a couple of bugs: it would read the section
- * table to try to figure out how many dynamic symbols there were (it
- * shouldn't have looked at the section table at all) and, if there
- * were no SHT_SYNDYM section table entry, it would use an
- * uninitialized value for the number of symbols.  An empty DYNSYM
- * table would work, but I see no reason not to write a valid one (and
- * keep full performance for old Go programs).  This hack is only
- * needed on x86_64.
- *
- * The bug was introduced on 2012-08-31 by:
- * https://code.google.com/p/go/source/detail?r=56ea40aac72b
- * and was fixed on 2014-06-13 by:
- * https://code.google.com/p/go/source/detail?r=fc1cd5e12595
- *
- * Binutils has issues debugging the vDSO: it reads the section table to
- * find SHT_NOTE; it won't look at PT_NOTE for the in-memory vDSO, which
- * would break build-id if we removed the section table.  Binutils
- * also requires that shstrndx != 0.  See:
- * https://sourceware.org/bugzilla/show_bug.cgi?id=17064
- *
- * elfutils might not look for PT_NOTE if there is a section table at
- * all.  I don't know whether this matters for any practical purpose.
- *
- * For simplicity, rather than hacking up a partial section table, we
- * just write a mostly complete one.  We omit non-dynamic symbols,
- * though, since they're rather large.
- *
- * Once binutils gets fixed, we might be able to drop this for all but
- * the 64-bit vdso, since build-id only works in kernel RPMs, and
- * systems that update to new enough kernel RPMs will likely update
- * binutils in sync.  build-id has never worked for home-built kernel
- * RPMs without manual symlinking, and I suspect that no one ever does
- * that.
- */
-struct BITSFUNC(fake_sections)
-{
-	ELF(Shdr) *table;
-	unsigned long table_offset;
-	int count, max_count;
-
-	int in_shstrndx;
-	unsigned long shstr_offset;
-	const char *shstrtab;
-	size_t shstrtab_len;
-
-	int out_shstrndx;
-};
-
-static unsigned int BITSFUNC(find_shname)(struct BITSFUNC(fake_sections) *out,
-					  const char *name)
-{
-	const char *outname = out->shstrtab;
-	while (outname - out->shstrtab < out->shstrtab_len) {
-		if (!strcmp(name, outname))
-			return (outname - out->shstrtab) + out->shstr_offset;
-		outname += strlen(outname) + 1;
-	}
-
-	if (*name)
-		printf("Warning: could not find output name \"%s\"\n", name);
-	return out->shstr_offset + out->shstrtab_len - 1;  /* Use a null. */
-}
-
-static void BITSFUNC(init_sections)(struct BITSFUNC(fake_sections) *out)
-{
-	if (!out->in_shstrndx)
-		fail("didn't find the fake shstrndx\n");
-
-	memset(out->table, 0, out->max_count * sizeof(ELF(Shdr)));
-
-	if (out->max_count < 1)
-		fail("we need at least two fake output sections\n");
-
-	PUT_LE(&out->table[0].sh_type, SHT_NULL);
-	PUT_LE(&out->table[0].sh_name, BITSFUNC(find_shname)(out, ""));
-
-	out->count = 1;
-}
-
-static void BITSFUNC(copy_section)(struct BITSFUNC(fake_sections) *out,
-				   int in_idx, const ELF(Shdr) *in,
-				   const char *name)
-{
-	uint64_t flags = GET_LE(&in->sh_flags);
-
-	bool copy = flags & SHF_ALLOC &&
-		(GET_LE(&in->sh_size) ||
-		 (GET_LE(&in->sh_type) != SHT_RELA &&
-		  GET_LE(&in->sh_type) != SHT_REL)) &&
-		strcmp(name, ".altinstructions") &&
-		strcmp(name, ".altinstr_replacement");
-
-	if (!copy)
-		return;
-
-	if (out->count >= out->max_count)
-		fail("too many copied sections (max = %d)\n", out->max_count);
-
-	if (in_idx == out->in_shstrndx)
-		out->out_shstrndx = out->count;
-
-	out->table[out->count] = *in;
-	PUT_LE(&out->table[out->count].sh_name,
-	       BITSFUNC(find_shname)(out, name));
-
-	/* elfutils requires that a strtab have the correct type. */
-	if (!strcmp(name, ".fake_shstrtab"))
-		PUT_LE(&out->table[out->count].sh_type, SHT_STRTAB);
-
-	out->count++;
-}
-
-static void BITSFUNC(go)(void *addr, size_t len,
+static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
+			 void *stripped_addr, size_t stripped_len,
 			 FILE *outfile, const char *name)
 {
 	int found_load = 0;
 	unsigned long load_size = -1;  /* Work around bogus warning */
-	unsigned long data_size;
-	ELF(Ehdr) *hdr = (ELF(Ehdr) *)addr;
+	unsigned long mapping_size;
+	ELF(Ehdr) *hdr = (ELF(Ehdr) *)raw_addr;
 	int i;
 	unsigned long j;
 	ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr,
 		*alt_sec = NULL;
 	ELF(Dyn) *dyn = 0, *dyn_end = 0;
 	const char *secstrings;
-	uint64_t syms[NSYMS] = {};
-
-	struct BITSFUNC(fake_sections) fake_sections = {};
+	INT_BITS syms[NSYMS] = {};
 
-	ELF(Phdr) *pt = (ELF(Phdr) *)(addr + GET_LE(&hdr->e_phoff));
+	ELF(Phdr) *pt = (ELF(Phdr) *)(raw_addr + GET_LE(&hdr->e_phoff));
 
 	/* Walk the segment table. */
 	for (i = 0; i < GET_LE(&hdr->e_phnum); i++) {
@@ -154,14 +38,16 @@ static void BITSFUNC(go)(void *addr, size_t len,
 			load_size = GET_LE(&pt[i].p_memsz);
 			found_load = 1;
 		} else if (GET_LE(&pt[i].p_type) == PT_DYNAMIC) {
-			dyn = addr + GET_LE(&pt[i].p_offset);
-			dyn_end = addr + GET_LE(&pt[i].p_offset) +
+			dyn = raw_addr + GET_LE(&pt[i].p_offset);
+			dyn_end = raw_addr + GET_LE(&pt[i].p_offset) +
 				GET_LE(&pt[i].p_memsz);
 		}
 	}
 	if (!found_load)
 		fail("no PT_LOAD seg\n");
-	data_size = (load_size + 4095) / 4096 * 4096;
+
+	if (stripped_len < load_size)
+		fail("stripped input is too short\n");
 
 	/* Walk the dynamic table */
 	for (i = 0; dyn + i < dyn_end &&
@@ -173,11 +59,11 @@ static void BITSFUNC(go)(void *addr, size_t len,
 	}
 
 	/* Walk the section table */
-	secstrings_hdr = addr + GET_LE(&hdr->e_shoff) +
+	secstrings_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
 		GET_LE(&hdr->e_shentsize)*GET_LE(&hdr->e_shstrndx);
-	secstrings = addr + GET_LE(&secstrings_hdr->sh_offset);
+	secstrings = raw_addr + GET_LE(&secstrings_hdr->sh_offset);
 	for (i = 0; i < GET_LE(&hdr->e_shnum); i++) {
-		ELF(Shdr) *sh = addr + GET_LE(&hdr->e_shoff) +
+		ELF(Shdr) *sh = raw_addr + GET_LE(&hdr->e_shoff) +
 			GET_LE(&hdr->e_shentsize) * i;
 		if (GET_LE(&sh->sh_type) == SHT_SYMTAB)
 			symtab_hdr = sh;
@@ -190,7 +76,7 @@ static void BITSFUNC(go)(void *addr, size_t len,
 	if (!symtab_hdr)
 		fail("no symbol table\n");
 
-	strtab_hdr = addr + GET_LE(&hdr->e_shoff) +
+	strtab_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
 		GET_LE(&hdr->e_shentsize) * GET_LE(&symtab_hdr->sh_link);
 
 	/* Walk the symbol table */
@@ -198,9 +84,9 @@ static void BITSFUNC(go)(void *addr, size_t len,
 	     i < GET_LE(&symtab_hdr->sh_size) / GET_LE(&symtab_hdr->sh_entsize);
 	     i++) {
 		int k;
-		ELF(Sym) *sym = addr + GET_LE(&symtab_hdr->sh_offset) +
+		ELF(Sym) *sym = raw_addr + GET_LE(&symtab_hdr->sh_offset) +
 			GET_LE(&symtab_hdr->sh_entsize) * i;
-		const char *name = addr + GET_LE(&strtab_hdr->sh_offset) +
+		const char *name = raw_addr + GET_LE(&strtab_hdr->sh_offset) +
 			GET_LE(&sym->st_name);
 
 		for (k = 0; k < NSYMS; k++) {
@@ -209,51 +95,17 @@ static void BITSFUNC(go)(void *addr, size_t len,
 					fail("duplicate symbol %s\n",
 					     required_syms[k].name);
 				}
+
+				/*
+				 * Careful: we use negative addresses, but
+				 * st_value is unsigned, so we rely
+				 * on syms[k] being a signed type of the
+				 * correct width.
+				 */
 				syms[k] = GET_LE(&sym->st_value);
 			}
 		}
-
-		if (!strcmp(name, "fake_shstrtab")) {
-			ELF(Shdr) *sh;
-
-			fake_sections.in_shstrndx = GET_LE(&sym->st_shndx);
-			fake_sections.shstrtab = addr + GET_LE(&sym->st_value);
-			fake_sections.shstrtab_len = GET_LE(&sym->st_size);
-			sh = addr + GET_LE(&hdr->e_shoff) +
-				GET_LE(&hdr->e_shentsize) *
-				fake_sections.in_shstrndx;
-			fake_sections.shstr_offset = GET_LE(&sym->st_value) -
-				GET_LE(&sh->sh_addr);
-		}
-	}
-
-	/* Build the output section table. */
-	if (!syms[sym_VDSO_FAKE_SECTION_TABLE_START] ||
-	    !syms[sym_VDSO_FAKE_SECTION_TABLE_END])
-		fail("couldn't find fake section table\n");
-	if ((syms[sym_VDSO_FAKE_SECTION_TABLE_END] -
-	     syms[sym_VDSO_FAKE_SECTION_TABLE_START]) % sizeof(ELF(Shdr)))
-		fail("fake section table size isn't a multiple of sizeof(Shdr)\n");
-	fake_sections.table = addr + syms[sym_VDSO_FAKE_SECTION_TABLE_START];
-	fake_sections.table_offset = syms[sym_VDSO_FAKE_SECTION_TABLE_START];
-	fake_sections.max_count = (syms[sym_VDSO_FAKE_SECTION_TABLE_END] -
-				   syms[sym_VDSO_FAKE_SECTION_TABLE_START]) /
-		sizeof(ELF(Shdr));
-
-	BITSFUNC(init_sections)(&fake_sections);
-	for (i = 0; i < GET_LE(&hdr->e_shnum); i++) {
-		ELF(Shdr) *sh = addr + GET_LE(&hdr->e_shoff) +
-			GET_LE(&hdr->e_shentsize) * i;
-		BITSFUNC(copy_section)(&fake_sections, i, sh,
-				       secstrings + GET_LE(&sh->sh_name));
 	}
-	if (!fake_sections.out_shstrndx)
-		fail("didn't generate shstrndx?!?\n");
-
-	PUT_LE(&hdr->e_shoff, fake_sections.table_offset);
-	PUT_LE(&hdr->e_shentsize, sizeof(ELF(Shdr)));
-	PUT_LE(&hdr->e_shnum, fake_sections.count);
-	PUT_LE(&hdr->e_shstrndx, fake_sections.out_shstrndx);
 
 	/* Validate mapping addresses. */
 	for (i = 0; i < sizeof(special_pages) / sizeof(special_pages[0]); i++) {
@@ -263,21 +115,23 @@ static void BITSFUNC(go)(void *addr, size_t len,
 		if (syms[i] % 4096)
 			fail("%s must be a multiple of 4096\n",
 			     required_syms[i].name);
-		if (syms[i] < data_size)
-			fail("%s must be after the text mapping\n",
+		if (syms[sym_vvar_start] > syms[i] + 4096)
+			fail("%s underruns begin_vvar\n",
 			     required_syms[i].name);
-		if (syms[sym_end_mapping] < syms[i] + 4096)
-			fail("%s overruns end_mapping\n",
+		if (syms[i] + 4096 > 0)
+			fail("%s is on the wrong side of the vdso text\n",
 			     required_syms[i].name);
 	}
-	if (syms[sym_end_mapping] % 4096)
-		fail("end_mapping must be a multiple of 4096\n");
+	if (syms[sym_vvar_start] % 4096)
+		fail("vvar_begin must be a multiple of 4096\n");
 
 	if (!name) {
-		fwrite(addr, load_size, 1, outfile);
+		fwrite(stripped_addr, stripped_len, 1, outfile);
 		return;
 	}
 
+	mapping_size = (stripped_len + 4095) / 4096 * 4096;
+
 	fprintf(outfile, "/* AUTOMATICALLY GENERATED -- DO NOT EDIT */\n\n");
 	fprintf(outfile, "#include <linux/linkage.h>\n");
 	fprintf(outfile, "#include <asm/page_types.h>\n");
@@ -285,20 +139,21 @@ static void BITSFUNC(go)(void *addr, size_t len,
 	fprintf(outfile, "\n");
 	fprintf(outfile,
 		"static unsigned char raw_data[%lu] __page_aligned_data = {",
-		data_size);
-	for (j = 0; j < load_size; j++) {
+		mapping_size);
+	for (j = 0; j < stripped_len; j++) {
 		if (j % 10 == 0)
 			fprintf(outfile, "\n\t");
-		fprintf(outfile, "0x%02X, ", (int)((unsigned char *)addr)[j]);
+		fprintf(outfile, "0x%02X, ",
+			(int)((unsigned char *)stripped_addr)[j]);
 	}
 	fprintf(outfile, "\n};\n\n");
 
 	fprintf(outfile, "static struct page *pages[%lu];\n\n",
-		data_size / 4096);
+		mapping_size / 4096);
 
 	fprintf(outfile, "const struct vdso_image %s = {\n", name);
 	fprintf(outfile, "\t.data = raw_data,\n");
-	fprintf(outfile, "\t.size = %lu,\n", data_size);
+	fprintf(outfile, "\t.size = %lu,\n", mapping_size);
 	fprintf(outfile, "\t.text_mapping = {\n");
 	fprintf(outfile, "\t\t.name = \"[vdso]\",\n");
 	fprintf(outfile, "\t\t.pages = pages,\n");
@@ -311,8 +166,8 @@ static void BITSFUNC(go)(void *addr, size_t len,
 	}
 	for (i = 0; i < NSYMS; i++) {
 		if (required_syms[i].export && syms[i])
-			fprintf(outfile, "\t.sym_%s = 0x%" PRIx64 ",\n",
-				required_syms[i].name, syms[i]);
+			fprintf(outfile, "\t.sym_%s = %" PRIi64 ",\n",
+				required_syms[i].name, (int64_t)syms[i]);
 	}
 	fprintf(outfile, "};\n");
 }