diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/vdso/Makefile | 16 | ||||
| -rw-r--r-- | arch/x86/vdso/vdso-fakesections.c | 21 | ||||
| -rw-r--r-- | arch/x86/vdso/vdso2c.c | 116 | ||||
| -rw-r--r-- | arch/x86/vdso/vdso2c.h | 202 |
4 files changed, 126 insertions, 229 deletions
diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile index 61b04fe..5a4affe 100644 --- a/arch/x86/vdso/Makefile +++ b/arch/x86/vdso/Makefile @@ -10,7 +10,7 @@ VDSO32-$(CONFIG_X86_32) := y VDSO32-$(CONFIG_COMPAT) := y # files to link into the vdso -vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o vdso-fakesections.o +vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o # files to link into kernel obj-y += vma.o @@ -37,7 +37,8 @@ vdso_img_sodbg := $(vdso_img-y:%=vdso%.so.dbg) obj-y += $(vdso_img_objs) targets += $(vdso_img_cfiles) targets += $(vdso_img_sodbg) -.SECONDARY: $(vdso_img-y:%=$(obj)/vdso-image-%.c) +.SECONDARY: $(vdso_img-y:%=$(obj)/vdso-image-%.c) \ + $(vdso_img-y:%=$(obj)/vdso%.so) export CPPFLAGS_vdso.lds += -P -C @@ -54,10 +55,10 @@ hostprogs-y += vdso2c quiet_cmd_vdso2c = VDSO2C $@ define cmd_vdso2c - $(obj)/vdso2c $< $@ + $(obj)/vdso2c $< $(<:%.dbg=%) $@ endef -$(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso2c FORCE +$(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE $(call if_changed,vdso2c) # @@ -113,6 +114,10 @@ $(obj)/%-x32.o: $(obj)/%.o FORCE targets += vdsox32.lds $(vobjx32s-y) +$(obj)/%.so: OBJCOPYFLAGS := -S +$(obj)/%.so: $(obj)/%.so.dbg + $(call if_changed,objcopy) + $(obj)/vdsox32.so.dbg: $(src)/vdsox32.lds $(vobjx32s) FORCE $(call if_changed,vdso) @@ -134,7 +139,7 @@ override obj-dirs = $(dir $(obj)) $(obj)/vdso32/ targets += vdso32/vdso32.lds targets += vdso32/note.o vdso32/vclock_gettime.o $(vdso32.so-y:%=vdso32/%.o) -targets += vdso32/vclock_gettime.o vdso32/vdso-fakesections.o +targets += vdso32/vclock_gettime.o $(obj)/vdso32.o: $(vdso32-images:%=$(obj)/%) @@ -156,7 +161,6 @@ $(vdso32-images:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_32) $(vdso32-images:%=$(obj)/%.dbg): $(obj)/vdso32-%.so.dbg: FORCE \ $(obj)/vdso32/vdso32.lds \ $(obj)/vdso32/vclock_gettime.o \ - $(obj)/vdso32/vdso-fakesections.o \ $(obj)/vdso32/note.o \ $(obj)/vdso32/%.o $(call if_changed,vdso) diff --git a/arch/x86/vdso/vdso-fakesections.c b/arch/x86/vdso/vdso-fakesections.c deleted file mode 100644 index aa5fbfa..0000000 --- a/arch/x86/vdso/vdso-fakesections.c +++ /dev/null @@ -1,21 +0,0 @@ -/* - * Copyright 2014 Andy Lutomirski - * Subject to the GNU Public License, v.2 - * - * String table for loadable section headers. See vdso2c.h for why - * this exists. - */ - -const char fake_shstrtab[] __attribute__((section(".fake_shstrtab"))) = - ".hash\0" - ".dynsym\0" - ".dynstr\0" - ".gnu.version\0" - ".gnu.version_d\0" - ".dynamic\0" - ".rodata\0" - ".fake_shstrtab\0" /* Yay, self-referential code. */ - ".note\0" - ".eh_frame_hdr\0" - ".eh_frame\0" - ".text"; diff --git a/arch/x86/vdso/vdso2c.c b/arch/x86/vdso/vdso2c.c index 22c54d0..8627db2 100644 --- a/arch/x86/vdso/vdso2c.c +++ b/arch/x86/vdso/vdso2c.c @@ -1,3 +1,53 @@ +/* + * vdso2c - A vdso image preparation tool + * Copyright (c) 2014 Andy Lutomirski and others + * Licensed under the GPL v2 + * + * vdso2c requires stripped and unstripped input. It would be trivial + * to fully strip the input in here, but, for reasons described below, + * we need to write a section table. Doing this is more or less + * equivalent to dropping all non-allocatable sections, but it's + * easier to let objcopy handle that instead of doing it ourselves. + * If we ever need to do something fancier than what objcopy provides, + * it would be straightforward to add here. + * + * We're keep 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. + */ + #include <inttypes.h> #include <stdint.h> #include <unistd.h> @@ -61,7 +111,8 @@ static void fail(const char *format, ...) va_start(ap, format); fprintf(stderr, "Error: "); vfprintf(stderr, format, ap); - unlink(outfilename); + if (outfilename) + unlink(outfilename); exit(1); va_end(ap); } @@ -114,30 +165,53 @@ extern void bad_put_le(void); #include "vdso2c.h" #undef ELF_BITS -static void go(void *addr, size_t len, FILE *outfile, const char *name) +static void go(void *raw_addr, size_t raw_len, + void *stripped_addr, size_t stripped_len, + FILE *outfile, const char *name) { - Elf64_Ehdr *hdr = (Elf64_Ehdr *)addr; + Elf64_Ehdr *hdr = (Elf64_Ehdr *)raw_addr; if (hdr->e_ident[EI_CLASS] == ELFCLASS64) { - go64(addr, len, outfile, name); + go64(raw_addr, raw_len, stripped_addr, stripped_len, + outfile, name); } else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) { - go32(addr, len, outfile, name); + go32(raw_addr, raw_len, stripped_addr, stripped_len, + outfile, name); } else { fail("unknown ELF class\n"); } } +static void map_input(const char *name, void **addr, size_t *len, int prot) +{ + off_t tmp_len; + + int fd = open(name, O_RDONLY); + if (fd == -1) + err(1, "%s", name); + + tmp_len = lseek(fd, 0, SEEK_END); + if (tmp_len == (off_t)-1) + err(1, "lseek"); + *len = (size_t)tmp_len; + + *addr = mmap(NULL, tmp_len, prot, MAP_PRIVATE, fd, 0); + if (*addr == MAP_FAILED) + err(1, "mmap"); + + close(fd); +} + int main(int argc, char **argv) { - int fd; - off_t len; - void *addr; + size_t raw_len, stripped_len; + void *raw_addr, *stripped_addr; FILE *outfile; char *name, *tmp; int namelen; - if (argc != 3) { - printf("Usage: vdso2c INPUT OUTPUT\n"); + if (argc != 4) { + printf("Usage: vdso2c RAW_INPUT STRIPPED_INPUT OUTPUT\n"); return 1; } @@ -145,7 +219,7 @@ int main(int argc, char **argv) * Figure out the struct name. If we're writing to a .so file, * generate raw output insted. */ - name = strdup(argv[2]); + name = strdup(argv[3]); namelen = strlen(name); if (namelen >= 3 && !strcmp(name + namelen - 3, ".so")) { name = NULL; @@ -161,26 +235,18 @@ int main(int argc, char **argv) *tmp = '_'; } - fd = open(argv[1], O_RDONLY); - if (fd == -1) - err(1, "%s", argv[1]); - - len = lseek(fd, 0, SEEK_END); - if (len == (off_t)-1) - err(1, "lseek"); - - addr = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0); - if (addr == MAP_FAILED) - err(1, "mmap"); + map_input(argv[1], &raw_addr, &raw_len, PROT_READ); + map_input(argv[2], &stripped_addr, &stripped_len, PROT_READ); - outfilename = argv[2]; + outfilename = argv[3]; outfile = fopen(outfilename, "w"); if (!outfile) err(1, "%s", argv[2]); - go(addr, (size_t)len, outfile, name); + go(raw_addr, raw_len, stripped_addr, stripped_len, outfile, name); - munmap(addr, len); + munmap(raw_addr, raw_len); + munmap(stripped_addr, stripped_len); fclose(outfile); return 0; diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h index 2da32fbc..fd57829 100644 --- a/arch/x86/vdso/vdso2c.h +++ b/arch/x86/vdso/vdso2c.h @@ -4,128 +4,14 @@ * 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, @@ -134,9 +20,7 @@ static void BITSFUNC(go)(void *addr, size_t len, const char *secstrings; INT_BITS syms[NSYMS] = {}; - struct BITSFUNC(fake_sections) fake_sections = {}; - - 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++) { @@ -219,48 +105,7 @@ static void BITSFUNC(go)(void *addr, size_t len, 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++) { @@ -281,10 +126,12 @@ static void BITSFUNC(go)(void *addr, size_t len, 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"); @@ -292,20 +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"); |
