summaryrefslogtreecommitdiffstats
path: root/arch/x86/vdso/vdso2c.h
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/vdso/vdso2c.h')
-rw-r--r--arch/x86/vdso/vdso2c.h227
1 files changed, 41 insertions, 186 deletions
diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h
index 11b65d4f941..fd57829b30d 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");
}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-11-23 04:18:49 +0000