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Message-ID: <176834888556.510.1391225459380426538.tip-bot2@tip-bot2>
Date: Wed, 14 Jan 2026 00:01:25 -0000
From: "tip-bot2 for H. Peter Anvin" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "H. Peter Anvin (Intel)" <hpa@...or.com>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/entry] x86/entry/vdso: Move vdso2c to arch/x86/tools
The following commit has been merged into the x86/entry branch of tip:
Commit-ID: a76108d05ee13cddb72b620752a80b2c3e87aee1
Gitweb: https://git.kernel.org/tip/a76108d05ee13cddb72b620752a80b2c3e87aee1
Author: H. Peter Anvin <hpa@...or.com>
AuthorDate: Tue, 16 Dec 2025 13:25:56 -08:00
Committer: Dave Hansen <dave.hansen@...ux.intel.com>
CommitterDate: Tue, 13 Jan 2026 15:33:20 -08:00
x86/entry/vdso: Move vdso2c to arch/x86/tools
It is generally better to build tools in arch/x86/tools to keep host
cflags proliferation down, and to reduce makefile sequencing issues.
Move the vdso build tool vdso2c into arch/x86/tools in preparation for
refactoring the vdso makefiles.
Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Link: https://patch.msgid.link/20251216212606.1325678-3-hpa@zytor.com
---
arch/x86/Makefile | 2 +-
arch/x86/entry/vdso/Makefile | 7 +-
arch/x86/entry/vdso/vdso2c.c | 233 +----------------------------------
arch/x86/entry/vdso/vdso2c.h | 208 +------------------------------
arch/x86/tools/Makefile | 15 +-
arch/x86/tools/vdso2c.c | 233 ++++++++++++++++++++++++++++++++++-
arch/x86/tools/vdso2c.h | 208 ++++++++++++++++++++++++++++++-
7 files changed, 455 insertions(+), 451 deletions(-)
delete mode 100644 arch/x86/entry/vdso/vdso2c.c
delete mode 100644 arch/x86/entry/vdso/vdso2c.h
create mode 100644 arch/x86/tools/vdso2c.c
create mode 100644 arch/x86/tools/vdso2c.h
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 1d403a3..9ab7522 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -252,7 +252,7 @@ endif
archscripts: scripts_basic
- $(Q)$(MAKE) $(build)=arch/x86/tools relocs
+ $(Q)$(MAKE) $(build)=arch/x86/tools relocs vdso2c
###
# Syscall table generation
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 7f83302..3d9b09f 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -38,13 +38,12 @@ VDSO_LDFLAGS_vdso.lds = -m elf_x86_64 -soname linux-vdso.so.1 \
$(obj)/vdso64.so.dbg: $(obj)/vdso.lds $(vobjs) FORCE
$(call if_changed,vdso_and_check)
-HOST_EXTRACFLAGS += -I$(srctree)/tools/include -I$(srctree)/include/uapi -I$(srctree)/arch/$(SUBARCH)/include/uapi
-hostprogs += vdso2c
+VDSO2C = $(objtree)/arch/x86/tools/vdso2c
quiet_cmd_vdso2c = VDSO2C $@
- cmd_vdso2c = $(obj)/vdso2c $< $(<:%.dbg=%) $@
+ cmd_vdso2c = $(VDSO2C) $< $(<:%.dbg=%) $@
-$(obj)/vdso%-image.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
+$(obj)/vdso%-image.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(VDSO2C) FORCE
$(call if_changed,vdso2c)
#
diff --git a/arch/x86/entry/vdso/vdso2c.c b/arch/x86/entry/vdso/vdso2c.c
deleted file mode 100644
index f84e8f8..0000000
--- a/arch/x86/entry/vdso/vdso2c.c
+++ /dev/null
@@ -1,233 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * vdso2c - A vdso image preparation tool
- * Copyright (c) 2014 Andy Lutomirski and others
- *
- * 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>
-#include <stdarg.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <string.h>
-#include <fcntl.h>
-#include <err.h>
-
-#include <sys/mman.h>
-#include <sys/types.h>
-
-#include <tools/le_byteshift.h>
-
-#include <linux/elf.h>
-#include <linux/types.h>
-#include <linux/kernel.h>
-
-const char *outfilename;
-
-struct vdso_sym {
- const char *name;
- bool export;
-};
-
-struct vdso_sym required_syms[] = {
- {"VDSO32_NOTE_MASK", true},
- {"__kernel_vsyscall", true},
- {"__kernel_sigreturn", true},
- {"__kernel_rt_sigreturn", true},
- {"int80_landing_pad", true},
- {"vdso32_rt_sigreturn_landing_pad", true},
- {"vdso32_sigreturn_landing_pad", true},
-};
-
-__attribute__((format(printf, 1, 2))) __attribute__((noreturn))
-static void fail(const char *format, ...)
-{
- va_list ap;
- va_start(ap, format);
- fprintf(stderr, "Error: ");
- vfprintf(stderr, format, ap);
- if (outfilename)
- unlink(outfilename);
- exit(1);
- va_end(ap);
-}
-
-/*
- * Evil macros for little-endian reads and writes
- */
-#define GLE(x, bits, ifnot) \
- __builtin_choose_expr( \
- (sizeof(*(x)) == bits/8), \
- (__typeof__(*(x)))get_unaligned_le##bits(x), ifnot)
-
-extern void bad_get_le(void);
-#define LAST_GLE(x) \
- __builtin_choose_expr(sizeof(*(x)) == 1, *(x), bad_get_le())
-
-#define GET_LE(x) \
- GLE(x, 64, GLE(x, 32, GLE(x, 16, LAST_GLE(x))))
-
-#define PLE(x, val, bits, ifnot) \
- __builtin_choose_expr( \
- (sizeof(*(x)) == bits/8), \
- put_unaligned_le##bits((val), (x)), ifnot)
-
-extern void bad_put_le(void);
-#define LAST_PLE(x, val) \
- __builtin_choose_expr(sizeof(*(x)) == 1, *(x) = (val), bad_put_le())
-
-#define PUT_LE(x, val) \
- PLE(x, val, 64, PLE(x, val, 32, PLE(x, val, 16, LAST_PLE(x, val))))
-
-
-#define NSYMS ARRAY_SIZE(required_syms)
-
-#define BITSFUNC3(name, bits, suffix) name##bits##suffix
-#define BITSFUNC2(name, bits, suffix) BITSFUNC3(name, bits, suffix)
-#define BITSFUNC(name) BITSFUNC2(name, ELF_BITS, )
-
-#define INT_BITS BITSFUNC2(int, ELF_BITS, _t)
-
-#define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
-#define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
-#define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
-
-#define ELF_BITS 64
-#include "vdso2c.h"
-#undef ELF_BITS
-
-#define ELF_BITS 32
-#include "vdso2c.h"
-#undef ELF_BITS
-
-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 *)raw_addr;
-
- if (hdr->e_ident[EI_CLASS] == ELFCLASS64) {
- go64(raw_addr, raw_len, stripped_addr, stripped_len,
- outfile, name);
- } else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) {
- 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, "open(%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)
-{
- size_t raw_len, stripped_len;
- void *raw_addr, *stripped_addr;
- FILE *outfile;
- char *name, *tmp;
- int namelen;
-
- if (argc != 4) {
- printf("Usage: vdso2c RAW_INPUT STRIPPED_INPUT OUTPUT\n");
- return 1;
- }
-
- /*
- * Figure out the struct name. If we're writing to a .so file,
- * generate raw output instead.
- */
- name = strdup(argv[3]);
- namelen = strlen(name);
- if (namelen >= 3 && !strcmp(name + namelen - 3, ".so")) {
- name = NULL;
- } else {
- tmp = strrchr(name, '/');
- if (tmp)
- name = tmp + 1;
- tmp = strchr(name, '.');
- if (tmp)
- *tmp = '\0';
- for (tmp = name; *tmp; tmp++)
- if (*tmp == '-')
- *tmp = '_';
- }
-
- map_input(argv[1], &raw_addr, &raw_len, PROT_READ);
- map_input(argv[2], &stripped_addr, &stripped_len, PROT_READ);
-
- outfilename = argv[3];
- outfile = fopen(outfilename, "w");
- if (!outfile)
- err(1, "fopen(%s)", outfilename);
-
- go(raw_addr, raw_len, stripped_addr, stripped_len, outfile, name);
-
- munmap(raw_addr, raw_len);
- munmap(stripped_addr, stripped_len);
- fclose(outfile);
-
- return 0;
-}
diff --git a/arch/x86/entry/vdso/vdso2c.h b/arch/x86/entry/vdso/vdso2c.h
deleted file mode 100644
index 78ed1c1..0000000
--- a/arch/x86/entry/vdso/vdso2c.h
+++ /dev/null
@@ -1,208 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * This file is included twice from vdso2c.c. It generates code for 32-bit
- * and 64-bit vDSOs. We need both for 64-bit builds, since 32-bit vDSOs
- * are built for 32-bit userspace.
- */
-
-static void BITSFUNC(copy)(FILE *outfile, const unsigned char *data, size_t len)
-{
- size_t i;
-
- for (i = 0; i < len; i++) {
- if (i % 10 == 0)
- fprintf(outfile, "\n\t");
- fprintf(outfile, "0x%02X, ", (int)(data)[i]);
- }
-}
-
-
-/*
- * Extract a section from the input data into a standalone blob. Used to
- * capture kernel-only data that needs to persist indefinitely, e.g. the
- * exception fixup tables, but only in the kernel, i.e. the section can
- * be stripped from the final vDSO image.
- */
-static void BITSFUNC(extract)(const unsigned char *data, size_t data_len,
- FILE *outfile, ELF(Shdr) *sec, const char *name)
-{
- unsigned long offset;
- size_t len;
-
- offset = (unsigned long)GET_LE(&sec->sh_offset);
- len = (size_t)GET_LE(&sec->sh_size);
-
- if (offset + len > data_len)
- fail("section to extract overruns input data");
-
- fprintf(outfile, "static const unsigned char %s[%zu] = {", name, len);
- BITSFUNC(copy)(outfile, data + offset, len);
- fprintf(outfile, "\n};\n\n");
-}
-
-static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
- void *stripped_addr, size_t stripped_len,
- FILE *outfile, const char *image_name)
-{
- int found_load = 0;
- unsigned long load_size = -1; /* Work around bogus warning */
- unsigned long mapping_size;
- ELF(Ehdr) *hdr = (ELF(Ehdr) *)raw_addr;
- unsigned long i, syms_nr;
- ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr,
- *alt_sec = NULL, *extable_sec = NULL;
- ELF(Dyn) *dyn = 0, *dyn_end = 0;
- const char *secstrings;
- INT_BITS syms[NSYMS] = {};
-
- ELF(Phdr) *pt = (ELF(Phdr) *)(raw_addr + GET_LE(&hdr->e_phoff));
-
- if (GET_LE(&hdr->e_type) != ET_DYN)
- fail("input is not a shared object\n");
-
- /* Walk the segment table. */
- for (i = 0; i < GET_LE(&hdr->e_phnum); i++) {
- if (GET_LE(&pt[i].p_type) == PT_LOAD) {
- if (found_load)
- fail("multiple PT_LOAD segs\n");
-
- if (GET_LE(&pt[i].p_offset) != 0 ||
- GET_LE(&pt[i].p_vaddr) != 0)
- fail("PT_LOAD in wrong place\n");
-
- if (GET_LE(&pt[i].p_memsz) != GET_LE(&pt[i].p_filesz))
- fail("cannot handle memsz != filesz\n");
-
- load_size = GET_LE(&pt[i].p_memsz);
- found_load = 1;
- } else if (GET_LE(&pt[i].p_type) == PT_DYNAMIC) {
- 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");
-
- if (stripped_len < load_size)
- fail("stripped input is too short\n");
-
- if (!dyn)
- fail("input has no PT_DYNAMIC section -- your toolchain is buggy\n");
-
- /* Walk the dynamic table */
- for (i = 0; dyn + i < dyn_end &&
- GET_LE(&dyn[i].d_tag) != DT_NULL; i++) {
- typeof(dyn[i].d_tag) tag = GET_LE(&dyn[i].d_tag);
- if (tag == DT_REL || tag == DT_RELSZ || tag == DT_RELA ||
- tag == DT_RELENT || tag == DT_TEXTREL)
- fail("vdso image contains dynamic relocations\n");
- }
-
- /* Walk the section table */
- secstrings_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
- GET_LE(&hdr->e_shentsize)*GET_LE(&hdr->e_shstrndx);
- secstrings = raw_addr + GET_LE(&secstrings_hdr->sh_offset);
- for (i = 0; i < GET_LE(&hdr->e_shnum); i++) {
- 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;
-
- if (!strcmp(secstrings + GET_LE(&sh->sh_name),
- ".altinstructions"))
- alt_sec = sh;
- if (!strcmp(secstrings + GET_LE(&sh->sh_name), "__ex_table"))
- extable_sec = sh;
- }
-
- if (!symtab_hdr)
- fail("no symbol table\n");
-
- strtab_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
- GET_LE(&hdr->e_shentsize) * GET_LE(&symtab_hdr->sh_link);
-
- syms_nr = GET_LE(&symtab_hdr->sh_size) / GET_LE(&symtab_hdr->sh_entsize);
- /* Walk the symbol table */
- for (i = 0; i < syms_nr; i++) {
- unsigned int k;
- ELF(Sym) *sym = raw_addr + GET_LE(&symtab_hdr->sh_offset) +
- GET_LE(&symtab_hdr->sh_entsize) * i;
- const char *sym_name = raw_addr +
- GET_LE(&strtab_hdr->sh_offset) +
- GET_LE(&sym->st_name);
-
- for (k = 0; k < NSYMS; k++) {
- if (!strcmp(sym_name, required_syms[k].name)) {
- if (syms[k]) {
- 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 (!image_name) {
- 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 <linux/init.h>\n");
- fprintf(outfile, "#include <asm/page_types.h>\n");
- fprintf(outfile, "#include <asm/vdso.h>\n");
- fprintf(outfile, "\n");
- fprintf(outfile,
- "static unsigned char raw_data[%lu] __ro_after_init __aligned(PAGE_SIZE) = {",
- mapping_size);
- for (i = 0; i < stripped_len; i++) {
- if (i % 10 == 0)
- fprintf(outfile, "\n\t");
- fprintf(outfile, "0x%02X, ",
- (int)((unsigned char *)stripped_addr)[i]);
- }
- fprintf(outfile, "\n};\n\n");
- if (extable_sec)
- BITSFUNC(extract)(raw_addr, raw_len, outfile,
- extable_sec, "extable");
-
- fprintf(outfile, "const struct vdso_image %s = {\n", image_name);
- fprintf(outfile, "\t.data = raw_data,\n");
- fprintf(outfile, "\t.size = %lu,\n", mapping_size);
- if (alt_sec) {
- fprintf(outfile, "\t.alt = %lu,\n",
- (unsigned long)GET_LE(&alt_sec->sh_offset));
- fprintf(outfile, "\t.alt_len = %lu,\n",
- (unsigned long)GET_LE(&alt_sec->sh_size));
- }
- if (extable_sec) {
- fprintf(outfile, "\t.extable_base = %lu,\n",
- (unsigned long)GET_LE(&extable_sec->sh_offset));
- fprintf(outfile, "\t.extable_len = %lu,\n",
- (unsigned long)GET_LE(&extable_sec->sh_size));
- fprintf(outfile, "\t.extable = extable,\n");
- }
-
- for (i = 0; i < NSYMS; i++) {
- if (required_syms[i].export && syms[i])
- fprintf(outfile, "\t.sym_%s = %" PRIi64 ",\n",
- required_syms[i].name, (int64_t)syms[i]);
- }
- fprintf(outfile, "};\n\n");
- fprintf(outfile, "static __init int init_%s(void) {\n", image_name);
- fprintf(outfile, "\treturn init_vdso_image(&%s);\n", image_name);
- fprintf(outfile, "};\n");
- fprintf(outfile, "subsys_initcall(init_%s);\n", image_name);
-
-}
diff --git a/arch/x86/tools/Makefile b/arch/x86/tools/Makefile
index 7278e25..39a183f 100644
--- a/arch/x86/tools/Makefile
+++ b/arch/x86/tools/Makefile
@@ -38,9 +38,14 @@ $(obj)/insn_decoder_test.o: $(srctree)/tools/arch/x86/lib/insn.c $(srctree)/tool
$(obj)/insn_sanity.o: $(srctree)/tools/arch/x86/lib/insn.c $(srctree)/tools/arch/x86/lib/inat.c $(srctree)/tools/arch/x86/include/asm/inat_types.h $(srctree)/tools/arch/x86/include/asm/inat.h $(srctree)/tools/arch/x86/include/asm/insn.h $(objtree)/arch/x86/lib/inat-tables.c
-HOST_EXTRACFLAGS += -I$(srctree)/tools/include
-hostprogs += relocs
-relocs-objs := relocs_32.o relocs_64.o relocs_common.o
-PHONY += relocs
-relocs: $(obj)/relocs
+HOST_EXTRACFLAGS += -I$(srctree)/tools/include -I$(srctree)/include/uapi \
+ -I$(srctree)/arch/$(SUBARCH)/include/uapi
+
+hostprogs += relocs vdso2c
+relocs-objs := relocs_32.o relocs_64.o relocs_common.o
+
+always-y := $(hostprogs)
+
+PHONY += $(hostprogs)
+$(hostprogs): %: $(obj)/%
@:
diff --git a/arch/x86/tools/vdso2c.c b/arch/x86/tools/vdso2c.c
new file mode 100644
index 0000000..f84e8f8
--- /dev/null
+++ b/arch/x86/tools/vdso2c.c
@@ -0,0 +1,233 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * vdso2c - A vdso image preparation tool
+ * Copyright (c) 2014 Andy Lutomirski and others
+ *
+ * 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>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <err.h>
+
+#include <sys/mman.h>
+#include <sys/types.h>
+
+#include <tools/le_byteshift.h>
+
+#include <linux/elf.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+
+const char *outfilename;
+
+struct vdso_sym {
+ const char *name;
+ bool export;
+};
+
+struct vdso_sym required_syms[] = {
+ {"VDSO32_NOTE_MASK", true},
+ {"__kernel_vsyscall", true},
+ {"__kernel_sigreturn", true},
+ {"__kernel_rt_sigreturn", true},
+ {"int80_landing_pad", true},
+ {"vdso32_rt_sigreturn_landing_pad", true},
+ {"vdso32_sigreturn_landing_pad", true},
+};
+
+__attribute__((format(printf, 1, 2))) __attribute__((noreturn))
+static void fail(const char *format, ...)
+{
+ va_list ap;
+ va_start(ap, format);
+ fprintf(stderr, "Error: ");
+ vfprintf(stderr, format, ap);
+ if (outfilename)
+ unlink(outfilename);
+ exit(1);
+ va_end(ap);
+}
+
+/*
+ * Evil macros for little-endian reads and writes
+ */
+#define GLE(x, bits, ifnot) \
+ __builtin_choose_expr( \
+ (sizeof(*(x)) == bits/8), \
+ (__typeof__(*(x)))get_unaligned_le##bits(x), ifnot)
+
+extern void bad_get_le(void);
+#define LAST_GLE(x) \
+ __builtin_choose_expr(sizeof(*(x)) == 1, *(x), bad_get_le())
+
+#define GET_LE(x) \
+ GLE(x, 64, GLE(x, 32, GLE(x, 16, LAST_GLE(x))))
+
+#define PLE(x, val, bits, ifnot) \
+ __builtin_choose_expr( \
+ (sizeof(*(x)) == bits/8), \
+ put_unaligned_le##bits((val), (x)), ifnot)
+
+extern void bad_put_le(void);
+#define LAST_PLE(x, val) \
+ __builtin_choose_expr(sizeof(*(x)) == 1, *(x) = (val), bad_put_le())
+
+#define PUT_LE(x, val) \
+ PLE(x, val, 64, PLE(x, val, 32, PLE(x, val, 16, LAST_PLE(x, val))))
+
+
+#define NSYMS ARRAY_SIZE(required_syms)
+
+#define BITSFUNC3(name, bits, suffix) name##bits##suffix
+#define BITSFUNC2(name, bits, suffix) BITSFUNC3(name, bits, suffix)
+#define BITSFUNC(name) BITSFUNC2(name, ELF_BITS, )
+
+#define INT_BITS BITSFUNC2(int, ELF_BITS, _t)
+
+#define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
+#define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
+#define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
+
+#define ELF_BITS 64
+#include "vdso2c.h"
+#undef ELF_BITS
+
+#define ELF_BITS 32
+#include "vdso2c.h"
+#undef ELF_BITS
+
+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 *)raw_addr;
+
+ if (hdr->e_ident[EI_CLASS] == ELFCLASS64) {
+ go64(raw_addr, raw_len, stripped_addr, stripped_len,
+ outfile, name);
+ } else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) {
+ 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, "open(%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)
+{
+ size_t raw_len, stripped_len;
+ void *raw_addr, *stripped_addr;
+ FILE *outfile;
+ char *name, *tmp;
+ int namelen;
+
+ if (argc != 4) {
+ printf("Usage: vdso2c RAW_INPUT STRIPPED_INPUT OUTPUT\n");
+ return 1;
+ }
+
+ /*
+ * Figure out the struct name. If we're writing to a .so file,
+ * generate raw output instead.
+ */
+ name = strdup(argv[3]);
+ namelen = strlen(name);
+ if (namelen >= 3 && !strcmp(name + namelen - 3, ".so")) {
+ name = NULL;
+ } else {
+ tmp = strrchr(name, '/');
+ if (tmp)
+ name = tmp + 1;
+ tmp = strchr(name, '.');
+ if (tmp)
+ *tmp = '\0';
+ for (tmp = name; *tmp; tmp++)
+ if (*tmp == '-')
+ *tmp = '_';
+ }
+
+ map_input(argv[1], &raw_addr, &raw_len, PROT_READ);
+ map_input(argv[2], &stripped_addr, &stripped_len, PROT_READ);
+
+ outfilename = argv[3];
+ outfile = fopen(outfilename, "w");
+ if (!outfile)
+ err(1, "fopen(%s)", outfilename);
+
+ go(raw_addr, raw_len, stripped_addr, stripped_len, outfile, name);
+
+ munmap(raw_addr, raw_len);
+ munmap(stripped_addr, stripped_len);
+ fclose(outfile);
+
+ return 0;
+}
diff --git a/arch/x86/tools/vdso2c.h b/arch/x86/tools/vdso2c.h
new file mode 100644
index 0000000..78ed1c1
--- /dev/null
+++ b/arch/x86/tools/vdso2c.h
@@ -0,0 +1,208 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * This file is included twice from vdso2c.c. It generates code for 32-bit
+ * and 64-bit vDSOs. We need both for 64-bit builds, since 32-bit vDSOs
+ * are built for 32-bit userspace.
+ */
+
+static void BITSFUNC(copy)(FILE *outfile, const unsigned char *data, size_t len)
+{
+ size_t i;
+
+ for (i = 0; i < len; i++) {
+ if (i % 10 == 0)
+ fprintf(outfile, "\n\t");
+ fprintf(outfile, "0x%02X, ", (int)(data)[i]);
+ }
+}
+
+
+/*
+ * Extract a section from the input data into a standalone blob. Used to
+ * capture kernel-only data that needs to persist indefinitely, e.g. the
+ * exception fixup tables, but only in the kernel, i.e. the section can
+ * be stripped from the final vDSO image.
+ */
+static void BITSFUNC(extract)(const unsigned char *data, size_t data_len,
+ FILE *outfile, ELF(Shdr) *sec, const char *name)
+{
+ unsigned long offset;
+ size_t len;
+
+ offset = (unsigned long)GET_LE(&sec->sh_offset);
+ len = (size_t)GET_LE(&sec->sh_size);
+
+ if (offset + len > data_len)
+ fail("section to extract overruns input data");
+
+ fprintf(outfile, "static const unsigned char %s[%zu] = {", name, len);
+ BITSFUNC(copy)(outfile, data + offset, len);
+ fprintf(outfile, "\n};\n\n");
+}
+
+static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
+ void *stripped_addr, size_t stripped_len,
+ FILE *outfile, const char *image_name)
+{
+ int found_load = 0;
+ unsigned long load_size = -1; /* Work around bogus warning */
+ unsigned long mapping_size;
+ ELF(Ehdr) *hdr = (ELF(Ehdr) *)raw_addr;
+ unsigned long i, syms_nr;
+ ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr,
+ *alt_sec = NULL, *extable_sec = NULL;
+ ELF(Dyn) *dyn = 0, *dyn_end = 0;
+ const char *secstrings;
+ INT_BITS syms[NSYMS] = {};
+
+ ELF(Phdr) *pt = (ELF(Phdr) *)(raw_addr + GET_LE(&hdr->e_phoff));
+
+ if (GET_LE(&hdr->e_type) != ET_DYN)
+ fail("input is not a shared object\n");
+
+ /* Walk the segment table. */
+ for (i = 0; i < GET_LE(&hdr->e_phnum); i++) {
+ if (GET_LE(&pt[i].p_type) == PT_LOAD) {
+ if (found_load)
+ fail("multiple PT_LOAD segs\n");
+
+ if (GET_LE(&pt[i].p_offset) != 0 ||
+ GET_LE(&pt[i].p_vaddr) != 0)
+ fail("PT_LOAD in wrong place\n");
+
+ if (GET_LE(&pt[i].p_memsz) != GET_LE(&pt[i].p_filesz))
+ fail("cannot handle memsz != filesz\n");
+
+ load_size = GET_LE(&pt[i].p_memsz);
+ found_load = 1;
+ } else if (GET_LE(&pt[i].p_type) == PT_DYNAMIC) {
+ 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");
+
+ if (stripped_len < load_size)
+ fail("stripped input is too short\n");
+
+ if (!dyn)
+ fail("input has no PT_DYNAMIC section -- your toolchain is buggy\n");
+
+ /* Walk the dynamic table */
+ for (i = 0; dyn + i < dyn_end &&
+ GET_LE(&dyn[i].d_tag) != DT_NULL; i++) {
+ typeof(dyn[i].d_tag) tag = GET_LE(&dyn[i].d_tag);
+ if (tag == DT_REL || tag == DT_RELSZ || tag == DT_RELA ||
+ tag == DT_RELENT || tag == DT_TEXTREL)
+ fail("vdso image contains dynamic relocations\n");
+ }
+
+ /* Walk the section table */
+ secstrings_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
+ GET_LE(&hdr->e_shentsize)*GET_LE(&hdr->e_shstrndx);
+ secstrings = raw_addr + GET_LE(&secstrings_hdr->sh_offset);
+ for (i = 0; i < GET_LE(&hdr->e_shnum); i++) {
+ 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;
+
+ if (!strcmp(secstrings + GET_LE(&sh->sh_name),
+ ".altinstructions"))
+ alt_sec = sh;
+ if (!strcmp(secstrings + GET_LE(&sh->sh_name), "__ex_table"))
+ extable_sec = sh;
+ }
+
+ if (!symtab_hdr)
+ fail("no symbol table\n");
+
+ strtab_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
+ GET_LE(&hdr->e_shentsize) * GET_LE(&symtab_hdr->sh_link);
+
+ syms_nr = GET_LE(&symtab_hdr->sh_size) / GET_LE(&symtab_hdr->sh_entsize);
+ /* Walk the symbol table */
+ for (i = 0; i < syms_nr; i++) {
+ unsigned int k;
+ ELF(Sym) *sym = raw_addr + GET_LE(&symtab_hdr->sh_offset) +
+ GET_LE(&symtab_hdr->sh_entsize) * i;
+ const char *sym_name = raw_addr +
+ GET_LE(&strtab_hdr->sh_offset) +
+ GET_LE(&sym->st_name);
+
+ for (k = 0; k < NSYMS; k++) {
+ if (!strcmp(sym_name, required_syms[k].name)) {
+ if (syms[k]) {
+ 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 (!image_name) {
+ 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 <linux/init.h>\n");
+ fprintf(outfile, "#include <asm/page_types.h>\n");
+ fprintf(outfile, "#include <asm/vdso.h>\n");
+ fprintf(outfile, "\n");
+ fprintf(outfile,
+ "static unsigned char raw_data[%lu] __ro_after_init __aligned(PAGE_SIZE) = {",
+ mapping_size);
+ for (i = 0; i < stripped_len; i++) {
+ if (i % 10 == 0)
+ fprintf(outfile, "\n\t");
+ fprintf(outfile, "0x%02X, ",
+ (int)((unsigned char *)stripped_addr)[i]);
+ }
+ fprintf(outfile, "\n};\n\n");
+ if (extable_sec)
+ BITSFUNC(extract)(raw_addr, raw_len, outfile,
+ extable_sec, "extable");
+
+ fprintf(outfile, "const struct vdso_image %s = {\n", image_name);
+ fprintf(outfile, "\t.data = raw_data,\n");
+ fprintf(outfile, "\t.size = %lu,\n", mapping_size);
+ if (alt_sec) {
+ fprintf(outfile, "\t.alt = %lu,\n",
+ (unsigned long)GET_LE(&alt_sec->sh_offset));
+ fprintf(outfile, "\t.alt_len = %lu,\n",
+ (unsigned long)GET_LE(&alt_sec->sh_size));
+ }
+ if (extable_sec) {
+ fprintf(outfile, "\t.extable_base = %lu,\n",
+ (unsigned long)GET_LE(&extable_sec->sh_offset));
+ fprintf(outfile, "\t.extable_len = %lu,\n",
+ (unsigned long)GET_LE(&extable_sec->sh_size));
+ fprintf(outfile, "\t.extable = extable,\n");
+ }
+
+ for (i = 0; i < NSYMS; i++) {
+ if (required_syms[i].export && syms[i])
+ fprintf(outfile, "\t.sym_%s = %" PRIi64 ",\n",
+ required_syms[i].name, (int64_t)syms[i]);
+ }
+ fprintf(outfile, "};\n\n");
+ fprintf(outfile, "static __init int init_%s(void) {\n", image_name);
+ fprintf(outfile, "\treturn init_vdso_image(&%s);\n", image_name);
+ fprintf(outfile, "};\n");
+ fprintf(outfile, "subsys_initcall(init_%s);\n", image_name);
+
+}
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