linux-user: Add gen-vdso tool
This tool will be used for post-processing the linked vdso image,
turning it into something that is easy to include into elfload.c.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/linux-user/gen-vdso-elfn.c.inc b/linux-user/gen-vdso-elfn.c.inc
new file mode 100644
index 0000000..7034c36
--- /dev/null
+++ b/linux-user/gen-vdso-elfn.c.inc
@@ -0,0 +1,307 @@
+/*
+ * Post-process a vdso elf image for inclusion into qemu.
+ * Elf size specialization.
+ *
+ * Copyright 2023 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+static void elfN(bswap_ehdr)(ElfN(Ehdr) *ehdr)
+{
+ bswaps(&ehdr->e_type); /* Object file type */
+ bswaps(&ehdr->e_machine); /* Architecture */
+ bswaps(&ehdr->e_version); /* Object file version */
+ bswaps(&ehdr->e_entry); /* Entry point virtual address */
+ bswaps(&ehdr->e_phoff); /* Program header table file offset */
+ bswaps(&ehdr->e_shoff); /* Section header table file offset */
+ bswaps(&ehdr->e_flags); /* Processor-specific flags */
+ bswaps(&ehdr->e_ehsize); /* ELF header size in bytes */
+ bswaps(&ehdr->e_phentsize); /* Program header table entry size */
+ bswaps(&ehdr->e_phnum); /* Program header table entry count */
+ bswaps(&ehdr->e_shentsize); /* Section header table entry size */
+ bswaps(&ehdr->e_shnum); /* Section header table entry count */
+ bswaps(&ehdr->e_shstrndx); /* Section header string table index */
+}
+
+static void elfN(bswap_phdr)(ElfN(Phdr) *phdr)
+{
+ bswaps(&phdr->p_type); /* Segment type */
+ bswaps(&phdr->p_flags); /* Segment flags */
+ bswaps(&phdr->p_offset); /* Segment file offset */
+ bswaps(&phdr->p_vaddr); /* Segment virtual address */
+ bswaps(&phdr->p_paddr); /* Segment physical address */
+ bswaps(&phdr->p_filesz); /* Segment size in file */
+ bswaps(&phdr->p_memsz); /* Segment size in memory */
+ bswaps(&phdr->p_align); /* Segment alignment */
+}
+
+static void elfN(bswap_shdr)(ElfN(Shdr) *shdr)
+{
+ bswaps(&shdr->sh_name);
+ bswaps(&shdr->sh_type);
+ bswaps(&shdr->sh_flags);
+ bswaps(&shdr->sh_addr);
+ bswaps(&shdr->sh_offset);
+ bswaps(&shdr->sh_size);
+ bswaps(&shdr->sh_link);
+ bswaps(&shdr->sh_info);
+ bswaps(&shdr->sh_addralign);
+ bswaps(&shdr->sh_entsize);
+}
+
+static void elfN(bswap_sym)(ElfN(Sym) *sym)
+{
+ bswaps(&sym->st_name);
+ bswaps(&sym->st_value);
+ bswaps(&sym->st_size);
+ bswaps(&sym->st_shndx);
+}
+
+static void elfN(bswap_dyn)(ElfN(Dyn) *dyn)
+{
+ bswaps(&dyn->d_tag); /* Dynamic type tag */
+ bswaps(&dyn->d_un.d_ptr); /* Dynamic ptr or val, in union */
+}
+
+static void elfN(search_symtab)(ElfN(Shdr) *shdr, unsigned sym_idx,
+ void *buf, bool need_bswap)
+{
+ unsigned str_idx = shdr[sym_idx].sh_link;
+ ElfN(Sym) *sym = buf + shdr[sym_idx].sh_offset;
+ unsigned sym_n = shdr[sym_idx].sh_size / sizeof(*sym);
+ const char *str = buf + shdr[str_idx].sh_offset;
+
+ for (unsigned i = 0; i < sym_n; ++i) {
+ const char *name;
+
+ if (need_bswap) {
+ elfN(bswap_sym)(sym + i);
+ }
+ name = str + sym[i].st_name;
+
+ if (sigreturn_sym && strcmp(sigreturn_sym, name) == 0) {
+ sigreturn_addr = sym[i].st_value;
+ }
+ if (rt_sigreturn_sym && strcmp(rt_sigreturn_sym, name) == 0) {
+ rt_sigreturn_addr = sym[i].st_value;
+ }
+ }
+}
+
+static void elfN(process)(FILE *outf, void *buf, bool need_bswap)
+{
+ ElfN(Ehdr) *ehdr = buf;
+ ElfN(Phdr) *phdr;
+ ElfN(Shdr) *shdr;
+ unsigned phnum, shnum;
+ unsigned dynamic_ofs = 0;
+ unsigned dynamic_addr = 0;
+ unsigned symtab_idx = 0;
+ unsigned dynsym_idx = 0;
+ unsigned first_segsz = 0;
+ int errors = 0;
+
+ if (need_bswap) {
+ elfN(bswap_ehdr)(ehdr);
+ }
+
+ phnum = ehdr->e_phnum;
+ phdr = buf + ehdr->e_phoff;
+ if (need_bswap) {
+ for (unsigned i = 0; i < phnum; ++i) {
+ elfN(bswap_phdr)(phdr + i);
+ }
+ }
+
+ shnum = ehdr->e_shnum;
+ shdr = buf + ehdr->e_shoff;
+ if (need_bswap) {
+ for (unsigned i = 0; i < shnum; ++i) {
+ elfN(bswap_shdr)(shdr + i);
+ }
+ }
+ for (unsigned i = 0; i < shnum; ++i) {
+ switch (shdr[i].sh_type) {
+ case SHT_SYMTAB:
+ symtab_idx = i;
+ break;
+ case SHT_DYNSYM:
+ dynsym_idx = i;
+ break;
+ }
+ }
+
+ /*
+ * Validate the VDSO is created as we expect: that PT_PHDR,
+ * PT_DYNAMIC, and PT_NOTE located in a writable data segment.
+ * PHDR and DYNAMIC require relocation, and NOTE will get the
+ * linux version number.
+ */
+ for (unsigned i = 0; i < phnum; ++i) {
+ if (phdr[i].p_type != PT_LOAD) {
+ continue;
+ }
+ if (first_segsz != 0) {
+ fprintf(stderr, "Multiple LOAD segments\n");
+ errors++;
+ }
+ if (phdr[i].p_offset != 0) {
+ fprintf(stderr, "LOAD segment does not cover EHDR\n");
+ errors++;
+ }
+ if (phdr[i].p_vaddr != 0) {
+ fprintf(stderr, "LOAD segment not loaded at address 0\n");
+ errors++;
+ }
+ first_segsz = phdr[i].p_filesz;
+ if (first_segsz < ehdr->e_phoff + phnum * sizeof(*phdr)) {
+ fprintf(stderr, "LOAD segment does not cover PHDRs\n");
+ errors++;
+ }
+ if ((phdr[i].p_flags & (PF_R | PF_W)) != (PF_R | PF_W)) {
+ fprintf(stderr, "LOAD segment is not read-write\n");
+ errors++;
+ }
+ }
+ for (unsigned i = 0; i < phnum; ++i) {
+ const char *which;
+
+ switch (phdr[i].p_type) {
+ case PT_PHDR:
+ which = "PT_PHDR";
+ break;
+ case PT_NOTE:
+ which = "PT_NOTE";
+ break;
+ case PT_DYNAMIC:
+ dynamic_ofs = phdr[i].p_offset;
+ dynamic_addr = phdr[i].p_vaddr;
+ which = "PT_DYNAMIC";
+ break;
+ default:
+ continue;
+ }
+ if (first_segsz < phdr[i].p_vaddr + phdr[i].p_filesz) {
+ fprintf(stderr, "LOAD segment does not cover %s\n", which);
+ errors++;
+ }
+ }
+ if (errors) {
+ exit(EXIT_FAILURE);
+ }
+
+ /* Relocate the program headers. */
+ for (unsigned i = 0; i < phnum; ++i) {
+ output_reloc(outf, buf, &phdr[i].p_vaddr);
+ output_reloc(outf, buf, &phdr[i].p_paddr);
+ }
+
+ /* Relocate the DYNAMIC entries. */
+ if (dynamic_addr) {
+ ElfN(Dyn) *dyn = buf + dynamic_ofs;
+ __typeof(dyn->d_tag) tag;
+
+ do {
+
+ if (need_bswap) {
+ elfN(bswap_dyn)(dyn);
+ }
+ tag = dyn->d_tag;
+
+ switch (tag) {
+ case DT_HASH:
+ case DT_SYMTAB:
+ case DT_STRTAB:
+ case DT_VERDEF:
+ case DT_VERSYM:
+ case DT_PLTGOT:
+ case DT_ADDRRNGLO ... DT_ADDRRNGHI:
+ /* These entries store an address in the entry. */
+ output_reloc(outf, buf, &dyn->d_un.d_val);
+ break;
+
+ case DT_NULL:
+ case DT_STRSZ:
+ case DT_SONAME:
+ case DT_DEBUG:
+ case DT_FLAGS:
+ case DT_FLAGS_1:
+ case DT_SYMBOLIC:
+ case DT_BIND_NOW:
+ case DT_VERDEFNUM:
+ case DT_VALRNGLO ... DT_VALRNGHI:
+ /* These entries store an integer in the entry. */
+ break;
+
+ case DT_SYMENT:
+ if (dyn->d_un.d_val != sizeof(ElfN(Sym))) {
+ fprintf(stderr, "VDSO has incorrect dynamic symbol size\n");
+ errors++;
+ }
+ break;
+
+ case DT_REL:
+ case DT_RELSZ:
+ case DT_RELA:
+ case DT_RELASZ:
+ /*
+ * These entries indicate that the VDSO was built incorrectly.
+ * It should not have any real relocations.
+ * ??? The RISC-V toolchain will emit these even when there
+ * are no relocations. Validate zeros.
+ */
+ if (dyn->d_un.d_val != 0) {
+ fprintf(stderr, "VDSO has dynamic relocations\n");
+ errors++;
+ }
+ break;
+ case DT_RELENT:
+ case DT_RELAENT:
+ case DT_TEXTREL:
+ /* These entries store an integer in the entry. */
+ /* Should not be required; see above. */
+ break;
+
+ case DT_NEEDED:
+ case DT_VERNEED:
+ case DT_PLTREL:
+ case DT_JMPREL:
+ case DT_RPATH:
+ case DT_RUNPATH:
+ fprintf(stderr, "VDSO has external dependencies\n");
+ errors++;
+ break;
+
+ default:
+ /* This is probably something target specific. */
+ fprintf(stderr, "VDSO has unknown DYNAMIC entry (%lx)\n",
+ (unsigned long)tag);
+ errors++;
+ break;
+ }
+ dyn++;
+ } while (tag != DT_NULL);
+ if (errors) {
+ exit(EXIT_FAILURE);
+ }
+ }
+
+ /* Relocate the dynamic symbol table. */
+ if (dynsym_idx) {
+ ElfN(Sym) *sym = buf + shdr[dynsym_idx].sh_offset;
+ unsigned sym_n = shdr[dynsym_idx].sh_size / sizeof(*sym);
+
+ for (unsigned i = 0; i < sym_n; ++i) {
+ output_reloc(outf, buf, &sym[i].st_value);
+ }
+ }
+
+ /* Search both dynsym and symtab for the signal return symbols. */
+ if (dynsym_idx) {
+ elfN(search_symtab)(shdr, dynsym_idx, buf, need_bswap);
+ }
+ if (symtab_idx) {
+ elfN(search_symtab)(shdr, symtab_idx, buf, need_bswap);
+ }
+}
diff --git a/linux-user/gen-vdso.c b/linux-user/gen-vdso.c
new file mode 100644
index 0000000..31e333b
--- /dev/null
+++ b/linux-user/gen-vdso.c
@@ -0,0 +1,223 @@
+/*
+ * Post-process a vdso elf image for inclusion into qemu.
+ *
+ * Copyright 2023 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <endian.h>
+#include <unistd.h>
+#include "elf.h"
+
+
+#define bswap_(p) _Generic(*(p), \
+ uint16_t: __builtin_bswap16, \
+ uint32_t: __builtin_bswap32, \
+ uint64_t: __builtin_bswap64, \
+ int16_t: __builtin_bswap16, \
+ int32_t: __builtin_bswap32, \
+ int64_t: __builtin_bswap64)
+#define bswaps(p) (*(p) = bswap_(p)(*(p)))
+
+static void output_reloc(FILE *outf, void *buf, void *loc)
+{
+ fprintf(outf, " 0x%08tx,\n", loc - buf);
+}
+
+static const char *sigreturn_sym;
+static const char *rt_sigreturn_sym;
+
+static unsigned sigreturn_addr;
+static unsigned rt_sigreturn_addr;
+
+#define N 32
+#define elfN(x) elf32_##x
+#define ElfN(x) Elf32_##x
+#include "gen-vdso-elfn.c.inc"
+#undef N
+#undef elfN
+#undef ElfN
+
+#define N 64
+#define elfN(x) elf64_##x
+#define ElfN(x) Elf64_##x
+#include "gen-vdso-elfn.c.inc"
+#undef N
+#undef elfN
+#undef ElfN
+
+
+int main(int argc, char **argv)
+{
+ FILE *inf, *outf;
+ long total_len;
+ const char *prefix = "vdso";
+ const char *inf_name;
+ const char *outf_name = NULL;
+ unsigned char *buf;
+ bool need_bswap;
+
+ while (1) {
+ int opt = getopt(argc, argv, "o:p:r:s:");
+ if (opt < 0) {
+ break;
+ }
+ switch (opt) {
+ case 'o':
+ outf_name = optarg;
+ break;
+ case 'p':
+ prefix = optarg;
+ break;
+ case 'r':
+ rt_sigreturn_sym = optarg;
+ break;
+ case 's':
+ sigreturn_sym = optarg;
+ break;
+ default:
+ usage:
+ fprintf(stderr, "usage: [-p prefix] [-r rt-sigreturn-name] "
+ "[-s sigreturn-name] -o output-file input-file\n");
+ return EXIT_FAILURE;
+ }
+ }
+
+ if (optind >= argc || outf_name == NULL) {
+ goto usage;
+ }
+ inf_name = argv[optind];
+
+ /*
+ * Open the input and output files.
+ */
+ inf = fopen(inf_name, "rb");
+ if (inf == NULL) {
+ goto perror_inf;
+ }
+ outf = fopen(outf_name, "w");
+ if (outf == NULL) {
+ goto perror_outf;
+ }
+
+ /*
+ * Read the input file into a buffer.
+ * We expect the vdso to be small, on the order of one page,
+ * therefore we do not expect a partial read.
+ */
+ fseek(inf, 0, SEEK_END);
+ total_len = ftell(inf);
+ fseek(inf, 0, SEEK_SET);
+
+ buf = malloc(total_len);
+ if (buf == NULL) {
+ goto perror_inf;
+ }
+
+ errno = 0;
+ if (fread(buf, 1, total_len, inf) != total_len) {
+ if (errno) {
+ goto perror_inf;
+ }
+ fprintf(stderr, "%s: incomplete read\n", inf_name);
+ return EXIT_FAILURE;
+ }
+ fclose(inf);
+
+ /*
+ * Write out the vdso image now, before we make local changes.
+ */
+
+ fprintf(outf,
+ "/* Automatically generated from linux-user/gen-vdso.c. */\n"
+ "\n"
+ "static const uint8_t %s_image[] = {",
+ prefix);
+ for (long i = 0; i < total_len; ++i) {
+ if (i % 12 == 0) {
+ fputs("\n ", outf);
+ }
+ fprintf(outf, " 0x%02x,", buf[i]);
+ }
+ fprintf(outf, "\n};\n\n");
+
+ /*
+ * Identify which elf flavor we're processing.
+ * The first 16 bytes of the file are e_ident.
+ */
+
+ if (buf[EI_MAG0] != ELFMAG0 || buf[EI_MAG1] != ELFMAG1 ||
+ buf[EI_MAG2] != ELFMAG2 || buf[EI_MAG3] != ELFMAG3) {
+ fprintf(stderr, "%s: not an elf file\n", inf_name);
+ return EXIT_FAILURE;
+ }
+ switch (buf[EI_DATA]) {
+ case ELFDATA2LSB:
+ need_bswap = BYTE_ORDER != LITTLE_ENDIAN;
+ break;
+ case ELFDATA2MSB:
+ need_bswap = BYTE_ORDER != BIG_ENDIAN;
+ break;
+ default:
+ fprintf(stderr, "%s: invalid elf EI_DATA (%u)\n",
+ inf_name, buf[EI_DATA]);
+ return EXIT_FAILURE;
+ }
+
+ /*
+ * We need to relocate the VDSO image. The one built into the kernel
+ * is built for a fixed address. The one we built for QEMU is not,
+ * since that requires close control of the guest address space.
+ *
+ * Output relocation addresses as we go.
+ */
+
+ fprintf(outf, "static const unsigned %s_relocs[] = {\n", prefix);
+
+ switch (buf[EI_CLASS]) {
+ case ELFCLASS32:
+ elf32_process(outf, buf, need_bswap);
+ break;
+ case ELFCLASS64:
+ elf64_process(outf, buf, need_bswap);
+ break;
+ default:
+ fprintf(stderr, "%s: invalid elf EI_CLASS (%u)\n",
+ inf_name, buf[EI_CLASS]);
+ return EXIT_FAILURE;
+ }
+
+ fprintf(outf, "};\n\n"); /* end vdso_relocs. */
+
+ fprintf(outf, "static const VdsoImageInfo %s_image_info = {\n", prefix);
+ fprintf(outf, " .image = %s_image,\n", prefix);
+ fprintf(outf, " .relocs = %s_relocs,\n", prefix);
+ fprintf(outf, " .image_size = sizeof(%s_image),\n", prefix);
+ fprintf(outf, " .reloc_count = ARRAY_SIZE(%s_relocs),\n", prefix);
+ fprintf(outf, " .sigreturn_ofs = 0x%x,\n", sigreturn_addr);
+ fprintf(outf, " .rt_sigreturn_ofs = 0x%x,\n", rt_sigreturn_addr);
+ fprintf(outf, "};\n");
+
+ /*
+ * Everything should have gone well.
+ */
+ if (fclose(outf)) {
+ goto perror_outf;
+ }
+ return EXIT_SUCCESS;
+
+ perror_inf:
+ perror(inf_name);
+ return EXIT_FAILURE;
+
+ perror_outf:
+ perror(outf_name);
+ return EXIT_FAILURE;
+}
diff --git a/linux-user/meson.build b/linux-user/meson.build
index 7171dc6..e4cb70e 100644
--- a/linux-user/meson.build
+++ b/linux-user/meson.build
@@ -28,9 +28,13 @@
linux_user_ss.add(when: 'TARGET_I386', if_true: files('vm86.c'))
linux_user_ss.add(when: 'CONFIG_ARM_COMPATIBLE_SEMIHOSTING', if_true: files('semihost.c'))
-
syscall_nr_generators = {}
+gen_vdso_exe = executable('gen-vdso', 'gen-vdso.c',
+ native: true, build_by_default: false)
+gen_vdso = generator(gen_vdso_exe, output: '@BASENAME@.c.inc',
+ arguments: ['-o', '@OUTPUT@', '@EXTRA_ARGS@', '@INPUT@'])
+
subdir('alpha')
subdir('arm')
subdir('hppa')
