From 2fa536d1079772983b935ac86395a41adc391754 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Thu, 17 Jun 2021 14:30:09 -0700 Subject: [PATCH] linux-user: Add gen-vdso tool MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Richard Henderson --- linux-user/gen-vdso-elfn.c.inc | 307 +++++++++++++++++++++++++++++++++ linux-user/gen-vdso.c | 223 ++++++++++++++++++++++++ linux-user/meson.build | 6 +- 3 files changed, 535 insertions(+), 1 deletion(-) create mode 100644 linux-user/gen-vdso-elfn.c.inc create mode 100644 linux-user/gen-vdso.c diff --git a/linux-user/gen-vdso-elfn.c.inc b/linux-user/gen-vdso-elfn.c.inc new file mode 100644 index 0000000000..7034c36d5e --- /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 0000000000..31e333be80 --- /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 +#include +#include +#include +#include +#include +#include +#include +#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 7171dc60be..e4cb70ed2d 100644 --- a/linux-user/meson.build +++ b/linux-user/meson.build @@ -28,9 +28,13 @@ linux_user_ss.add(when: 'TARGET_HAS_BFLT', if_true: files('flatload.c')) 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')