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[174.21.143.238]) by smtp.gmail.com with ESMTPSA id i7sm285744pjj.33.2020.05.19.12.44.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2020 12:44:56 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH 2/2] linux-user: Load a VDSO for x86-64. Date: Tue, 19 May 2020 12:44:52 -0700 Message-Id: <20200519194452.9009-3-richard.henderson@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200519194452.9009-1-richard.henderson@linaro.org> References: <20200519194452.9009-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::441; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x441.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: laurent@vivier.eu, Richard Henderson Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" From: Richard Henderson Signed-off-by: Richard Henderson --- linux-user/elfload.c | 203 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 198 insertions(+), 5 deletions(-) -- 2.20.1 diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 01a9323a63..d70e27cb62 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -199,6 +199,8 @@ static void elf_core_copy_regs(target_elf_gregset_t *regs, const CPUX86State *en (*regs)[26] = env->segs[R_GS].selector & 0xffff; } +#define VDSO_BASENAME "vdso-linux-x64.so" + #else #define ELF_START_MMAP 0x80000000 @@ -1499,6 +1501,10 @@ static void elf_core_copy_regs(target_elf_gregset_t *regs, #define STACK_ALIGNMENT 16 #endif +#ifndef VDSO_BASENAME +#define VDSO_BASENAME NULL +#endif + #ifdef TARGET_ABI32 #undef ELF_CLASS #define ELF_CLASS ELFCLASS32 @@ -1859,7 +1865,8 @@ static abi_ulong loader_build_fdpic_loadmap(struct image_info *info, abi_ulong s static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc, struct elfhdr *exec, struct image_info *info, - struct image_info *interp_info) + struct image_info *interp_info, + struct image_info *vdso_info) { abi_ulong sp; abi_ulong u_argc, u_argv, u_envp, u_auxv; @@ -1931,8 +1938,12 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc, } size = (DLINFO_ITEMS + 1) * 2; - if (k_platform) + if (k_platform) { size += 2; + } + if (vdso_info) { + size += 4; + } #ifdef DLINFO_ARCH_ITEMS size += DLINFO_ARCH_ITEMS * 2; #endif @@ -2009,6 +2020,10 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc, if (u_platform) { NEW_AUX_ENT(AT_PLATFORM, u_platform); } + if (vdso_info) { + NEW_AUX_ENT(AT_SYSINFO, vdso_info->entry); + NEW_AUX_ENT(AT_SYSINFO_EHDR, vdso_info->load_addr); + } NEW_AUX_ENT (AT_NULL, 0); #undef NEW_AUX_ENT @@ -2614,6 +2629,177 @@ static void load_elf_interp(const char *filename, struct image_info *info, exit(-1); } +static void load_elf_vdso(const char *basename, struct image_info *info, + char bprm_buf[BPRM_BUF_SIZE]) +{ + const char *errmsg; + char *filename; + int fd, retval, i; + abi_ulong load_bias; + + /* + * ??? What we really need access to is qemu_find_file, but that is + * only built for system targets at the moment. + */ + filename = g_build_filename(CONFIG_QEMU_DATADIR, basename, NULL); + fd = open(filename, O_RDONLY); + if (fd < 0) { + goto exit_perror; + } + g_free(filename); + + retval = read(fd, bprm_buf, BPRM_BUF_SIZE); + if (retval < 0) { + goto exit_perror; + } + if (retval < BPRM_BUF_SIZE) { + memset(bprm_buf + retval, 0, BPRM_BUF_SIZE - retval); + } + + load_elf_image(basename, fd, info, NULL, bprm_buf); + load_bias = info->load_bias; + + /* + * We most likely need to relocate the VDSO image. The one built into + * the kernel is built for a fixed address. The one built for QEMU is + * not, since that requires close control of the guest address space. + */ + if (load_bias) { + struct elfhdr *ehdr = (struct elfhdr *)bprm_buf; + struct elf_phdr *phdr; + abi_ulong dynamic_addr = -1; + abi_ulong dynsym_addr = -1; + + /* + * ??? Assume QEMU's VDSO is built "properly", which arranges + * for the PHDRs, and all the sections manipulated below, to + * be included with a writable load segment. + * + * ??? One might think that we'd need to relocate ehdr.e_entry, + * but for some reason glibc does that one itself, though that + * is also available via the AT_SYSINFO entry. + */ + + /* Relocate the program headers. */ + phdr = (struct elf_phdr *)g2h(info->load_addr + ehdr->e_phoff); + bswap_phdr(phdr, ehdr->e_phnum); + for (i = 0; i < ehdr->e_phnum; ++i) { + phdr[i].p_vaddr += load_bias; + phdr[i].p_paddr += load_bias; + if (phdr[i].p_type == PT_DYNAMIC) { + dynamic_addr = phdr[i].p_vaddr; + } + } + bswap_phdr(phdr, ehdr->e_phnum); + + /* Relocate the DYNAMIC entries. */ + if (dynamic_addr != -1) { + abi_ulong tag, val, *dyn = (abi_ulong *)g2h(dynamic_addr); + do { + tag = tswapl(dyn[0]); + val = tswapl(dyn[1]); + switch (tag) { + case DT_SYMTAB: + dynsym_addr = load_bias + val; + dyn[1] = tswapl(dynsym_addr); + break; + case DT_SYMENT: + if (val != sizeof(struct elf_sym)) { + errmsg = "VDSO has an unexpected dynamic symbol size"; + goto exit_errmsg; + } + break; + + case DT_HASH: + case DT_STRTAB: + case DT_VERDEF: + case DT_VERSYM: + case DT_ADDRRNGLO ... DT_ADDRRNGHI: + /* These entries store an address in the entry. */ + dyn[1] = tswapl(load_bias + val); + break; + + case DT_NULL: + case DT_STRSZ: + case DT_SONAME: + case DT_DEBUG: + case DT_FLAGS: + case DT_FLAGS_1: + case DT_VERDEFNUM: + case DT_VALRNGLO ... DT_VALRNGHI: + /* These entries store an integer in the entry. */ + break; + + case DT_REL: + case DT_RELA: + /* + * These entries indicate that the VDSO was built + * incorrectly. It should not have real relocations. + */ + errmsg = "VDSO has relocations"; + goto exit_errmsg; + case DT_NEEDED: + case DT_VERNEED: + errmsg = "VDSO has external dependancies"; + goto exit_errmsg; + + default: + /* This is probably something target specific. */ + errmsg = "VDSO has unknown DYNAMIC entry"; + goto exit_errmsg; + } + dyn += 2; + } while (tag != DT_NULL); + } + + /* Relocate the dynamic symbol table. */ + if (dynsym_addr != -1) { + struct elf_shdr *shdr; + struct elf_sym *sym; + int dynsym_size = 0; + + /* + * Read the section headers to find out the size of the + * dynamic symbol table. + */ + shdr = (struct elf_shdr *)g2h(info->load_addr + ehdr->e_shoff); + for (i = 0; i < ehdr->e_shnum; ++i) { + abi_ulong addr = tswapl(shdr[i].sh_addr) + load_bias; + if (addr == dynsym_addr) { + dynsym_size = tswapl(shdr[i].sh_size); + break; + } + } + + sym = (struct elf_sym *)g2h(dynsym_addr); + for (i = 0; i < dynsym_size / sizeof(*sym); ++i) { + sym[i].st_value = tswapl(tswapl(sym[i].st_value) + load_bias); + } + } + } + + /* + * Mark the VDSO writable segment read-only. + * + * ??? This assumes that the VDSO implementation doesn't actually + * have any truely writable data. Perhaps we should instead use + * the PT_GNU_RELRO header to indicate that we really want this. + */ + retval = target_mprotect(info->start_data, info->brk - info->start_data, + PROT_READ); + if (retval < 0) { + goto exit_perror; + } + return; + + exit_perror: + errmsg = strerror(errno); + exit_errmsg: + fprintf(stderr, "%s: %s\n", filename, errmsg); + exit(-1); +} + + static int symfind(const void *s0, const void *s1) { target_ulong addr = *(target_ulong *)s0; @@ -2803,7 +2989,7 @@ uint32_t get_elf_eflags(int fd) int load_elf_binary(struct linux_binprm *bprm, struct image_info *info) { - struct image_info interp_info; + struct image_info interp_info, vdso_info; struct elfhdr elf_ex; char *elf_interpreter = NULL; char *scratch; @@ -2879,8 +3065,15 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info) #endif } - bprm->p = create_elf_tables(bprm->p, bprm->argc, bprm->envc, &elf_ex, - info, (elf_interpreter ? &interp_info : NULL)); + /* If we've been given a VDSO to load, do so. */ + if (VDSO_BASENAME) { + load_elf_vdso(VDSO_BASENAME, &vdso_info, bprm->buf); + } + + bprm->p = create_elf_tables(bprm->p, bprm->argc, bprm->envc, + &elf_ex, info, + (elf_interpreter ? &interp_info : NULL), + (VDSO_BASENAME ? &vdso_info : NULL)); info->start_stack = bprm->p; /* If we have an interpreter, set that as the program's entry point.