From 682674b84189d0cd1426eb9b9d4b6b0d4c24be52 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Tue, 27 Jul 2010 10:25:33 -0700 Subject: [PATCH] linux-user: Load symbols from the interpreter. First, adjust load_symbols to accept a load_bias parameter. At the same time, read the entire section header table in one go, use pread instead f lseek+read for the symbol and string tables, and properly free allocated structures on error exit paths. Second, adjust load_elf_interp to compute load_bias. This requires finding out the built-in load addresses. Which allows us to honor a pre-linked interpreter image when possible, and eliminate the hard-coded INTERP_MAP_SIZE value. Signed-off-by: Richard Henderson Signed-off-by: Edgar E. Iglesias --- linux-user/elfload.c | 189 +++++++++++++++++++++++-------------------- 1 file changed, 101 insertions(+), 88 deletions(-) diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 3cbb1f4bb8..6b57a91a3e 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -829,9 +829,6 @@ struct exec #define ZMAGIC 0413 #define QMAGIC 0314 -/* max code+data+bss space allocated to elf interpreter */ -#define INTERP_MAP_SIZE (32 * 1024 * 1024) - /* max code+data+bss+brk space allocated to ET_DYN executables */ #define ET_DYN_MAP_SIZE (128 * 1024 * 1024) @@ -920,6 +917,7 @@ static inline void bswap_sym(struct elf_sym *sym) { } #ifdef USE_ELF_CORE_DUMP static int elf_core_dump(int, const CPUState *); #endif /* USE_ELF_CORE_DUMP */ +static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias); /* * 'copy_elf_strings()' copies argument/envelope strings from user @@ -1146,15 +1144,11 @@ static abi_ulong load_elf_interp(struct elfhdr * interp_elf_ex, char bprm_buf[BPRM_BUF_SIZE]) { struct elf_phdr *elf_phdata = NULL; - struct elf_phdr *eppnt; - abi_ulong load_addr = 0; - int load_addr_set = 0; + abi_ulong load_addr, load_bias, loaddr, hiaddr; int retval; abi_ulong error; int i; - error = 0; - bswap_ehdr(interp_elf_ex); /* First of all, some simple consistency checks */ if ((interp_elf_ex->e_type != ET_EXEC && @@ -1163,7 +1157,6 @@ static abi_ulong load_elf_interp(struct elfhdr * interp_elf_ex, return ~((abi_ulong)0UL); } - /* Now read in all of the header information */ if (sizeof(struct elf_phdr) * interp_elf_ex->e_phnum > TARGET_PAGE_SIZE) @@ -1196,41 +1189,56 @@ static abi_ulong load_elf_interp(struct elfhdr * interp_elf_ex, } bswap_phdr(elf_phdata, interp_elf_ex->e_phnum); + /* Find the maximum size of the image and allocate an appropriate + amount of memory to handle that. */ + loaddr = -1, hiaddr = 0; + for (i = 0; i < interp_elf_ex->e_phnum; ++i) { + if (elf_phdata[i].p_type == PT_LOAD) { + abi_ulong a = elf_phdata[i].p_vaddr; + if (a < loaddr) { + loaddr = a; + } + a += elf_phdata[i].p_memsz; + if (a > hiaddr) { + hiaddr = a; + } + } + } + + load_addr = loaddr; if (interp_elf_ex->e_type == ET_DYN) { - /* in order to avoid hardcoding the interpreter load - address in qemu, we allocate a big enough memory zone */ - error = target_mmap(0, INTERP_MAP_SIZE, - PROT_NONE, MAP_PRIVATE | MAP_ANON, - -1, 0); - if (error == -1) { + /* The image indicates that it can be loaded anywhere. Find a + location that can hold the memory space required. If the + image is pre-linked, LOADDR will be non-zero. Since we do + not supply MAP_FIXED here we'll use that address if and + only if it remains available. */ + load_addr = target_mmap(loaddr, hiaddr - loaddr, PROT_NONE, + MAP_PRIVATE | MAP_ANON | MAP_NORESERVE, + -1, 0); + if (load_addr == -1) { perror("mmap"); exit(-1); } - load_addr = error; - load_addr_set = 1; } + load_bias = load_addr - loaddr; - eppnt = elf_phdata; - for(i=0; ie_phnum; i++, eppnt++) + for (i = 0; i < interp_elf_ex->e_phnum; i++) { + struct elf_phdr *eppnt = elf_phdata + i; if (eppnt->p_type == PT_LOAD) { - int elf_type = MAP_PRIVATE | MAP_DENYWRITE; + abi_ulong vaddr, vaddr_po, vaddr_ps, vaddr_ef, vaddr_em; int elf_prot = 0; - abi_ulong vaddr = 0; if (eppnt->p_flags & PF_R) elf_prot = PROT_READ; if (eppnt->p_flags & PF_W) elf_prot |= PROT_WRITE; if (eppnt->p_flags & PF_X) elf_prot |= PROT_EXEC; - if (interp_elf_ex->e_type == ET_EXEC || load_addr_set) { - elf_type |= MAP_FIXED; - vaddr = eppnt->p_vaddr; - } - error = target_mmap(load_addr+TARGET_ELF_PAGESTART(vaddr), - eppnt->p_filesz + TARGET_ELF_PAGEOFFSET(eppnt->p_vaddr), - elf_prot, - elf_type, - interpreter_fd, - eppnt->p_offset - TARGET_ELF_PAGEOFFSET(eppnt->p_vaddr)); + vaddr = load_bias + eppnt->p_vaddr; + vaddr_po = TARGET_ELF_PAGEOFFSET(vaddr); + vaddr_ps = TARGET_ELF_PAGESTART(vaddr); + + error = target_mmap(vaddr_ps, eppnt->p_filesz + vaddr_po, + elf_prot, MAP_PRIVATE | MAP_FIXED, + interpreter_fd, eppnt->p_offset - vaddr_po); if (error == -1) { /* Real error */ close(interpreter_fd); @@ -1238,26 +1246,25 @@ static abi_ulong load_elf_interp(struct elfhdr * interp_elf_ex, return ~((abi_ulong)0UL); } - if (!load_addr_set && interp_elf_ex->e_type == ET_DYN) { - load_addr = error; - load_addr_set = 1; - } + vaddr_ef = vaddr + eppnt->p_filesz; + vaddr_em = vaddr + eppnt->p_memsz; /* If the load segment requests extra zeros (e.g. bss), map it. */ - if (eppnt->p_filesz < eppnt->p_memsz) { - abi_ulong base = load_addr + eppnt->p_vaddr; - zero_bss(base + eppnt->p_filesz, - base + eppnt->p_memsz, elf_prot); + if (vaddr_ef < vaddr_em) { + zero_bss(vaddr_ef, vaddr_em, elf_prot); } } + } - /* Now use mmap to map the library into memory. */ + if (qemu_log_enabled()) { + load_symbols(interp_elf_ex, interpreter_fd, load_bias); + } close(interpreter_fd); free(elf_phdata); *interp_load_addr = load_addr; - return ((abi_ulong) interp_elf_ex->e_entry) + load_addr; + return ((abi_ulong) interp_elf_ex->e_entry) + load_bias; } static int symfind(const void *s0, const void *s1) @@ -1306,82 +1313,87 @@ static int symcmp(const void *s0, const void *s1) } /* Best attempt to load symbols from this ELF object. */ -static void load_symbols(struct elfhdr *hdr, int fd) +static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias) { - unsigned int i, nsyms; - struct elf_shdr sechdr, symtab, strtab; + int i, shnum, nsyms, sym_idx = 0, str_idx = 0; + struct elf_shdr *shdr; char *strings; struct syminfo *s; struct elf_sym *syms; - lseek(fd, hdr->e_shoff, SEEK_SET); - for (i = 0; i < hdr->e_shnum; i++) { - if (read(fd, &sechdr, sizeof(sechdr)) != sizeof(sechdr)) - return; - bswap_shdr(&sechdr, 1); - if (sechdr.sh_type == SHT_SYMTAB) { - symtab = sechdr; - lseek(fd, hdr->e_shoff - + sizeof(sechdr) * sechdr.sh_link, SEEK_SET); - if (read(fd, &strtab, sizeof(strtab)) - != sizeof(strtab)) - return; - bswap_shdr(&strtab, 1); + shnum = hdr->e_shnum; + i = shnum * sizeof(struct elf_shdr); + shdr = (struct elf_shdr *)alloca(i); + if (pread(fd, shdr, i, hdr->e_shoff) != i) { + return; + } + + bswap_shdr(shdr, shnum); + for (i = 0; i < shnum; ++i) { + if (shdr[i].sh_type == SHT_SYMTAB) { + sym_idx = i; + str_idx = shdr[i].sh_link; goto found; } } - return; /* Shouldn't happen... */ + + /* There will be no symbol table if the file was stripped. */ + return; found: - /* Now know where the strtab and symtab are. Snarf them. */ + /* Now know where the strtab and symtab are. Snarf them. */ s = malloc(sizeof(*s)); - syms = malloc(symtab.sh_size); - if (!syms) + if (!s) { return; - s->disas_strtab = strings = malloc(strtab.sh_size); - if (!s->disas_strtab) + } + + i = shdr[str_idx].sh_size; + s->disas_strtab = strings = malloc(i); + if (!strings || pread(fd, strings, i, shdr[str_idx].sh_offset) != i) { + free(s); + free(strings); return; + } - lseek(fd, symtab.sh_offset, SEEK_SET); - if (read(fd, syms, symtab.sh_size) != symtab.sh_size) + i = shdr[sym_idx].sh_size; + syms = malloc(i); + if (!syms || pread(fd, syms, i, shdr[sym_idx].sh_offset) != i) { + free(s); + free(strings); + free(syms); return; + } - nsyms = symtab.sh_size / sizeof(struct elf_sym); - - i = 0; - while (i < nsyms) { + nsyms = i / sizeof(struct elf_sym); + for (i = 0; i < nsyms; ) { bswap_sym(syms + i); - // Throw away entries which we do not need. - if (syms[i].st_shndx == SHN_UNDEF || - syms[i].st_shndx >= SHN_LORESERVE || - ELF_ST_TYPE(syms[i].st_info) != STT_FUNC) { - nsyms--; - if (i < nsyms) { + /* Throw away entries which we do not need. */ + if (syms[i].st_shndx == SHN_UNDEF + || syms[i].st_shndx >= SHN_LORESERVE + || ELF_ST_TYPE(syms[i].st_info) != STT_FUNC) { + if (i < --nsyms) { syms[i] = syms[nsyms]; } - continue; - } + } else { #if defined(TARGET_ARM) || defined (TARGET_MIPS) - /* The bottom address bit marks a Thumb or MIPS16 symbol. */ - syms[i].st_value &= ~(target_ulong)1; + /* The bottom address bit marks a Thumb or MIPS16 symbol. */ + syms[i].st_value &= ~(target_ulong)1; #endif - i++; + syms[i].st_value += load_bias; + i++; + } } - syms = realloc(syms, nsyms * sizeof(*syms)); + syms = realloc(syms, nsyms * sizeof(*syms)); qsort(syms, nsyms, sizeof(*syms), symcmp); - lseek(fd, strtab.sh_offset, SEEK_SET); - if (read(fd, strings, strtab.sh_size) != strtab.sh_size) - return; s->disas_num_syms = nsyms; #if ELF_CLASS == ELFCLASS32 s->disas_symtab.elf32 = syms; - s->lookup_symbol = lookup_symbolxx; #else s->disas_symtab.elf64 = syms; - s->lookup_symbol = lookup_symbolxx; #endif + s->lookup_symbol = lookup_symbolxx; s->next = syminfos; syminfos = s; } @@ -1788,8 +1800,9 @@ int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs, free(elf_phdata); - if (qemu_log_enabled()) - load_symbols(&elf_ex, bprm->fd); + if (qemu_log_enabled()) { + load_symbols(&elf_ex, bprm->fd, load_bias); + } if (interpreter_type != INTERPRETER_AOUT) close(bprm->fd); info->personality = (ibcs2_interpreter ? PER_SVR4 : PER_LINUX);