Re: [Qemu-devel] [PATCH 12/14] linux-user: Re-use load_elf_image for the main binary.

[malc]

On Mon, 5 Apr 2010, Richard Henderson wrote:

> This requires moving the PT_INTERP extraction and GUEST_BASE
> handling into load_elf_image.  Key this off a non-null pointer
> argument to receive the interpreter name.
> 
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  linux-user/elfload.c |  269 
> ++++++++++----------------------------------------
>  1 files changed, 53 insertions(+), 216 deletions(-)
> 
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index c58387a..100efdc 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+brk space allocated to ET_DYN executables */
> -#define ET_DYN_MAP_SIZE (128 * 1024 * 1024)
> -
>  /* Necessary parameters */
>  #define TARGET_ELF_EXEC_PAGESIZE TARGET_PAGE_SIZE
>  #define TARGET_ELF_PAGESTART(_v) ((_v) & ~(unsigned 
> long)(TARGET_ELF_EXEC_PAGESIZE-1))
> @@ -1168,7 +1165,7 @@ static abi_ulong create_elf_tables(abi_ulong p, int 
> argc, int envc,
>     On return: INFO values will be filled in, as necessary or available.  */
>  
>  static void load_elf_image(const char *image_name, int image_fd,
> -                           struct image_info *info,
> +                           struct image_info *info, char **pinterp_name,
>                             char bprm_buf[BPRM_BUF_SIZE])
>  {
>      struct elfhdr *ehdr = (struct elfhdr *)bprm_buf;
> @@ -1228,6 +1225,20 @@ static void load_elf_image(const char *image_name, int 
> image_fd,
>          if (load_addr == -1) {
>              goto exit_perror;
>          }
> +    } else if (pinterp_name != NULL) {
> +        /* This is the main executable.  Make sure that the low
> +           address does not conflict with MMAP_MIN_ADDR.  */
> +        /* ??? Ideally, we'd check against more than just the
> +           minimum mmap address, but also against the QEMU program
> +           image itself.  I.e. find a range that does not conflict
> +           with PAGE_RESERVED entries.  Except that we havn't read
> +           those in yet, since that code uses the guest_base that
> +           we set up here.  Blah.  */
> +#if defined(CONFIG_USE_GUEST_BASE)
> +        if (HOST_PAGE_ALIGN(loaddr) < mmap_min_addr) {
> +            guest_base = HOST_PAGE_ALIGN(mmap_min_addr);
> +        }
> +#endif
>      }
>      load_bias = load_addr - loaddr;
>  
> @@ -1289,6 +1300,30 @@ static void load_elf_image(const char *image_name, int 
> image_fd,
>                      info->brk = vaddr_em;
>                  }
>              }
> +        } else if (eppnt->p_type == PT_INTERP && pinterp_name) {
> +            char *interp_name;
> +
> +            if (*pinterp_name) {
> +                errmsg = "Multiple PT_INTERP entries";
> +                goto exit_errmsg;
> +            }
> +            interp_name = malloc(eppnt->p_filesz);

malloc can fail

> +
> +            if (eppnt->p_offset + eppnt->p_filesz <= BPRM_BUF_SIZE) {
> +                memcpy(interp_name, bprm_buf + eppnt->p_offset,
> +                       eppnt->p_filesz);
> +            } else {
> +             retval = pread(image_fd, interp_name, eppnt->p_filesz,

Indentation seems off.
> +                               eppnt->p_offset);
> +                if (retval != eppnt->p_filesz) {
> +                    goto exit_perror;
> +                }
> +            }
> +            if (interp_name[eppnt->p_filesz - 1] != 0) {
> +                errmsg = "Invalid PT_INTERP entry";
> +                goto exit_errmsg;
> +            }
> +            *pinterp_name = interp_name;
>          }
>      }
>  
> @@ -1335,7 +1370,7 @@ static void load_elf_interp(const char *filename, 
> struct image_info *info,
>          memset(bprm_buf + retval, 0, BPRM_BUF_SIZE - retval);
>      }
>  
> -    load_elf_image(filename, fd, info, bprm_buf);
> +    load_elf_image(filename, fd, info, NULL, bprm_buf);
>      return;
>  
>   exit_perror:
> @@ -1479,230 +1514,31 @@ int load_elf_binary(struct linux_binprm * bprm, 
> struct target_pt_regs * regs,
>  {
>      struct image_info interp_info;
>      struct elfhdr elf_ex;
> -    abi_ulong load_addr, load_bias;
> -    int load_addr_set = 0;
> -    int i;
> -    struct elf_phdr * elf_ppnt;
> -    struct elf_phdr *elf_phdata;
> -    abi_ulong k, elf_brk;
> -    int retval;
>      char *elf_interpreter = NULL;
> -    abi_ulong elf_entry;
> -    int status;
> -    abi_ulong start_code, end_code, start_data, end_data;
> -    abi_ulong elf_stack;
>  
> -    status = 0;
> -    load_addr = 0;
> -    load_bias = 0;
> -    elf_ex = *((struct elfhdr *) bprm->buf);          /* exec-header */
> +    info->start_mmap = (abi_ulong)ELF_START_MMAP;
> +    info->mmap = 0;
> +    info->rss = 0;
> +
> +    load_elf_image(bprm->filename, bprm->fd, info,
> +                   &elf_interpreter, bprm->buf);
>  
> -    /* First of all, some simple consistency checks */
> -    if (!elf_check_ident(&elf_ex)) {
> -        return -ENOEXEC;
> -    }
> -    bswap_ehdr(&elf_ex);
> -    if (!elf_check_ehdr(&elf_ex)) {
> -        return -ENOEXEC;
> -    }
> +    /* ??? We need a copy of the elf header for passing to create_elf_tables.
> +       If we do nothing, we'll have overwritten this when we re-use bprm->buf
> +       when we load the interpreter.  */
> +    elf_ex = *(struct elfhdr *)bprm->buf;
>  
>      bprm->p = copy_elf_strings(1, &bprm->filename, bprm->page, bprm->p);
>      bprm->p = copy_elf_strings(bprm->envc,bprm->envp,bprm->page,bprm->p);
>      bprm->p = copy_elf_strings(bprm->argc,bprm->argv,bprm->page,bprm->p);
>      if (!bprm->p) {
> -        retval = -E2BIG;
> -    }
> -
> -    /* Now read in all of the header information */
> -    elf_phdata = (struct elf_phdr *)
> -        malloc(elf_ex.e_phnum * sizeof(struct elf_phdr));
> -    if (elf_phdata == NULL) {
> -     return -ENOMEM;
> -    }
> -
> -    i = elf_ex.e_phnum * sizeof(struct elf_phdr);
> -    if (elf_ex.e_phoff + i <= BPRM_BUF_SIZE) {
> -        memcpy(elf_phdata, bprm->buf + elf_ex.e_phoff, i);
> -    } else {
> -     retval = pread(bprm->fd, (char *) elf_phdata, i, elf_ex.e_phoff);
> -        if (retval != i) {
> -            perror("load_elf_binary");
> -            exit(-1);
> -        }
> -    }
> -    bswap_phdr(elf_phdata, elf_ex.e_phnum);
> -
> -    elf_brk = 0;
> -    elf_stack = ~((abi_ulong)0UL);
> -    start_code = ~((abi_ulong)0UL);
> -    end_code = 0;
> -    start_data = 0;
> -    end_data = 0;
> -
> -    elf_ppnt = elf_phdata;
> -    for(i=0;i < elf_ex.e_phnum; i++) {
> -     if (elf_ppnt->p_type == PT_INTERP) {
> -            if (elf_ppnt->p_offset + elf_ppnt->p_filesz <= BPRM_BUF_SIZE) {
> -                elf_interpreter = bprm->buf + elf_ppnt->p_offset;
> -            } else {
> -                elf_interpreter = alloca(elf_ppnt->p_filesz);
> -             retval = pread(bprm->fd, elf_interpreter, elf_ppnt->p_filesz,
> -                               elf_ppnt->p_offset);
> -                if (retval != elf_ppnt->p_filesz) {
> -                    perror("load_elf_binary");
> -                    exit(-1);
> -                }
> -         }
> -     }
> -     elf_ppnt++;
> -    }
> -
> -    /* OK, This is the point of no return */
> -    info->end_data = 0;
> -    info->end_code = 0;
> -    info->start_mmap = (abi_ulong)ELF_START_MMAP;
> -    info->mmap = 0;
> -    elf_entry = (abi_ulong) elf_ex.e_entry;
> -
> -#if defined(CONFIG_USE_GUEST_BASE)
> -    /*
> -     * In case where user has not explicitly set the guest_base, we
> -     * probe here that should we set it automatically.
> -     */
> -    if (!have_guest_base) {
> -        /*
> -         * Go through ELF program header table and find out whether
> -      * any of the segments drop below our current mmap_min_addr and
> -         * in that case set guest_base to corresponding address.
> -         */
> -        for (i = 0, elf_ppnt = elf_phdata; i < elf_ex.e_phnum;
> -             i++, elf_ppnt++) {
> -            if (elf_ppnt->p_type != PT_LOAD)
> -                continue;
> -            if (HOST_PAGE_ALIGN(elf_ppnt->p_vaddr) < mmap_min_addr) {
> -                guest_base = HOST_PAGE_ALIGN(mmap_min_addr);
> -                break;
> -            }
> -        }
> +        fprintf(stderr, "%s: %s\n", bprm->filename, strerror(E2BIG));
> +        exit(-1);
>      }
> -#endif /* CONFIG_USE_GUEST_BASE */
>  
>      /* Do this so that we can load the interpreter, if need be.  We will
>         change some of these later */
> -    info->rss = 0;
>      bprm->p = setup_arg_pages(bprm->p, bprm, info);
> -    info->start_stack = bprm->p;
> -
> -    /* Now we do a little grungy work by mmaping the ELF image into
> -     * the correct location in memory.  At this point, we assume that
> -     * the image should be loaded at fixed address, not at a variable
> -     * address.
> -     */
> -
> -    for(i = 0, elf_ppnt = elf_phdata; i < elf_ex.e_phnum; i++, elf_ppnt++) {
> -        int elf_prot = 0;
> -        int elf_flags = 0;
> -        abi_ulong error;
> -
> -     if (elf_ppnt->p_type != PT_LOAD)
> -            continue;
> -
> -        if (elf_ppnt->p_flags & PF_R) elf_prot |= PROT_READ;
> -        if (elf_ppnt->p_flags & PF_W) elf_prot |= PROT_WRITE;
> -        if (elf_ppnt->p_flags & PF_X) elf_prot |= PROT_EXEC;
> -        elf_flags = MAP_PRIVATE | MAP_DENYWRITE;
> -        if (elf_ex.e_type == ET_EXEC || load_addr_set) {
> -            elf_flags |= MAP_FIXED;
> -        } else if (elf_ex.e_type == ET_DYN) {
> -            /* Try and get dynamic programs out of the way of the default 
> mmap
> -               base, as well as whatever program they might try to exec.  
> This
> -               is because the brk will follow the loader, and is not 
> movable.  */
> -            /* NOTE: for qemu, we do a big mmap to get enough space
> -               without hardcoding any address */
> -            error = target_mmap(0, ET_DYN_MAP_SIZE,
> -                                PROT_NONE, MAP_PRIVATE | MAP_ANON,
> -                                -1, 0);
> -            if (error == -1) {
> -                perror("mmap");
> -                exit(-1);
> -            }
> -            load_bias = TARGET_ELF_PAGESTART(error - elf_ppnt->p_vaddr);
> -        }
> -
> -        error = target_mmap(TARGET_ELF_PAGESTART(load_bias + 
> elf_ppnt->p_vaddr),
> -                            (elf_ppnt->p_filesz +
> -                             TARGET_ELF_PAGEOFFSET(elf_ppnt->p_vaddr)),
> -                            elf_prot,
> -                            (MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE),
> -                            bprm->fd,
> -                            (elf_ppnt->p_offset -
> -                             TARGET_ELF_PAGEOFFSET(elf_ppnt->p_vaddr)));
> -        if (error == -1) {
> -            perror("mmap");
> -            exit(-1);
> -        }
> -
> -#ifdef LOW_ELF_STACK
> -        if (TARGET_ELF_PAGESTART(elf_ppnt->p_vaddr) < elf_stack)
> -            elf_stack = TARGET_ELF_PAGESTART(elf_ppnt->p_vaddr);
> -#endif
> -
> -        if (!load_addr_set) {
> -            load_addr_set = 1;
> -            load_addr = elf_ppnt->p_vaddr - elf_ppnt->p_offset;
> -            if (elf_ex.e_type == ET_DYN) {
> -                load_bias += error -
> -                    TARGET_ELF_PAGESTART(load_bias + elf_ppnt->p_vaddr);
> -                load_addr += load_bias;
> -            }
> -        }
> -        k = elf_ppnt->p_vaddr;
> -        if (k < start_code)
> -            start_code = k;
> -        if (start_data < k)
> -            start_data = k;
> -        k = elf_ppnt->p_vaddr + elf_ppnt->p_filesz;
> -        if ((elf_ppnt->p_flags & PF_X) && end_code <  k)
> -            end_code = k;
> -        if (end_data < k)
> -            end_data = k;
> -        k = elf_ppnt->p_vaddr + elf_ppnt->p_memsz;
> -        if (k > elf_brk) {
> -            elf_brk = TARGET_PAGE_ALIGN(k);
> -        }
> -
> -        /* If the load segment requests extra zeros (e.g. bss), map it.  */
> -        if (elf_ppnt->p_filesz < elf_ppnt->p_memsz) {
> -            abi_ulong base = load_bias + elf_ppnt->p_vaddr;
> -            zero_bss(base + elf_ppnt->p_filesz,
> -                     base + elf_ppnt->p_memsz, elf_prot);
> -        }
> -    }
> -
> -    elf_entry += load_bias;
> -    elf_brk += load_bias;
> -    start_code += load_bias;
> -    end_code += load_bias;
> -    start_data += load_bias;
> -    end_data += load_bias;
> -
> -    info->load_bias = load_bias;
> -    info->load_addr = load_addr;
> -    info->entry = elf_entry;
> -    info->start_brk = info->brk = elf_brk;
> -    info->end_code = end_code;
> -    info->start_code = start_code;
> -    info->start_data = start_data;
> -    info->end_data = end_data;
> -    info->personality = PER_LINUX;
> -
> -    free(elf_phdata);
> -
> -    if (qemu_log_enabled()) {
> -     load_symbols(&elf_ex, bprm->fd, load_bias);
> -    }
> -
> -    close(bprm->fd);
>  
>      if (elf_interpreter) {
>          load_elf_interp(elf_interpreter, &interp_info, bprm->buf);
> @@ -1734,6 +1570,7 @@ int load_elf_binary(struct linux_binprm * bprm, struct 
> target_pt_regs * regs,
>      if (elf_interpreter) {
>          info->load_addr = interp_info.load_addr;
>          info->entry = interp_info.entry;
> +        free(elf_interpreter);
>      }
>  
>  #ifdef USE_ELF_CORE_DUMP
> 

-- 
mailto:address@hidden