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authorAndy Wingo <wingo@pobox.com>2012-06-01 21:33:46 +0200
committerAndy Wingo <wingo@pobox.com>2012-06-22 13:40:50 +0200
commitafc74c2920d2f8f8424db9d6f554a91866cbac01 (patch)
tree399212d59decf24bac2129a4600a0a11446d01cc /libguile/objcodes.c
parent83e7c58408ad227b38cc8c2e0542a514ebcdc2c8 (diff)
downloadguile-afc74c2920d2f8f8424db9d6f554a91866cbac01.tar.gz
add ELF loader
* libguile/objcodes.h: * libguile/objcodes.c (scm_load_thunk_from_file) (scm_load_thunk_from_memory): New procedures. * libguile/elf.h: Import from glibc. Not installed. * libguile/Makefile.am: Adapt for elf.h. * module/system/vm/objcode.scm: (load-thunk-from-file) (load-thunk-from-memory): New exports.
Diffstat (limited to 'libguile/objcodes.c')
-rw-r--r--libguile/objcodes.c552
1 files changed, 551 insertions, 1 deletions
diff --git a/libguile/objcodes.c b/libguile/objcodes.c
index df10ea3ce..73422c40c 100644
--- a/libguile/objcodes.c
+++ b/libguile/objcodes.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
@@ -37,9 +37,559 @@
#include <full-read.h>
#include "_scm.h"
+#include "elf.h"
#include "programs.h"
#include "objcodes.h"
+/* This file contains the loader for Guile's ELF format. It is followed
+ by the old loader. We'll remove the old loader at some point. */
+
+#if SIZEOF_SCM_T_BITS == 4
+#define Elf_Half Elf32_Half
+#define Elf_Word Elf32_Word
+#define Elf_Ehdr Elf32_Ehdr
+#define ELFCLASS ELFCLASS32
+#define Elf_Phdr Elf32_Phdr
+#define Elf_Dyn Elf32_Dyn
+#elif SIZEOF_SCM_T_BITS == 8
+#define Elf_Half Elf64_Half
+#define Elf_Word Elf64_Word
+#define Elf_Ehdr Elf64_Ehdr
+#define ELFCLASS ELFCLASS64
+#define Elf_Phdr Elf64_Phdr
+#define Elf_Dyn Elf64_Dyn
+#else
+#error
+#endif
+
+#define DT_LOGUILE 0x37146000 /* Start of Guile-specific */
+#define DT_GUILE_GC_ROOT 0x37146000 /* Offset of GC roots */
+#define DT_GUILE_GC_ROOT_SZ 0x37146001 /* Size in machine words of GC
+ roots */
+#define DT_GUILE_ENTRY 0x37146002 /* Address of entry thunk */
+#define DT_GUILE_RTL_VERSION 0x37146003 /* Bytecode version */
+#define DT_HIGUILE 0x37146fff /* End of Guile-specific */
+
+#ifdef WORDS_BIGENDIAN
+#define ELFDATA ELFDATA2MSB
+#else
+#define ELFDATA ELFDATA2LSB
+#endif
+
+enum bytecode_kind
+ {
+ BYTECODE_KIND_NONE,
+ BYTECODE_KIND_GUILE_2_0
+ };
+
+static SCM
+pointer_to_procedure (enum bytecode_kind bytecode_kind, char *ptr)
+{
+ switch (bytecode_kind)
+ {
+ case BYTECODE_KIND_GUILE_2_0:
+ {
+ SCM objcode;
+ scm_t_bits tag = SCM_MAKE_OBJCODE_TAG (SCM_OBJCODE_TYPE_MMAP, 0);
+
+ objcode = scm_double_cell (tag, (scm_t_bits) ptr, SCM_BOOL_F_BITS, 0);
+ return scm_make_program (objcode, SCM_BOOL_F, SCM_UNDEFINED);
+ }
+ case BYTECODE_KIND_NONE:
+ default:
+ abort ();
+ }
+}
+
+static const char*
+check_elf_header (const Elf_Ehdr *header)
+{
+ if (!(header->e_ident[EI_MAG0] == ELFMAG0
+ && header->e_ident[EI_MAG1] == ELFMAG1
+ && header->e_ident[EI_MAG2] == ELFMAG2
+ && header->e_ident[EI_MAG3] == ELFMAG3))
+ return "not an ELF file";
+
+ if (header->e_ident[EI_CLASS] != ELFCLASS)
+ return "ELF file does not have native word size";
+
+ if (header->e_ident[EI_DATA] != ELFDATA)
+ return "ELF file does not have native byte order";
+
+ if (header->e_ident[EI_VERSION] != EV_CURRENT)
+ return "bad ELF version";
+
+ if (header->e_ident[EI_OSABI] != ELFOSABI_STANDALONE)
+ return "unexpected OS ABI";
+
+ if (header->e_ident[EI_ABIVERSION] != 0)
+ return "unexpected ABI version";
+
+ if (header->e_type != ET_DYN)
+ return "unexpected ELF type";
+
+ if (header->e_machine != EM_NONE)
+ return "unexpected machine";
+
+ if (header->e_version != EV_CURRENT)
+ return "unexpected ELF version";
+
+ if (header->e_ehsize != sizeof *header)
+ return "unexpected header size";
+
+ if (header->e_phentsize != sizeof (Elf_Phdr))
+ return "unexpected program header size";
+
+ return NULL;
+}
+
+static int
+segment_flags_to_prot (Elf_Word flags)
+{
+ int prot = 0;
+
+ if (flags & PF_X)
+ prot |= PROT_EXEC;
+ if (flags & PF_W)
+ prot |= PROT_WRITE;
+ if (flags & PF_R)
+ prot |= PROT_READ;
+
+ return prot;
+}
+
+static int
+map_segments (int fd, char **base,
+ const Elf_Phdr *from, const Elf_Phdr *to)
+{
+ int prot = segment_flags_to_prot (from->p_flags);
+ char *ret;
+
+ ret = mmap (*base + from->p_vaddr,
+ to->p_offset + to->p_filesz - from->p_offset,
+ prot, MAP_PRIVATE, fd, from->p_offset);
+
+ if (ret == (char *) -1)
+ return 1;
+
+ if (!*base)
+ *base = ret;
+
+ return 0;
+}
+
+static int
+mprotect_segments (char *base, const Elf_Phdr *from, const Elf_Phdr *to)
+{
+ return mprotect (base + from->p_vaddr,
+ to->p_vaddr + to->p_memsz - from->p_vaddr,
+ segment_flags_to_prot (from->p_flags));
+}
+
+static char*
+process_dynamic_segment (char *base, Elf_Phdr *dyn_phdr,
+ SCM *init_out, SCM *entry_out)
+{
+ char *dyn_addr = base + dyn_phdr->p_vaddr;
+ Elf_Dyn *dyn = (Elf_Dyn *) dyn_addr;
+ size_t i, dyn_size = dyn_phdr->p_memsz / sizeof (Elf_Dyn);
+ char *init = 0, *gc_root = 0, *entry = 0;
+ scm_t_ptrdiff gc_root_size = 0;
+ enum bytecode_kind bytecode_kind = BYTECODE_KIND_NONE;
+
+ for (i = 0; i < dyn_size; i++)
+ {
+ if (dyn[i].d_tag == DT_NULL)
+ break;
+
+ switch (dyn[i].d_tag)
+ {
+ case DT_INIT:
+ if (init)
+ return "duplicate DT_INIT";
+ init = base + dyn[i].d_un.d_val;
+ break;
+ case DT_GUILE_GC_ROOT:
+ if (gc_root)
+ return "duplicate DT_GUILE_GC_ROOT";
+ gc_root = base + dyn[i].d_un.d_val;
+ break;
+ case DT_GUILE_GC_ROOT_SZ:
+ if (gc_root_size)
+ return "duplicate DT_GUILE_GC_ROOT_SZ";
+ gc_root_size = dyn[i].d_un.d_val;
+ break;
+ case DT_GUILE_ENTRY:
+ if (entry)
+ return "duplicate DT_GUILE_ENTRY";
+ entry = base + dyn[i].d_un.d_val;
+ break;
+ case DT_GUILE_RTL_VERSION:
+ if (bytecode_kind != BYTECODE_KIND_NONE)
+ return "duplicate DT_GUILE_RTL_VERSION";
+ {
+ scm_t_uint16 major = dyn[i].d_un.d_val >> 16;
+ scm_t_uint16 minor = dyn[i].d_un.d_val & 0xffff;
+ if (major != 0x0200)
+ return "incompatible bytecode kind";
+ if (minor > SCM_OBJCODE_MINOR_VERSION)
+ return "incompatible bytecode version";
+ bytecode_kind = BYTECODE_KIND_GUILE_2_0;
+ break;
+ }
+ }
+ }
+
+ if (bytecode_kind != BYTECODE_KIND_GUILE_2_0)
+ return "missing DT_GUILE_RTL_VERSION";
+ if (init)
+ return "unexpected DT_INIT";
+ if ((scm_t_uintptr) entry % 8)
+ return "unaligned DT_GUILE_ENTRY";
+ if (!entry)
+ return "missing DT_GUILE_ENTRY";
+
+ if (gc_root)
+ GC_add_roots (gc_root, gc_root + gc_root_size);
+
+ *init_out = SCM_BOOL_F;
+ *entry_out = pointer_to_procedure (bytecode_kind, entry);
+ return NULL;
+}
+
+#define ABORT(msg) do { err_msg = msg; goto cleanup; } while (0)
+
+#ifdef HAVE_SYS_MMAN_H
+static SCM
+load_thunk_from_fd_using_mmap (int fd)
+#define FUNC_NAME "load-thunk-from-disk"
+{
+ Elf_Ehdr header;
+ Elf_Phdr *ph;
+ const char *err_msg = 0;
+ char *base = 0;
+ size_t n;
+ int i;
+ int start_segment = -1;
+ int prev_segment = -1;
+ int dynamic_segment = -1;
+ SCM init = SCM_BOOL_F, entry = SCM_BOOL_F;
+
+ if (full_read (fd, &header, sizeof header) != sizeof header)
+ ABORT ("object file too small");
+
+ if ((err_msg = check_elf_header (&header)))
+ goto cleanup;
+
+ if (lseek (fd, header.e_phoff, SEEK_SET) == (off_t) -1)
+ goto cleanup;
+
+ n = header.e_phnum;
+ ph = scm_gc_malloc_pointerless (n * sizeof (Elf_Phdr), "segment headers");
+
+ if (full_read (fd, ph, n * sizeof (Elf_Phdr)) != n * sizeof (Elf_Phdr))
+ ABORT ("failed to read program headers");
+
+ for (i = 0; i < n; i++)
+ {
+ if (!ph[i].p_memsz)
+ continue;
+
+ if (ph[i].p_filesz != ph[i].p_memsz)
+ ABORT ("expected p_filesz == p_memsz");
+
+ if (!ph[i].p_flags)
+ ABORT ("expected nonzero segment flags");
+
+ if (ph[i].p_type == PT_DYNAMIC)
+ {
+ if (dynamic_segment >= 0)
+ ABORT ("expected only one PT_DYNAMIC segment");
+ dynamic_segment = i;
+ }
+
+ if (start_segment < 0)
+ {
+ if (!base && ph[i].p_vaddr)
+ ABORT ("first loadable vaddr is not 0");
+
+ start_segment = prev_segment = i;
+ continue;
+ }
+
+ if (ph[i].p_flags == ph[start_segment].p_flags)
+ {
+ if (ph[i].p_vaddr - ph[prev_segment].p_vaddr
+ != ph[i].p_offset - ph[prev_segment].p_offset)
+ ABORT ("coalesced segments not contiguous");
+
+ prev_segment = i;
+ continue;
+ }
+
+ /* Otherwise we have a new kind of segment. Map previous
+ segments. */
+ if (map_segments (fd, &base, &ph[start_segment], &ph[prev_segment]))
+ goto cleanup;
+
+ /* Open a new set of segments. */
+ start_segment = prev_segment = i;
+ }
+
+ /* Map last segments. */
+ if (start_segment < 0)
+ ABORT ("no loadable segments");
+
+ if (map_segments (fd, &base, &ph[start_segment], &ph[prev_segment]))
+ goto cleanup;
+
+ if (dynamic_segment < 0)
+ ABORT ("no PT_DYNAMIC segment");
+
+ if ((err_msg = process_dynamic_segment (base, &ph[dynamic_segment],
+ &init, &entry)))
+ goto cleanup;
+
+ if (scm_is_true (init))
+ scm_call_0 (init);
+
+ /* Finally! Return the thunk. */
+ return entry;
+
+ /* FIXME: munmap on error? */
+ cleanup:
+ {
+ int errno_save = errno;
+ (void) close (fd);
+ errno = errno_save;
+ if (errno)
+ SCM_SYSERROR;
+ scm_misc_error (FUNC_NAME, err_msg ? err_msg : "error loading ELF file",
+ SCM_EOL);
+ }
+}
+#undef FUNC_NAME
+#endif /* HAVE_SYS_MMAN_H */
+
+static SCM
+load_thunk_from_memory (char *data, size_t len)
+#define FUNC_NAME "load-thunk-from-memory"
+{
+ Elf_Ehdr header;
+ Elf_Phdr *ph;
+ const char *err_msg = 0;
+ char *base = 0;
+ size_t n, memsz = 0, alignment = 8;
+ int i;
+ int first_loadable = -1;
+ int start_segment = -1;
+ int prev_segment = -1;
+ int dynamic_segment = -1;
+ SCM init = SCM_BOOL_F, entry = SCM_BOOL_F;
+
+ if (len < sizeof header)
+ ABORT ("object file too small");
+
+ memcpy (&header, data, sizeof header);
+
+ if ((err_msg = check_elf_header (&header)))
+ goto cleanup;
+
+ n = header.e_phnum;
+ if (len < header.e_phoff + n * sizeof (Elf_Phdr))
+ goto cleanup;
+ ph = (Elf_Phdr*) (data + header.e_phoff);
+
+ for (i = 0; i < n; i++)
+ {
+ if (!ph[i].p_memsz)
+ continue;
+
+ if (ph[i].p_filesz != ph[i].p_memsz)
+ ABORT ("expected p_filesz == p_memsz");
+
+ if (!ph[i].p_flags)
+ ABORT ("expected nonzero segment flags");
+
+ if (ph[i].p_align < alignment)
+ {
+ if (ph[i].p_align % alignment)
+ ABORT ("expected new alignment to be multiple of old");
+ alignment = ph[i].p_align;
+ }
+
+ if (ph[i].p_type == PT_DYNAMIC)
+ {
+ if (dynamic_segment >= 0)
+ ABORT ("expected only one PT_DYNAMIC segment");
+ dynamic_segment = i;
+ }
+
+ if (first_loadable < 0)
+ {
+ if (ph[i].p_vaddr)
+ ABORT ("first loadable vaddr is not 0");
+
+ first_loadable = i;
+ }
+
+ if (ph[i].p_vaddr < memsz)
+ ABORT ("overlapping segments");
+
+ if (ph[i].p_offset + ph[i].p_filesz > len)
+ ABORT ("segment beyond end of byte array");
+
+ memsz = ph[i].p_vaddr + ph[i].p_memsz;
+ }
+
+ if (first_loadable < 0)
+ ABORT ("no loadable segments");
+
+ if (dynamic_segment < 0)
+ ABORT ("no PT_DYNAMIC segment");
+
+ /* Now copy segments. */
+
+ /* We leak this memory, as we leak the memory mappings in
+ load_thunk_from_fd_using_mmap.
+
+ If the file is has an alignment of 8, use the standard malloc.
+ (FIXME to ensure alignment on non-GNU malloc.) Otherwise use
+ posix_memalign. We only use mprotect if the aligment is 4096. */
+ if (alignment == 8)
+ {
+ base = malloc (memsz);
+ if (!base)
+ goto cleanup;
+ }
+ else
+ if ((errno = posix_memalign ((void **) &base, alignment, memsz)))
+ goto cleanup;
+
+ memset (base, 0, memsz);
+
+ for (i = 0; i < n; i++)
+ {
+ if (!ph[i].p_memsz)
+ continue;
+
+ memcpy (base + ph[i].p_vaddr,
+ data + ph[i].p_offset,
+ ph[i].p_memsz);
+
+ if (start_segment < 0)
+ {
+ start_segment = prev_segment = i;
+ continue;
+ }
+
+ if (ph[i].p_flags == ph[start_segment].p_flags)
+ {
+ prev_segment = i;
+ continue;
+ }
+
+ if (alignment == 4096)
+ if (mprotect_segments (base, &ph[start_segment], &ph[prev_segment]))
+ goto cleanup;
+
+ /* Open a new set of segments. */
+ start_segment = prev_segment = i;
+ }
+
+ /* Mprotect the last segments. */
+ if (alignment == 4096)
+ if (mprotect_segments (base, &ph[start_segment], &ph[prev_segment]))
+ goto cleanup;
+
+ if ((err_msg = process_dynamic_segment (base, &ph[dynamic_segment],
+ &init, &entry)))
+ goto cleanup;
+
+ if (scm_is_true (init))
+ scm_call_0 (init);
+
+ /* Finally! Return the thunk. */
+ return entry;
+
+ cleanup:
+ {
+ if (errno)
+ SCM_SYSERROR;
+ scm_misc_error (FUNC_NAME, err_msg ? err_msg : "error loading ELF file",
+ SCM_EOL);
+ }
+}
+#undef FUNC_NAME
+
+#ifndef HAVE_SYS_MMAN_H
+static SCM
+load_thunk_from_fd_using_read (int fd)
+#define FUNC_NAME "load-thunk-from-disk"
+{
+ char *data;
+ size_t len;
+ struct stat st;
+ int ret;
+
+ ret = fstat (fd, &st);
+ if (ret < 0)
+ SCM_SYSERROR;
+ len = st.st_size;
+ data = scm_gc_malloc_pointerless (len, "objcode");
+ if (full_read (fd, data, len) != len)
+ {
+ int errno_save = errno;
+ (void) close (fd);
+ errno = errno_save;
+ if (errno)
+ SCM_SYSERROR;
+ scm_misc_error (FUNC_NAME, "short read while loading objcode",
+ SCM_EOL);
+ }
+ (void) close (fd);
+ return load_thunk_from_memory (data, len);
+}
+#undef FUNC_NAME
+#endif /* ! HAVE_SYS_MMAN_H */
+
+SCM_DEFINE (scm_load_thunk_from_file, "load-thunk-from-file", 1, 0, 0,
+ (SCM filename),
+ "")
+#define FUNC_NAME s_scm_load_thunk_from_file
+{
+ char *c_filename;
+ int fd;
+
+ SCM_VALIDATE_STRING (1, filename);
+
+ c_filename = scm_to_locale_string (filename);
+ fd = open (c_filename, O_RDONLY | O_CLOEXEC);
+ free (c_filename);
+ if (fd < 0) SCM_SYSERROR;
+
+#ifdef HAVE_SYS_MMAN_H
+ return load_thunk_from_fd_using_mmap (fd);
+#else
+ return load_thunk_from_fd_using_read (fd);
+#endif
+}
+#undef FUNC_NAME
+
+SCM_DEFINE (scm_load_thunk_from_memory, "load-thunk-from-memory", 1, 0, 0,
+ (SCM bv),
+ "")
+#define FUNC_NAME s_scm_load_thunk_from_memory
+{
+ SCM_VALIDATE_BYTEVECTOR (1, bv);
+
+ return load_thunk_from_memory ((char *) SCM_BYTEVECTOR_CONTENTS (bv),
+ SCM_BYTEVECTOR_LENGTH (bv));
+}
+#undef FUNC_NAME
+
+
+
/* SCM_OBJCODE_COOKIE, defined in _scm.h, is a magic value prepended
to objcode on disk but not in memory.