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authorAlan Modra <amodra@gmail.com>2014-04-02 12:07:33 +1030
committerAlan Modra <amodra@gmail.com>2014-04-02 12:07:33 +1030
commit5979d6b69b20a8355ea94b75fad97415fce4788c (patch)
tree896462cf9849c42674901897808ad7c4108cd759 /bfd/elfcode.h
parentcf2a3e990524cb794c75e0493169736dee6a660c (diff)
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Handle VDSO section headers past end of page
When a VDSO gets large enough that it doesn't entirely fit in one page, but not so large that the part described by the program header exceeds one page, then gdb/BFD doesn't read the section headers and symbol table information. This patch cures that by passing the size of the vdso to BFD, and fixes a number of other issues in the BFD code. bfd/ * elfcode.h (bfd_from_remote_memory): Add "size" parameter. Consolidate code handling possible section headers past end of segment. Don't use p_align for page size guess, instead use minpagesize. Take note of ld.so clearing section headers when p_memsz > p_filesz. Handle file header specifying no section headers. Handle zero p_align throughout. Default loadbase to zero. Add comments. Rename contents_size to high_offset, and make it a bfd_vma. Delete unnecessary bfd_set_error calls. * bfd-in.h (bfd_elf_bfd_from_remote_memory): Update prototpe. * elf-bfd.h (struct elf_backend_data <elf_backend_from_remote_memory>): Likewise. (_bfd_elf32_bfd_from_remote_memory): Likewise. (_bfd_elf64_bfd_from_remote_memory): Likewise. * elf.c (bfd_elf_bfd_from_remote_memory): Adjust. * bfd-in2.h: Regnerate. gdb/ * symfile-mem.c (symbol_file_add_from_memory): Add size parameter. Pass to bfd_elf_bfd_from_remote_memory. Adjust all callers. (struct symbol_file_add_from_memory_args): Add size field. (find_vdso_size): New function. (add_vsyscall_page): Attempt to find vdso size.
Diffstat (limited to 'bfd/elfcode.h')
-rw-r--r--bfd/elfcode.h153
1 files changed, 92 insertions, 61 deletions
diff --git a/bfd/elfcode.h b/bfd/elfcode.h
index 20101be..f840065 100644
--- a/bfd/elfcode.h
+++ b/bfd/elfcode.h
@@ -1587,37 +1587,40 @@ elf_debug_file (Elf_Internal_Ehdr *ehdrp)
#endif
/* Create a new BFD as if by bfd_openr. Rather than opening a file,
- reconstruct an ELF file by reading the segments out of remote memory
- based on the ELF file header at EHDR_VMA and the ELF program headers it
- points to. If not null, *LOADBASEP is filled in with the difference
- between the VMAs from which the segments were read, and the VMAs the
- file headers (and hence BFD's idea of each section's VMA) put them at.
-
- The function TARGET_READ_MEMORY is called to copy LEN bytes from the
- remote memory at target address VMA into the local buffer at MYADDR; it
- should return zero on success or an `errno' code on failure. TEMPL must
- be a BFD for a target with the word size and byte order found in the
- remote memory. */
+ reconstruct an ELF file by reading the segments out of remote
+ memory based on the ELF file header at EHDR_VMA and the ELF program
+ headers it points to. If non-zero, SIZE is the known extent of the
+ object. If not null, *LOADBASEP is filled in with the difference
+ between the VMAs from which the segments were read, and the VMAs
+ the file headers (and hence BFD's idea of each section's VMA) put
+ them at.
+
+ The function TARGET_READ_MEMORY is called to copy LEN bytes from
+ the remote memory at target address VMA into the local buffer at
+ MYADDR; it should return zero on success or an `errno' code on
+ failure. TEMPL must be a BFD for a target with the word size and
+ byte order found in the remote memory. */
bfd *
NAME(_bfd_elf,bfd_from_remote_memory)
(bfd *templ,
bfd_vma ehdr_vma,
+ size_t size,
bfd_vma *loadbasep,
int (*target_read_memory) (bfd_vma, bfd_byte *, bfd_size_type))
{
Elf_External_Ehdr x_ehdr; /* Elf file header, external form */
Elf_Internal_Ehdr i_ehdr; /* Elf file header, internal form */
Elf_External_Phdr *x_phdrs;
- Elf_Internal_Phdr *i_phdrs, *last_phdr;
+ Elf_Internal_Phdr *i_phdrs, *last_phdr, *first_phdr;
bfd *nbfd;
struct bfd_in_memory *bim;
- int contents_size;
bfd_byte *contents;
int err;
unsigned int i;
+ bfd_vma high_offset;
+ bfd_vma shdr_end;
bfd_vma loadbase;
- bfd_boolean loadbase_set;
/* Read in the ELF header in external format. */
err = target_read_memory (ehdr_vma, (bfd_byte *) &x_ehdr, sizeof x_ehdr);
@@ -1677,10 +1680,7 @@ NAME(_bfd_elf,bfd_from_remote_memory)
x_phdrs = (Elf_External_Phdr *)
bfd_malloc (i_ehdr.e_phnum * (sizeof *x_phdrs + sizeof *i_phdrs));
if (x_phdrs == NULL)
- {
- bfd_set_error (bfd_error_no_memory);
- return NULL;
- }
+ return NULL;
err = target_read_memory (ehdr_vma + i_ehdr.e_phoff, (bfd_byte *) x_phdrs,
i_ehdr.e_phnum * sizeof x_phdrs[0]);
if (err)
@@ -1692,34 +1692,44 @@ NAME(_bfd_elf,bfd_from_remote_memory)
}
i_phdrs = (Elf_Internal_Phdr *) &x_phdrs[i_ehdr.e_phnum];
- contents_size = 0;
+ high_offset = 0;
+ loadbase = 0;
+ first_phdr = NULL;
last_phdr = NULL;
- loadbase = ehdr_vma;
- loadbase_set = FALSE;
for (i = 0; i < i_ehdr.e_phnum; ++i)
{
elf_swap_phdr_in (templ, &x_phdrs[i], &i_phdrs[i]);
if (i_phdrs[i].p_type == PT_LOAD)
{
- bfd_vma segment_end;
- segment_end = (i_phdrs[i].p_offset + i_phdrs[i].p_filesz
- + i_phdrs[i].p_align - 1) & -i_phdrs[i].p_align;
- if (segment_end > (bfd_vma) contents_size)
- contents_size = segment_end;
-
- /* LOADADDR is the `Base address' from the gELF specification:
- `lowest p_vaddr value for a PT_LOAD segment' is P_VADDR from the
- first PT_LOAD as PT_LOADs are ordered by P_VADDR. */
- if (!loadbase_set && (i_phdrs[i].p_offset & -i_phdrs[i].p_align) == 0)
+ bfd_vma segment_end = i_phdrs[i].p_offset + i_phdrs[i].p_filesz;
+
+ if (segment_end > high_offset)
{
- loadbase = ehdr_vma - (i_phdrs[i].p_vaddr & -i_phdrs[i].p_align);
- loadbase_set = TRUE;
+ high_offset = segment_end;
+ last_phdr = &i_phdrs[i];
}
- last_phdr = &i_phdrs[i];
+ /* If this program header covers offset zero, where the file
+ header sits, then we can figure out the loadbase. */
+ if (first_phdr == NULL)
+ {
+ bfd_vma p_offset = i_phdrs[i].p_offset;
+ bfd_vma p_vaddr = i_phdrs[i].p_vaddr;
+
+ if (i_phdrs[i].p_align > 1)
+ {
+ p_offset &= -i_phdrs[i].p_align;
+ p_vaddr &= -i_phdrs[i].p_align;
+ }
+ if (p_offset == 0)
+ {
+ loadbase = ehdr_vma - p_vaddr;
+ first_phdr = &i_phdrs[i];
+ }
+ }
}
}
- if (last_phdr == NULL)
+ if (high_offset == 0)
{
/* There were no PT_LOAD segments, so we don't have anything to read. */
free (x_phdrs);
@@ -1727,40 +1737,64 @@ NAME(_bfd_elf,bfd_from_remote_memory)
return NULL;
}
- /* Trim the last segment so we don't bother with zeros in the last page
- that are off the end of the file. However, if the extra bit in that
- page includes the section headers, keep them. */
- if ((bfd_vma) contents_size > last_phdr->p_offset + last_phdr->p_filesz
- && (bfd_vma) contents_size >= (i_ehdr.e_shoff
- + i_ehdr.e_shnum * i_ehdr.e_shentsize))
+ shdr_end = 0;
+ if (i_ehdr.e_shoff != 0 && i_ehdr.e_shnum != 0 && i_ehdr.e_shentsize != 0)
{
- contents_size = last_phdr->p_offset + last_phdr->p_filesz;
- if ((bfd_vma) contents_size < (i_ehdr.e_shoff
- + i_ehdr.e_shnum * i_ehdr.e_shentsize))
- contents_size = i_ehdr.e_shoff + i_ehdr.e_shnum * i_ehdr.e_shentsize;
+ shdr_end = i_ehdr.e_shoff + i_ehdr.e_shnum * i_ehdr.e_shentsize;
+
+ if (last_phdr->p_filesz != last_phdr->p_memsz)
+ {
+ /* If the last PT_LOAD header has a bss area then ld.so will
+ have cleared anything past p_filesz, zapping the section
+ headers. */
+ }
+ else if (size >= shdr_end)
+ high_offset = shdr_end;
+ else
+ {
+ bfd_vma page_size = get_elf_backend_data (templ)->minpagesize;
+ bfd_vma segment_end = last_phdr->p_offset + last_phdr->p_filesz;
+
+ /* Assume we loaded full pages, allowing us to sometimes see
+ section headers. */
+ if (page_size > 1 && shdr_end > segment_end)
+ {
+ bfd_vma page_end = (segment_end + page_size - 1) & -page_size;
+
+ if (page_end >= shdr_end)
+ /* Whee, section headers covered. */
+ high_offset = shdr_end;
+ }
+ }
}
- else
- contents_size = last_phdr->p_offset + last_phdr->p_filesz;
/* Now we know the size of the whole image we want read in. */
- contents = (bfd_byte *) bfd_zmalloc (contents_size);
+ contents = (bfd_byte *) bfd_zmalloc (high_offset);
if (contents == NULL)
{
free (x_phdrs);
- bfd_set_error (bfd_error_no_memory);
return NULL;
}
for (i = 0; i < i_ehdr.e_phnum; ++i)
if (i_phdrs[i].p_type == PT_LOAD)
{
- bfd_vma start = i_phdrs[i].p_offset & -i_phdrs[i].p_align;
- bfd_vma end = (i_phdrs[i].p_offset + i_phdrs[i].p_filesz
- + i_phdrs[i].p_align - 1) & -i_phdrs[i].p_align;
- if (end > (bfd_vma) contents_size)
- end = contents_size;
- err = target_read_memory ((loadbase + i_phdrs[i].p_vaddr)
- & -i_phdrs[i].p_align,
+ bfd_vma start = i_phdrs[i].p_offset;
+ bfd_vma end = start + i_phdrs[i].p_filesz;
+ bfd_vma vaddr = i_phdrs[i].p_vaddr;
+
+ /* Extend the beginning of the first pt_load to cover file
+ header and program headers, if we proved earlier that its
+ aligned offset is 0. */
+ if (first_phdr == &i_phdrs[i])
+ {
+ vaddr -= start;
+ start = 0;
+ }
+ /* Extend the end of the last pt_load to cover section headers. */
+ if (last_phdr == &i_phdrs[i])
+ end = high_offset;
+ err = target_read_memory (loadbase + vaddr,
contents + start, end - start);
if (err)
{
@@ -1775,8 +1809,7 @@ NAME(_bfd_elf,bfd_from_remote_memory)
/* If the segments visible in memory didn't include the section headers,
then clear them from the file header. */
- if ((bfd_vma) contents_size < (i_ehdr.e_shoff
- + i_ehdr.e_shnum * i_ehdr.e_shentsize))
+ if (high_offset < shdr_end)
{
memset (&x_ehdr.e_shoff, 0, sizeof x_ehdr.e_shoff);
memset (&x_ehdr.e_shnum, 0, sizeof x_ehdr.e_shnum);
@@ -1792,7 +1825,6 @@ NAME(_bfd_elf,bfd_from_remote_memory)
if (bim == NULL)
{
free (contents);
- bfd_set_error (bfd_error_no_memory);
return NULL;
}
nbfd = _bfd_new_bfd ();
@@ -1800,12 +1832,11 @@ NAME(_bfd_elf,bfd_from_remote_memory)
{
free (bim);
free (contents);
- bfd_set_error (bfd_error_no_memory);
return NULL;
}
nbfd->filename = xstrdup ("<in-memory>");
nbfd->xvec = templ->xvec;
- bim->size = contents_size;
+ bim->size = high_offset;
bim->buffer = contents;
nbfd->iostream = bim;
nbfd->flags = BFD_IN_MEMORY;