mirrors/emacs
1
Fork 0
mirror of git://git.sv.gnu.org/emacs.git synced 2025-12-31 01:20:37 -08:00
Code Issues Projects Releases Wiki Activity

ELF unexec: Tidy code

Browse source 
Separate out some of the more mechanical changes so following patches
are smaller.

* unexelf.c (unexec): Rearrange initialisation of program
header vars.  Use pointer vars in loops rather than indexing
section header array via macros.  Simplify _OBJC_ sym code
and reloc handling code.
This commit is contained in:
Alan Modra 2015-11-08 09:28:59 -08:00 • committed by Paul Eggert
parent 0bcd08ef05
commit 856f4eaba8
1 changed files with 96 additions and 114 deletions
Download patch file Download diff file Expand all files Collapse all files

210
src/unexelf.c
View file

@ -812,20 +812,11 @@ unexec (const char *new_name, const char *old_name)
if (new_base == MAP_FAILED)
fatal ("Can't allocate buffer for %s: %s", old_name, strerror (errno));
new_file_h = (ElfW (Ehdr) *) new_base;
new_program_h = (ElfW (Phdr) *) ((byte *) new_base + old_file_h->e_phoff);
new_section_h = (ElfW (Shdr) *)
((byte *) new_base + old_file_h->e_shoff + new_data2_incr);
/* Make our new file, program and section headers as copies of the
originals. */
new_file_h = (ElfW (Ehdr) *) new_base;
memcpy (new_file_h, old_file_h, old_file_h->e_ehsize);
memcpy (new_program_h, old_program_h,
old_file_h->e_phnum * old_file_h->e_phentsize);
/* Modify the e_shstrndx if necessary. */
PATCH_INDEX (new_file_h->e_shstrndx);
/* Fix up file header. We'll add one section. Section header is
further away now. */
@ -833,6 +824,16 @@ unexec (const char *new_name, const char *old_name)
new_file_h->e_shoff += new_data2_incr;
new_file_h->e_shnum += 1;
/* Modify the e_shstrndx if necessary. */
PATCH_INDEX (new_file_h->e_shstrndx);
new_program_h = (ElfW (Phdr) *) ((byte *) new_base + old_file_h->e_phoff);
new_section_h = (ElfW (Shdr) *)
((byte *) new_base + old_file_h->e_shoff + new_data2_incr);
memcpy (new_program_h, old_program_h,
old_file_h->e_phnum * old_file_h->e_phentsize);
#ifdef UNEXELF_DEBUG
DEBUG_LOG (old_file_h->e_shoff);
fprintf (stderr, "Old section count %td\n", (ptrdiff_t) old_file_h->e_shnum);
@ -905,32 +906,35 @@ unexec (const char *new_name, const char *old_name)
for (n = 1, nn = 1; n < old_file_h->e_shnum; n++, nn++)
{
caddr_t src;
ElfW (Shdr) *old_shdr = &OLD_SECTION_H (n);
ElfW (Shdr) *new_shdr = &NEW_SECTION_H (nn);
/* If it is (s)bss section, insert the new data2 section before it. */
/* new_data2_index is the index of either old_sbss or old_bss, that was
chosen as a section for new_data2. */
if (n == new_data2_index)
{
/* Steal the data section header for this data2 section. */
memcpy (&NEW_SECTION_H (nn), &OLD_SECTION_H (old_data_index),
memcpy (new_shdr, &OLD_SECTION_H (old_data_index),
new_file_h->e_shentsize);
NEW_SECTION_H (nn).sh_addr = new_data2_addr;
NEW_SECTION_H (nn).sh_offset = new_data2_offset;
NEW_SECTION_H (nn).sh_size = new_data2_size;
new_shdr->sh_addr = new_data2_addr;
new_shdr->sh_offset = new_data2_offset;
new_shdr->sh_size = new_data2_size;
/* Use the bss section's alignment. This will assure that the
new data2 section always be placed in the same spot as the old
bss section by any other application. */
NEW_SECTION_H (nn).sh_addralign = OLD_SECTION_H (n).sh_addralign;
new_shdr->sh_addralign = old_shdr->sh_addralign;
/* Now copy over what we have in the memory now. */
memcpy (NEW_SECTION_H (nn).sh_offset + new_base,
(caddr_t) OLD_SECTION_H (n).sh_addr,
memcpy (new_shdr->sh_offset + new_base,
(caddr_t) old_shdr->sh_addr,
new_data2_size);
nn++;
new_shdr++;
}
memcpy (&NEW_SECTION_H (nn), &OLD_SECTION_H (n),
old_file_h->e_shentsize);
memcpy (new_shdr, old_shdr, old_file_h->e_shentsize);
if (n == old_bss_index
/* The new bss and sbss section's size is zero, and its file offset
@ -939,13 +943,13 @@ unexec (const char *new_name, const char *old_name)
)
{
/* NN should be `old_s?bss_index + 1' at this point. */
NEW_SECTION_H (nn).sh_offset = new_data2_offset + new_data2_size;
NEW_SECTION_H (nn).sh_addr = new_data2_addr + new_data2_size;
new_shdr->sh_offset = new_data2_offset + new_data2_size;
new_shdr->sh_addr = new_data2_addr + new_data2_size;
/* Let the new bss section address alignment be the same as the
section address alignment followed the old bss section, so
this section will be placed in exactly the same place. */
NEW_SECTION_H (nn).sh_addralign = OLD_SECTION_H (nn).sh_addralign;
NEW_SECTION_H (nn).sh_size = 0;
new_shdr->sh_addralign = OLD_SECTION_H (nn).sh_addralign;
new_shdr->sh_size = 0;
}
else
{
@ -975,53 +979,50 @@ temacs:
25 1709 0x4 0x10
*/
if (NEW_SECTION_H (nn).sh_offset >= old_bss_offset
|| (NEW_SECTION_H (nn).sh_offset + NEW_SECTION_H (nn).sh_size
if (new_shdr->sh_offset >= old_bss_offset
|| (new_shdr->sh_offset + new_shdr->sh_size
> new_data2_offset))
NEW_SECTION_H (nn).sh_offset += new_data2_incr;
new_shdr->sh_offset += new_data2_incr;
/* Any section that was originally placed after the section
header table should now be off by the size of one section
header table entry. */
if (NEW_SECTION_H (nn).sh_offset > new_file_h->e_shoff)
NEW_SECTION_H (nn).sh_offset += new_file_h->e_shentsize;
if (new_shdr->sh_offset > new_file_h->e_shoff)
new_shdr->sh_offset += new_file_h->e_shentsize;
}
/* If any section hdr refers to the section after the new .data
section, make it refer to next one because we have inserted
a new section in between. */
PATCH_INDEX (NEW_SECTION_H (nn).sh_link);
PATCH_INDEX (new_shdr->sh_link);
/* For symbol tables, info is a symbol table index,
so don't change it. */
if (NEW_SECTION_H (nn).sh_type != SHT_SYMTAB
&& NEW_SECTION_H (nn).sh_type != SHT_DYNSYM)
PATCH_INDEX (NEW_SECTION_H (nn).sh_info);
if (new_shdr->sh_type != SHT_SYMTAB
&& new_shdr->sh_type != SHT_DYNSYM)
PATCH_INDEX (new_shdr->sh_info);
if (old_sbss_index != -1)
if (!strcmp (old_section_names + NEW_SECTION_H (nn).sh_name, ".sbss"))
if (!strcmp (old_section_names + new_shdr->sh_name, ".sbss"))
{
NEW_SECTION_H (nn).sh_offset =
round_up (NEW_SECTION_H (nn).sh_offset,
NEW_SECTION_H (nn).sh_addralign);
NEW_SECTION_H (nn).sh_type = SHT_PROGBITS;
new_shdr->sh_offset =
round_up (new_shdr->sh_offset,
new_shdr->sh_addralign);
new_shdr->sh_type = SHT_PROGBITS;
}
/* Now, start to copy the content of sections. */
if (NEW_SECTION_H (nn).sh_type == SHT_NULL
|| NEW_SECTION_H (nn).sh_type == SHT_NOBITS)
if (new_shdr->sh_type == SHT_NULL
|| new_shdr->sh_type == SHT_NOBITS)
continue;
/* Write out the sections. .data and .data1 (and data2, called
".data" in the strings table) get copied from the current process
instead of the old file. */
if (!strcmp (old_section_names + NEW_SECTION_H (nn).sh_name, ".data")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".sdata")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".lit4")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".lit8")
if (!strcmp (old_section_names + new_shdr->sh_name, ".data")
|| !strcmp (old_section_names + new_shdr->sh_name, ".sdata")
|| !strcmp (old_section_names + new_shdr->sh_name, ".lit4")
|| !strcmp (old_section_names + new_shdr->sh_name, ".lit8")
/* The conditional bit below was in Oliva's original code
(1999-08-25) and seems to have been dropped by mistake
subsequently. It prevents a crash at startup under X in
@ -1043,28 +1044,22 @@ temacs:
loader, but I never got anywhere with an SGI support call
seeking clues. -- fx 2002-11-29. */
#ifdef IRIX6_5
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".got")
|| !strcmp (old_section_names + new_shdr->sh_name, ".got")
#endif
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".sdata1")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".data1")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".sbss"))
src = (caddr_t) OLD_SECTION_H (n).sh_addr;
|| !strcmp (old_section_names + new_shdr->sh_name, ".sdata1")
|| !strcmp (old_section_names + new_shdr->sh_name, ".data1")
|| !strcmp (old_section_names + new_shdr->sh_name, ".sbss"))
src = (caddr_t) old_shdr->sh_addr;
else
src = old_base + OLD_SECTION_H (n).sh_offset;
src = old_base + old_shdr->sh_offset;
memcpy (NEW_SECTION_H (nn).sh_offset + new_base, src,
NEW_SECTION_H (nn).sh_size);
memcpy (new_shdr->sh_offset + new_base, src, new_shdr->sh_size);
#if defined __alpha__ && !defined __OpenBSD__
/* Update Alpha COFF symbol table: */
if (strcmp (old_section_names + OLD_SECTION_H (n).sh_name, ".mdebug")
== 0)
if (strcmp (old_section_names + old_shdr->sh_name, ".mdebug") == 0)
{
pHDRR symhdr = (pHDRR) (NEW_SECTION_H (nn).sh_offset + new_base);
pHDRR symhdr = (pHDRR) (new_shdr->sh_offset + new_base);
symhdr->cbLineOffset += new_data2_size;
symhdr->cbDnOffset += new_data2_size;
@ -1081,13 +1076,13 @@ temacs:
#endif /* __alpha__ && !__OpenBSD__ */
#if defined (_SYSTYPE_SYSV)
if (NEW_SECTION_H (nn).sh_type == SHT_MIPS_DEBUG
if (new_shdr->sh_type == SHT_MIPS_DEBUG
&& old_mdebug_index != -1)
{
ptrdiff_t new_offset = NEW_SECTION_H (nn).sh_offset;
ptrdiff_t new_offset = new_shdr->sh_offset;
ptrdiff_t old_offset = OLD_SECTION_H (old_mdebug_index).sh_offset;
ptrdiff_t diff = new_offset - old_offset;
HDRR *phdr = (HDRR *)(NEW_SECTION_H (nn).sh_offset + new_base);
HDRR *phdr = (HDRR *) (new_shdr->sh_offset + new_base);
if (diff)
{
@ -1123,8 +1118,8 @@ temacs:
n_phdrr->__fileaddr += movement; \
}
HDRR * o_phdrr = (HDRR *)((byte *)old_base + OLD_SECTION_H (n).sh_offset);
HDRR * n_phdrr = (HDRR *)((byte *)new_base + NEW_SECTION_H (nn).sh_offset);
HDRR *o_phdrr = (HDRR *) ((byte *) old_base + old_shdr->sh_offset);
HDRR *n_phdrr = (HDRR *) ((byte *) new_base + new_shdr->sh_offset);
unsigned movement = new_data2_size;
MDEBUGADJUST (idnMax, cbDnOffset);
@ -1141,8 +1136,8 @@ temacs:
requires special handling. */
if (n_phdrr->cbLine > 0)
{
if (o_phdrr->cbLineOffset > (OLD_SECTION_H (n).sh_offset
+ OLD_SECTION_H (n).sh_size))
if (o_phdrr->cbLineOffset > (old_shdr->sh_offset
+ old_shdr->sh_size))
{
/* line data is in a hole in elf. do special copy and adjust
for this ld mistake.
@ -1162,13 +1157,11 @@ temacs:
#endif /* __sgi */
/* If it is the symbol table, its st_shndx field needs to be patched. */
if (NEW_SECTION_H (nn).sh_type == SHT_SYMTAB
|| NEW_SECTION_H (nn).sh_type == SHT_DYNSYM)
if (new_shdr->sh_type == SHT_SYMTAB
|| new_shdr->sh_type == SHT_DYNSYM)
{
ElfW (Shdr) *spt = &NEW_SECTION_H (nn);
ptrdiff_t num = spt->sh_size / spt->sh_entsize;
ElfW (Sym) * sym = (ElfW (Sym) *) (NEW_SECTION_H (nn).sh_offset +
new_base);
ptrdiff_t num = new_shdr->sh_size / new_shdr->sh_entsize;
ElfW (Sym) *sym = (ElfW (Sym) *) (new_shdr->sh_offset + new_base);
for (; num--; sym++)
{
if ((sym->st_shndx == SHN_UNDEF)
@ -1186,15 +1179,16 @@ temacs:
{
byte *symnames;
ElfW (Sym) *symp, *symendp;
ElfW (Shdr) *sym_shdr = &NEW_SECTION_H (n);
if (NEW_SECTION_H (n).sh_type != SHT_DYNSYM
&& NEW_SECTION_H (n).sh_type != SHT_SYMTAB)
if (sym_shdr->sh_type != SHT_DYNSYM
&& sym_shdr->sh_type != SHT_SYMTAB)
continue;
symnames = ((byte *) new_base
+ NEW_SECTION_H (NEW_SECTION_H (n).sh_link).sh_offset);
symp = (ElfW (Sym) *) (NEW_SECTION_H (n).sh_offset + new_base);
symendp = (ElfW (Sym) *) ((byte *)symp + NEW_SECTION_H (n).sh_size);
+ NEW_SECTION_H (sym_shdr->sh_link).sh_offset);
symp = (ElfW (Sym) *) (sym_shdr->sh_offset + new_base);
symendp = (ElfW (Sym) *) ((byte *) symp + sym_shdr->sh_size);
for (; symp < symendp; symp ++)
{
@ -1218,22 +1212,21 @@ temacs:
if (strncmp ((char *) (symnames + symp->st_name),
"_OBJC_", sizeof ("_OBJC_") - 1) == 0)
{
caddr_t old, new;
ElfW (Shdr) *new_shdr = &NEW_SECTION_H (symp->st_shndx);
ptrdiff_t reladdr = symp->st_value - new_shdr->sh_addr;
ptrdiff_t newoff = reladdr + new_shdr->sh_offset;
new = ((symp->st_value - NEW_SECTION_H (symp->st_shndx).sh_addr)
+ NEW_SECTION_H (symp->st_shndx).sh_offset + new_base);
/* "Unpatch" index. */
nn = symp->st_shndx;
if (nn > old_bss_index)
nn--;
if (nn == old_bss_index)
memset (new, 0, symp->st_size);
memset (new_base + newoff, 0, symp->st_size);
else
{
old = ((symp->st_value
- NEW_SECTION_H (symp->st_shndx).sh_addr)
+ OLD_SECTION_H (nn).sh_offset + old_base);
memcpy (new, old, symp->st_size);
ElfW (Shdr) *old_shdr = &OLD_SECTION_H (nn);
ptrdiff_t oldoff = reladdr + old_shdr->sh_offset;
memcpy (new_base + newoff, old_base + oldoff, symp->st_size);
}
}
#endif
@ -1244,13 +1237,10 @@ temacs:
that it can undo relocations performed by the runtime linker. */
for (n = new_file_h->e_shnum; 0 < --n; )
{
ElfW (Shdr) section = NEW_SECTION_H (n);
ElfW (Shdr) *rel_shdr = &NEW_SECTION_H (n);
ElfW (Shdr) *shdr;
/* Cause a compilation error if anyone uses n instead of nn below. */
#define n ((void) 0);
n /* Prevent 'macro "n" is not used' warnings. */
switch (section.sh_type)
switch (rel_shdr->sh_type)
{
default:
break;
@ -1259,28 +1249,22 @@ temacs:
/* This code handles two different size structs, but there should
be no harm in that provided that r_offset is always the first
member. */
nn = section.sh_info;
if (!strcmp (old_section_names + NEW_SECTION_H (nn).sh_name, ".data")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".sdata")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".lit4")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".lit8")
shdr = &NEW_SECTION_H (rel_shdr->sh_info);
if (!strcmp (old_section_names + shdr->sh_name, ".data")
|| !strcmp (old_section_names + shdr->sh_name, ".sdata")
|| !strcmp (old_section_names + shdr->sh_name, ".lit4")
|| !strcmp (old_section_names + shdr->sh_name, ".lit8")
#ifdef IRIX6_5 /* see above */
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".got")
|| !strcmp (old_section_names + shdr->sh_name, ".got")
#endif
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".sdata1")
|| !strcmp ((old_section_names + NEW_SECTION_H (nn).sh_name),
".data1"))
|| !strcmp (old_section_names + shdr->sh_name, ".sdata1")
|| !strcmp (old_section_names + shdr->sh_name, ".data1"))
{
ElfW (Addr) offset = (NEW_SECTION_H (nn).sh_addr
- NEW_SECTION_H (nn).sh_offset);
caddr_t reloc = old_base + section.sh_offset, end;
for (end = reloc + section.sh_size; reloc < end;
reloc += section.sh_entsize)
ElfW (Addr) offset = shdr->sh_addr - shdr->sh_offset;
caddr_t reloc = old_base + rel_shdr->sh_offset, end;
for (end = reloc + rel_shdr->sh_size;
reloc < end;
reloc += rel_shdr->sh_entsize)
{
ElfW (Addr) addr = ((ElfW (Rel) *) reloc)->r_offset - offset;
#ifdef __alpha__
@ -1295,8 +1279,6 @@ temacs:
}
break;
}
#undef n
}
/* Write out new_file, and free the buffers. */