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elfcopy/strip: Ensure sections have required alignment on output

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Object files may specify insufficient alignment on certain sections, for
example due to a bug in NASM[1].  When we detect that case in elfcopy or
strip, emit a warning and increase the alignment to the minimum
required.

The NASM bug was fixed in 2015[2], but we might as well have this fixup
(and warning) in elfcopy in case we encounter such a file for any other
reason.

This might be reworked somewhat upstream - see ELF Tool Chain
ticket 485[3].

[1] https://bugzilla.nasm.us/show_bug.cgi?id=3392307
[2] 1f0cb0f2c1
[3] https://sourceforge.net/p/elftoolchain/tickets/485/

PR:		198611
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D2292
This commit is contained in:
Ed Maste 2019-11-08 14:59:41 +00:00
parent 9dc7ed6253
commit 4133f23624
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=354544
1 changed files with 45 additions and 0 deletions
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45
contrib/elftoolchain/elfcopy/sections.c
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@ -879,6 +879,43 @@ pad_section(struct elfcopy *ecp, struct section *s)
elf_errmsg(-1));
}
static int
section_type_alignment(int sht, int class)
{
switch (sht)
{
case SHT_DYNAMIC:
case SHT_DYNSYM:
case SHT_FINI_ARRAY:
case SHT_GNU_HASH:
case SHT_INIT_ARRAY:
case SHT_PREINIT_ARRAY:
case SHT_REL:
case SHT_RELA:
case SHT_SYMTAB:
return (class == ELFCLASS64 ? 8 : 4);
case SHT_SUNW_move:
return (8);
case SHT_GNU_LIBLIST:
case SHT_GROUP:
case SHT_HASH:
case SHT_NOTE:
case SHT_SUNW_verdef: /* == SHT_GNU_verdef */
case SHT_SUNW_verneed: /* == SHT_GNU_verneed */
case SHT_SYMTAB_SHNDX:
return (4);
case SHT_SUNW_syminfo:
case SHT_SUNW_versym: /* == SHT_GNU_versym */
return (2);
case SHT_NOBITS:
case SHT_PROGBITS:
case SHT_STRTAB:
case SHT_SUNW_dof:
return (1);
}
return (1);
}
void
resync_sections(struct elfcopy *ecp)
{
@ -886,6 +923,7 @@ resync_sections(struct elfcopy *ecp)
GElf_Shdr osh;
uint64_t off;
int first;
int min_alignment;
ps = NULL;
first = 1;
@ -908,6 +946,12 @@ resync_sections(struct elfcopy *ecp)
/* Align section offset. */
if (s->align == 0)
s->align = 1;
min_alignment = section_type_alignment(s->type, ecp->oec);
if (s->align < INT_MAX && (int)s->align < min_alignment) {
warnx("section %s alignment %d increased to %d",
s->name, (int)s->align, min_alignment);
s->align = min_alignment;
}
if (off <= s->off) {
if (!s->loadable || (ecp->flags & RELOCATABLE))
s->off = roundup(off, s->align);
@ -937,6 +981,7 @@ resync_sections(struct elfcopy *ecp)
errx(EXIT_FAILURE, "gelf_getshdr() failed: %s",
elf_errmsg(-1));
osh.sh_addr = s->vma;
osh.sh_addralign = s->align;
osh.sh_offset = s->off;
osh.sh_size = s->sz;
if (!gelf_update_shdr(s->os, &osh))