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compel/handle-elf: override unexpected precalculated addresses

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We've seen addresses in parasite.built-in.o precalculated by linker but
in some unexpected manner:

readelf -WS criu/pie/parasite.built-in.o
Section Headers:
  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
  [ 1] .text             PROGBITS        0000000000000000 000040 00400a 00  AX  0   0 16
  [87] .data             PROGBITS        0000000000000000 005000 000068 00  WA  0   0 4096
  [88] .rodata           PROGBITS        0000000000000080 005080 001016 00   A  0   0 32

(Notes: All other sections does not have SHF_ALLOC or are of size 0, so I
skip them. Need to add "-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1" to
CFLAGS to reproduce.)

Section 88 has address 0x80 in elf file but in our "consequent"
addresses precalculation algorithm it should be at 0x5080:

  addr(.text) == 0x0
  addr(.data) == 0x400a + (0x1000 - 0x400a % 0x1000) + 0x68 == 0x5068
  addr(.rodata) == 0x5068 + (0x20 - 0x5068 % 0x20) == 0x5080

Probably the linker advises us to move 4096 aligned section to the
beginning to save some space, but it's just a guess.

So probably we should be ready to "non-consequent" alignments
precalculated and just override them.

https://github.com/checkpoint-restore/criu/issues/1301

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
This commit is contained in:
Pavel Tikhomirov 2020-12-03 10:22:18 +03:00 committed by Andrei Vagin
parent 6a7bb0b9f6
commit 98fbb766d6
1 changed files with 5 additions and 7 deletions
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12
compel/src/lib/handle-elf.c
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@ -212,13 +212,11 @@ int __handle_elf(void *mem, size_t size)
if (sh->sh_addralign > 0 && k % sh->sh_addralign != 0) {
k += sh->sh_addralign - k % sh->sh_addralign;
}
if (sh->sh_addr && sh->sh_addr != k) {
pr_err("Unexpected precalculated address of section (section %s addr 0x%lx expected 0x%lx)\n",
&secstrings[sh->sh_name],
(unsigned long) sh->sh_addr,
(unsigned long) k);
goto err;
}
if (sh->sh_addr && sh->sh_addr != k)
pr_info("Overriding unexpected precalculated address of section (section %s addr 0x%lx expected 0x%lx)\n",
&secstrings[sh->sh_name],
(unsigned long) sh->sh_addr,
(unsigned long) k);
sh->sh_addr = k;
k += sh->sh_size;
}