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PR28824, relro security issues, x86 keep COMMONPAGESIZE relro

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x86 treats MAXPAGESIZE as a memory optimisation parameter, actual
hardware paging is always COMMPAGESIZE of 4k.  Use COMMONPAGESIZE for
the end of the relro segment alignment.

The previous patch regresses pr18176, increasing the testcase file
size from 322208 to 2099872 bytes.  Fixing this on x86 will require
introducing a gap after the end of the relro segment (of up to
relropagesize-1 bytes).

	PR 28824
	PR 18176
	* ld.h (ld_config_type): Add relro_use_commonpagesize field.
	* ldexp.c (fold_segment_align): Set relropagesize depending on
	relro_use_commonpagesize.
	* emultempl/elf-x86.em (elf_x86_create_output_section_statements):
	Set relro_use_commonpagesize.
	* testsuite/ld-x86-64/pr18176.d: xfail.
This commit is contained in:
Alan Modra 2022-02-03 08:57:47 +10:30
parent 9833b7757d
commit 31b4d3a16f
4 changed files with 10 additions and 1 deletions
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1
ld/emultempl/elf-x86.em
View File

@ -33,6 +33,7 @@ static struct elf_linker_x86_params params;
static void
elf_x86_create_output_section_statements (void)
{
config.relro_use_commonpagesize = true;
_bfd_elf_linker_x86_set_options (&link_info, &params);
}

4
ld/ld.h
View File

@ -276,6 +276,10 @@ typedef struct
/* If set, code and non-code sections should never be in one segment. */
bool separate_code;
/* TRUE if the end of the relro segment should be aligned to
COMMONPAGESIZE rather than MAXPAGESIZE. */
bool relro_use_commonpagesize;
/* The rpath separation character. Usually ':'. */
char rpath_separator;

5
ld/ldexp.c
View File

@ -481,7 +481,10 @@ fold_segment_align (seg_align_type *seg, etree_value_type *lhs)
seg->base = expld.result.value;
seg->commonpagesize = commonpage;
seg->maxpagesize = maxpage;
seg->relropagesize = maxpage;
if (config.relro_use_commonpagesize)
seg->relropagesize = commonpage;
else
seg->relropagesize = maxpage;
seg->relro_end = 0;
}
else

1
ld/testsuite/ld-x86-64/pr18176.d
View File

@ -3,6 +3,7 @@
#ld: -melf_x86_64 -shared -z relro -T pr18176.t -z max-page-size=0x200000 -z common-page-size=0x1000 $NO_DT_RELR_LDFLAGS
#readelf: -l --wide
#target: x86_64-*-linux*
#xfail: *-*-*
#...
GNU_RELRO 0x04bd17 0x000000000024bd17 0x000000000024bd17 0x0022e9 0x0022e9 R 0x1