binutils-gdb/ld/scripttempl/pep.sc
Mark Harmstone 8819b23615 Avoid unaligned pointer reads in PEP .idata section
This is something I discovered when working on aarch64, though it's
relevant to x86_64 too.

The PE32+ imports are located in the .idata section, which starts off
with a 20-byte structure for each DLL, containing offsets into the rest
of the section. This is the Import Directory Table in
https://learn.microsoft.com/en-us/windows/win32/debug/pe-format, which
is a concatenation of the .idata$2 sections. This is then followed by an
20 zero bytes generated by the linker script, which calls this .idata$3.

After this comes the .idata$4 entries for each function, which the
loader overwrites with the function pointers. Because there's no padding
between .idata$3 and .idata$4, this means that if there's an even number
of DLLs, the function pointers won't be aligned on an 8-byte boundary.

Misaligned reads are slower on x86_64, but this is more important on
aarch64, as the e.g. `ldr x0, [x0, :lo12:__imp__func]` the compiler
might generate requires __imp__func (the .idata$4 entry) to be aligned
to 8 bytes. Without this you get IMAGE_REL_ARM64_PAGEOFFSET_12L overflow
errors.
2023-01-04 03:47:09 +00:00

512 lines
14 KiB
Scala

# Linker script for PE.
#
# Copyright (C) 2014-2023 Free Software Foundation, Inc.
#
# Copying and distribution of this file, with or without modification,
# are permitted in any medium without royalty provided the copyright
# notice and this notice are preserved.
if test -z "${RELOCATEABLE_OUTPUT_FORMAT}"; then
RELOCATEABLE_OUTPUT_FORMAT=${OUTPUT_FORMAT}
fi
# We can't easily and portably get an unquoted $ in a shell
# substitution, so we do this instead.
# Sorting of the .foo$* sections is required by the definition of
# grouped sections in PE.
# Sorting of the file names in R_IDATA is required by the
# current implementation of dlltool (this could probably be changed to
# use grouped sections instead).
if test "${RELOCATING}"; then
R_TEXT='*(SORT(.text$*))'
if test "x$LD_FLAG" = "xauto_import" ; then
R_DATA='*(SORT(.data$*))
*(.rdata)
*(SORT(.rdata$*))'
R_RDATA=''
else
R_DATA='*(SORT(.data$*))'
R_RDATA='*(.rdata)
*(SORT(.rdata$*))'
fi
R_IDATA234='
KEEP (SORT(*)(.idata$2))
KEEP (SORT(*)(.idata$3))
/* These zeroes mark the end of the import list. */
LONG (0); LONG (0); LONG (0); LONG (0); LONG (0);
. = ALIGN(8);
KEEP (SORT(*)(.idata$4))'
R_IDATA5='SORT(*)(.idata$5)'
R_IDATA67='
KEEP (SORT(*)(.idata$6))
KEEP (SORT(*)(.idata$7))'
R_CRT_XC='KEEP (*(SORT(.CRT$XC*))) /* C initialization */'
R_CRT_XI='KEEP (*(SORT(.CRT$XI*))) /* C++ initialization */'
R_CRT_XL='KEEP (*(SORT(.CRT$XL*))) /* TLS callbacks */'
R_CRT_XP='KEEP (*(SORT(.CRT$XP*))) /* Pre-termination */'
R_CRT_XT='KEEP (*(SORT(.CRT$XT*))) /* Termination */'
R_TLS='
KEEP (*(.tls$AAA))
KEEP (*(.tls))
KEEP (*(.tls$))
KEEP (*(SORT(.tls$*)))
KEEP (*(.tls$ZZZ))'
R_RSRC='
KEEP (*(.rsrc))
KEEP (*(.rsrc$*))'
else
R_TEXT=
R_DATA=
R_RDATA='*(.rdata)'
R_IDATA234=
R_IDATA5=
R_IDATA67=
R_CRT_XC=
R_CRT_XI=
R_CRT_XL=
R_CRT_XP=
R_CRT_XT=
R_TLS='*(.tls)'
R_RSRC='*(.rsrc)'
fi
cat <<EOF
/* Copyright (C) 2014-2023 Free Software Foundation, Inc.
Copying and distribution of this script, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. */
${RELOCATING+OUTPUT_FORMAT(${OUTPUT_FORMAT})}
${RELOCATING-OUTPUT_FORMAT(${RELOCATEABLE_OUTPUT_FORMAT})}
${OUTPUT_ARCH+OUTPUT_ARCH(${OUTPUT_ARCH})}
${LIB_SEARCH_DIRS}
SECTIONS
{
${RELOCATING+/* Make the virtual address and file offset synced if the alignment is}
${RELOCATING+ lower than the target page size. */}
${RELOCATING+. = SIZEOF_HEADERS;}
${RELOCATING+. = ALIGN(__section_alignment__);}
.text ${RELOCATING+ __image_base__ + ( __section_alignment__ < ${TARGET_PAGE_SIZE} ? . : __section_alignment__ )} :
{
${RELOCATING+KEEP (*(SORT_NONE(.init)))}
*(.text)
${R_TEXT}
${RELOCATING+ *(.text.*)}
${RELOCATING+ *(.gnu.linkonce.t.*)}
${RELOCATING+*(.glue_7t)}
${RELOCATING+*(.glue_7)}
${CONSTRUCTING+. = ALIGN(8);}
${CONSTRUCTING+
/* Note: we always define __CTOR_LIST__ and ___CTOR_LIST__ here,
we do not PROVIDE them. This is because the ctors.o startup
code in libgcc defines them as common symbols, with the
expectation that they will be overridden by the definitions
here. If we PROVIDE the symbols then they will not be
overridden and global constructors will not be run.
See PR 22762 for more details.
This does mean that it is not possible for a user to define
their own __CTOR_LIST__ and __DTOR_LIST__ symbols; if they do,
the content from those variables are included but the symbols
defined here silently take precedence. If they truly need to
be redefined, a custom linker script will have to be used.
(The custom script can just be a copy of this script with the
PROVIDE() qualifiers added).
In particular this means that ld -Ur does not work, because
the proper __CTOR_LIST__ set by ld -Ur is overridden by a
bogus __CTOR_LIST__ set by the final link. See PR 46. */
___CTOR_LIST__ = .;
__CTOR_LIST__ = .;
LONG (-1); LONG (-1);
KEEP (*(.ctors));
KEEP (*(.ctor));
KEEP (*(SORT_BY_NAME(.ctors.*)));
LONG (0); LONG (0);
}
${CONSTRUCTING+
/* See comment about __CTOR_LIST__ above. The same reasoning
applies here too. */
___DTOR_LIST__ = .;
__DTOR_LIST__ = .;
LONG (-1); LONG (-1);
KEEP (*(.dtors));
KEEP (*(.dtor));
KEEP (*(SORT_BY_NAME(.dtors.*)));
LONG (0); LONG (0);
}
${RELOCATING+KEEP (*(SORT_NONE(.fini)))}
${RELOCATING+/* ??? Why is .gcc_exc here? */}
${RELOCATING+ *(.gcc_exc)}
${RELOCATING+PROVIDE (etext = .);}
${RELOCATING+ KEEP (*(.gcc_except_table))}
}
/* The Cygwin32 library uses a section to avoid copying certain data
on fork. This used to be named ".data$nocopy". The linker used
to include this between __data_start__ and __data_end__, but that
breaks building the cygwin32 dll. Instead, we name the section
".data_cygwin_nocopy" and explicitly include it after __data_end__. */
.data ${RELOCATING+BLOCK(__section_alignment__)} :
{
${RELOCATING+__data_start__ = . ;}
*(.data)
${RELOCATING+*(.data2)}
${R_DATA}
KEEP(*(.jcr))
${RELOCATING+__data_end__ = . ;}
${RELOCATING+*(.data_cygwin_nocopy)}
}
.rdata ${RELOCATING+BLOCK(__section_alignment__)} :
{
${R_RDATA}
. = ALIGN(4);
${RELOCATING+__rt_psrelocs_start = .;}
${RELOCATING+KEEP(*(.rdata_runtime_pseudo_reloc))}
${RELOCATING+__rt_psrelocs_end = .;}
}
${RELOCATING+__rt_psrelocs_size = __rt_psrelocs_end - __rt_psrelocs_start;}
${RELOCATING+___RUNTIME_PSEUDO_RELOC_LIST_END__ = .;}
${RELOCATING+__RUNTIME_PSEUDO_RELOC_LIST_END__ = .;}
${RELOCATING+___RUNTIME_PSEUDO_RELOC_LIST__ = . - __rt_psrelocs_size;}
${RELOCATING+__RUNTIME_PSEUDO_RELOC_LIST__ = . - __rt_psrelocs_size;}
.eh_frame ${RELOCATING+BLOCK(__section_alignment__)} :
{
KEEP (*(.eh_frame${RELOCATING+*}))
}
.pdata ${RELOCATING+BLOCK(__section_alignment__)} :
{
KEEP(*(.pdata${RELOCATING+*}))
}
.xdata ${RELOCATING+BLOCK(__section_alignment__)} :
{
KEEP(*(.xdata${RELOCATING+*}))
}
.bss ${RELOCATING+BLOCK(__section_alignment__)} :
{
${RELOCATING+__bss_start__ = . ;}
*(.bss)
*(COMMON)
${RELOCATING+__bss_end__ = . ;}
}
.edata ${RELOCATING+BLOCK(__section_alignment__)} :
{
*(.edata)
}
/DISCARD/ :
{
*(.debug\$S)
*(.debug\$T)
*(.debug\$F)
${RELOCATING+ *(.drectve)}
${RELOCATING+ *(.note.GNU-stack)}
${RELOCATING+ *(.gnu.lto_*)}
}
.idata ${RELOCATING+BLOCK(__section_alignment__)} :
{
/* This cannot currently be handled with grouped sections.
See pep.em:sort_sections. */
${R_IDATA234}
${RELOCATING+__IAT_start__ = .;}
${R_IDATA5}
${RELOCATING+__IAT_end__ = .;}
${R_IDATA67}
}
.CRT ${RELOCATING+BLOCK(__section_alignment__)} :
{
${RELOCATING+___crt_xc_start__ = . ;}
${R_CRT_XC}
${RELOCATING+___crt_xc_end__ = . ;}
${RELOCATING+___crt_xi_start__ = . ;}
${R_CRT_XI}
${RELOCATING+___crt_xi_end__ = . ;}
${RELOCATING+___crt_xl_start__ = . ;}
${R_CRT_XL}
/* ___crt_xl_end__ is defined in the TLS Directory support code */
${RELOCATING+___crt_xp_start__ = . ;}
${R_CRT_XP}
${RELOCATING+___crt_xp_end__ = . ;}
${RELOCATING+___crt_xt_start__ = . ;}
${R_CRT_XT}
${RELOCATING+___crt_xt_end__ = . ;}
}
/* Windows TLS expects .tls\$AAA to be at the start and .tls\$ZZZ to be
at the end of the .tls section. This is important because _tls_start MUST
be at the beginning of the section to enable SECREL32 relocations with TLS
data. */
.tls ${RELOCATING+BLOCK(__section_alignment__)} :
{
${RELOCATING+___tls_start__ = . ;}
${R_TLS}
${RELOCATING+___tls_end__ = . ;}
}
.endjunk ${RELOCATING+BLOCK(__section_alignment__)} :
{
/* end is deprecated, don't use it */
${RELOCATING+PROVIDE (end = .);}
${RELOCATING+PROVIDE ( _end = .);}
${RELOCATING+ __end__ = .;}
}
.rsrc ${RELOCATING+BLOCK(__section_alignment__)} : SUBALIGN(4)
{
${R_RSRC}
}
.reloc ${RELOCATING+BLOCK(__section_alignment__)} :
{
*(.reloc)
}
.stab ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.stab)
}
.stabstr ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.stabstr)
}
/* DWARF debug sections.
Symbols in the DWARF debugging sections are relative to the beginning
of the section. Unlike other targets that fake this by putting the
section VMA at 0, the PE format will not allow it. */
/* DWARF 1.1 and DWARF 2. */
.debug_aranges ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_aranges)
}
.zdebug_aranges ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_aranges)
}
.debug_pubnames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_pubnames)
}
.zdebug_pubnames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_pubnames)
}
/* DWARF 2. */
.debug_info ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_info${RELOCATING+ .gnu.linkonce.wi.*})
}
.zdebug_info ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_info${RELOCATING+ .zdebug.gnu.linkonce.wi.*})
}
.debug_abbrev ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_abbrev)
}
.zdebug_abbrev ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_abbrev)
}
.debug_line ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_line)
}
.zdebug_line ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_line)
}
.debug_frame ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_frame*)
}
.zdebug_frame ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_frame*)
}
.debug_str ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_str)
}
.zdebug_str ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_str)
}
.debug_loc ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_loc)
}
.zdebug_loc ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_loc)
}
.debug_macinfo ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_macinfo)
}
.zdebug_macinfo ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_macinfo)
}
/* SGI/MIPS DWARF 2 extensions. */
.debug_weaknames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_weaknames)
}
.zdebug_weaknames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_weaknames)
}
.debug_funcnames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_funcnames)
}
.zdebug_funcnames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_funcnames)
}
.debug_typenames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_typenames)
}
.zdebug_typenames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_typenames)
}
.debug_varnames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_varnames)
}
.zdebug_varnames ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_varnames)
}
/* DWARF 3. */
.debug_pubtypes ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_pubtypes)
}
.zdebug_pubtypes ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_pubtypes)
}
.debug_ranges ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_ranges)
}
.zdebug_ranges ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_ranges)
}
/* DWARF 4. */
.debug_types ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_types${RELOCATING+ .gnu.linkonce.wt.*})
}
.zdebug_types ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_types${RELOCATING+ .gnu.linkonce.wt.*})
}
/* DWARF 5. */
.debug_addr ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_addr)
}
.zdebug_addr ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_addr)
}
.debug_line_str ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_line_str)
}
.zdebug_line_str ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_line_str)
}
.debug_loclists ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_loclists)
}
.zdebug_loclists ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_loclists)
}
.debug_macro ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_macro)
}
.zdebug_macro ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_macro)
}
.debug_names ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_names)
}
.zdebug_names ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_names)
}
.debug_rnglists ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_rnglists)
}
.zdebug_rnglists ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_rnglists)
}
.debug_str_offsets ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_str_offsets)
}
.zdebug_str_offsets ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_str_offsets)
}
.debug_sup ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_sup)
}
/* For Go and Rust. */
.debug_gdb_scripts ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.debug_gdb_scripts)
}
.zdebug_gdb_scripts ${RELOCATING+BLOCK(__section_alignment__)} ${RELOCATING+(NOLOAD)} :
{
*(.zdebug_gdb_scripts)
}
}
EOF