Align linkerscript symbols according to ABI
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Commit Message
Apply ABI specific alignment to symbols generated in the default
linker script.
No regressions on x86 and s390x. Linkerscript on x86 does not change
with that.
Ok for mainline?
Bye,
Andreas
--- ld/emulparams/elf64_s390.sh | 1 +
ld/emulparams/elf_s390.sh | 1 + ld/scripttempl/elf.sc | 50
+++++++++++++++++++++++-------------- 3 files changed, 33
insertions(+), 19 deletions(-)
Comments
Hi Andreas,
> Apply ABI specific alignment to symbols generated in the default
> linker script.
>
> No regressions on x86 and s390x. Linkerscript on x86 does not change
> with that.
>
> Ok for mainline?
Approved - please apply.
I suspect that we will get some complaints about using a user defined
function in a shell script. Presumably from people where /bin/sh is a
shell interpreter that does not support user functions. Maybe I am
being pessimistic however. Surely these days everyone is using a modern
interpreter ?
Cheers
Nick
On 7/5/23 11:44, Nick Clifton wrote:
> Hi Andreas,
>
>> Apply ABI specific alignment to symbols generated in the default
>> linker script.
>>
>> No regressions on x86 and s390x. Linkerscript on x86 does not change
>> with that.
>>
>> Ok for mainline?
>
> Approved - please apply.
Thanks!
> I suspect that we will get some complaints about using a user defined
> function in a shell script. Presumably from people where /bin/sh is a
> shell interpreter that does not support user functions. Maybe I am
> being pessimistic however. Surely these days everyone is using a modern
> interpreter ?
ld/genscripts.sh already uses a couple of shell functions. So I hope it doesn't create new issues.
Bye,
Andreas
On Wed, Jul 05, 2023 at 11:53:35AM +0200, Andreas Krebbel via Binutils wrote:
> >> Apply ABI specific alignment to symbols generated in the default
> >> linker script.
I think this change is potentially wrong for symbols defined inside an
output section. Do you really want symbols marking the start and end
of a section to disagree with the actual section, if the section
itself is wrongly aligned?
On 7/7/23 05:03, Alan Modra wrote:
> On Wed, Jul 05, 2023 at 11:53:35AM +0200, Andreas Krebbel via Binutils wrote:
>>>> Apply ABI specific alignment to symbols generated in the default
>>>> linker script.
>
> I think this change is potentially wrong for symbols defined inside an
> output section. Do you really want symbols marking the start and end
> of a section to disagree with the actual section, if the section
> itself is wrongly aligned?
Hopefully all our output sections are at least aligned to our symbol ABI alignment otherwise that's
what I would fix I guess. You are right that having a gap there would be bad.
Andreas
Align dot before symbols defined outside of output sections. Before _end
is already aligned.
I'm inclined to think that with this patch the alignment in def_symbol
ought to disappear, but for now I'm leaving it in.
* scripttempl/elf.sc (def_symbol): Tidy excess space.
(_edata): Align before emitting symbol when SYMBOL_ABI_ALIGNMENT.
diff --git a/ld/scripttempl/elf.sc b/ld/scripttempl/elf.sc
index 9e95e6b4162..bfd8b5ed4b3 100644
--- a/ld/scripttempl/elf.sc
+++ b/ld/scripttempl/elf.sc
@@ -171,7 +171,7 @@ fi
def_symbol()
{
if [ -z "${SYMBOL_ABI_ALIGNMENT}" ]; then
- echo "${USER_LABEL_PREFIX}$1 = . "
+ echo "${USER_LABEL_PREFIX}$1 = ."
else
echo "${USER_LABEL_PREFIX}$1 = ALIGN(${SYMBOL_ABI_ALIGNMENT})"
fi
@@ -688,6 +688,7 @@ cat <<EOF
${SDATA_GOT+${OTHER_GOT_SECTIONS}}
${DATA_SDATA-${SDATA}}
${DATA_SDATA-${OTHER_SDATA_SECTIONS}}
+ ${RELOCATING+${SYMBOL_ABI_ALIGNMENT+. = ALIGN(${SYMBOL_ABI_ALIGNMENT});}}
${RELOCATING+${DATA_END_SYMBOLS-${CREATE_SHLIB+PROVIDE (}$(def_symbol "_edata")${CREATE_SHLIB+)}; PROVIDE ($(def_symbol "edata"));}}
${PERSISTENT}
${RELOCATING+. = .;}
@@ -17,6 +17,7 @@ EXTRA_EM_FILE=s390
IREL_IN_PLT=
SEPARATE_GOTPLT=0
test -z "$RELRO" && unset SEPARATE_GOTPLT
+SYMBOL_ABI_ALIGNMENT=2
# Treat a host that matches the target with the possible exception of "x"
# in the name as if it were native.
@@ -12,3 +12,4 @@ GENERATE_SHLIB_SCRIPT=yes
GENERATE_PIE_SCRIPT=yes
NO_SMALL_DATA=yes
IREL_IN_PLT=
+SYMBOL_ABI_ALIGNMENT=2
@@ -78,6 +78,8 @@
# USER_LABEL_PREFIX - prefix to add to user-visible symbols.
# RODATA_NAME, SDATA_NAME, SBSS_NAME, BSS_NAME - base parts of names
# for standard sections, without initial "." or suffixes.
+# SYMBOL_ABI_ALIGNMENT - minimum alignment in bytes which needs to be
+# applied to every symbol definition
#
# When adding sections, do note that the names of some sections are used
# when specifying the start address of the next.
@@ -165,19 +167,29 @@ if test -z "$GOT"; then
GOTPLT=".got.plt ${RELOCATING-0} : { *(.got.plt)${RELOCATING+ *(.igot.plt)} }"
fi
fi
+
+def_symbol()
+{
+ if [ -z "${SYMBOL_ABI_ALIGNMENT}" ]; then
+ echo "${USER_LABEL_PREFIX}$1 = . "
+ else
+ echo "${USER_LABEL_PREFIX}$1 = ALIGN(${SYMBOL_ABI_ALIGNMENT})"
+ fi
+}
+
REL_IFUNC=".rel.ifunc ${RELOCATING-0} : { *(.rel.ifunc) }"
RELA_IFUNC=".rela.ifunc ${RELOCATING-0} : { *(.rela.ifunc) }"
REL_IPLT=".rel.iplt ${RELOCATING-0} :
{
- ${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__rel_iplt_start = .);}}
+ ${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN ($(def_symbol "__rel_iplt_start"));}}
*(.rel.iplt)
- ${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__rel_iplt_end = .);}}
+ ${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN ($(def_symbol "__rel_iplt_end"));}}
}"
RELA_IPLT=".rela.iplt ${RELOCATING-0} :
{
- ${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__rela_iplt_start = .);}}
+ ${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN ($(def_symbol "__rela_iplt_start"));}}
*(.rela.iplt)
- ${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__rela_iplt_end = .);}}
+ ${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN ($(def_symbol "__rela_iplt_end"));}}
}"
DYNAMIC=".dynamic ${RELOCATING-0} : { *(.dynamic) }"
RODATA=".${RODATA_NAME} ${RELOCATING-0} : { *(.${RODATA_NAME}${RELOCATING+ .${RODATA_NAME}.* .gnu.linkonce.r.*}) }"
@@ -267,23 +279,23 @@ else
fi
PREINIT_ARRAY=".preinit_array :
{
- ${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__preinit_array_start = .);}
+ ${CREATE_SHLIB-PROVIDE_HIDDEN ($(def_symbol "__preinit_array_start"));}
KEEP (*(.preinit_array))
- ${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__preinit_array_end = .);}
+ ${CREATE_SHLIB-PROVIDE_HIDDEN ($(def_symbol "__preinit_array_end"));}
}"
INIT_ARRAY=".init_array :
{
- ${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__init_array_start = .);}
+ ${CREATE_SHLIB-PROVIDE_HIDDEN ($(def_symbol "__init_array_start"));}
${SORT_INIT_ARRAY}
KEEP (*(.init_array ${CTORS_IN_INIT_ARRAY}))
- ${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__init_array_end = .);}
+ ${CREATE_SHLIB-PROVIDE_HIDDEN ($(def_symbol "__init_array_end"));}
}"
FINI_ARRAY=".fini_array :
{
- ${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__fini_array_start = .);}
+ ${CREATE_SHLIB-PROVIDE_HIDDEN ($(def_symbol "__fini_array_start"));}
${SORT_FINI_ARRAY}
KEEP (*(.fini_array ${DTORS_IN_FINI_ARRAY}))
- ${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__fini_array_end = .);}
+ ${CREATE_SHLIB-PROVIDE_HIDDEN ($(def_symbol "__fini_array_end"));}
}"
CTOR=".ctors ${CONSTRUCTING-0} :
{
@@ -323,7 +335,7 @@ DTOR=".dtors ${CONSTRUCTING-0} :
}"
STACK=".stack ${RELOCATING-0}${RELOCATING+${STACK_ADDR}} :
{
- ${RELOCATING+${USER_LABEL_PREFIX}_stack = .;}
+ ${RELOCATING+$(def_symbol "_stack");}
*(.stack)
${RELOCATING+${STACK_SENTINEL}}
}"
@@ -494,16 +506,16 @@ cat >> ldscripts/dyntmp.$$ <<EOF
.rel.plt ${RELOCATING-0} :
{
*(.rel.plt)
- ${IREL_IN_PLT+${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__rel_iplt_start = .);}}}
+ ${IREL_IN_PLT+${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN ($(def_symbol "__rel_iplt_start"));}}}
${IREL_IN_PLT+${RELOCATING+*(.rel.iplt)}}
- ${IREL_IN_PLT+${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__rel_iplt_end = .);}}}
+ ${IREL_IN_PLT+${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN ($(def_symbol "__rel_iplt_end"));}}}
}
.rela.plt ${RELOCATING-0} :
{
*(.rela.plt)
- ${IREL_IN_PLT+${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__rela_iplt_start = .);}}}
+ ${IREL_IN_PLT+${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN ($(def_symbol "__rela_iplt_start"));}}}
${IREL_IN_PLT+${RELOCATING+*(.rela.iplt)}}
- ${IREL_IN_PLT+${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__rela_iplt_end = .);}}}
+ ${IREL_IN_PLT+${RELOCATING+${CREATE_PIC-PROVIDE_HIDDEN ($(def_symbol "__rela_iplt_end"));}}}
}
${OTHER_PLT_RELOC_SECTIONS}
EOF
@@ -628,7 +640,7 @@ cat <<EOF
/* Thread Local Storage sections */
.tdata ${RELOCATING-0} :
{
- ${RELOCATING+${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__tdata_start = .);}}
+ ${RELOCATING+${CREATE_SHLIB-PROVIDE_HIDDEN ($(def_symbol "__tdata_start"));}}
*(.tdata${RELOCATING+ .tdata.* .gnu.linkonce.td.*})
}
.tbss ${RELOCATING-0} : { *(.tbss${RELOCATING+ .tbss.* .gnu.linkonce.tb.*})${RELOCATING+ *(.tcommon)} }
@@ -676,10 +688,10 @@ cat <<EOF
${SDATA_GOT+${OTHER_GOT_SECTIONS}}
${DATA_SDATA-${SDATA}}
${DATA_SDATA-${OTHER_SDATA_SECTIONS}}
- ${RELOCATING+${DATA_END_SYMBOLS-${CREATE_SHLIB+PROVIDE (}${USER_LABEL_PREFIX}_edata = .${CREATE_SHLIB+)}; PROVIDE (${USER_LABEL_PREFIX}edata = .);}}
+ ${RELOCATING+${DATA_END_SYMBOLS-${CREATE_SHLIB+PROVIDE (}$(def_symbol "_edata")${CREATE_SHLIB+)}; PROVIDE ($(def_symbol "edata"));}}
${PERSISTENT}
${RELOCATING+. = .;}
- ${RELOCATING+${CREATE_SHLIB+PROVIDE (}${USER_LABEL_PREFIX}__bss_start = .${CREATE_SHLIB+)};}
+ ${RELOCATING+${CREATE_SHLIB+PROVIDE (}$(def_symbol "__bss_start")${CREATE_SHLIB+)};}
${RELOCATING+${OTHER_BSS_SYMBOLS}}
${DATA_SDATA-${SBSS}}
${BSS_PLT+${PLT}}
@@ -713,7 +725,7 @@ cat <<EOF
${LARGE_BSS_AFTER_BSS-${LARGE_BSS}}
${RELOCATING+. = ALIGN(${ALIGNMENT});}
${RELOCATING+${OTHER_END_SYMBOLS}}
- ${RELOCATING+${END_SYMBOLS-${CREATE_SHLIB+PROVIDE (}${USER_LABEL_PREFIX}_end = .${CREATE_SHLIB+)}; PROVIDE (${USER_LABEL_PREFIX}end = .);}}
+ ${RELOCATING+${END_SYMBOLS-${CREATE_SHLIB+PROVIDE (}$(def_symbol "_end")${CREATE_SHLIB+)}; PROVIDE ($(def_symbol "end"));}}
${RELOCATING+${DATA_SEGMENT_END}}
${TINY_DATA_SECTION}
${TINY_BSS_SECTION}