ld: optionally emit _etext last, before .data
Hans-Peter Nilsson
hp@bitrange.com
Sat Jul 18 00:55:56 GMT 2020
So, here's my suggestion for making _init .. __etext cover .text +
.rodata (including things like the read-only exception tables) for
elf64mmix. A quick web search gives that __etext (and friends) isn't
well defined, so each target can interpret the "end of text segment"
to their own liking. It seems likely this change is also a better fit
than the default for other ports, at least those with .rodata after
.text in the same segment.
The presence of a separate rodata-segment is optional (and not true
for elf64mmix). This is reflected in the name as SEPARATE_TEXT /
SEPARATE_CODE isn't considered, to keep it simple; each target has to
make sure their settings of variables make sense.
Ok to commit?
ld:
* scripttempl/elf.sc (ETEXT_LAST_IN_RODATA_SEGMENT): New variable.
* emulparams/elf64mmix.sh (ETEXT_LAST_IN_RODATA_SEGMENT): Define.
* testsuite/ld-mmix/sec-1.d: Adjust.
diff --git a/ld/emulparams/elf64mmix.sh b/ld/emulparams/elf64mmix.sh
index dffc6cc..75e24be 100644
--- a/ld/emulparams/elf64mmix.sh
+++ b/ld/emulparams/elf64mmix.sh
@@ -44,6 +44,10 @@ ${RELOCATING+
PROVIDE (Main = DEFINED (Main) ? Main : (DEFINED (_start) ? _start : _start.));
}"
+# We need a symbol at the end of the read-only data, which is
+# colocated with the code. We make __etext fit.
+ETEXT_LAST_IN_RODATA_SEGMENT=" "
+
OTHER_SECTIONS='
.MMIX.reg_contents :
{
diff --git a/ld/scripttempl/elf.sc b/ld/scripttempl/elf.sc
index 0b8b32a..eb74743 100644
--- a/ld/scripttempl/elf.sc
+++ b/ld/scripttempl/elf.sc
@@ -62,6 +62,9 @@
# OTHER_SYMBOLS - symbols to place right at the end of the script.
# ETEXT_NAME - name of a symbol for the end of the text section,
# normally etext.
+# ETEXT_LAST_IN_RODATA_SEGMENT - emit ETEXT_NAME after all sections in
+# the read-only data segment (which may or may not be equal to
+# the code segment), instead of after just the code parts.
# SEPARATE_CODE - if set, .text and similar sections containing
# actual machine instructions must be in wholly disjoint
# pages from any other data, including headers
@@ -526,9 +529,9 @@ cat <<EOF
KEEP (*(SORT_NONE(.fini)))
${RELOCATING+${FINI_END}}
} ${FILL}
- ${RELOCATING+PROVIDE (__${ETEXT_NAME} = .);}
- ${RELOCATING+PROVIDE (_${ETEXT_NAME} = .);}
- ${RELOCATING+PROVIDE (${ETEXT_NAME} = .);}
+ ${RELOCATING+${ETEXT_LAST_IN_RODATA_SEGMENT-PROVIDE (__${ETEXT_NAME} = .);}}
+ ${RELOCATING+${ETEXT_LAST_IN_RODATA_SEGMENT-PROVIDE (_${ETEXT_NAME} = .);}}
+ ${RELOCATING+${ETEXT_LAST_IN_RODATA_SEGMENT-PROVIDE (${ETEXT_NAME} = .);}}
${RELOCATING+${TEXT_SEGMENT_ALIGN}}
EOF
@@ -574,6 +577,10 @@ cat <<EOF
.exception_ranges ${RELOCATING-0} : ONLY_IF_RO { *(.exception_ranges${RELOCATING+*}) }
${TEXT_PLT+${PLT_NEXT_DATA+${PLT} ${OTHER_PLT_SECTIONS}}}
+ ${RELOCATING+${ETEXT_LAST_IN_RODATA_SEGMENT+PROVIDE (__${ETEXT_NAME} = .);}}
+ ${RELOCATING+${ETEXT_LAST_IN_RODATA_SEGMENT+PROVIDE (_${ETEXT_NAME} = .);}}
+ ${RELOCATING+${ETEXT_LAST_IN_RODATA_SEGMENT+PROVIDE (${ETEXT_NAME} = .);}}
+
${RELOCATING+/* Adjust the address for the data segment. We want to adjust up to
the same address within the page on the next page up. */}
${CREATE_SHLIB-${CREATE_PIE-${RELOCATING+. = ${DATA_ADDR-${DATA_SEGMENT_ALIGN}};}}}
diff --git a/ld/testsuite/ld-mmix/sec-1.d b/ld/testsuite/ld-mmix/sec-1.d
index 5e31b3f..6f82c8e 100644
--- a/ld/testsuite/ld-mmix/sec-1.d
+++ b/ld/testsuite/ld-mmix/sec-1.d
@@ -24,7 +24,7 @@ Idx Name Size VMA LMA File off Algn
SYMBOL TABLE:
#...
-0+1d g +\*ABS\* _etext
+0+30 g +\*ABS\* _etext
#...
2000000000000013 g +\*ABS\* __bss_start
2000000000000013 g +\*ABS\* _edata
brgds, H-P
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