[Patch] Gas support for MIPS Compact EH
Richard Sandiford
rdsandiford@googlemail.com
Wed Mar 19 23:45:00 GMT 2014
"Moore, Catherine" <Catherine_Moore@mentor.com> writes:
> I've been working on getting ".word X-." to work in the assembler. It looks like I can produce the relocation, but I'm seeing failures for the lui-1.s and lui-2.s tests.
> I've added these two definitions to tc-mips.h:
>
> +#define DIFF_EXPR_OK
> +#define md_register_arithmetic 0
>
> The first thing is that I'm not sure if the setting for md_register_arithmetic is correct. The MIPS port currently uses the default of 1 (that's got to be wrong).
> There is interaction between DIFF_EXPR_OK, md_register_arithmetic and the FORCE_RELOC macros that is confusing.
>
> This definition of TC_FORCE_RELOCATION_SUB_LOCAL (write.c) needs to have md_register_arithmetic defined to zero, when DIFF_EXPR_OK is set.
>
> #ifndef TC_FORCE_RELOCATION_SUB_LOCAL
> #ifdef DIFF_EXPR_OK
> #define TC_FORCE_RELOCATION_SUB_LOCAL(FIX, SEG) \
> (!md_register_arithmetic && (SEG) == reg_section)
> #else
> #define TC_FORCE_RELOCATION_SUB_LOCAL(FIX, SEG) 1
> #endif
> #endif
>
> Needs to have md_register_arithmetic set to zero if DIFF_EXPR_OK is set.
I think we should leave md_register_arithmetic as it is. The
"(SEG) == reg_section" means that the special handling only applies
to "register minus something" expressions.
> Assuming that defining md_register_arithmetic to zero is the correct thing to do, then the error message in md_pcrel_from looks wrong:
>
> long
> md_pcrel_from (fixS *fixP)
> {
> valueT addr = fixP->fx_where + fixP->fx_frag->fr_address;
> switch (fixP->fx_r_type)
> {
> case BFD_RELOC_MICROMIPS_7_PCREL_S1:
> case BFD_RELOC_MICROMIPS_10_PCREL_S1:
> /* Return the address of the delay slot. */
> return addr + 2;
>
> case BFD_RELOC_MICROMIPS_16_PCREL_S1:
> case BFD_RELOC_MICROMIPS_JMP:
> case BFD_RELOC_16_PCREL_S2:
> case BFD_RELOC_MIPS_JMP:
> /* Return the address of the delay slot. */
> return addr + 4;
>
> case BFD_RELOC_32_PCREL:
> return addr;
>
> default:
> /* We have no relocation type for PC relative MIPS16 instructions. */
> if (fixP->fx_addsy && S_GET_SEGMENT (fixP->fx_addsy) != now_seg)
> as_bad_where (fixP->fx_file, fixP->fx_line,
> _("PC relative MIPS16 instruction references"
> " a different section"));
> return addr;
> }
> }
>
>
> fixup_segment now treats many relocs as "possibly pc-relative" and waits for md_apply_fix to make the call.
> Should the default be to return addr for any reloc that's encountered and try to process errors later? I don't have any state on how a MIPS16 reloc ends up here.
The change comes from:
https://www.sourceware.org/ml/binutils/2006-11/msg00029.html
but I'm not sure which case it was handling.
I agree it'd make sense to check this elsewhere. I think the best place
would be...
> Then there is an assert in md_apply_fix that assumes a pc relative reloc is one of a handful of relocs. The fx_pcrel field needs to be reset for relocations that aren't pc-relative. Is md_apply_fix the correct place to do that?
...instead of this assert.
> Then the test cases in question. This is lui-1.s:
>
> .text
> foo:
> lui $2, -1
> lui $2, 65536
> lui $2, 0x10000000000000000
> lui $2, $3
> lui $2, ($3)
> lui $2, 0+$3 <<--- this statement
> lui $2, (($3))
>
> Old error message:
> lui-1.s:10: Error: register value used as expression `lui $2,0+$3'
>
> New error message:
> None, for the entire test case, but a new file with just the offending line causes a assertion failure in bfd_elf32_swap_symbol_out. (That's wrong, I need to track it down).
Yeah, this is a consequence of changing md_register_arithmetic.
The old behaviour was right.
> Then lui-2.s:
>
> .text
> foo:
> lui $2, bar - foo
> lui $2, baz - bar
> lui $2, foo - baz
> lui $2, bar / baz
>
> Should any of these be supported now?
>
> Old error messages:
> lui-2.s:10: Error: invalid operands (*UND* and *UND* sections) for `/'
> lui-2.s:7: Error: can't resolve `bar' {*UND* section} - `foo' {.text section}
> lui-2.s:8: Error: can't resolve `baz' {*UND* section} - `bar' {*UND* section}
> lui-2.s:9: Error: can't resolve `.text' {.text section} - `baz' {*UND* section}
>
> New error messages:
> lui-2.s:10: Error: invalid operands (*UND* and *UND* sections) for `/'
> lui-2.s:8: Error: can't resolve `baz' {*UND* section} - `bar' {*UND* section}
> lui-2.s:9: Error: can't resolve `.text' {.text section} - `baz' {*UND* section}
>
> Notice that lui $2 bar-foo seems to be accepted. Should it be?
No, the old behaviour was right here too, since we don't have a PC-relative
form of R_MIPS_LO16. The new error you mentioned should catch it.
How about the patch below? Tested on various MIPSy targets against
the binutils testsuite, but nothing beyond that so far.
Thanks,
Richard
gas/
* config/tc-mips.h (DIFF_EXPR_OK, CFI_DIFF_EXPR_OK): Define.
* config/tc-mips.c (md_pcrel_from): Remove error message.
(md_apply_fix): Convert PC-relative BFD_RELOC_32s to
BFD_RELOC_32_PCREL. Report a specific error message for unhandled
PC-relative expressions. Handle BFD_RELOC_8.
gas/testsuite/
* gas/all/gas.exp: Remove XFAIL of forward.d for MIPS.
* gas/mips/pcrel-1.s, gas/mips/pcrel-1.d, gas/mips/pcrel-2.s,
gas/mips/pcrel-2.d, gas/mips/pcrel-3.s, gas/mips/pcrel-3.l,
gas/mips/pcrel-4.s, gas/mips/pcrel-4-32.d, gas/mips/pcrel-4-n32.d,
gas/mips/pcrel-4-64.d: New tests.
* gas/mips/mips.exp: Run them.
* gas/mips/lui-2.l: Tweak error message for line 7.
ld/testsuite/
* ld-elf/merge.d: Remove MIPS XFAIL.
Index: gas/config/tc-mips.h
===================================================================
--- gas/config/tc-mips.h 2014-03-19 22:44:18.584854477 +0000
+++ gas/config/tc-mips.h 2014-03-19 23:43:50.695861764 +0000
@@ -189,4 +189,9 @@ extern int tc_mips_regname_to_dw2regnum
#define DWARF2_DEFAULT_RETURN_COLUMN 31
#define DWARF2_CIE_DATA_ALIGNMENT (-4)
+#define DIFF_EXPR_OK
+/* We define DIFF_EXPR_OK because of R_MIPS_PC32, but we have no
+ 64-bit form for n64 CFIs. */
+#define CFI_DIFF_EXPR_OK 0
+
#endif /* TC_MIPS */
Index: gas/config/tc-mips.c
===================================================================
--- gas/config/tc-mips.c 2014-03-19 22:44:18.584854477 +0000
+++ gas/config/tc-mips.c 2014-03-19 23:12:27.340621113 +0000
@@ -14057,15 +14057,7 @@ md_pcrel_from (fixS *fixP)
/* Return the address of the delay slot. */
return addr + 4;
- case BFD_RELOC_32_PCREL:
- return addr;
-
default:
- /* We have no relocation type for PC relative MIPS16 instructions. */
- if (fixP->fx_addsy && S_GET_SEGMENT (fixP->fx_addsy) != now_seg)
- as_bad_where (fixP->fx_file, fixP->fx_line,
- _("PC relative MIPS16 instruction references"
- " a different section"));
return addr;
}
}
@@ -14262,13 +14254,38 @@ md_apply_fix (fixS *fixP, valueT *valP,
unsigned long insn;
reloc_howto_type *howto;
- /* We ignore generic BFD relocations we don't know about. */
- howto = bfd_reloc_type_lookup (stdoutput, fixP->fx_r_type);
- if (! howto)
- return;
+ if (fixP->fx_pcrel)
+ switch (fixP->fx_r_type)
+ {
+ case BFD_RELOC_16_PCREL_S2:
+ case BFD_RELOC_MICROMIPS_7_PCREL_S1:
+ case BFD_RELOC_MICROMIPS_10_PCREL_S1:
+ case BFD_RELOC_MICROMIPS_16_PCREL_S1:
+ case BFD_RELOC_32_PCREL:
+ break;
+
+ case BFD_RELOC_32:
+ fixP->fx_r_type = BFD_RELOC_32_PCREL;
+ break;
+
+ default:
+ as_bad_where (fixP->fx_file, fixP->fx_line,
+ _("PC-relative reference to a different section"));
+ break;
+ }
+
+ /* Handle BFD_RELOC_8, since it's easy. Punt on other bfd relocations
+ that have no MIPS ELF equivalent. */
+ if (fixP->fx_r_type != BFD_RELOC_8)
+ {
+ howto = bfd_reloc_type_lookup (stdoutput, fixP->fx_r_type);
+ if (!howto)
+ return;
+ }
gas_assert (fixP->fx_size == 2
|| fixP->fx_size == 4
+ || fixP->fx_r_type == BFD_RELOC_8
|| fixP->fx_r_type == BFD_RELOC_16
|| fixP->fx_r_type == BFD_RELOC_64
|| fixP->fx_r_type == BFD_RELOC_CTOR
@@ -14280,12 +14297,6 @@ md_apply_fix (fixS *fixP, valueT *valP,
buf = fixP->fx_frag->fr_literal + fixP->fx_where;
- gas_assert (!fixP->fx_pcrel || fixP->fx_r_type == BFD_RELOC_16_PCREL_S2
- || fixP->fx_r_type == BFD_RELOC_MICROMIPS_7_PCREL_S1
- || fixP->fx_r_type == BFD_RELOC_MICROMIPS_10_PCREL_S1
- || fixP->fx_r_type == BFD_RELOC_MICROMIPS_16_PCREL_S1
- || fixP->fx_r_type == BFD_RELOC_32_PCREL);
-
/* Don't treat parts of a composite relocation as done. There are two
reasons for this:
@@ -14435,6 +14446,7 @@ md_apply_fix (fixS *fixP, valueT *valP,
case BFD_RELOC_32:
case BFD_RELOC_32_PCREL:
case BFD_RELOC_16:
+ case BFD_RELOC_8:
/* If we are deleting this reloc entry, we must fill in the
value now. This can happen if we have a .word which is not
resolved when it appears but is later defined. */
Index: gas/testsuite/gas/all/gas.exp
===================================================================
--- gas/testsuite/gas/all/gas.exp 2014-03-19 21:26:29.344209431 +0000
+++ gas/testsuite/gas/all/gas.exp 2014-03-19 23:28:58.492008472 +0000
@@ -99,7 +99,7 @@ case $target_triplet in {
default {
# Some targets don't manage to resolve BFD_RELOC_8 for constants.
setup_xfail "alpha*-*-*" "*c30*-*-*" "*c4x*-*-*" \
- "d\[13\]0v*-*-*" "i860-*-*" "mips*-*-*" \
+ "d\[13\]0v*-*-*" "i860-*-*" \
"nds32*-*-*" "pdp11-*-*" "xtensa*-*-*"
run_dump_test forward
}
Index: gas/testsuite/gas/mips/pcrel-1.s
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-1.s 2014-03-19 23:12:27.341621122 +0000
@@ -0,0 +1,13 @@
+ .text
+ .ent func
+func:
+ lui $4,%hi(foo-.)
+ addiu $4,%lo(foo-.)
+ .end func
+
+ .space 0x8008
+
+ .ent foo
+foo:
+ nop
+ .end foo
Index: gas/testsuite/gas/mips/pcrel-1.d
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-1.d 2014-03-19 23:12:27.341621122 +0000
@@ -0,0 +1,14 @@
+#objdump: -dr
+#name: Locally-resolvable PC-relative code references
+
+.*: file format .*
+
+Disassembly of section .text:
+
+00000000 <func>:
+ 0: 3c040001 lui a0,0x1
+ 4: 2484800c addiu a0,a0,-32756
+ ...
+
+00008010 <foo>:
+#pass
Index: gas/testsuite/gas/mips/pcrel-2.s
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-2.s 2014-03-19 23:12:27.342621131 +0000
@@ -0,0 +1,7 @@
+ .data
+ .byte 0xff
+ .byte frob-.
+ .half frob-.
+ .word frob-.
+ .quad frob-.
+frob:
Index: gas/testsuite/gas/mips/pcrel-2.d
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-2.d 2014-03-19 23:12:27.342621131 +0000
@@ -0,0 +1,8 @@
+#objdump: -s
+#name: Locally-resolvable PC-relative data references
+#as: -EB
+
+#...
+Contents of section \.data:
+ 0000 ff0f000e 0000000c 00000000 00000008 .*
+#pass
Index: gas/testsuite/gas/mips/pcrel-3.s
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-3.s 2014-03-19 23:12:27.342621131 +0000
@@ -0,0 +1,11 @@
+ .text
+ .ent func
+func:
+ lui $4,%hi(foo-.)
+ addiu $4,%lo(foo-.)
+ lw $4,%got(foo-.)($gp)
+ .end func
+
+ .byte foo-.
+ .half foo-.
+ .quad foo-.
Index: gas/testsuite/gas/mips/pcrel-3.l
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-3.l 2014-03-19 23:12:27.342621131 +0000
@@ -0,0 +1,7 @@
+.*: Assembler messages:
+.*:4: Error: PC-relative reference to a different section
+.*:5: Error: PC-relative reference to a different section
+.*:6: Error: PC-relative reference to a different section
+.*:9: Error: PC-relative reference to a different section
+.*:10: Error: PC-relative reference to a different section
+.*:11: Error: PC-relative reference to a different section
Index: gas/testsuite/gas/mips/pcrel-4.s
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-4.s 2014-03-19 23:12:27.343621139 +0000
@@ -0,0 +1,6 @@
+ .data
+ .word foo-.
+ .word foo-(.-4)
+ .word foo+8-.
+ .word foo-.-16
+
Index: gas/testsuite/gas/mips/pcrel-4-32.d
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-4-32.d 2014-03-19 23:12:27.342621131 +0000
@@ -0,0 +1,18 @@
+#objdump: -sr
+#name: Valid cross-section PC-relative references (o32)
+#as: -32 -EB
+#source: pcrel-4.s
+
+.*: file format .*
+
+RELOCATION RECORDS FOR \[\.data\]:
+OFFSET TYPE VALUE
+00000000 R_MIPS_PC32 foo
+00000004 R_MIPS_PC32 foo
+00000008 R_MIPS_PC32 foo
+0000000c R_MIPS_PC32 foo
+
+#...
+Contents of section \.data:
+ 0000 00000000 00000004 00000008 fffffff0 ................
+#pass
Index: gas/testsuite/gas/mips/pcrel-4-n32.d
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-4-n32.d 2014-03-19 23:26:47.946909763 +0000
@@ -0,0 +1,13 @@
+#objdump: -r
+#name: Valid cross-section PC-relative references (n32)
+#as: -n32 -mips3
+#source: pcrel-4.s
+
+.*: file format .*
+
+RELOCATION RECORDS FOR \[\.data\]:
+OFFSET TYPE VALUE
+00000000 R_MIPS_PC32 foo
+00000004 R_MIPS_PC32 foo\+0x00000004
+00000008 R_MIPS_PC32 foo\+0x00000008
+0000000c R_MIPS_PC32 foo-0x00000010
Index: gas/testsuite/gas/mips/pcrel-4-64.d
===================================================================
--- /dev/null 2014-03-15 14:12:32.004596490 +0000
+++ gas/testsuite/gas/mips/pcrel-4-64.d 2014-03-19 23:26:58.591999264 +0000
@@ -0,0 +1,21 @@
+#objdump: -r
+#name: Valid cross-section PC-relative references (n64)
+#as: -64 -mips3
+#source: pcrel-4.s
+
+.*: file format .*
+
+RELOCATION RECORDS FOR \[\.data\]:
+OFFSET TYPE VALUE
+0+000 R_MIPS_PC32 foo
+0+000 R_MIPS_NONE \*ABS\*
+0+000 R_MIPS_NONE \*ABS\*
+0+004 R_MIPS_PC32 foo\+0x0+004
+0+004 R_MIPS_NONE \*ABS\*\+0x0+004
+0+004 R_MIPS_NONE \*ABS\*\+0x0+004
+0+008 R_MIPS_PC32 foo\+0x0+008
+0+008 R_MIPS_NONE \*ABS\*\+0x0+008
+0+008 R_MIPS_NONE \*ABS\*\+0x0+008
+0+00c R_MIPS_PC32 foo-0x0+010
+0+00c R_MIPS_NONE \*ABS\*-0x0+010
+0+00c R_MIPS_NONE \*ABS\*-0x0+010
Index: gas/testsuite/gas/mips/mips.exp
===================================================================
--- gas/testsuite/gas/mips/mips.exp 2014-03-19 22:44:18.584854477 +0000
+++ gas/testsuite/gas/mips/mips.exp 2014-03-19 23:12:27.341621122 +0000
@@ -1169,4 +1169,13 @@ if { [istarget mips*-*-vxworks*] } {
run_dump_test_arches "msa64" [mips_arch_list_matching mips64r2]
run_dump_test_arches "msa-relax" [mips_arch_list_matching mips32r2]
run_dump_test_arches "msa-branch" [mips_arch_list_matching mips32r2]
+
+ run_dump_test "pcrel-1"
+ run_dump_test "pcrel-2"
+ run_list_test "pcrel-3" "" "Invalid cross-section PC-relative references"
+ run_dump_test "pcrel-4-32"
+ if $has_newabi {
+ run_dump_test "pcrel-4-n32"
+ run_dump_test "pcrel-4-64"
+ }
}
Index: gas/testsuite/gas/mips/lui-2.l
===================================================================
--- gas/testsuite/gas/mips/lui-2.l 2014-03-19 22:44:18.584854477 +0000
+++ gas/testsuite/gas/mips/lui-2.l 2014-03-19 23:12:27.343621139 +0000
@@ -1,5 +1,5 @@
.*\.s: Assembler messages:
.*\.s:10: Error: invalid operands \(\*UND\* and \*UND\* sections\) for `/'
-.*\.s:7: Error: can't resolve `bar' {\*UND\* section} - `foo' {\.text section}
+.*\.s:7: Error: PC-relative reference to a different section
.*\.s:8: Error: can't resolve `baz' {\*UND\* section} - `bar' {\*UND\* section}
.*\.s:9: Error: can't resolve `\.text' {\.text section} - `baz' {\*UND\* section}
Index: ld/testsuite/ld-elf/merge.d
===================================================================
--- ld/testsuite/ld-elf/merge.d 2013-11-13 21:08:01.200582091 +0000
+++ ld/testsuite/ld-elf/merge.d 2014-03-19 23:30:33.635810673 +0000
@@ -4,7 +4,7 @@
#xfail: "arc-*-*" "avr-*-*" "bfin-*-*" "cr16-*-*" "cris*-*-*" "crx-*-*" "d10v-*-*" "d30v-*-*"
#xfail: "dlx-*-*" "fr30-*-*" "frv-*-*" "hppa*64*-*-*" "h8300-*-*" "score-*-*"
#xfail: "i370-*-*" "i860-*-*" "i960-*-*" "ip2k-*-*" "iq2000-*-*" "lm32-*-*"
-#xfail: "mcore-*-*" "mn102*-*-*" "mips*-*-*" "ms1-*-*" "mep-*-*"
+#xfail: "mcore-*-*" "mn102*-*-*" "ms1-*-*" "mep-*-*"
#xfail: "or32-*-*" "pj-*-*" "sparc*-*-*" "tic6x-*-*" "vax-*-*" "xstormy16-*-*"
#xfail: "xtensa*-*-*" "metag-*-*"
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