[PATCH] [RISCV] Support subtraction of .uleb128.
Kuan-Lin Chen
kuanlinchentw@gmail.com
Tue Dec 10 05:43:00 GMT 2019
Hi Palmer,
> GCC gives me -Wmaybe-uninitialized for both of these.
May I know your gcc version?
I tried gcc-7.3.0 and gcc-8.2.0, and I didn't get the warning.
> I don't understand how this could possibly work: uleb128s can be long, so we
> can't just treat them as a single byte.
Yes, uleb128s can be long so I implement riscv_elf_ignore_reloc to
ignore the overflow checking.
And I relocate uleb128s by myself in perform_relocation.
> I'm having trouble testing it, though,
> as I can't figure out how to emit R_RISCV_SET_ULEB128 alone. For example, when
> I try to insert a uleb128 in the assembler I'm not even getting a relocation:
.uleb128 only support subtract format. (.uleb128 .L1 - .L0)
It is impossible to get final the value and the length for ".uleb128
symbol" in assemble-time.
I think ".uleb128 symbol" is meaningless.
Therefore, all targets just fill the value as assemble-time value
without relocations.
>I can get a R_RISCV_SUB_ULEB128, but it appears to be both producing the wrong
>value and garbaging up bytes after the relocation. For example:
I get the same result in the object file but the different result in executable.
pal.o: file format elf64-littleriscv
Disassembly of section .text:
0000000000000000 <_start>:
0: 00000013 nop
0000000000000004 <.L0>:
4: 00000013 nop
0000000000000008 <uleb_l1_l0>:
8: 00100013 li zero,1
c: aa04 fsd fs1,16(a2)
c: R_RISCV_SET_ULEB128 .L1
c: R_RISCV_SUB_ULEB128 .L0
e: aaaa fsd fa0,336(sp)
10: 00200013 li zero,2
a.out: file format elf64-littleriscv
Disassembly of section .text:
0000000000010078 <_start>:
10078: 00000013 nop
1007c: 00000013 nop
0000000000010080 <uleb_l1_l0>:
10080: 00100013 li zero,1
10084: aa04 fsd fs1,16(a2)
10086: aaaa fsd fa0,336(sp)
10088: 00200013 li zero,2
Maybe there is something mismatched. But I don't have any idea currently.
Could you please give me more information about your flow?
Thanks.
> Presumably that's why I can't get a _SET alone.
I think it's meaningless to use _SET alone in assembly.
> It looks like alignment is broken here after uleb128s, but it's not actually
> triggering an error in all cases. Having two of them in this test case doesn't
> trigger the issue, but an odd number does. For example, the following source
I think this alignment issue can be fixed by the following patch:
https://sourceware.org/ml/binutils/2019-12/msg00024.html
Thanks for your review.
Palmer Dabbelt <palmerdabbelt@google.com> 於 2019年12月7日 週六 上午7:47寫道：
>
> On Wed, 27 Nov 2019 00:11:50 PST (-0800), kuanlinchentw@gmail.com wrote:
> > The data length of uleb128 is variable. So linker must recalculate the
> > value of the subtraction. The patch leave relocations in object files
> > so that linker can relocate again after relaxation.
> >
> > bfd/ChangeLog:
> > * bfd-in2.h: Regenerated.
> > * elfnn-riscv.c (write_uleb128): New function.
> > (perform_relocation): Perform R_RISCV_SUB_ULEB128 and
> > R_RISCV_SET_ULEB128 relocation.
> > (riscv_elf_relocate_section): Likewise.
> > * elfxx-riscv.c (howto_table): Add R_RISCV_SUB_ULEB128 and
> > R_RISCV_SET_ULEB128.
> > (riscv_elf_ignore_reloc): New function.
> > * libbfd.h: Regenerated.
> > * reloc.c (BFD_RELOC_RISCV_SET_ULEB128, BFD_RELOC_RISCV_SUB_ULEB128):
> > New relocations to support .uleb128.
> >
> > gas/ChangeLog:
> > * config/tc-riscv.c (md_apply_fix): Add BFD_RELOC_RISCV_SET_ULEB128 and
> > BFD_RELOC_RISCV_SUB_ULEB128.
> > (riscv_insert_uleb128_fixes): New function.
> > (riscv_md_end): Scan rs_leb128 fragments.
> > (riscv_pseudo_table): Remove uleb128.
> >
> > include/ChangeLog:
> > * elf/riscv.h ((R_RISCV_SET_ULEB128, (R_RISCV_SUB_ULEB128): Define.
> >
> > ld/ChangeLog:
> > * testsuite/ld-riscv-elf/ld-riscv-elf.exp: Add uleb128.
> > * testsuite/ld-riscv-elf/uleb128.d: New test.
> > * testsuite/ld-riscv-elf/uleb128.s: New file.
> >
> > OK to commit?
>
> I'm having a lot of trouble trying to figure out how this works. LMK if I'm
> missing something, there's some comments in line:
>
> > From 9f7f0aaa484dee2b32c550f8cca4de18959f01e1 Mon Sep 17 00:00:00 2001
> > From: Kuan-Lin Chen <rufus@andestech.com>
> > Date: Thu, 14 Nov 2019 14:24:22 +0800
> > Subject: [PATCH] RISC-V: Support subtraction of .uleb128.
> >
> > The data length of uleb128 is variable. So linker must recalculate the
> > value of the subtraction. The patch leave relocations in object files
> > so that linker can relocate again after relaxation.
> >
> > bfd/ChangeLog:
> > * bfd-in2.h: Regenerated.
> > * elfnn-riscv.c (write_uleb128): New function.
> > (perform_relocation): Perform R_RISCV_SUB_ULEB128 and
> > R_RISCV_SET_ULEB128 relocation.
> > (riscv_elf_relocate_section): Likewise.
> > * elfxx-riscv.c (howto_table): Add R_RISCV_SUB_ULEB128 and
> > R_RISCV_SET_ULEB128.
> > (riscv_elf_ignore_reloc): New function.
> > * libbfd.h: Regenerated.
> > * reloc.c (BFD_RELOC_RISCV_SET_ULEB128, BFD_RELOC_RISCV_SUB_ULEB128):
> > New relocations to support .uleb128.
> >
> > gas/ChangeLog:
> > * config/tc-riscv.c (md_apply_fix): Add BFD_RELOC_RISCV_SET_ULEB128 and
> > BFD_RELOC_RISCV_SUB_ULEB128.
> > (riscv_insert_uleb128_fixes): New function.
> > (riscv_md_end): Scan rs_leb128 fragments.
> > (riscv_pseudo_table): Remove uleb128.
> >
> > include/ChangeLog:
> > * elf/riscv.h ((R_RISCV_SET_ULEB128, (R_RISCV_SUB_ULEB128): Define.
> >
> > ld/ChangeLog:
> > * testsuite/ld-riscv-elf/ld-riscv-elf.exp: Add uleb128.
> > * testsuite/ld-riscv-elf/uleb128.d: New test.
> > * testsuite/ld-riscv-elf/uleb128.s: New file.
> > ---
> > bfd/ChangeLog | 14 ++++
> > bfd/bfd-in2.h | 2 +
> > bfd/elfnn-riscv.c | 82 ++++++++++++++++++++++
> > bfd/elfxx-riscv.c | 51 ++++++++++++++
> > bfd/libbfd.h | 2 +
> > bfd/reloc.c | 4 ++
> > gas/ChangeLog | 8 +++
> > gas/config/tc-riscv.c | 47 ++++++++++++-
> > include/ChangeLog | 4 ++
> > include/elf/riscv.h | 2 +
> > ld/ChangeLog | 6 ++
> > ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp | 1 +
> > ld/testsuite/ld-riscv-elf/uleb128.d | 18 +++++
> > ld/testsuite/ld-riscv-elf/uleb128.s | 18 +++++
> > 14 files changed, 258 insertions(+), 1 deletion(-)
> > create mode 100644 ld/testsuite/ld-riscv-elf/uleb128.d
> > create mode 100644 ld/testsuite/ld-riscv-elf/uleb128.s
> >
> > diff --git a/bfd/ChangeLog b/bfd/ChangeLog
> > index 4a0852e577..d11ffde74c 100644
> > --- a/bfd/ChangeLog
> > +++ b/bfd/ChangeLog
> > @@ -1,3 +1,17 @@
> > +2019-11-27 Kuan-Lin Chen <kuanlinchentw@gmail.com>
> > +
> > + * bfd-in2.h: Regenerated.
> > + * elfnn-riscv.c (write_uleb128): New function.
> > + (perform_relocation): Perform R_RISCV_SUB_ULEB128 and
> > + R_RISCV_SET_ULEB128 relocation.
> > + (riscv_elf_relocate_section): Likewise.
> > + * elfxx-riscv.c (howto_table): Add R_RISCV_SUB_ULEB128 and
> > + R_RISCV_SET_ULEB128.
> > + (riscv_elf_ignore_reloc): New function.
> > + * libbfd.h: Regenerated.
> > + * reloc.c (BFD_RELOC_RISCV_SET_ULEB128, BFD_RELOC_RISCV_SUB_ULEB128):
> > + New relocations to support .uleb128.
> > +
> > 2019-11-27 Alan Modra <amodra@gmail.com>
> >
> > PR 23652
> > diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
> > index 44902fc8d0..a32708ebc2 100644
> > --- a/bfd/bfd-in2.h
> > +++ b/bfd/bfd-in2.h
> > @@ -4380,6 +4380,8 @@ number for the SBIC, SBIS, SBI and CBI instructions */
> > BFD_RELOC_RISCV_SET16,
> > BFD_RELOC_RISCV_SET32,
> > BFD_RELOC_RISCV_32_PCREL,
> > + BFD_RELOC_RISCV_SET_ULEB128,
> > + BFD_RELOC_RISCV_SUB_ULEB128,
> >
> > /* Renesas RL78 Relocations. */
> > BFD_RELOC_RL78_NEG8,
> > diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
> > index 997f786602..075ef6b82d 100644
> > --- a/bfd/elfnn-riscv.c
> > +++ b/bfd/elfnn-riscv.c
> > @@ -1419,6 +1419,26 @@ riscv_global_pointer_value (struct bfd_link_info *info)
> > return h->u.def.value + sec_addr (h->u.def.section);
> > }
> >
> > +/* Write VAL in uleb128 format to P, returning a pointer to the
> > + following byte.
> > + This code is copied from elf-attr.c. */
> > +
> > +static bfd_byte *
> > +write_uleb128 (bfd_byte *p, unsigned int val)
> > +{
> > + bfd_byte c;
> > + do
> > + {
> > + c = val & 0x7f;
> > + val >>= 7;
> > + if (val)
> > + c |= 0x80;
> > + *(p++) = c;
> > + }
> > + while (val);
> > + return p;
> > +}
> > +
> > /* Emplace a static relocation. */
> >
> > static bfd_reloc_status_type
> > @@ -1512,6 +1532,25 @@ perform_relocation (const reloc_howto_type *howto,
> > value = ENCODE_RVC_LUI_IMM (RISCV_CONST_HIGH_PART (value));
> > break;
> >
> > + case R_RISCV_SET_ULEB128:
> > + case R_RISCV_SUB_ULEB128:
> > + {
> > + unsigned int len = 0;
> > + bfd_byte *endp, *p;
> > +
> > + _bfd_read_unsigned_leb128 (input_bfd, contents + rel->r_offset, &len);
> > +
> > + /* Clean the contents value to zero. Do not reduce the length. */
> > + p = contents + rel->r_offset;
> > + endp = p + len -1;
> > + memset (p, 0x80, len);
> > + *(endp) = 0;
> > + p = write_uleb128 (p, value) - 1;
> > + if (p < endp)
> > + *p |= 0x80;
> > + return bfd_reloc_ok;
> > + }
> > +
> > case R_RISCV_32:
> > case R_RISCV_64:
> > case R_RISCV_ADD8:
> > @@ -1767,6 +1806,8 @@ riscv_elf_relocate_section (bfd *output_bfd,
> > struct elf_link_hash_entry **sym_hashes = elf_sym_hashes (input_bfd);
> > bfd_vma *local_got_offsets = elf_local_got_offsets (input_bfd);
> > bfd_boolean absolute;
> > + bfd_vma uleb128_vma;
> > + Elf_Internal_Rela *uleb128_rel = NULL;
> >
> > if (!riscv_init_pcrel_relocs (&pcrel_relocs))
> > return FALSE;
> > @@ -1871,6 +1912,47 @@ riscv_elf_relocate_section (bfd *output_bfd,
> > case R_RISCV_DELETE:
> > /* These require no special handling beyond perform_relocation. */
> > break;
> > + case R_RISCV_SET_ULEB128:
> > + if (!uleb128_rel)
> > + {
> > + /* Save the minuend to use later. */
> > + uleb128_vma = relocation;
> > + uleb128_rel = rel;
> > + continue;
> > + }
> > + else
> > + {
> > + if (uleb128_rel->r_offset != rel->r_offset)
> > + {
> > + (*_bfd_error_handler) (_("%pB: relocation %s mismatched. "),
> > + input_bfd, howto->name);
> > + bfd_set_error (bfd_error_bad_value);
> > + }
> > + relocation = relocation - uleb128_vma;
> > + uleb128_rel = NULL;
> > + break;
> > + }
> > +
> > + case R_RISCV_SUB_ULEB128:
> > + if (uleb128_rel)
> > + {
> > + if (uleb128_rel->r_offset != rel->r_offset)
> > + {
> > + (*_bfd_error_handler) (_("%pB: relocation %s mismatched. "),
> > + input_bfd, howto->name);
> > + bfd_set_error (bfd_error_bad_value);
> > + }
> > + relocation = uleb128_vma - relocation;
>
> GCC gives me -Wmaybe-uninitialized for both of these.
>
> > + uleb128_rel = NULL;
> > + break;
> > + }
> > + else
> > + {
> > + /* Save the subtrahend to use later. */
> > + uleb128_vma = relocation;
> > + uleb128_rel = rel;
> > + continue;
> > + }
> >
> > case R_RISCV_GOT_HI20:
> > if (h != NULL)
> > diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
> > index 245717f70f..c136ba2207 100644
> > --- a/bfd/elfxx-riscv.c
> > +++ b/bfd/elfxx-riscv.c
> > @@ -38,6 +38,8 @@
> > relocations for the debug info. */
> > static bfd_reloc_status_type riscv_elf_add_sub_reloc
> > (bfd *, arelent *, asymbol *, void *, asection *, bfd *, char **);
> > +static bfd_reloc_status_type riscv_elf_ignore_reloc
> > + (bfd *, arelent *, asymbol *, void *, asection *, bfd *, char **);
> >
> > /* The relocation table used for SHT_RELA sections. */
> >
> > @@ -855,8 +857,41 @@ static reloc_howto_type howto_table[] =
> > 0, /* src_mask */
> > MINUS_ONE, /* dst_mask */
> > FALSE), /* pcrel_offset */
> > +
> > + /* The length of unsigned-leb128 is variant, just assume the
> > + size is one byte here. */
> > + HOWTO (R_RISCV_SET_ULEB128, /* type */
> > + 0, /* rightshift */
> > + 0, /* size */
> > + 0, /* bitsize */
> > + FALSE, /* pc_relative */
> > + 0, /* bitpos */
> > + complain_overflow_dont, /* complain_on_overflow */
> > + riscv_elf_ignore_reloc, /* special_function */
> > + "R_RISCV_SET_ULEB128", /* name */
> > + FALSE, /* partial_inplace */
> > + 0, /* src_mask */
> > + 0, /* dst_mask */
> > + FALSE), /* pcrel_offset */
>
> I don't understand how this could possibly work: uleb128s can be long, so we
> can't just treat them as a single byte. I'm having trouble testing it, though,
> as I can't figure out how to emit R_RISCV_SET_ULEB128 alone. For example, when
> I try to insert a uleb128 in the assembler I'm not even getting a relocation:
>
> .text
> .globl _start
> _start:
> nop
> .L0:
> nop
> .L1:
> uleb_l0:
> addi x0, x0, 1
> .uleb128 .L0
> # Manually fix up the alignment, as .align is broken.
> .rept 3
> .byte 0xAA
> .endr
> addi x0, x0, 2
>
> $ objdump -dr
> test.o: file format elf64-littleriscv
>
>
> Disassembly of section .text:
>
> 0000000000000000 <_start>:
> 0: 00000013 nop
> 4: 00000013 nop
>
> 0000000000000008 <uleb_l0>:
> 8: 00100013 li zero,1
> c: aa04 fsd fs1,16(a2)
> e: aaaa fsd fa0,336(sp)
> 10: 00200013 li zero,2
>
> so then when I link I'm just getting the wrong value entirely.
>
> test: file format elf64-littleriscv
>
>
> Disassembly of section .text:
>
> 0000000000010078 <_start>:
> 10078: 00000013 nop
> 1007c: 00000013 nop
>
> 0000000000010080 <uleb_l0>:
> 10080: 00100013 li zero,1
> 10084: aa04 fsd fs1,16(a2)
> 10086: aaaa fsd fa0,336(sp)
> 10088: 00200013 li zero,2
>
> > + /* The length of unsigned-leb128 is variant, just assume the
> > + size is one byte here. */
> > + HOWTO (R_RISCV_SUB_ULEB128, /* type */
> > + 0, /* rightshift */
> > + 0, /* size */
> > + 0, /* bitsize */
> > + FALSE, /* pc_relative */
> > + 0, /* bitpos */
> > + complain_overflow_dont, /* complain_on_overflow */
> > + riscv_elf_ignore_reloc, /* special_function */
> > + "R_RISCV_SUB_ULEB128", /* name */
> > + FALSE, /* partial_inplace */
> > + 0, /* src_mask */
> > + 0, /* dst_mask */
> > + FALSE), /* pcrel_offset */
> > };
>
> I can get a R_RISCV_SUB_ULEB128, but it appears to be both producing the wrong
> value and garbaging up bytes after the relocation. For example:
>
> .text
> .globl _start
> _start:
> nop
> .L0:
> nop
> .L1:
> uleb_l1_l0:
> addi x0, x0, 1
> .uleb128 .L1 - .L0
> # Manually fix up the alignment, as .align is broken
> .rept 3
> .byte 0xAA
> .endr
> addi x0, x0, 2
>
> produces the relocation
>
> test.o: file format elf64-littleriscv
>
>
> Disassembly of section .text:
>
> 0000000000000000 <_start>:
> 0: 00000013 nop
>
> 0000000000000004 <.L0>:
> 4: 00000013 nop
>
> 0000000000000008 <uleb_l1_l0>:
> 8: 00100013 li zero,1
> c: aa04 fsd fs1,16(a2)
> c: R_RISCV_SET_ULEB128 .L1
> c: R_RISCV_SUB_ULEB128 .L0
> e: aaaa fsd fa0,336(sp)
> 10: 00200013 li zero,2
>
> but then goes and corrupts the resulting executable
>
>
> test: file format elf64-littleriscv
> Disassembly of section .text:
>
> 0000000000010078 <_start>:
> 10078: 00000013 nop
> 1007c: 00000013 nop
>
> 0000000000010080 <uleb_l1_l0>:
> 10080: 00100013 li zero,1
> 10084: ff84 sd s1,56(a5)
> 10086: 000ffffb 0xffffb
> 1008a: 0020 addi s0,sp,8
>
> I can't think of a way to make this work aside from just emitting uleb128s at
> their full length, which would make them work but would really defeat the
> purpose of the format. I guess we could then relax these, but that seems like
> a lot of work.
>
> > +
> > /* A mapping from BFD reloc types to RISC-V ELF reloc types. */
> >
> > struct elf_reloc_map
> > @@ -917,6 +952,8 @@ static const struct elf_reloc_map riscv_reloc_map[] =
> > { BFD_RELOC_RISCV_SET16, R_RISCV_SET16 },
> > { BFD_RELOC_RISCV_SET32, R_RISCV_SET32 },
> > { BFD_RELOC_RISCV_32_PCREL, R_RISCV_32_PCREL },
> > + { BFD_RELOC_RISCV_SET_ULEB128, R_RISCV_SET_ULEB128 },
> > + { BFD_RELOC_RISCV_SUB_ULEB128, R_RISCV_SUB_ULEB128 },
> > };
> >
> > /* Given a BFD reloc type, return a howto structure. */
> > @@ -1011,6 +1048,20 @@ riscv_elf_add_sub_reloc (bfd *abfd,
> > return bfd_reloc_ok;
> > }
> >
> > +/* Special handler for relocations which don't have to be relocated.
> > + This function just simply return bfd_reloc_ok. */
> > +static bfd_reloc_status_type
> > +riscv_elf_ignore_reloc (bfd *abfd ATTRIBUTE_UNUSED, arelent *reloc_entry,
> > + asymbol *symbol ATTRIBUTE_UNUSED,
> > + void *data ATTRIBUTE_UNUSED, asection *input_section,
> > + bfd *output_bfd, char **error_message ATTRIBUTE_UNUSED)
> > +{
> > + if (output_bfd != NULL)
> > + reloc_entry->address += input_section->output_offset;
> > +
> > + return bfd_reloc_ok;
> > +}
> > +
> > /* Parsing subset version.
> >
> > Return Value:
> > diff --git a/bfd/libbfd.h b/bfd/libbfd.h
> > index 77b732ee4b..7aa8f91504 100644
> > --- a/bfd/libbfd.h
> > +++ b/bfd/libbfd.h
> > @@ -2327,6 +2327,8 @@ static const char *const bfd_reloc_code_real_names[] = { "@@uninitialized@@",
> > "BFD_RELOC_RISCV_SET16",
> > "BFD_RELOC_RISCV_SET32",
> > "BFD_RELOC_RISCV_32_PCREL",
> > + "BFD_RELOC_RISCV_SET_ULEB128",
> > + "BFD_RELOC_RISCV_SUB_ULEB128",
> > "BFD_RELOC_RL78_NEG8",
> > "BFD_RELOC_RL78_NEG16",
> > "BFD_RELOC_RL78_NEG24",
> > diff --git a/bfd/reloc.c b/bfd/reloc.c
> > index b00b79f319..9b8b75ad21 100644
> > --- a/bfd/reloc.c
> > +++ b/bfd/reloc.c
> > @@ -5212,6 +5212,10 @@ ENUMX
> > BFD_RELOC_RISCV_SET32
> > ENUMX
> > BFD_RELOC_RISCV_32_PCREL
> > +ENUMX
> > + BFD_RELOC_RISCV_SET_ULEB128
> > +ENUMX
> > + BFD_RELOC_RISCV_SUB_ULEB128
> > ENUMDOC
> > RISC-V relocations.
> >
> > diff --git a/gas/ChangeLog b/gas/ChangeLog
> > index 09991524da..e53ac0895b 100644
> > --- a/gas/ChangeLog
> > +++ b/gas/ChangeLog
> > @@ -1,3 +1,11 @@
> > +2019-11-27 Kuan-Lin Chen <kuanlinchentw@gmail.com>
> > +
> > + * config/tc-riscv.c (md_apply_fix): Add BFD_RELOC_RISCV_SET_ULEB128 and
> > + BFD_RELOC_RISCV_SUB_ULEB128.
> > + (riscv_insert_uleb128_fixes): New function.
> > + (riscv_md_end): Scan rs_leb128 fragments.
> > + (riscv_pseudo_table): Remove uleb128.
> > +
> > 2019-11-25 Andrew Pinski <apinski@marvell.com>
> >
> > * config/tc-aarch64.c (md_begin): Use correct
> > diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
> > index e50505138e..c35c591c0a 100644
> > --- a/gas/config/tc-riscv.c
> > +++ b/gas/config/tc-riscv.c
> > @@ -2392,6 +2392,9 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
> > case BFD_RELOC_RISCV_SUB32:
> > case BFD_RELOC_RISCV_SUB64:
> > case BFD_RELOC_RISCV_RELAX:
> > + /* cvt_frag_to_fill () has called output_leb128 (). */
> > + case BFD_RELOC_RISCV_SET_ULEB128:
> > + case BFD_RELOC_RISCV_SUB_ULEB128:
> > break;
> >
> > case BFD_RELOC_RISCV_TPREL_HI20:
> > @@ -3127,11 +3130,54 @@ riscv_set_public_attributes (void)
> > riscv_write_out_arch_attr ();
> > }
> >
> > +/* Scan uleb128 subtraction expressions and insert fixups for them.
> > + e.g., .uleb128 .L1 - .L0
> > + Becuase relaxation may change the value of the subtraction, we
> > + must resolve them in link-time. */
> > +
> > +static void
> > +riscv_insert_uleb128_fixes (bfd *abfd ATTRIBUTE_UNUSED,
> > + asection *sec, void *xxx ATTRIBUTE_UNUSED)
> > +{
> > + segment_info_type *seginfo = seg_info (sec);
> > + struct frag *fragP;
> > +
> > + subseg_set (sec, 0);
> > +
> > + for (fragP = seginfo->frchainP->frch_root;
> > + fragP; fragP = fragP->fr_next)
> > + {
> > + expressionS *exp, *exp_dup;
> > +
> > + if (fragP->fr_type != rs_leb128 || fragP->fr_symbol == NULL)
> > + continue;
> > +
> > + exp = symbol_get_value_expression (fragP->fr_symbol);
> > +
> > + if (exp->X_op != O_subtract)
> > + continue;
>
> Presumably that's why I can't get a _SET alone.
>
> > +
> > + /* Only unsigned leb128 can be handle. */
> > + gas_assert (fragP->fr_subtype == 0);
> > + exp_dup = xmemdup (exp, sizeof (*exp), sizeof (*exp));
> > + exp_dup->X_op = O_symbol;
> > + exp_dup->X_op_symbol = NULL;
> > +
> > + /* Insert relocations to resolve the subtraction in link-time. */
> > + fix_new_exp (fragP, fragP->fr_fix, 0,
> > + exp_dup, 0, BFD_RELOC_RISCV_SET_ULEB128);
> > + exp_dup->X_add_symbol = exp->X_op_symbol;
> > + fix_new_exp (fragP, fragP->fr_fix, 0,
> > + exp_dup, 0, BFD_RELOC_RISCV_SUB_ULEB128);
> > + }
> > +}
> > +
> > /* Called after all assembly has been done. */
> >
> > void
> > riscv_md_end (void)
> > {
> > + bfd_map_over_sections (stdoutput, riscv_insert_uleb128_fixes, NULL);
> > riscv_set_public_attributes ();
> > }
> >
> > @@ -3215,7 +3261,6 @@ static const pseudo_typeS riscv_pseudo_table[] =
> > {"dtprelword", s_dtprel, 4},
> > {"dtpreldword", s_dtprel, 8},
> > {"bss", s_bss, 0},
> > - {"uleb128", s_riscv_leb128, 0},
> > {"sleb128", s_riscv_leb128, 1},
> > {"insn", s_riscv_insn, 0},
> > {"attribute", s_riscv_attribute, 0},
> > diff --git a/include/ChangeLog b/include/ChangeLog
> > index 47bb86cf71..c290b245c6 100644
> > --- a/include/ChangeLog
> > +++ b/include/ChangeLog
> > @@ -1,3 +1,7 @@
> > +2019-11-27 Kuan-Lin Chen <kuanlinchentw@gmail.com>
> > +
> > + * elf/riscv.h ((R_RISCV_SET_ULEB128, (R_RISCV_SUB_ULEB128): Define.
> > +
> > 2019-11-25 Alan Modra <amodra@gmail.com>
> >
> > * coff/ti.h (GET_SCNHDR_SIZE, PUT_SCNHDR_SIZE, GET_SCN_SCNLEN),
> > diff --git a/include/elf/riscv.h b/include/elf/riscv.h
> > index 2f98aa4a3e..030679b35f 100644
> > --- a/include/elf/riscv.h
> > +++ b/include/elf/riscv.h
> > @@ -88,6 +88,8 @@ START_RELOC_NUMBERS (elf_riscv_reloc_type)
> > RELOC_NUMBER (R_RISCV_SET16, 55)
> > RELOC_NUMBER (R_RISCV_SET32, 56)
> > RELOC_NUMBER (R_RISCV_32_PCREL, 57)
> > + RELOC_NUMBER (R_RISCV_SET_ULEB128, 58)
> > + RELOC_NUMBER (R_RISCV_SUB_ULEB128, 59)
> > END_RELOC_NUMBERS (R_RISCV_max)
> >
> > /* Processor specific flags for the ELF header e_flags field. */
> > diff --git a/ld/ChangeLog b/ld/ChangeLog
> > index 969ab78035..5c2e406101 100644
> > --- a/ld/ChangeLog
> > +++ b/ld/ChangeLog
> > @@ -1,3 +1,9 @@
> > +2019-11-27 Kuan-Lin Chen <kuanlinchentw@gmail.com>
> > +
> > + * testsuite/ld-riscv-elf/ld-riscv-elf.exp: Add uleb128.
> > + * testsuite/ld-riscv-elf/uleb128.d: New test.
> > + * testsuite/ld-riscv-elf/uleb128.s: New file.
> > +
> > 2019-11-26 Martin Liska <mliska@suse.cz>
> >
> > * scripttempl/arclinux.sc: Add .text.sorted.* which is sorted
> > diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> > index 7aabbdd641..809e40f08d 100644
> > --- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> > +++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> > @@ -38,6 +38,7 @@ if [istarget "riscv*-*-*"] {
> > run_dump_test "attr-merge-priv-spec"
> > run_dump_test "attr-merge-arch-failed-01"
> > run_dump_test "attr-merge-stack-align-failed"
> > + run_dump_test "uleb128"
> > run_ld_link_tests {
> > { "Weak reference 32" "-T weakref.ld -melf32lriscv" ""
> > "-march=rv32i -mabi=ilp32" {weakref32.s}
> > diff --git a/ld/testsuite/ld-riscv-elf/uleb128.d b/ld/testsuite/ld-riscv-elf/uleb128.d
> > new file mode 100644
> > index 0000000000..a921478e98
> > --- /dev/null
> > +++ b/ld/testsuite/ld-riscv-elf/uleb128.d
> > @@ -0,0 +1,18 @@
> > +#source: uleb128.s
> > +#as: -march=rv32ic
> > +#ld: -melf32lriscv
> > +#objdump: -d
> > +
> > +.*:[ ]+file format .*
> > +
> > +Disassembly of section .text:
> > +
> > +.* <_start>:
> > +.*jal.*<bar>
> > +.*jal.*<bar>
> > +.*jal.*<bar>
> > +.*jal.*<bar>
> > +.*jal.*<bar>
> > +.*jal.*<bar>
> > +.*:[ ]+0e0c.*
> > +#pass
> > diff --git a/ld/testsuite/ld-riscv-elf/uleb128.s b/ld/testsuite/ld-riscv-elf/uleb128.s
> > new file mode 100644
> > index 0000000000..f7d23be163
> > --- /dev/null
> > +++ b/ld/testsuite/ld-riscv-elf/uleb128.s
> > @@ -0,0 +1,18 @@
> > +.text
> > +.globl bar
> > +.globl _start
> > +.option rvc
> > +.align 2
> > +_start:
> > +.L0:
> > + .rept 6
> > + call bar
> > + .endr
> > +.align 2
> > +.L1:
> > + .uleb128 .L1 - .L0
> > + .uleb128 .L2 - .L0
> > +.L2:
> > +.align 2
> > +bar:
> > + nop
>
> It looks like alignment is broken here after uleb128s, but it's not actually
> triggering an error in all cases. Having two of them in this test case doesn't
> trigger the issue, but an odd number does. For example, the following source
>
> .text
> .globl _start
> .align 2
> _start:
> .uleb128 _start
> .align 2
> _end:
> nop
>
> links _end to a misaligned symbol
>
> Disassembly of section .text:
>
> 0000000000010078 <_start>:
> ...
>
> 0000000000010079 <_end>:
> 10079: 00000013 nop
> 1007d: 0000 unimp
> ...
>
> I'm assuming that's because norvc assumes 4-byte alignment in text sections, so
> it's just eliding the alingment directives. With RVC I do get an error message
>
> .text
> .globl _start
> .option rvc
> .align 2
> _start:
> .uleb128 _start
> .align 2
> _end:
> nop
>
> ./install/bin/riscv64-unknown-linux-gnu-ld: test.o(.text+0x1): 3 bytes required for alignment to 4-byte boundary, but only 2 present
> ./install/bin/riscv64-unknown-linux-gnu-ld: can't relax section: bad value
>
>
--
Best regards,
Kuan-Lin Chen.
kuanlinchentw@gmail.com
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