* [binutils-gdb] RISC-V: Support subtraction of .uleb128.
@ 2023-05-19 8:34 Nelson Chu
0 siblings, 0 replies; only message in thread
From: Nelson Chu @ 2023-05-19 8:34 UTC (permalink / raw)
To: bfd-cvs
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f1cd8b94e7c941c2a9107c1112ab2339916b8efd
commit f1cd8b94e7c941c2a9107c1112ab2339916b8efd
Author: Kuan-Lin Chen <rufus@andestech.com>
Date: Thu Nov 14 14:24:22 2019 +0800
RISC-V: Support subtraction of .uleb128.
https://github.com/riscv-non-isa/riscv-elf-psabi-doc/commit/96d6e190e9fc04a8517f9ff7fb9aed3e9876cbd6
There are some known limitations for now,
* Do not shrink the length of the uleb128 value, even if the value is reduced
after relaxations. Also reports error if the length grows up.
* The R_RISCV_SET_ULEB128 needs to be paired with and be placed before the
R_RISCV_SUB_ULEB128.
bfd/
* bfd-in2.h: Regenerated.
* elfnn-riscv.c (perform_relocation): Perform R_RISCV_SUB_ULEB128 and
R_RISCV_SET_ULEB128 relocations. Do not shrink the length of the
uleb128 value, and report error if the length grows up. Called the
generic functions, _bfd_read_unsigned_leb128 and _bfd_write_unsigned_leb128,
to encode the uleb128 into the section contents.
(riscv_elf_relocate_section): Make sure that the R_RISCV_SET_ULEB128
must be paired with and be placed before the R_RISCV_SUB_ULEB128.
* elfxx-riscv.c (howto_table): Added R_RISCV_SUB_ULEB128 and
R_RISCV_SET_ULEB128.
(riscv_reloc_map): Likewise.
(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 subtraction.
gas/
* config/tc-riscv.c (md_apply_fix): Added BFD_RELOC_RISCV_SET_ULEB128
and BFD_RELOC_RISCV_SUB_ULEB128.
(s_riscv_leb128): Updated to allow uleb128 subtraction.
(riscv_insert_uleb128_fixes): New function, scan uleb128 subtraction
expressions and insert fixups for them.
(riscv_md_finish): Called riscv_insert_uleb128_fixes for all sections.
include/
* elf/riscv.h ((R_RISCV_SET_ULEB128, (R_RISCV_SUB_ULEB128): Defined.
ld/
* testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated.
* testsuite/ld-riscv-elf/uleb128*: New testcase for uleb128 subtraction.
binutils/
* testsuite/binutils-all/nm.exp: Updated since RISCV supports .uleb128.
Diff:
---
bfd/bfd-in2.h | 2 +
bfd/elfnn-riscv.c | 83 ++++++++++++++++++++++++++++++
bfd/elfxx-riscv.c | 54 +++++++++++++++++++
bfd/libbfd.h | 2 +
bfd/reloc.c | 4 ++
binutils/testsuite/binutils-all/nm.exp | 2 -
gas/config/tc-riscv.c | 56 +++++++++++++++++++-
include/elf/riscv.h | 3 ++
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 +++++++
11 files changed, 239 insertions(+), 4 deletions(-)
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index 7be18db20a8..363a6b35a5c 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -5394,6 +5394,8 @@ 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 a23b91ac15c..75af040cf92 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -1792,6 +1792,55 @@ perform_relocation (const reloc_howto_type *howto,
value = ENCODE_CITYPE_LUI_IMM (RISCV_CONST_HIGH_PART (value));
break;
+ /* SUB_ULEB128 must be applied after SET_ULEB128, so we only write the
+ value back for SUB_ULEB128 should be enough. */
+ case R_RISCV_SET_ULEB128:
+ break;
+ case R_RISCV_SUB_ULEB128:
+ {
+ unsigned int len = 0;
+ _bfd_read_unsigned_leb128 (input_bfd, contents + rel->r_offset, &len);
+
+ /* Clean the contents value to zero (0x80), but keep the original
+ length. */
+ bfd_byte *p = contents + rel->r_offset;
+ bfd_byte *endp = p + len - 1;
+ memset (p, 0x80, len - 1);
+ *(endp) = 0;
+
+ /* Make sure the length of the new uleb128 value within the
+ original (available) length. */
+ unsigned int new_len = 0;
+ unsigned int val_t = value;
+ do
+ {
+ new_len++;
+ val_t >>= 7;
+ }
+ while (val_t);
+ if (new_len > len)
+ {
+ _bfd_error_handler
+ (_("final size of uleb128 value at offset 0x%lx in %pA from "
+ "%pB exceeds available space"),
+ (long) rel->r_offset, input_section, input_bfd);
+ return bfd_reloc_dangerous;
+ }
+ else
+ {
+ p = _bfd_write_unsigned_leb128 (p, endp, value);
+ BFD_ASSERT (p);
+
+ /* If the length of the value is reduced and shorter than the
+ original uleb128 length, then _bfd_write_unsigned_leb128 may
+ clear the 0x80 to 0x0 for the last byte that was written.
+ So reset it to keep the the original uleb128 length. */
+ if (--p < endp)
+ *p |= 0x80;
+ }
+ return bfd_reloc_ok;
+ }
+
case R_RISCV_32:
case R_RISCV_64:
case R_RISCV_ADD8:
@@ -2086,6 +2135,8 @@ riscv_elf_relocate_section (bfd *output_bfd,
Elf_Internal_Shdr *symtab_hdr = &elf_symtab_hdr (input_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_vma uleb128_set_vma = 0;
+ Elf_Internal_Rela *uleb128_set_rel = NULL;
bool absolute;
if (!riscv_init_pcrel_relocs (&pcrel_relocs))
@@ -2427,6 +2478,38 @@ riscv_elf_relocate_section (bfd *output_bfd,
/* These require no special handling beyond perform_relocation. */
break;
+ case R_RISCV_SET_ULEB128:
+ if (uleb128_set_rel == NULL)
+ {
+ /* Saved for later usage. */
+ uleb128_set_vma = relocation;
+ uleb128_set_rel = rel;
+ continue;
+ }
+ else
+ {
+ msg = ("Mismatched R_RISCV_SET_ULEB128, it must be paired with"
+ "and applied before R_RISCV_SUB_ULEB128");
+ r = bfd_reloc_dangerous;
+ }
+ break;
+
+ case R_RISCV_SUB_ULEB128:
+ if (uleb128_set_rel != NULL
+ && uleb128_set_rel->r_offset == rel->r_offset)
+ {
+ relocation = uleb128_set_vma - relocation;
+ uleb128_set_vma = 0;
+ uleb128_set_rel = NULL;
+ }
+ else
+ {
+ msg = ("Mismatched R_RISCV_SUB_ULEB128, it must be paired with"
+ "and applied after R_RISCV_SET_ULEB128");
+ r = bfd_reloc_dangerous;
+ }
+ break;
+
case R_RISCV_GOT_HI20:
if (h != NULL)
{
diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
index bd0c7c81329..7f453246449 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. */
@@ -844,6 +846,39 @@ static reloc_howto_type howto_table[] =
0, /* src_mask */
0xffffffff, /* dst_mask */
false), /* pcrel_offset */
+
+ /* Reserved for R_RISCV_PLT32. */
+ EMPTY_HOWTO (59),
+
+ /* N-bit in-place setting, for unsigned-leb128 local label subtraction. */
+ 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 */
+
+ /* N-bit in-place addition, for unsigned-leb128 local label subtraction. */
+ 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 */
};
/* A mapping from BFD reloc types to RISC-V ELF reloc types. */
@@ -905,6 +940,8 @@ 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. */
@@ -1010,6 +1047,23 @@ 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;
+}
+
/* Always add the IMPLICIT for the SUBSET. */
static bool
diff --git a/bfd/libbfd.h b/bfd/libbfd.h
index 05508c986ad..f29a65a4b22 100644
--- a/bfd/libbfd.h
+++ b/bfd/libbfd.h
@@ -2417,6 +2417,8 @@ 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 aab5d49bdb3..c7d11cf5f40 100644
--- a/bfd/reloc.c
+++ b/bfd/reloc.c
@@ -5048,6 +5048,10 @@ 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/binutils/testsuite/binutils-all/nm.exp b/binutils/testsuite/binutils-all/nm.exp
index d0f4c3e275c..91b519d9074 100644
--- a/binutils/testsuite/binutils-all/nm.exp
+++ b/binutils/testsuite/binutils-all/nm.exp
@@ -246,8 +246,6 @@ if [is_elf_format] {
# Test nm --line-numbers on DWARF-4 debug info.
set testname "nm --line-numbers on DWARF-4 debug info"
- # The RISCV target does not (currently) support .uleb128.
- setup_xfail "riscv*-*-*"
# The SH targets complain that the pseudo-ops used to construct
# the DWARF data are misaligned.
setup_xfail "sh*-*-*"
diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index 0cc2484b049..fceb53e54a6 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -3950,6 +3950,9 @@ 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:
@@ -4714,8 +4717,11 @@ s_riscv_leb128 (int sign)
char *save_in = input_line_pointer;
expression (&exp);
- if (exp.X_op != O_constant)
- as_bad (_("non-constant .%cleb128 is not supported"), sign ? 's' : 'u');
+ if (sign && exp.X_op != O_constant)
+ as_bad (_("non-constant .sleb128 is not supported"));
+ else if (!sign && exp.X_op != O_constant && exp.X_op != O_subtract)
+ as_bad (_(".uleb128 only supports constant or subtract expressions"));
+
demand_empty_rest_of_line ();
input_line_pointer = save_in;
@@ -4835,12 +4841,58 @@ riscv_set_public_attributes (void)
riscv_write_out_attrs ();
}
+/* Scan uleb128 subtraction expressions and insert fixups for them.
+ e.g., .uleb128 .L1 - .L0
+ Because relaxation may change the value of the subtraction, we
+ must resolve them at 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;
+
+ /* Only unsigned leb128 can be handled. */
+ 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 at link-time.
+ Emit the SET relocation first in riscv. */
+ exp_dup->X_add_symbol = exp->X_add_symbol;
+ 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_finish (void)
{
riscv_set_public_attributes ();
+ if (riscv_opts.relax)
+ bfd_map_over_sections (stdoutput, riscv_insert_uleb128_fixes, NULL);
}
/* Adjust the symbol table. */
diff --git a/include/elf/riscv.h b/include/elf/riscv.h
index aabc71cf979..0aa8b3359c4 100644
--- a/include/elf/riscv.h
+++ b/include/elf/riscv.h
@@ -87,6 +87,9 @@ START_RELOC_NUMBERS (elf_riscv_reloc_type)
RELOC_NUMBER (R_RISCV_SET32, 56)
RELOC_NUMBER (R_RISCV_32_PCREL, 57)
RELOC_NUMBER (R_RISCV_IRELATIVE, 58)
+ /* Reserved 59 for R_RISCV_PLT32. */
+ RELOC_NUMBER (R_RISCV_SET_ULEB128, 60)
+ RELOC_NUMBER (R_RISCV_SUB_ULEB128, 61)
END_RELOC_NUMBERS (R_RISCV_max)
/* Processor specific flags for the ELF header e_flags field. */
diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
index 9e103b283f7..947a266ba72 100644
--- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
+++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
@@ -172,6 +172,7 @@ if [istarget "riscv*-*-*"] {
run_dump_test "attr-merge-priv-spec-failed-06"
run_dump_test "attr-phdr"
run_dump_test "relax-max-align-gp"
+ run_dump_test "uleb128"
run_ld_link_tests [list \
[list "Weak reference 32" "-T weakref.ld -m[riscv_choose_ilp32_emul]" "" \
"-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 00000000000..a921478e988
--- /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 00000000000..f7d23be1635
--- /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
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