Re: [PATCHv2] xtensa: add R_XTENSA_PDIFF_ULEB128 for DWARF uleb128 diffs
Alexey Lapshin <[email protected]>
| Newsgroups | gmane.comp.gnu.binutils |
|---|---|
| Message-ID | <[email protected]> |
Gentle ping. A review would be much appreciated.
If review needs more time, could we at least
reserve reloc type 63 for R_XTENSA_PDIFF_ULEB128?
Thanks
On Mon, 2026-08-10 at 18:50 +0700, Alexey Lapshin wrote:
> Max, sorry for the inconvenience. I resent the patch for the master branch
> (the previous patch was for 2.46).
>
> Also, I'm sending the patch as a file for you. I'm not sure if my mail
> client sends messages as plain text even though I chose this method.
>
>
> On Mon, 2026-08-10 at 18:46 +0700, Alexey Lapshin wrote:
> > DWARF 5 location and range lists encode many same-section symbol
> > differences as uleb128. Today the assembler must mark all covered code
> > no_transform so linker relaxation cannot change those differences, which
> > effectively disables relaxation for nearly every function that has DWARF 5
> > debug info.
> >
> > Emit R_XTENSA_PDIFF_ULEB128 instead: like R_XTENSA_PDIFF32 the difference
> > stays in the section contents and the reloc records the subtracted symbol,
> > but the assembler pads the uleb128 to a fixed width (minimal encoding plus
> > one spare byte) and the linker rewrites the value in place after
> > relaxation.
> >
> > sleb128 and cross-section differences still fall back to no_transform.
> > Growth that needs more than the reserved spare byte is reported as a
> > relocation overflow.
> >
> > bfd/
> > * bfd-in2.h: Regenerated.
> > * elf32-xtensa.c (elf_howto_table): New entry for
> > R_XTENSA_PDIFF_ULEB128.
> > (elf_xtensa_reloc_type_lookup, elf_xtensa_do_reloc): Handle it.
> > (relax_section): Rewrite padded uleb128 differences in place.
> > * libbfd.h (bfd_reloc_code_real_names): Add
> > BFD_RELOC_XTENSA_PDIFF_ULEB128.
> > * reloc.c: Document BFD_RELOC_XTENSA_PDIFF_ULEB128.
> >
> > binutils/
> > * readelf.c (is_none_reloc): Recognize R_XTENSA_PDIFF_ULEB128.
> >
> > gas/
> > * write.c (cvt_frag_to_fill): Pad leb128 frags to the reserved
> > size when md_leb128_frag_size grew them.
> > (relax_segment): Call md_leb128_frag_size if defined.
> > * config/tc-xtensa.h (xtensa_symfield_type): Add
> > has_leb128_diff_reloc.
> > (md_leb128_frag_size): Define.
> > * config/tc-xtensa.c (xtensa_md_finish): Insert uleb128 fixes.
> > (xtensa_insert_uleb128_fixes, xtensa_leb128_frag_size): New.
> > (xtensa_mark_difference_of_two_symbols): Skip relocated diffs.
> > (md_apply_fix): Ignore BFD_RELOC_XTENSA_PDIFF_ULEB128.
> > * testsuite/gas/xtensa/pdiff-uleb128.s: New test.
> > * testsuite/gas/xtensa/pdiff-uleb128.d: New test.
> > * testsuite/gas/xtensa/pdiff-uleb128-norelax.d: New test.
> >
> > include/
> > * elf/xtensa.h (elf_xtensa_reloc_type): Add
> > R_XTENSA_PDIFF_ULEB128.
> >
> > ld/
> > * testsuite/ld-xtensa/relax-uleb128.s: New test.
> > * testsuite/ld-xtensa/relax-uleb128.d: New test.
> > * testsuite/ld-xtensa/relax-uleb128-2.s: New test.
> > * testsuite/ld-xtensa/relax-uleb128-2.d: New test.
> > * testsuite/ld-xtensa/xtensa.exp: Run them.
> > ---
> > bfd/bfd-in2.h | 10 +++
> > bfd/elf32-xtensa.c | 80 +++++++++++++++++
> > bfd/libbfd.h | 1 +
> > bfd/reloc.c | 12 +++
> > binutils/readelf.c | 3 +-
> > gas/config/tc-xtensa.c | 90 ++++++++++++++++++-
> > gas/config/tc-xtensa.h | 5 ++
> > .../gas/xtensa/pdiff-uleb128-norelax.d | 20 +++++
> > gas/testsuite/gas/xtensa/pdiff-uleb128.d | 12 +++
> > gas/testsuite/gas/xtensa/pdiff-uleb128.s | 7 ++
> > gas/write.c | 20 +++++
> > include/elf/xtensa.h | 3 +
> > ld/testsuite/ld-xtensa/relax-uleb128-2.d | 12 +++
> > ld/testsuite/ld-xtensa/relax-uleb128-2.s | 18 ++++
> > ld/testsuite/ld-xtensa/relax-uleb128.d | 11 +++
> > ld/testsuite/ld-xtensa/relax-uleb128.s | 16 ++++
> > ld/testsuite/ld-xtensa/xtensa.exp | 2 +
> > 17 files changed, 318 insertions(+), 4 deletions(-)
> > create mode 100644 gas/testsuite/gas/xtensa/pdiff-uleb128-norelax.d
> > create mode 100644 gas/testsuite/gas/xtensa/pdiff-uleb128.d
> > create mode 100644 gas/testsuite/gas/xtensa/pdiff-uleb128.s
> > create mode 100644 ld/testsuite/ld-xtensa/relax-uleb128-2.d
> > create mode 100644 ld/testsuite/ld-xtensa/relax-uleb128-2.s
> > create mode 100644 ld/testsuite/ld-xtensa/relax-uleb128.d
> > create mode 100644 ld/testsuite/ld-xtensa/relax-uleb128.s
> >
> > diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
> > index 8d12ddf6723..84b21cb78b8 100644
> > --- a/bfd/bfd-in2.h
> > +++ b/bfd/bfd-in2.h
> > @@ -6168,6 +6168,16 @@ enum bfd_reloc_code_real
> > BFD_RELOC_XTENSA_NDIFF16,
> > BFD_RELOC_XTENSA_NDIFF32,
> >
> > + /* Xtensa relocation to mark a positive difference of two local symbols
> > + encoded as an unsigned LEB128 value. This works like
> > + BFD_RELOC_XTENSA_PDIFF32, but the linker rewrites the difference in
> > + place using the number of bytes the assembler originally emitted, so
> > + that the size of the containing section never changes. Without it the
> > + assembler would have to inhibit linker relaxation of all code covered
> > + by such a difference, which DWARF 5 location and range lists produce
> > + for virtually every function. */
> > + BFD_RELOC_XTENSA_PDIFF_ULEB128,
> > +
> > /* 8 bit signed offset in (ix+d) or (iy+d). */
> > BFD_RELOC_Z80_DISP8,
> >
> > diff --git a/bfd/elf32-xtensa.c b/bfd/elf32-xtensa.c
> > index b1733345fc8..2c279bcbe95 100644
> > --- a/bfd/elf32-xtensa.c
> > +++ b/bfd/elf32-xtensa.c
> > @@ -346,6 +346,8 @@ static reloc_howto_type elf_howto_table[] =
> > bfd_elf_xtensa_reloc, "R_XTENSA_NDIFF16", false, 0, 0xffff, false),
> > HOWTO (R_XTENSA_NDIFF32, 0, 4, 32, false, 0, complain_overflow_bitfield,
> > bfd_elf_xtensa_reloc, "R_XTENSA_NDIFF32", false, 0, 0xffffffff, false),
> > + HOWTO (R_XTENSA_PDIFF_ULEB128, 0, 0, 0, false, 0, complain_overflow_dont,
> > + bfd_elf_xtensa_reloc, "R_XTENSA_PDIFF_ULEB128", false, 0, 0, false),
> > };
> >
> > #if DEBUG_GEN_RELOC
> > @@ -409,6 +411,10 @@ elf_xtensa_reloc_type_lookup (bfd *abfd ATTRIBUTE_UNUSED,
> > TRACE ("BFD_RELOC_XTENSA_NDIFF32");
> > return &elf_howto_table[(unsigned) R_XTENSA_NDIFF32 ];
> >
> > + case BFD_RELOC_XTENSA_PDIFF_ULEB128:
> > + TRACE ("BFD_RELOC_XTENSA_PDIFF_ULEB128");
> > + return &elf_howto_table[(unsigned) R_XTENSA_PDIFF_ULEB128 ];
> > +
> > case BFD_RELOC_XTENSA_RTLD:
> > TRACE ("BFD_RELOC_XTENSA_RTLD");
> > return &elf_howto_table[(unsigned) R_XTENSA_RTLD ];
> > @@ -1891,6 +1897,7 @@ elf_xtensa_do_reloc (reloc_howto_type *howto,
> > case R_XTENSA_NDIFF8:
> > case R_XTENSA_NDIFF16:
> > case R_XTENSA_NDIFF32:
> > + case R_XTENSA_PDIFF_ULEB128:
> > case R_XTENSA_TLS_FUNC:
> > case R_XTENSA_TLS_ARG:
> > case R_XTENSA_TLS_CALL:
> > @@ -9650,6 +9657,79 @@ relax_section (bfd *abfd, asection *sec, struct bfd_link_info *link_info)
> > r_reloc new_reloc;
> > target_sec = translate_reloc (&r_rel, &new_reloc, target_sec);
> >
> > + if (r_type == R_XTENSA_PDIFF_ULEB128)
> > + {
> > + bfd_vma diff_value, new_end_offset;
> > + unsigned int len, new_len = 0;
> > + bfd_byte *p, *q, *endp;
> > +
> > + if (sec_size <= old_source_offset)
> > + {
> > + (*link_info->callbacks->reloc_dangerous)
> > + (link_info, _("invalid relocation address"),
> > + abfd, sec, old_source_offset);
> > + goto error_return;
> > + }
> > +
> > + /* The value is read back from the section contents, so
> > + it must not be trusted to be a well formed uleb128
> > + that ends before the end of the section. */
> > + p = q = &contents[old_source_offset];
> > + diff_value = _bfd_safe_read_leb128 (abfd, &q, false,
> > + contents + sec_size);
> > + len = q - p;
> > + if (len == 0 || (q[-1] & 0x80) != 0)
> > + {
> > + (*link_info->callbacks->reloc_dangerous)
> > + (link_info, _("invalid uleb128 difference"),
> > + abfd, sec, old_source_offset);
> > + goto error_return;
> > + }
> > +
> > + new_end_offset = offset_with_removed_text_map
> > + (&target_relax_info->action_list,
> > + r_rel.target_offset + diff_value);
> > + if (new_end_offset < new_reloc.target_offset)
> > + {
> > + (*link_info->callbacks->reloc_dangerous)
> > + (link_info, _("uleb128 difference is negative after "
> > + "relaxation"),
> > + abfd, sec, old_source_offset);
> > + goto error_return;
> > + }
> > + diff_value = new_end_offset - new_reloc.target_offset;
> > +
> > + /* Byte length of the minimal uleb128 encoding of
> > + DIFF_VALUE. */
> > + for (bfd_vma v = diff_value; new_len++, v >>= 7; )
> > + ;
> > + /* The assembler reserves one spare byte for these
> > + differences, but reject growth that still needs more
> > + bytes than were emitted. */
> > + if (new_len > len)
> > + {
> > + (*link_info->callbacks->reloc_dangerous)
> > + (link_info, _("uleb128 difference overflows after "
> > + "relaxation"),
> > + abfd, sec, old_source_offset);
> > + goto error_return;
> > + }
> > +
> > + /* Rewrite the difference in place, always using the
> > + number of bytes the assembler emitted so that the size
> > + of this section does not change. A value that now
> > + needs fewer bytes is padded with uleb128 zeroes. */
> > + endp = p + len - 1;
> > + memset (p, 0x80, len - 1);
> > + *endp = 0;
> > + p = _bfd_write_unsigned_leb128 (p, endp, diff_value);
> > + BFD_ASSERT (p);
> > + if (--p < endp)
> > + *p |= 0x80;
> > +
> > + pin_contents (sec, contents);
> > + }
> > +
> > if (r_type == R_XTENSA_DIFF8
> > || r_type == R_XTENSA_DIFF16
> > || r_type == R_XTENSA_DIFF32
> > diff --git a/bfd/libbfd.h b/bfd/libbfd.h
> > index 6e737e468df..72e7d60e903 100644
> > --- a/bfd/libbfd.h
> > +++ b/bfd/libbfd.h
> > @@ -2797,6 +2797,7 @@ static const char *const bfd_reloc_code_real_names[] = { "@@uninitialized@@",
> > "BFD_RELOC_XTENSA_NDIFF8",
> > "BFD_RELOC_XTENSA_NDIFF16",
> > "BFD_RELOC_XTENSA_NDIFF32",
> > + "BFD_RELOC_XTENSA_PDIFF_ULEB128",
> > "BFD_RELOC_Z80_DISP8",
> > "BFD_RELOC_Z80_BYTE0",
> > "BFD_RELOC_Z80_BYTE1",
> > diff --git a/bfd/reloc.c b/bfd/reloc.c
> > index 29288f8099d..0e2cb187e34 100644
> > --- a/bfd/reloc.c
> > +++ b/bfd/reloc.c
> > @@ -6031,6 +6031,18 @@ ENUMDOC
> > differences. The difference value is treated as unsigned with these
> > relocation types, giving full 8/16 value ranges.
> >
> > +ENUM
> > + BFD_RELOC_XTENSA_PDIFF_ULEB128
> > +ENUMDOC
> > + Xtensa relocation to mark a positive difference of two local symbols
> > + encoded as an unsigned LEB128 value. This works like
> > + BFD_RELOC_XTENSA_PDIFF32, but the linker rewrites the difference in
> > + place using the number of bytes the assembler originally emitted, so
> > + that the size of the containing section never changes. Without it the
> > + assembler would have to inhibit linker relaxation of all code covered
> > + by such a difference, which DWARF 5 location and range lists produce
> > + for virtually every function.
> > +
> > ENUM
> > BFD_RELOC_Z80_DISP8
> > ENUMDOC
> > diff --git a/binutils/readelf.c b/binutils/readelf.c
> > index b5865d9717e..e82a90e605c 100644
> > --- a/binutils/readelf.c
> > +++ b/binutils/readelf.c
> > @@ -16853,7 +16853,8 @@ is_none_reloc (Filedata * filedata, unsigned int reloc_type)
> > || reloc_type == 59 /* R_XTENSA_PDIFF32. */
> > || reloc_type == 60 /* R_XTENSA_NDIFF8. */
> > || reloc_type == 61 /* R_XTENSA_NDIFF16. */
> > - || reloc_type == 62 /* R_XTENSA_NDIFF32. */);
> > + || reloc_type == 62 /* R_XTENSA_NDIFF32. */
> > + || reloc_type == 63 /* R_XTENSA_PDIFF_ULEB128. */);
> > }
> > return false;
> > }
> > diff --git a/gas/config/tc-xtensa.c b/gas/config/tc-xtensa.c
> > index 397744f742b..631b61c5128 100644
> > --- a/gas/config/tc-xtensa.c
> > +++ b/gas/config/tc-xtensa.c
> > @@ -6104,6 +6104,7 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg)
> > break;
> >
> > case BFD_RELOC_XTENSA_ASM_EXPAND:
> > + case BFD_RELOC_XTENSA_PDIFF_ULEB128:
> > case BFD_RELOC_XTENSA_TLS_FUNC:
> > case BFD_RELOC_XTENSA_TLS_ARG:
> > case BFD_RELOC_XTENSA_TLS_CALL:
> > @@ -7361,6 +7362,7 @@ static void xtensa_fix_target_frags (void);
> > static void xtensa_mark_narrow_branches (void);
> > static void xtensa_mark_zcl_first_insns (void);
> > static void xtensa_mark_difference_of_two_symbols (void);
> > +static void xtensa_insert_uleb128_fixes (bfd *, asection *, void *);
> > static void xtensa_fix_a0_b_retw_frags (void);
> > static void xtensa_fix_b_j_loop_end_frags (void);
> > static void xtensa_fix_close_loop_end_frags (void);
> > @@ -7401,6 +7403,9 @@ xtensa_md_finish (void)
> > xtensa_add_config_info ();
> >
> > xtensa_check_frag_count ();
> > +
> > + if (linkrelax)
> > + bfd_map_over_sections (stdoutput, xtensa_insert_uleb128_fixes, NULL);
> > }
> >
> > struct trampoline_chain_entry
> > @@ -8234,11 +8239,87 @@ xtensa_mark_zcl_first_insns (void)
> > }
> > }
> >
> > +/* A difference of two symbols encoded as a uleb128 value can be handed to
> > + the linker as a BFD_RELOC_XTENSA_PDIFF_ULEB128 relocation: the difference
> > + itself stays in the section contents and the relocation records the
> > + address of the subtracted symbol, which is all the linker needs to
> > + rewrite the value after relaxation. DWARF 5 location and range lists
> > + are made almost entirely of such differences, so without this the code
> > + covered by them could never be relaxed.
> > +
> > + This has to run before relaxation turns the rs_leb128 frags into plain
> > + data. Differences that cannot be represented this way are left to
> > + xtensa_mark_difference_of_two_symbols.
> > +
> > + Mark the expression symbol so xtensa_leb128_frag_size can reserve one
> > + spare byte: Xtensa linker relaxation can grow code, which may push a
> > + difference across a uleb128 byte boundary. */
> > +
> > +static void
> > +xtensa_insert_uleb128_fixes (bfd *abfd ATTRIBUTE_UNUSED,
> > + asection *sec,
> > + void *unused ATTRIBUTE_UNUSED)
> > +{
> > + segment_info_type *seginfo = seg_info (sec);
> > + fragS *fragP;
> > +
> > + if (seginfo == NULL || seginfo->frchainP == NULL)
> > + return;
> > +
> > + subseg_set (sec, 0);
> > +
> > + for (fragP = seginfo->frchainP->frch_root; fragP; fragP = fragP->fr_next)
> > + {
> > + expressionS *exp;
> > + symbolS *op_sym;
> > +
> > + /* Non-zero fr_subtype is sleb128 (no relocation). */
> > + if (fragP->fr_type != rs_leb128 || fragP->fr_subtype != 0
> > + || fragP->fr_symbol == NULL)
> > + continue;
> > +
> > + exp = symbol_get_value_expression (fragP->fr_symbol);
> > + if (exp->X_op != O_subtract)
> > + continue;
> > +
> > + op_sym = exp->X_op_symbol;
> > +
> > + /* R_XTENSA_PDIFF_ULEB128 only encodes same-section differences. */
> > + if (S_GET_SEGMENT (exp->X_add_symbol) != S_GET_SEGMENT (op_sym))
> > + continue;
> > +
> > + /* Only code sections are relaxed. */
> > + if (!(bfd_section_flags (S_GET_SEGMENT (op_sym)) & SEC_CODE))
> > + continue;
> > +
> > + fix_new (fragP, fragP->fr_fix, 0, op_sym, 0, 0,
> > + BFD_RELOC_XTENSA_PDIFF_ULEB128);
> > + symbol_get_tc (fragP->fr_symbol)->has_leb128_diff_reloc = 1;
> > + }
> > +}
> > +
> > +/* For uleb128 diffs with R_XTENSA_PDIFF_ULEB128, reserve one spare byte so
> > + linker relaxation can grow the value across one 7-bit boundary without
> > + overflowing. Growth that needs more than one extra byte still errors in
> > + the linker. frag_var already allocated sizeof_leb128 (~0, 0) bytes;
> > + clamp if the value already needs that many. */
> > +
> > +offsetT
> > +xtensa_leb128_frag_size (const fragS *fragP, offsetT size)
> > +{
> > + if (fragP->fr_symbol != NULL
> > + && symbol_get_tc (fragP->fr_symbol)->has_leb128_diff_reloc
> > + && size < (offsetT) sizeof_leb128 (~(valueT) 0, 0))
> > + size++;
> > + return size;
> > +}
> > +
> >
> > /* When a difference-of-symbols expression is encoded as a uleb128 or
> > - sleb128 value, the linker is unable to adjust that value to account for
> > - link-time relaxation. Mark all the code between such symbols so that
> > - its size cannot be changed by linker relaxation. */
> > + sleb128 value and no relocation can express it, the linker is unable to
> > + adjust that value to account for link-time relaxation. Mark all the code
> > + between such symbols so that its size cannot be changed by linker
> > + relaxation. */
> >
> > static void
> > xtensa_mark_difference_of_two_symbols (void)
> > @@ -8250,6 +8331,9 @@ xtensa_mark_difference_of_two_symbols (void)
> > {
> > expressionS *exp = symbol_get_value_expression (expr_sym);
> >
> > + if (symbol_get_tc (expr_sym)->has_leb128_diff_reloc)
> > + continue;
> > +
> > if (exp->X_op == O_subtract)
> > {
> > symbolS *left = exp->X_add_symbol;
> > diff --git a/gas/config/tc-xtensa.h b/gas/config/tc-xtensa.h
> > index 64d735144d7..afd7478dd8d 100644
> > --- a/gas/config/tc-xtensa.h
> > +++ b/gas/config/tc-xtensa.h
> > @@ -297,6 +297,9 @@ typedef struct xtensa_symfield_type
> > {
> > unsigned int is_loop_target : 1;
> > unsigned int is_branch_target : 1;
> > + /* Set when a uleb128 difference got R_XTENSA_PDIFF_ULEB128, so code
> > + between the symbols may still be relaxed. */
> > + unsigned int has_leb128_diff_reloc : 1;
> > symbolS *next_expr_symbol;
> > } xtensa_symfield_type;
> >
> > @@ -341,6 +344,7 @@ extern int xtensa_unrecognized_line (int);
> > extern bool xtensa_check_inside_bundle (void);
> > extern void xtensa_handle_align (fragS *);
> > extern char *xtensa_section_rename (const char *);
> > +extern offsetT xtensa_leb128_frag_size (const fragS *, offsetT);
> >
> > /* We need to set the target endianness in xtensa_init and not in md_begin.
> > This is because xtensa_target_format is called before md_begin, and we
> > @@ -374,6 +378,7 @@ extern void xtensa_init (int, char **);
> > #define md_elf_section_change_hook xtensa_elf_section_change_hook
> > #define md_finish xtensa_md_finish
> > #define md_flush_pending_output() xtensa_flush_pending_output ()
> > +#define md_leb128_frag_size(frag, size) xtensa_leb128_frag_size (frag, size)
> > #define md_operand(x)
> > #define TEXT_SECTION_NAME xtensa_section_rename (".text")
> > #define DATA_SECTION_NAME xtensa_section_rename (".data")
> > diff --git a/gas/testsuite/gas/xtensa/pdiff-uleb128-norelax.d b/gas/testsuite/gas/xtensa/pdiff-uleb128-norelax.d
> > new file mode 100644
> > index 00000000000..dcd4641083f
> > --- /dev/null
> > +++ b/gas/testsuite/gas/xtensa/pdiff-uleb128-norelax.d
> > @@ -0,0 +1,20 @@
> > +#as: --no-link-relax
> > +#source: pdiff-uleb128.s
> > +#objdump: -r -s -j .debug_info -j .xt.prop
> > +#name: uleb128 difference without link-relax
> > +
> > +# Without link-relax, no R_XTENSA_PDIFF_ULEB128 is emitted. The assembler
> > +# falls back to marking the covered code no_transform via .xt.prop, and the
> > +# uleb128 uses the minimal encoding (no spare byte).
> > +
> > +.*: +file format .*xtensa.*
> > +
> > +RELOCATION RECORDS FOR \[.xt.prop\]:
> > +OFFSET +TYPE +VALUE
> > +0+ R_XTENSA_32 +.text.*
> > +
> > +Contents of section .debug_info:
> > + 0000 c801.*
> > +#...
> > +Contents of section .xt.prop:
> > + 0000 .*
> > diff --git a/gas/testsuite/gas/xtensa/pdiff-uleb128.d b/gas/testsuite/gas/xtensa/pdiff-uleb128.d
> > new file mode 100644
> > index 00000000000..5c38f56ca66
> > --- /dev/null
> > +++ b/gas/testsuite/gas/xtensa/pdiff-uleb128.d
> > @@ -0,0 +1,12 @@
> > +#objdump: -r -s -j .debug_info
> > +#name: uleb128 difference reloc
> > +
> > +.*: +file format .*xtensa.*
> > +
> > +RELOCATION RECORDS FOR \[.debug_info\]:
> > +OFFSET +TYPE +VALUE
> > +0+ R_XTENSA_PDIFF_ULEB128 +.text.*
> > +
> > +# Difference is 200 (0xc8 0x01) plus one spare byte reserved for growth.
> > +Contents of section .debug_info:
> > + 0000 c88100.*
> > diff --git a/gas/testsuite/gas/xtensa/pdiff-uleb128.s b/gas/testsuite/gas/xtensa/pdiff-uleb128.s
> > new file mode 100644
> > index 00000000000..0b431a3ac26
> > --- /dev/null
> > +++ b/gas/testsuite/gas/xtensa/pdiff-uleb128.s
> > @@ -0,0 +1,7 @@
> > + .text
> > +.L1:
> > + .space 200
> > +.L2:
> > +
> > + .section .debug_info, "", @progbits
> > + .uleb128 .L2 - .L1
> > diff --git a/gas/write.c b/gas/write.c
> > index cd02d8c7fb8..467b51be7f8 100644
> > --- a/gas/write.c
> > +++ b/gas/write.c
> > @@ -461,6 +461,23 @@ cvt_frag_to_fill (segT sec ATTRIBUTE_UNUSED, fragS *fragP)
> > size = output_leb128 (fragP->fr_literal + fragP->fr_fix, value,
> > fragP->fr_subtype);
> >
> > + /* Relaxation may have reserved more room than the shortest encoding
> > + needs (see md_leb128_frag_size). Keep the reserved size by adding
> > + redundant high-order continuation bytes; inert unless a target
> > + hook grew fr_offset above the minimal encoding. */
> > + if ((offsetT) size < fragP->fr_offset)
> > + {
> > + char *p = fragP->fr_literal + fragP->fr_fix;
> > + char pad = fragP->fr_subtype && (offsetT) value < 0 ? 0x7f : 0;
> > +
> > + do
> > + {
> > + p[size - 1] |= 0x80;
> > + p[size++] = pad;
> > + }
> > + while ((offsetT) size < fragP->fr_offset);
> > + }
> > +
> > fragP->fr_fix += size;
> > fragP->fr_type = rs_fill;
> > fragP->fr_var = 0;
> > @@ -3124,6 +3141,9 @@ relax_segment (struct frag *segment_frag_root, segT segment, int pass)
> >
> > value = resolve_symbol_value (fragP->fr_symbol);
> > size = sizeof_leb128 (value, fragP->fr_subtype);
> > +#ifdef md_leb128_frag_size
> > + size = md_leb128_frag_size (fragP, size);
> > +#endif
> > growth = size - fragP->fr_offset;
> > fragP->fr_offset = size;
> > }
> > diff --git a/include/elf/xtensa.h b/include/elf/xtensa.h
> > index 1a9bdf95cf7..032b94ef94b 100644
> > --- a/include/elf/xtensa.h
> > +++ b/include/elf/xtensa.h
> > @@ -93,6 +93,9 @@ START_RELOC_NUMBERS (elf_xtensa_reloc_type)
> > RELOC_NUMBER (R_XTENSA_NDIFF8, 60)
> > RELOC_NUMBER (R_XTENSA_NDIFF16, 61)
> > RELOC_NUMBER (R_XTENSA_NDIFF32, 62)
> > + /* Positive same-section difference encoded as uleb128; rewritten
> > + in place after relaxation without changing the section size. */
> > + RELOC_NUMBER (R_XTENSA_PDIFF_ULEB128, 63)
> > END_RELOC_NUMBERS (R_XTENSA_max)
> >
> > /* Processor-specific flags for the ELF header e_flags field. */
> > diff --git a/ld/testsuite/ld-xtensa/relax-uleb128-2.d b/ld/testsuite/ld-xtensa/relax-uleb128-2.d
> > new file mode 100644
> > index 00000000000..c0f1c9ca378
> > --- /dev/null
> > +++ b/ld/testsuite/ld-xtensa/relax-uleb128-2.d
> > @@ -0,0 +1,12 @@
> > +#source: relax-uleb128-2.s
> > +#source: lcall2.s
> > +#ld: -T lcall.t
> > +#objdump: -s -j .debug_info
> > +#name: uleb128 difference shrinking below 128
> > +
> > +# The difference is 156 before relaxation and 108 after it, so the value no
> > +# longer needs two bytes. The assembler reserved one spare byte (three
> > +# total), and the linker must keep that fixed width with uleb128 padding.
> > +#...
> > + 0000 ec8000.*
> > +#...
> > diff --git a/ld/testsuite/ld-xtensa/relax-uleb128-2.s b/ld/testsuite/ld-xtensa/relax-uleb128-2.s
> > new file mode 100644
> > index 00000000000..c587ed8bb06
> > --- /dev/null
> > +++ b/ld/testsuite/ld-xtensa/relax-uleb128-2.s
> > @@ -0,0 +1,18 @@
> > + .globl _start
> > + .globl foo
> > + .text
> > + .align 4
> > +_start:
> > + .literal .Lunused, 0xffffffff
> > + entry a5, 16
> > +.L1:
> > + .space 60
> > + .begin longcalls
> > + .rept 16
> > + call4 foo
> > + .endr
> > + .end longcalls
> > +.L2:
> > +
> > + .section .debug_info, "", @progbits
> > + .uleb128 .L2 - .L1
> > diff --git a/ld/testsuite/ld-xtensa/relax-uleb128.d b/ld/testsuite/ld-xtensa/relax-uleb128.d
> > new file mode 100644
> > index 00000000000..08b017984d8
> > --- /dev/null
> > +++ b/ld/testsuite/ld-xtensa/relax-uleb128.d
> > @@ -0,0 +1,11 @@
> > +#source: relax-uleb128.s
> > +#source: lcall2.s
> > +#ld: -T lcall.t
> > +#objdump: -s -j .debug_info
> > +#name: uleb128 difference after longcall relax
> > +
> > +# Longcall relaxes from 6 bytes to 3; with the trailing nop the difference
> > +# is 5. Assembler reserved one spare byte (two total).
> > +#...
> > + 0000 8500.*
> > +#...
> > diff --git a/ld/testsuite/ld-xtensa/relax-uleb128.s b/ld/testsuite/ld-xtensa/relax-uleb128.s
> > new file mode 100644
> > index 00000000000..8e1c0058976
> > --- /dev/null
> > +++ b/ld/testsuite/ld-xtensa/relax-uleb128.s
> > @@ -0,0 +1,16 @@
> > + .globl _start
> > + .globl foo
> > + .text
> > + .align 4
> > +_start:
> > + .literal .Lunused, 0xffffffff
> > + entry a5, 16
> > +.L1:
> > + .begin longcalls
> > + call4 foo
> > + .end longcalls
> > + nop
> > +.L2:
> > +
> > + .section .debug_info, "", @progbits
> > + .uleb128 .L2 - .L1
> > diff --git a/ld/testsuite/ld-xtensa/xtensa.exp b/ld/testsuite/ld-xtensa/xtensa.exp
> > index 7173c6b21b2..66a6b7a60da 100644
> > --- a/ld/testsuite/ld-xtensa/xtensa.exp
> > +++ b/ld/testsuite/ld-xtensa/xtensa.exp
> > @@ -30,6 +30,8 @@ run_dump_test "lcall"
> > run_dump_test "relax-diff1"
> > run_dump_test "relax-loc"
> > run_dump_test "relax-ndiff"
> > +run_dump_test "relax-uleb128"
> > +run_dump_test "relax-uleb128-2"
> >
> > run_dump_test "relax-static-pie"
> > run_dump_test "relax-static-local-pie"
>