From: Lifang Xia <lifang_xia@linux.alibaba.com>
In the scenario of generating .ko files, the kernel does not relax the .ko
files. However, due to the large amount of relax and local relocation
information, this increases the size of the .ko files.
In this patch, it will finish the fixup of the local relocations while with
"-mno-relax" option. This can reduce the size of the relocation table.
gas/
* config/tc-riscv.c (struct riscv_pcrel_hi_reloc): New, reference
from bfd/elfnn-riscv.c.
(riscv_pcrel_hi_reloc_hash): Likewise.
(riscv_pcrel_reloc_hash): Likewise.
(riscv_pcrel_reloc_eq): Likewise.
(riscv_record_pcrel_reolc): Likewise.
(md_begin): Init pcrel_hi hash.
(md_apply_fix) <case BFD_RELOC_RISCV_PCREL_HI20>: Do fixup and
record the pcrel_hi relocs, mark as done while with
"-mno-relax".
(md_apply_fix) <case BFD_RELOC_RISCV_PCREL_LO12_I>:
(md_apply_fix) <case BFD_RELOC_RISCV_PCREL_LO12_S>: Do fixup
and mark as done while with "-mno-relax".
(riscv_md_end): New, delete riscv_pcrel_hi_reloc_hash.
* config/tc-riscv.h (md_end): Define md_end with riscv_md_end.
gas/
* testsuite/gas/riscv/fixup-local*: New tests.
---
gas/config/tc-riscv.c | 111 +++++++++++++++++-
gas/config/tc-riscv.h | 3 +
gas/testsuite/gas/riscv/fixup-local-norelax.d | 23 ++++
gas/testsuite/gas/riscv/fixup-local-relax.d | 41 +++++++
gas/testsuite/gas/riscv/fixup-local.s | 13 ++
5 files changed, 190 insertions(+), 1 deletion(-)
create mode 100644 gas/testsuite/gas/riscv/fixup-local-norelax.d
create mode 100644 gas/testsuite/gas/riscv/fixup-local-relax.d
create mode 100644 gas/testsuite/gas/riscv/fixup-local.s
@@ -1565,6 +1565,58 @@ init_opcode_hash (const struct riscv_opcode *opcodes,
return hash;
}
+/* Record all PC-relative high-part relocs we've encountered to help us
+ later resolve the corresponding low-part relocs. */
+struct riscv_pcrel_hi_reloc
+{
+ bfd_vma address;
+ symbolS *symbol;
+ bfd_vma target;
+};
+
+/* Handle of the pcrel_hi hash table. */
+static htab_t riscv_pcrel_hi_reloc_hash;
+
+/* Get the key of a entry from the pcrel_hi hash table. */
+
+static hashval_t
+riscv_pcrel_reloc_hash (const void *entry)
+{
+ const struct riscv_pcrel_hi_reloc *e = entry;
+ return (hashval_t) (e->address);
+}
+
+/* Compare the keys between two entries fo the pcrel_hi hash table. */
+
+static int
+riscv_pcrel_reloc_eq (const void *entry1, const void *entry2)
+{
+ const struct riscv_pcrel_hi_reloc *e1 = entry1, *e2 = entry2;
+ return e1->address == e2->address;
+}
+
+/* Record the pcrel_hi relocs. */
+
+static bool
+riscv_record_pcrel_reolc (htab_t p, bfd_vma address, symbolS *symbol,
+ bfd_vma target)
+{
+ struct riscv_pcrel_hi_reloc entry = { address, symbol, target };
+ struct riscv_pcrel_hi_reloc **slot
+ = (struct riscv_pcrel_hi_reloc **)htab_find_slot (p, &entry, INSERT);
+ if (slot == NULL)
+ return false;
+
+ *slot = (struct riscv_pcrel_hi_reloc *)xmalloc (
+ sizeof (struct riscv_pcrel_hi_reloc));
+ if (*slot != NULL)
+ {
+ **slot = entry;
+ return true;
+ }
+ return false;
+}
+
/* This function is called once, at assembler startup time. It should set up
all the tables, etc. that the MD part of the assembler will need. */
@@ -1601,6 +1653,11 @@ md_begin (void)
opcode_names_hash = str_htab_create ();
init_opcode_names_hash ();
+ /* Create pcrel_hi hash table to resolve the relocation while with
+ -mno-relax. */
+ riscv_pcrel_hi_reloc_hash
+ = htab_create (1024, riscv_pcrel_reloc_hash, riscv_pcrel_reloc_eq, free);
+
/* Set the default alignment for the text section. */
record_alignment (text_section, riscv_opts.rvc ? 1 : 2);
}
@@ -4220,9 +4277,52 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
break;
case BFD_RELOC_RISCV_PCREL_HI20:
+ /* record the pcrel_hi relocs of the local symbols. And evaluate the hi20
+ of the lcoal symbols. Fill in a tentative value to improve objdump
+ readability for -mrelax, and set fx_done for -mno-relax. */
+ if (S_IS_LOCAL (fixP->fx_addsy) && fixP->fx_addsy
+ && S_GET_SEGMENT (fixP->fx_addsy) == seg)
+ {
+ bfd_vma target = S_GET_VALUE (fixP->fx_addsy) + *valP;
+ bfd_vma value = target - md_pcrel_from (fixP);
+
+ /* Record PCREL_HI20. */
+ if (!riscv_record_pcrel_reolc (riscv_pcrel_hi_reloc_hash,
+ md_pcrel_from (fixP), fixP->fx_addsy,
+ target))
+ {
+ as_warn ("too many pcrel_hi");
+ }
+
+ bfd_putl32 (bfd_getl32 (buf)
+ | ENCODE_UTYPE_IMM (RISCV_CONST_HIGH_PART (value)),
+ buf);
+ if (!riscv_opts.relax)
+ fixP->fx_done = 1;
+ }
+ relaxable = riscv_opts.relax;
+ break;
case BFD_RELOC_RISCV_PCREL_LO12_S:
case BFD_RELOC_RISCV_PCREL_LO12_I:
- relaxable = riscv_opts.relax;
+ {
+ /* Resolve the low12 of the local symboles with the pcrel_hi relocs.
+ Fill in a tentative value to improve objdump readability for
+ -mrelax, and set fx_done for -mno-relax. */
+ bfd_vma location_pcrel_hi = S_GET_VALUE (fixP->fx_addsy) + *valP;
+ struct riscv_pcrel_hi_reloc search = { location_pcrel_hi, 0, 0 };
+ struct riscv_pcrel_hi_reloc *entry
+ = htab_find (riscv_pcrel_hi_reloc_hash, &search);
+ if (entry && entry->symbol && S_IS_LOCAL (entry->symbol)
+ && S_GET_SEGMENT (entry->symbol) == seg)
+ {
+ bfd_vma target = entry->target;
+ bfd_vma value = target - entry->address;
+ bfd_putl32 (bfd_getl32 (buf) | ENCODE_ITYPE_IMM (value), buf);
+ if (!riscv_opts.relax)
+ fixP->fx_done = 1;
+ }
+ relaxable = riscv_opts.relax;
+ }
break;
case BFD_RELOC_RISCV_ALIGN:
@@ -4987,6 +5087,15 @@ riscv_md_finish (void)
riscv_set_public_attributes ();
if (riscv_opts.relax)
bfd_map_over_sections (stdoutput, riscv_insert_uleb128_fixes, NULL);
+
+}
+
+/* Called just before the assembler exits. */
+
+void
+riscv_md_end (void)
+{
+ htab_delete (riscv_pcrel_hi_reloc_hash);
}
/* Adjust the symbol table. */
@@ -80,6 +80,9 @@ extern int riscv_parse_long_option (const char *);
extern void riscv_pre_output_hook (void);
#define GAS_SORT_RELOCS 1
+#define md_end riscv_md_end
+extern void riscv_md_end (void);
+
/* Let the linker resolve all the relocs due to relaxation. */
#define tc_fix_adjustable(fixp) 0
#define md_allow_local_subtract(l,r,s) 0
new file mode 100644
@@ -0,0 +1,23 @@
+#as: -march=rv64i -mno-relax
+#source: fixup-local.s
+#objdump: -dr
+
+tmpdir/fixup-local.o: file format elf64-littleriscv
+
+
+Disassembly of section .text:
+
+0+0000 <foo>:
+[ ]+0:[ ]+00000517[ ]+auipc a0,0x0
+[ ]+4:[ ]+00850513[ ]+addi a0,a0,8 # 8 <foo\+0x8>
+[ ]+8:[ ]+00000517[ ]+auipc a0,0x0
+[ ]+8: R_RISCV_PCREL_HI20 bar
+[ ]+c:[ ]+00050513[ ]+mv a0,a0
+[ ]+c: R_RISCV_PCREL_LO12_I .L0
+[ ]+10:[ ]+00000517[ ]+auipc a0,0x0
+[ ]+10: R_RISCV_PCREL_HI20 foo
+[ ]+14:[ ]+00050513[ ]+mv a0,a0
+[ ]+14: R_RISCV_PCREL_LO12_I .L0
+[ ]+18:[ ]+00000517[ ]+auipc a0,0x0
+[ ]+1c:[ ]+00852503[ ]+lw a0,8\(a0\) # 20 <foo\+0x20>
+[ ]+20:[ ]+00008067[ ]+ret
new file mode 100644
@@ -0,0 +1,41 @@
+#as: -march=rv64i
+#source: fixup-local.s
+#objdump: -dr
+
+tmpdir/fixup-local.o: file format elf64-littleriscv
+
+
+Disassembly of section .text:
+
+0+0000 <foo>:
+[ ]+0:[ ]+00000517[ ]+auipc a0,0x0
+[ ]+0: R_RISCV_PCREL_HI20 .LL0
+[ ]+0: R_RISCV_RELAX \*ABS\*
+[ ]+4:[ ]+00850513[ ]+addi a0,a0,8 # 8 <.LL0>
+[ ]+4: R_RISCV_PCREL_LO12_I .L0
+[ ]+4: R_RISCV_RELAX \*ABS\*
+
+0000000000000008 <.LL0>:
+[ ]+8:[ ]+00000517[ ]+auipc a0,0x0
+[ ]+8: R_RISCV_PCREL_HI20 bar
+[ ]+8: R_RISCV_RELAX \*ABS\*
+[ ]+c:[ ]+00050513[ ]+mv a0,a0
+[ ]+c: R_RISCV_PCREL_LO12_I .L0
+[ ]+c: R_RISCV_RELAX \*ABS\*
+[ ]+10:[ ]+00000517[ ]+auipc a0,0x0
+[ ]+10: R_RISCV_PCREL_HI20 foo
+[ ]+10: R_RISCV_RELAX \*ABS\*
+[ ]+14:[ ]+00050513[ ]+mv a0,a0
+[ ]+14: R_RISCV_PCREL_LO12_I .L0
+[ ]+14: R_RISCV_RELAX \*ABS\*
+
+0000000000000018 <.LL1>:
+[ ]+18:[ ]+00000517[ ]+auipc a0,0x0
+[ ]+18: R_RISCV_PCREL_HI20 .LL2
+[ ]+18: R_RISCV_RELAX \*ABS\*
+[ ]+1c:[ ]+00852503[ ]+lw a0,8\(a0\) # 20 <.LL2>
+[ ]+1c: R_RISCV_PCREL_LO12_I .LL1
+[ ]+1c: R_RISCV_RELAX \*ABS\*
+
+0000000000000020 <.LL2>:
+[ ]+20:[ ]+00008067[ ]+ret
new file mode 100644
@@ -0,0 +1,13 @@
+.global foo
+.global bar
+foo:
+ la a0, .LL0
+.LL0:
+ la a0, bar
+ la a0, foo
+.LL1:
+ auipc a0, %pcrel_hi(.LL2)
+ lw a0, %pcrel_lo(.LL1)(a0)
+
+.LL2:
+ ret