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MSP430: Enable relaxation of relocs in JMP instructions

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This patch fixes relocation overflows caused by an inability to relax
unconditional JMP instructions to BR instructions.

bfd/ChangeLog:

2020-02-10  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	* elf32-msp430.c (msp430_elf_relax_add_two_words): Rename to
	msp430_elf_relax_add_words. Support insertion of either one or two
	words.
	(msp430_elf_relax_section): Catch opcode of 0x3c00 when relocation
	needs to be grown. Handle insertion of branch instruction to replace
	jump.
This commit is contained in:
Jozef Lawrynowicz 2020-02-10 20:33:21 +00:00
parent d60f54486a
commit 8d6cb116f4
2 changed files with 75 additions and 30 deletions
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9
bfd/ChangeLog
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@ -1,3 +1,12 @@
2020-02-10 Jozef Lawrynowicz <jozef.l@mittosystems.com>
* elf32-msp430.c (msp430_elf_relax_add_two_words): Rename to
msp430_elf_relax_add_words. Support insertion of either one or two
words.
(msp430_elf_relax_section): Catch opcode of 0x3c00 when relocation
needs to be grown. Handle insertion of branch instruction to replace
jump.
2020-02-10 Jozef Lawrynowicz <jozef.l@mittosystems.com>
* elf32-msp430.c (msp430_final_link_relocate): Add printf statements for

96
bfd/elf32-msp430.c
View File

@ -1768,11 +1768,11 @@ msp430_elf_relax_delete_bytes (bfd * abfd, asection * sec, bfd_vma addr,
return TRUE;
}
/* Insert two words into a section whilst relaxing. */
/* Insert one or two words into a section whilst relaxing. */
static bfd_byte *
msp430_elf_relax_add_two_words (bfd * abfd, asection * sec, bfd_vma addr,
int word1, int word2)
msp430_elf_relax_add_words (bfd * abfd, asection * sec, bfd_vma addr,
int num_words, int word1, int word2)
{
Elf_Internal_Shdr *symtab_hdr;
unsigned int sec_shndx;
@ -1787,22 +1787,24 @@ msp430_elf_relax_add_two_words (bfd * abfd, asection * sec, bfd_vma addr,
bfd_vma sec_end;
asection *p;
if (debug_relocs)
printf (" adding two words at 0x%lx\n",
printf (" adding %d words at 0x%lx\n", num_words,
sec->output_section->vma + sec->output_offset + addr);
contents = elf_section_data (sec)->this_hdr.contents;
sec_end = sec->size;
int num_bytes = num_words * 2;
/* Make space for the new words. */
contents = bfd_realloc (contents, sec_end + 4);
memmove (contents + addr + 4, contents + addr, sec_end - addr);
contents = bfd_realloc (contents, sec_end + num_bytes);
memmove (contents + addr + num_bytes, contents + addr, sec_end - addr);
/* Insert the new words. */
bfd_put_16 (abfd, word1, contents + addr);
bfd_put_16 (abfd, word2, contents + addr + 2);
if (num_words == 2)
bfd_put_16 (abfd, word2, contents + addr + 2);
/* Update the section information. */
sec->size += 4;
sec->size += num_bytes;
elf_section_data (sec)->this_hdr.contents = contents;
/* Adjust all the relocs. */
@ -1811,12 +1813,12 @@ msp430_elf_relax_add_two_words (bfd * abfd, asection * sec, bfd_vma addr,
for (; irel < irelend; irel++)
if ((irel->r_offset >= addr && irel->r_offset < sec_end))
irel->r_offset += 4;
irel->r_offset += num_bytes;
/* Adjust the local symbols defined in this section. */
sec_shndx = _bfd_elf_section_from_bfd_section (abfd, sec);
for (p = abfd->sections; p != NULL; p = p->next)
msp430_elf_relax_adjust_locals (abfd, p, addr, -4,
msp430_elf_relax_adjust_locals (abfd, p, addr, -num_bytes,
sec_shndx, sec_end);
/* Adjust the global symbols affected by the move. */
@ -1830,8 +1832,8 @@ msp430_elf_relax_add_two_words (bfd * abfd, asection * sec, bfd_vma addr,
printf (" adjusting value of local symbol %s from 0x%lx to "
"0x%lx\n", bfd_elf_string_from_elf_section
(abfd, symtab_hdr->sh_link, isym->st_name),
isym->st_value, isym->st_value + 4);
isym->st_value += 4;
isym->st_value, isym->st_value + num_bytes);
isym->st_value += num_bytes;
}
/* Now adjust the global symbols defined in this section. */
@ -1848,7 +1850,7 @@ msp430_elf_relax_add_two_words (bfd * abfd, asection * sec, bfd_vma addr,
&& sym_hash->root.u.def.section == sec
&& sym_hash->root.u.def.value >= addr
&& sym_hash->root.u.def.value < sec_end)
sym_hash->root.u.def.value += 4;
sym_hash->root.u.def.value += num_bytes;
}
return contents;
@ -2015,8 +2017,12 @@ msp430_elf_relax_section (bfd * abfd, asection * sec,
opcode = bfd_get_16 (abfd, contents + irel->r_offset);
/* Compute the new opcode. We are going to convert:
JMP label
into:
BR[A] label
or
J<cond> label
into:
into:
J<inv-cond> 1f
BR[A] #label
1: */
@ -2036,8 +2042,14 @@ msp430_elf_relax_section (bfd * abfd, asection * sec,
1: br label
2: */
continue;
case 0x3c00:
if (uses_msp430x_relocs (abfd))
opcode = 0x0080; /* JMP -> BRA */
else
opcode = 0x4030; /* JMP -> BR */
break;
default:
/* Not a conditional branch instruction. */
/* Unhandled branch instruction. */
/* fprintf (stderr, "unrecog: %x\n", opcode); */
continue;
}
@ -2057,16 +2069,29 @@ msp430_elf_relax_section (bfd * abfd, asection * sec,
printf (" R_MSP430X_10_PCREL -> R_MSP430X_ABS20_ADR_SRC "
"(growing with new opcode 0x%x)\n", opcode);
/* Insert an absolute branch (aka MOVA) instruction. */
contents = msp430_elf_relax_add_two_words
(abfd, sec, irel->r_offset + 2, 0x0080, 0x0000);
/* Insert an absolute branch (aka MOVA) instruction.
Note that bits 19:16 of the address are stored in the first word
of the insn, so this is where r_offset will point to. */
if (opcode == 0x0080)
{
/* If we're inserting a BRA because we are converting from a JMP,
then only add one word for destination address; the BRA opcode
has already been written. */
contents = msp430_elf_relax_add_words
(abfd, sec, irel->r_offset + 2, 1, 0x0000, 0);
}
else
{
contents = msp430_elf_relax_add_words
(abfd, sec, irel->r_offset + 2, 2, 0x0080, 0x0000);
/* Update the relocation to point to the inserted branch
instruction. Note - we are changing a PC-relative reloc
into an absolute reloc, but this is OK because we have
arranged with the assembler to have the reloc's value be
a (local) symbol, not a section+offset value. */
irel->r_offset += 2;
}
/* Update the relocation to point to the inserted branch
instruction. Note - we are changing a PC-relative reloc
into an absolute reloc, but this is OK because we have
arranged with the assembler to have the reloc's value be
a (local) symbol, not a section+offset value. */
irel->r_offset += 2;
irel->r_info = ELF32_R_INFO (ELF32_R_SYM (irel->r_info),
R_MSP430X_ABS20_ADR_SRC);
}
@ -2075,12 +2100,23 @@ msp430_elf_relax_section (bfd * abfd, asection * sec,
if (debug_relocs)
printf (" R_MSP430_10_PCREL -> R_MSP430_16 "
"(growing with new opcode 0x%x)\n", opcode);
contents = msp430_elf_relax_add_two_words
(abfd, sec, irel->r_offset + 2, 0x4030, 0x0000);
/* See comment above about converting a 10-bit PC-rel
relocation into a 16-bit absolute relocation. */
irel->r_offset += 4;
if (opcode == 0x4030)
{
/* If we're inserting a BR because we are converting from a JMP,
then only add one word for destination address; the BR opcode
has already been written. */
contents = msp430_elf_relax_add_words
(abfd, sec, irel->r_offset + 2, 1, 0x0000, 0);
irel->r_offset += 2;
}
else
{
contents = msp430_elf_relax_add_words
(abfd, sec, irel->r_offset + 2, 2, 0x4030, 0x0000);
/* See comment above about converting a 10-bit PC-rel
relocation into a 16-bit absolute relocation. */
irel->r_offset += 4;
}
irel->r_info = ELF32_R_INFO (ELF32_R_SYM (irel->r_info),
R_MSP430_16);
}