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author | Nick Clifton <nickc@redhat.com> | 2006-03-03 15:25:31 +0000 |
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committer | Nick Clifton <nickc@redhat.com> | 2006-03-03 15:25:31 +0000 |
commit | df406460e9fc46e766dc418f85568062a4912bbe (patch) | |
tree | 8e1d5b1142214b245e59c01ed42f4a53510e7b07 /bfd/elf32-avr.c | |
parent | b92a518e7392026b969a7547e5b876ea9413f7ff (diff) | |
download | gdb-df406460e9fc46e766dc418f85568062a4912bbe.zip gdb-df406460e9fc46e766dc418f85568062a4912bbe.tar.gz gdb-df406460e9fc46e766dc418f85568062a4912bbe.tar.bz2 |
Add linker relaxation support for the AVR
Diffstat (limited to 'bfd/elf32-avr.c')
-rw-r--r-- | bfd/elf32-avr.c | 1047 |
1 files changed, 1036 insertions, 11 deletions
diff --git a/bfd/elf32-avr.c b/bfd/elf32-avr.c index 11b5d4f..32268cc 100644 --- a/bfd/elf32-avr.c +++ b/bfd/elf32-avr.c @@ -1,5 +1,5 @@ /* AVR-specific support for 32-bit ELF - Copyright 1999, 2000, 2001, 2002, 2003, 2004 + Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2006 Free Software Foundation, Inc. Contributed by Denis Chertykov <denisc@overta.ru> @@ -17,7 +17,8 @@ You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software - Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA. */ + Foundation, Inc., 51 Franklin Street - Fifth Floor, + Boston, MA 02110-1301, USA. */ #include "bfd.h" #include "sysdep.h" @@ -47,6 +48,15 @@ static bfd_boolean elf32_avr_relocate_section static void bfd_elf_avr_final_write_processing PARAMS ((bfd *, bfd_boolean)); static bfd_boolean elf32_avr_object_p PARAMS ((bfd *)); +/* Relaxing stuff */ +static bfd_boolean elf32_avr_relax_section + PARAMS((bfd *, asection *, struct bfd_link_info *, bfd_boolean *)); +static bfd_boolean elf32_avr_relax_delete_bytes + PARAMS((bfd *, asection *, bfd_vma, int)); +static bfd_byte *elf32_avr_get_relocated_section_contents + PARAMS((bfd *, struct bfd_link_info *, struct bfd_link_order *, + bfd_byte *, bfd_boolean, asymbol **)); + static reloc_howto_type elf_avr_howto_table[] = { HOWTO (R_AVR_NONE, /* type */ @@ -167,7 +177,8 @@ static reloc_howto_type elf_avr_howto_table[] = 0xffff, /* dst_mask */ FALSE), /* pcrel_offset */ /* A high 6 bit absolute relocation of 22 bit address. - For LDI command. */ + For LDI command. As well second most significant 8 bit value of + a 32 bit link-time constant. */ HOWTO (R_AVR_HH8_LDI, /* type */ 16, /* rightshift */ 1, /* size (0 = byte, 1 = short, 2 = long) */ @@ -196,7 +207,7 @@ static reloc_howto_type elf_avr_howto_table[] = 0xffff, /* src_mask */ 0xffff, /* dst_mask */ FALSE), /* pcrel_offset */ - /* A hegative high 8 bit absolute relocation of 16 bit address. + /* A negative high 8 bit absolute relocation of 16 bit address. For LDI command. */ HOWTO (R_AVR_HI8_LDI_NEG, /* type */ 8, /* rightshift */ @@ -211,7 +222,7 @@ static reloc_howto_type elf_avr_howto_table[] = 0xffff, /* src_mask */ 0xffff, /* dst_mask */ FALSE), /* pcrel_offset */ - /* A hegative high 6 bit absolute relocation of 22 bit address. + /* A negative high 6 bit absolute relocation of 22 bit address. For LDI command. */ HOWTO (R_AVR_HH8_LDI_NEG, /* type */ 16, /* rightshift */ @@ -374,7 +385,35 @@ static reloc_howto_type elf_avr_howto_table[] = FALSE, /* partial_inplace */ 0xffff, /* src_mask */ 0xffff, /* dst_mask */ - FALSE) /* pcrel_offset */ + FALSE), /* pcrel_offset */ + /* Most significant 8 bit value of a 32 bit link-time constant. */ + HOWTO (R_AVR_MS8_LDI, /* type */ + 24, /* rightshift */ + 1, /* size (0 = byte, 1 = short, 2 = long) */ + 8, /* bitsize */ + FALSE, /* pc_relative */ + 0, /* bitpos */ + complain_overflow_dont, /* complain_on_overflow */ + bfd_elf_generic_reloc, /* special_function */ + "R_AVR_MS8_LDI", /* name */ + FALSE, /* partial_inplace */ + 0xffff, /* src_mask */ + 0xffff, /* dst_mask */ + FALSE), /* pcrel_offset */ + /* Negative most significant 8 bit value of a 32 bit link-time constant. */ + HOWTO (R_AVR_MS8_LDI_NEG, /* type */ + 24, /* rightshift */ + 1, /* size (0 = byte, 1 = short, 2 = long) */ + 8, /* bitsize */ + FALSE, /* pc_relative */ + 0, /* bitpos */ + complain_overflow_dont, /* complain_on_overflow */ + bfd_elf_generic_reloc, /* special_function */ + "R_AVR_MS8_LDI_NEG", /* name */ + FALSE, /* partial_inplace */ + 0xffff, /* src_mask */ + 0xffff, /* dst_mask */ + FALSE) /* pcrel_offset */ }; /* Map BFD reloc types to AVR ELF reloc types. */ @@ -396,9 +435,11 @@ struct avr_reloc_map { BFD_RELOC_AVR_LO8_LDI, R_AVR_LO8_LDI}, { BFD_RELOC_AVR_HI8_LDI, R_AVR_HI8_LDI }, { BFD_RELOC_AVR_HH8_LDI, R_AVR_HH8_LDI }, + { BFD_RELOC_AVR_MS8_LDI, R_AVR_MS8_LDI }, { BFD_RELOC_AVR_LO8_LDI_NEG, R_AVR_LO8_LDI_NEG }, { BFD_RELOC_AVR_HI8_LDI_NEG, R_AVR_HI8_LDI_NEG }, { BFD_RELOC_AVR_HH8_LDI_NEG, R_AVR_HH8_LDI_NEG }, + { BFD_RELOC_AVR_MS8_LDI_NEG, R_AVR_MS8_LDI_NEG }, { BFD_RELOC_AVR_LO8_LDI_PM, R_AVR_LO8_LDI_PM }, { BFD_RELOC_AVR_HI8_LDI_PM, R_AVR_HI8_LDI_PM }, { BFD_RELOC_AVR_HH8_LDI_PM, R_AVR_HH8_LDI_PM }, @@ -411,6 +452,32 @@ struct avr_reloc_map { BFD_RELOC_AVR_6_ADIW, R_AVR_6_ADIW } }; +/* Meant to be filled one day with the wrap around address for the + specific device. I.e. should get the value 0x4000 for 16k devices, + 0x8000 for 32k devices and so on. + + We initialize it here with a value of 0x1000000 resulting in + that we will never suggest a wrap-around jump during relaxation. + The logic of the source code later on assumes that in + avr_pc_wrap_around one single bit is set. */ + +unsigned int avr_pc_wrap_around = 0x10000000; + +/* Calculates the effective distance of a pc relative jump/call. */ +static int +avr_relative_distance_considering_wrap_around (unsigned int distance) +{ + unsigned int wrap_around_mask = avr_pc_wrap_around - 1; + + int dist_with_wrap_around = distance & wrap_around_mask; + + if (dist_with_wrap_around > ((int) (avr_pc_wrap_around >> 1)) ) + dist_with_wrap_around -= avr_pc_wrap_around; + + return dist_with_wrap_around; +} + + static reloc_howto_type * bfd_elf32_bfd_reloc_type_lookup (abfd, code) bfd *abfd ATTRIBUTE_UNUSED; @@ -583,13 +650,17 @@ avr_final_link_relocate (howto, input_bfd, input_section, if (srel & 1) return bfd_reloc_outofrange; + srel = avr_relative_distance_considering_wrap_around (srel); + /* AVR addresses commands as words. */ srel >>= 1; /* Check for overflow. */ if (srel < -2048 || srel > 2047) { - /* Apply WRAPAROUND if possible. */ + /* Relative distance is too large. */ + + /* Always apply WRAPAROUND for avr2 and avr4. */ switch (bfd_get_mach (input_bfd)) { case bfd_mach_avr2: @@ -617,9 +688,11 @@ avr_final_link_relocate (howto, input_bfd, input_section, case R_AVR_LDI: contents += rel->r_offset; srel = (bfd_signed_vma) relocation + rel->r_addend; - if ((srel & 0xffff) > 255) - /* Remove offset for data/eeprom section. */ - return bfd_reloc_overflow; + if ( ((srel > 0) && (srel & 0xffff) > 255) + || ((srel < 0) && ( (-srel) & 0xffff) > 128)) + /* Remove offset for data/eeprom section. */ + return bfd_reloc_overflow; + x = bfd_get_16 (input_bfd, contents); x = (x & 0xf0f0) | (srel & 0xf) | ((srel << 4) & 0xf00); bfd_put_16 (input_bfd, x, contents); @@ -632,7 +705,8 @@ avr_final_link_relocate (howto, input_bfd, input_section, /* Remove offset for data/eeprom section. */ return bfd_reloc_overflow; x = bfd_get_16 (input_bfd, contents); - x = (x & 0xd3f8) | ((srel & 7) | ((srel & (3 << 3)) << 7) | ((srel & (1 << 5)) << 8)); + x = (x & 0xd3f8) | ((srel & 7) | ((srel & (3 << 3)) << 7) + | ((srel & (1 << 5)) << 8)); bfd_put_16 (input_bfd, x, contents); break; @@ -665,6 +739,15 @@ avr_final_link_relocate (howto, input_bfd, input_section, bfd_put_16 (input_bfd, x, contents); break; + case R_AVR_MS8_LDI: + contents += rel->r_offset; + srel = (bfd_signed_vma) relocation + rel->r_addend; + srel = (srel >> 24) & 0xff; + x = bfd_get_16 (input_bfd, contents); + x = (x & 0xf0f0) | (srel & 0xf) | ((srel << 4) & 0xf00); + bfd_put_16 (input_bfd, x, contents); + break; + case R_AVR_LO8_LDI_NEG: contents += rel->r_offset; srel = (bfd_signed_vma) relocation + rel->r_addend; @@ -694,6 +777,16 @@ avr_final_link_relocate (howto, input_bfd, input_section, bfd_put_16 (input_bfd, x, contents); break; + case R_AVR_MS8_LDI_NEG: + contents += rel->r_offset; + srel = (bfd_signed_vma) relocation + rel->r_addend; + srel = -srel; + srel = (srel >> 24) & 0xff; + x = bfd_get_16 (input_bfd, contents); + x = (x & 0xf0f0) | (srel & 0xf) | ((srel << 4) & 0xf00); + bfd_put_16 (input_bfd, x, contents); + break; + case R_AVR_LO8_LDI_PM: contents += rel->r_offset; srel = (bfd_signed_vma) relocation + rel->r_addend; @@ -943,6 +1036,7 @@ bfd_elf_avr_final_write_processing (abfd, linker) elf_elfheader (abfd)->e_machine = EM_AVR; elf_elfheader (abfd)->e_flags &= ~ EF_AVR_MACH; elf_elfheader (abfd)->e_flags |= val; + elf_elfheader (abfd)->e_flags |= EF_AVR_LINKRELAX_PREPARED; } /* Set the right machine number. */ @@ -984,6 +1078,933 @@ elf32_avr_object_p (abfd) e_set); } + +/* Enable debugging printout at stdout with a value of 1. */ +#define DEBUG_RELAX 0 + +/* This function handles relaxing for the avr. + Many important relaxing opportunities within functions are already + realized by the compiler itself. + Here we try to replace call (4 bytes) -> rcall (2 bytes) + and jump -> rjmp (safes also 2 bytes). + As well we now optimize seqences of + - call/rcall function + - ret + to yield + - jmp/rjmp function + - ret + . In case that within a sequence + - jmp/rjmp label + - ret + the ret could no longer be reached it is optimized away. In order + to check if the ret is no longer needed, it is checked that the ret's address + is not the target of a branch or jump within the same section, it is checked + that there is no skip instruction before the jmp/rjmp and that there + is no local or global label place at the address of the ret. + + We refrain from relaxing within sections ".vectors" and + ".jumptables" in order to maintain the position of the instructions. + There, however, we substitute jmp/call by a sequence rjmp,nop/rcall,nop + if possible. (In future one could possibly use the space of the nop + for the first instruction of the irq service function. + + The .jumptables sections is meant to be used for a future tablejump variant + for the devices with 3-byte program counter where the table itself + contains 4-byte jump instructions whose relative offset must not + be changed. */ + +static bfd_boolean +elf32_avr_relax_section (bfd *abfd, asection *sec, + struct bfd_link_info *link_info, + bfd_boolean *again) +{ + Elf_Internal_Shdr *symtab_hdr; + Elf_Internal_Rela *internal_relocs; + Elf_Internal_Rela *irel, *irelend; + bfd_byte *contents = NULL; + Elf_Internal_Sym *isymbuf = NULL; + static asection *last_input_section = NULL; + static Elf_Internal_Rela *last_reloc = NULL; + + /* Assume nothing changes. */ + *again = FALSE; + + /* We don't have to do anything for a relocatable link, if + this section does not have relocs, or if this is not a + code section. */ + if (link_info->relocatable + || (sec->flags & SEC_RELOC) == 0 + || sec->reloc_count == 0 + || (sec->flags & SEC_CODE) == 0) + return TRUE; + + /* Check if the object file to relax uses internal symbols so that we + could fix up the relocations. */ + + if (!(elf_elfheader (abfd)->e_flags & EF_AVR_LINKRELAX_PREPARED)) + return TRUE; + + + symtab_hdr = &elf_tdata (abfd)->symtab_hdr; + + /* Get a copy of the native relocations. */ + internal_relocs = (_bfd_elf_link_read_relocs + (abfd, sec, (PTR) NULL, (Elf_Internal_Rela *) NULL, + link_info->keep_memory)); + if (internal_relocs == NULL) + goto error_return; + + if (sec != last_input_section) + last_reloc = NULL; + + last_input_section = sec; + + /* Walk through the relocs looking for relaxing opportunities. */ + irelend = internal_relocs + sec->reloc_count; + for (irel = internal_relocs; irel < irelend; irel++) + { + bfd_vma symval; + + if (ELF32_R_TYPE (irel->r_info) != R_AVR_13_PCREL + && ELF32_R_TYPE (irel->r_info) != R_AVR_7_PCREL + && ELF32_R_TYPE (irel->r_info) != R_AVR_CALL) + continue; + + /* Get the section contents if we haven't done so already. */ + if (contents == NULL) + { + /* Get cached copy if it exists. */ + if (elf_section_data (sec)->this_hdr.contents != NULL) + contents = elf_section_data (sec)->this_hdr.contents; + else + { + /* Go get them off disk. */ + if (!bfd_malloc_and_get_section (abfd, sec, &contents)) + goto error_return; + } + } + + /* Read this BFD's local symbols if we haven't done so already. */ + if (isymbuf == NULL && symtab_hdr->sh_info != 0) + { + isymbuf = (Elf_Internal_Sym *) symtab_hdr->contents; + if (isymbuf == NULL) + isymbuf = bfd_elf_get_elf_syms (abfd, symtab_hdr, + symtab_hdr->sh_info, 0, + NULL, NULL, NULL); + if (isymbuf == NULL) + goto error_return; + } + + + /* Get the value of the symbol referred to by the reloc. */ + if (ELF32_R_SYM (irel->r_info) < symtab_hdr->sh_info) + { + /* A local symbol. */ + Elf_Internal_Sym *isym; + asection *sym_sec; + + isym = isymbuf + ELF32_R_SYM (irel->r_info); + sym_sec = bfd_section_from_elf_index (abfd, isym->st_shndx); + symval = isym->st_value; + /* If the reloc is absolute, it will not have + a symbol or section associated with it. */ + if (sym_sec) + symval += sym_sec->output_section->vma + + sym_sec->output_offset; + } + else + { + unsigned long indx; + struct elf_link_hash_entry *h; + + /* An external symbol. */ + indx = ELF32_R_SYM (irel->r_info) - symtab_hdr->sh_info; + h = elf_sym_hashes (abfd)[indx]; + BFD_ASSERT (h != NULL); + if (h->root.type != bfd_link_hash_defined + && h->root.type != bfd_link_hash_defweak) + { + /* This appears to be a reference to an undefined + symbol. Just ignore it--it will be caught by the + regular reloc processing. */ + continue; + } + symval = (h->root.u.def.value + + h->root.u.def.section->output_section->vma + + h->root.u.def.section->output_offset); + } + + /* For simplicity of coding, we are going to modify the section + contents, the section relocs, and the BFD symbol table. We + must tell the rest of the code not to free up this + information. It would be possible to instead create a table + of changes which have to be made, as is done in coff-mips.c; + that would be more work, but would require less memory when + the linker is run. */ + switch (ELF32_R_TYPE (irel->r_info)) + { + /* Try to turn a 22-bit absolute call/jump into an 13-bit + pc-relative rcall/rjmp. */ + case R_AVR_CALL: + { + bfd_vma value = symval + irel->r_addend; + bfd_vma dot, gap; + int distance_short_enough = 0; + + /* Get the address of this instruction. */ + dot = (sec->output_section->vma + + sec->output_offset + irel->r_offset); + + /* Compute the distance from this insn to the branch target. */ + gap = value - dot; + + /* If the distance is within -4094..+4098 inclusive, then we can + relax this jump/call. +4098 because the call/jump target + will be closer after the relaxation. */ + if ((int) gap >= -4094 && (int) gap <= 4098) + distance_short_enough = 1; + + /* Here we handle the wrap-around case. E.g. for a 16k device + we could use a rjmp to jump from address 0x100 to 0x3d00! + In order to make this work properly, we need to fill the + vaiable avr_pc_wrap_around with the appropriate value. + I.e. 0x4000 for a 16k device. */ + { + /* Shrinking the code size makes the gaps larger in the + case of wrap-arounds. So we use a heuristical safety + margin to avoid that during relax the distance gets + again too large for the short jumps. Let's assume + a typical code-size reduction due to relax for a + 16k device of 600 bytes. So let's use twice the + typical value as safety margin. */ + + int rgap; + int safety_margin; + + int assumed_shrink = 600; + if (avr_pc_wrap_around > 0x4000) + assumed_shrink = 900; + + safety_margin = 2 * assumed_shrink; + + rgap = avr_relative_distance_considering_wrap_around (gap); + + if (rgap >= (-4092 + safety_margin) + && rgap <= (4094 - safety_margin)) + distance_short_enough = 1; + } + + if (distance_short_enough) + { + unsigned char code_msb; + unsigned char code_lsb; + + if (DEBUG_RELAX) + printf ("shrinking jump/call instruction at address 0x%x" + " in section %s\n\n", + (int) dot, sec->name); + + /* Note that we've changed the relocs, section contents, + etc. */ + elf_section_data (sec)->relocs = internal_relocs; + elf_section_data (sec)->this_hdr.contents = contents; + symtab_hdr->contents = (unsigned char *) isymbuf; + + /* Get the instruction code for relaxing. */ + code_lsb = bfd_get_8 (abfd, contents + irel->r_offset); + code_msb = bfd_get_8 (abfd, contents + irel->r_offset + 1); + + /* Mask out the relocation bits. */ + code_msb &= 0x94; + code_lsb &= 0x0E; + if (code_msb == 0x94 && code_lsb == 0x0E) + { + /* we are changing call -> rcall . */ + bfd_put_8 (abfd, 0x00, contents + irel->r_offset); + bfd_put_8 (abfd, 0xD0, contents + irel->r_offset + 1); + } + else if (code_msb == 0x94 && code_lsb == 0x0C) + { + /* we are changeing jump -> rjmp. */ + bfd_put_8 (abfd, 0x00, contents + irel->r_offset); + bfd_put_8 (abfd, 0xC0, contents + irel->r_offset + 1); + } + else + abort (); + + /* Fix the relocation's type. */ + irel->r_info = ELF32_R_INFO (ELF32_R_SYM (irel->r_info), + R_AVR_13_PCREL); + + /* Check for the vector section. There we don't want to + modify the ordering! */ + + if (!strcmp (sec->name,".vectors") + || !strcmp (sec->name,".jumptables")) + { + /* Let's insert a nop. */ + bfd_put_8 (abfd, 0x00, contents + irel->r_offset + 2); + bfd_put_8 (abfd, 0x00, contents + irel->r_offset + 3); + } + else + { + /* Delete two bytes of data. */ + if (!elf32_avr_relax_delete_bytes (abfd, sec, + irel->r_offset + 2, 2)) + goto error_return; + + /* That will change things, so, we should relax again. + Note that this is not required, and it may be slow. */ + *again = TRUE; + } + } + } + default: + { + unsigned char code_msb; + unsigned char code_lsb; + bfd_vma dot; + + code_msb = bfd_get_8 (abfd, contents + irel->r_offset + 1); + code_lsb = bfd_get_8 (abfd, contents + irel->r_offset + 0); + + /* Get the address of this instruction. */ + dot = (sec->output_section->vma + + sec->output_offset + irel->r_offset); + + /* Here we look for rcall/ret or call/ret sequences that could be + safely replaced by rjmp/ret or jmp/ret */ + if (0xd0 == (code_msb & 0xf0)) + { + /* This insn is a rcall. */ + unsigned char next_insn_msb = 0; + unsigned char next_insn_lsb = 0; + + if (irel->r_offset + 3 < sec->size) + { + next_insn_msb = + bfd_get_8 (abfd, contents + irel->r_offset + 3); + next_insn_lsb = + bfd_get_8 (abfd, contents + irel->r_offset + 2); + } + if ((0x95 == next_insn_msb) && (0x08 == next_insn_lsb)) + { + /* The next insn is a ret. We now convert the rcall insn + into a rjmp instruction. */ + + code_msb &= 0xef; + bfd_put_8 (abfd, code_msb, contents + irel->r_offset + 1); + if (DEBUG_RELAX) + printf ("converted rcall/ret sequence at address 0x%x" + " into rjmp/ret sequence. Section is %s\n\n", + (int) dot, sec->name); + *again = TRUE; + break; + } + } + else if ((0x94 == (code_msb & 0xfe)) + && (0x0e == (code_lsb & 0x0e))) + { + /* This insn is a call. */ + unsigned char next_insn_msb = 0; + unsigned char next_insn_lsb = 0; + + if (irel->r_offset + 5 < sec->size) + { + next_insn_msb = + bfd_get_8 (abfd, contents + irel->r_offset + 5); + next_insn_lsb = + bfd_get_8 (abfd, contents + irel->r_offset + 4); + } + if ((0x95 == next_insn_msb) && (0x08 == next_insn_lsb)) + { + /* The next insn is a ret. We now convert the call insn + into a jmp instruction. */ + + code_lsb &= 0xfd; + bfd_put_8 (abfd, code_lsb, contents + irel->r_offset); + if (DEBUG_RELAX) + printf ("converted call/ret sequence at address 0x%x" + " into jmp/ret sequence. Section is %s\n\n", + (int) dot, sec->name); + *again = TRUE; + break; + } + } + else if ((0xc0 == (code_msb & 0xf0)) + || ((0x94 == (code_msb & 0xfe)) + && (0x0c == (code_lsb & 0x0e)))) + { + /* this insn is a rjmp or a jmp. */ + unsigned char next_insn_msb = 0; + unsigned char next_insn_lsb = 0; + int insn_size; + + if (0xc0 == (code_msb & 0xf0)) + insn_size = 2; /* rjmp insn */ + else + insn_size = 4; /* jmp insn */ + + if (irel->r_offset + insn_size + 1 < sec->size) + { + next_insn_msb = + bfd_get_8 (abfd, contents + irel->r_offset + + insn_size + 1); + next_insn_lsb = + bfd_get_8 (abfd, contents + irel->r_offset + + insn_size); + } + + if ((0x95 == next_insn_msb) && (0x08 == next_insn_lsb)) + { + /* The next insn is a ret. We possibly could delete + this ret. First we need to check for preceeding + sbis/sbic/sbrs or cpse "skip" instructions. */ + + int there_is_preceeding_non_skip_insn = 1; + bfd_vma address_of_ret; + + address_of_ret = dot + insn_size; + + if (DEBUG_RELAX && (insn_size == 2)) + printf ("found rjmp / ret sequence at " + "address 0x%x\n", + (int) dot); + if (DEBUG_RELAX && (insn_size == 4)) + printf ("found jmp / ret sequence at " + "address 0x%x\n", + (int) dot); + + /* We have to make sure that there is a preceeding insn. */ + if (irel->r_offset >= 2) + { + unsigned char preceeding_msb; + unsigned char preceeding_lsb; + preceeding_msb = + bfd_get_8 (abfd, contents + irel->r_offset - 1); + preceeding_lsb = + bfd_get_8 (abfd, contents + irel->r_offset - 2); + + /* sbic. */ + if (0x99 == preceeding_msb) + there_is_preceeding_non_skip_insn = 0; + + /* sbis. */ + if (0x9b == preceeding_msb) + there_is_preceeding_non_skip_insn = 0; + + /* sbrc */ + if ((0xfc == (preceeding_msb & 0xfe) + && (0x00 == (preceeding_lsb & 0x08)))) + there_is_preceeding_non_skip_insn = 0; + + /* sbrs */ + if ((0xfe == (preceeding_msb & 0xfe) + && (0x00 == (preceeding_lsb & 0x08)))) + there_is_preceeding_non_skip_insn = 0; + + /* cpse */ + if (0x10 == (preceeding_msb & 0xfc)) + there_is_preceeding_non_skip_insn = 0; + + if (there_is_preceeding_non_skip_insn == 0) + if (DEBUG_RELAX) + printf ("preceeding skip insn prevents deletion of" + " ret insn at addr 0x%x in section %s\n", + (int) dot + 2, sec->name); + } + else + { + /* There is no previous instruction. */ + there_is_preceeding_non_skip_insn = 0; + } + + if (there_is_preceeding_non_skip_insn) + { + /* We now only have to make sure that there is no + local label defined at the address of the ret + instruction and that there is no local relocation + in this section pointing to the ret. */ + + int deleting_ret_is_safe = 1; + unsigned int section_offset_of_ret_insn = + irel->r_offset + insn_size; + Elf_Internal_Sym *isym, *isymend; + unsigned int sec_shndx; + + sec_shndx = + _bfd_elf_section_from_bfd_section (abfd, sec); + + /* Check for local symbols. */ + isym = (Elf_Internal_Sym *) symtab_hdr->contents; + isymend = isym + symtab_hdr->sh_info; + for (; isym < isymend; isym++) + { + if (isym->st_value == section_offset_of_ret_insn + && isym->st_shndx == sec_shndx) + { + deleting_ret_is_safe = 0; + if (DEBUG_RELAX) + printf ("local label prevents deletion of ret " + "insn at address 0x%x\n", + (int) dot + insn_size); + } + } + + /* Now check for global symbols. */ + { + int symcount; + struct elf_link_hash_entry **sym_hashes; + struct elf_link_hash_entry **end_hashes; + + symcount = (symtab_hdr->sh_size + / sizeof (Elf32_External_Sym) + - symtab_hdr->sh_info); + sym_hashes = elf_sym_hashes (abfd); + end_hashes = sym_hashes + symcount; + for (; sym_hashes < end_hashes; sym_hashes++) + { + struct elf_link_hash_entry *sym_hash = + *sym_hashes; + if ((sym_hash->root.type == bfd_link_hash_defined + || sym_hash->root.type == + bfd_link_hash_defweak) + && sym_hash->root.u.def.section == sec + && sym_hash->root.u.def.value == + section_offset_of_ret_insn) + { + deleting_ret_is_safe = 0; + if (DEBUG_RELAX) + printf ("global label prevents deletion of " + "ret insn at address 0x%x\n", + (int) dot + insn_size); + } + } + } + /* Now we check for relocations pointing to ret. */ + { + Elf_Internal_Rela *irel; + Elf_Internal_Rela *relend; + Elf_Internal_Shdr *symtab_hdr; + + symtab_hdr = &elf_tdata (abfd)->symtab_hdr; + relend = elf_section_data (sec)->relocs + + sec->reloc_count; + + for (irel = elf_section_data (sec)->relocs; + irel < relend; irel++) + { + bfd_vma reloc_target = 0; + bfd_vma symval; + Elf_Internal_Sym *isymbuf = NULL; + + /* Read this BFD's local symbols if we haven't + done so already. */ + if (isymbuf == NULL && symtab_hdr->sh_info != 0) + { + isymbuf = (Elf_Internal_Sym *) + symtab_hdr->contents; + if (isymbuf == NULL) + isymbuf = bfd_elf_get_elf_syms ( + abfd, + symtab_hdr, + symtab_hdr->sh_info, 0, + NULL, NULL, NULL); + if (isymbuf == NULL) + break; + } + + /* Get the value of the symbol referred to + by the reloc. */ + if (ELF32_R_SYM (irel->r_info) + < symtab_hdr->sh_info) + { + /* A local symbol. */ + Elf_Internal_Sym *isym; + asection *sym_sec; + + isym = isymbuf + + ELF32_R_SYM (irel->r_info); + sym_sec = bfd_section_from_elf_index ( + abfd, isym->st_shndx); + symval = isym->st_value; + + /* If the reloc is absolute, it will not + have a symbol or section associated + with it. */ + + if (sym_sec) + { + symval += + sym_sec->output_section->vma + + sym_sec->output_offset; + reloc_target = symval + irel->r_addend; + } + else + { + reloc_target = symval + irel->r_addend; + /* reference symbol is absolute. */ + } + } + else + { + /* reference symbol is extern. */ + } + + if (address_of_ret == reloc_target) + { + deleting_ret_is_safe = 0; + if (DEBUG_RELAX) + printf ("ret from " + "rjmp/jmp ret sequence at address" + " 0x%x could not be deleted. ret" + " is target of a relocation.\n", + (int) address_of_ret); + } + } + } + + if (deleting_ret_is_safe) + { + if (DEBUG_RELAX) + printf ("unreachable ret instruction " + "at address 0x%x deleted.\n", + (int) dot + insn_size); + + /* Delete two bytes of data. */ + if (!elf32_avr_relax_delete_bytes (abfd, sec, + irel->r_offset + insn_size, 2)) + goto error_return; + + /* That will change things, so, we should relax + again. Note that this is not required, and it + may be slow. */ + + *again = TRUE; + break; + } + } + + } + } + break; + } + } + } + + if (contents != NULL + && elf_section_data (sec)->this_hdr.contents != contents) + { + if (! link_info->keep_memory) + free (contents); + else + { + /* Cache the section contents for elf_link_input_bfd. */ + elf_section_data (sec)->this_hdr.contents = contents; + } + } + + if (internal_relocs != NULL + && elf_section_data (sec)->relocs != internal_relocs) + free (internal_relocs); + + return TRUE; + + error_return: + if (isymbuf != NULL + && symtab_hdr->contents != (unsigned char *) isymbuf) + free (isymbuf); + if (contents != NULL + && elf_section_data (sec)->this_hdr.contents != contents) + free (contents); + if (internal_relocs != NULL + && elf_section_data (sec)->relocs != internal_relocs) + free (internal_relocs); + + return FALSE; +} + +/* Delete some bytes from a section while changing the size of an instruction. + The parameter "addr" denotes the section-relative offset pointing just + behind the shrinked instruction. "addr+count" point at the first + byte just behind the original unshrinked instruction. */ +static bfd_boolean +elf32_avr_relax_delete_bytes (bfd *abfd, asection *sec, + bfd_vma addr, int count) +{ + Elf_Internal_Shdr *symtab_hdr; + unsigned int sec_shndx; + bfd_byte *contents; + Elf_Internal_Rela *irel, *irelend; + Elf_Internal_Rela *irelalign; + Elf_Internal_Sym *isym; + Elf_Internal_Sym *isymbuf = NULL; + Elf_Internal_Sym *isymend; + bfd_vma toaddr; + struct elf_link_hash_entry **sym_hashes; + struct elf_link_hash_entry **end_hashes; + unsigned int symcount; + + symtab_hdr = &elf_tdata (abfd)->symtab_hdr; + sec_shndx = _bfd_elf_section_from_bfd_section (abfd, sec); + contents = elf_section_data (sec)->this_hdr.contents; + + /* The deletion must stop at the next ALIGN reloc for an aligment + power larger than the number of bytes we are deleting. */ + + irelalign = NULL; + toaddr = sec->size; + + irel = elf_section_data (sec)->relocs; + irelend = irel + sec->reloc_count; + + /* Actually delete the bytes. */ + if (toaddr - addr - count > 0) + memmove (contents + addr, contents + addr + count, + (size_t) (toaddr - addr - count)); + sec->size -= count; + + /* Adjust all the relocs. */ + for (irel = elf_section_data (sec)->relocs; irel < irelend; irel++) + { + bfd_vma symval; + bfd_vma old_reloc_address; + bfd_vma shrinked_insn_address; + + old_reloc_address = (sec->output_section->vma + + sec->output_offset + irel->r_offset); + shrinked_insn_address = (sec->output_section->vma + + sec->output_offset + addr - count); + + /* Get the new reloc address. */ + if ((irel->r_offset > addr + && irel->r_offset < toaddr)) + { + if (DEBUG_RELAX) + printf ("Relocation at address 0x%x needs to be moved.\n" + "Old section offset: 0x%x, New section offset: 0x%x \n", + (unsigned int) old_reloc_address, + (unsigned int) irel->r_offset, + (unsigned int) ((irel->r_offset) - count)); + + irel->r_offset -= count; + } + + /* The reloc's own addresses are now ok. However, we need to readjust + the reloc's addend if two conditions are met: + 1.) the reloc is relative to a symbol in this section that + is located in front of the shrinked instruction + 2.) symbol plus addend end up behind the shrinked instruction. + + This should happen only for local symbols that are progmem related. */ + + /* Read this BFD's local symbols if we haven't done so already. */ + if (isymbuf == NULL && symtab_hdr->sh_info != 0) + { + isymbuf = (Elf_Internal_Sym *) symtab_hdr->contents; + if (isymbuf == NULL) + isymbuf = bfd_elf_get_elf_syms (abfd, symtab_hdr, + symtab_hdr->sh_info, 0, + NULL, NULL, NULL); + if (isymbuf == NULL) + return FALSE; + } + + /* Get the value of the symbol referred to by the reloc. */ + if (ELF32_R_SYM (irel->r_info) < symtab_hdr->sh_info) + { + /* A local symbol. */ + Elf_Internal_Sym *isym; + asection *sym_sec; + + isym = isymbuf + ELF32_R_SYM (irel->r_info); + sym_sec = bfd_section_from_elf_index (abfd, isym->st_shndx); + symval = isym->st_value; + /* If the reloc is absolute, it will not have + a symbol or section associated with it. */ + if (sym_sec) + { + symval += sym_sec->output_section->vma + + sym_sec->output_offset; + + if (DEBUG_RELAX) + printf ("Checking if the relocation's " + "addend needs corrections.\n" + "Address of anchor symbol: 0x%x \n" + "Address of relocation target: 0x%x \n" + "Address of relaxed insn: 0x%x \n", + (unsigned int) symval, + (unsigned int) (symval + irel->r_addend), + (unsigned int) shrinked_insn_address); + + if ( symval <= shrinked_insn_address + && (symval + irel->r_addend) > shrinked_insn_address) + { + irel->r_addend -= count; + + if (DEBUG_RELAX) + printf ("Anchor symbol and relocation target bracket " + "shrinked insn address.\n" + "Need for new addend : 0x%x\n", + (unsigned int) irel->r_addend); + } + } + else + { + /* Reference symbol is absolute. No adjustment needed. */ + } + } + else + { + /* Reference symbol is extern. No need for adjusting the addend. */ + } + } + + /* Adjust the local symbols defined in this section. */ + isym = (Elf_Internal_Sym *) symtab_hdr->contents; + isymend = isym + symtab_hdr->sh_info; + for (; isym < isymend; isym++) + { + if (isym->st_shndx == sec_shndx + && isym->st_value > addr + && isym->st_value < toaddr) + isym->st_value -= count; + } + + /* Now adjust the global symbols defined in this section. */ + symcount = (symtab_hdr->sh_size / sizeof (Elf32_External_Sym) + - symtab_hdr->sh_info); + sym_hashes = elf_sym_hashes (abfd); + end_hashes = sym_hashes + symcount; + for (; sym_hashes < end_hashes; sym_hashes++) + { + struct elf_link_hash_entry *sym_hash = *sym_hashes; + if ((sym_hash->root.type == bfd_link_hash_defined + || sym_hash->root.type == bfd_link_hash_defweak) + && sym_hash->root.u.def.section == sec + && sym_hash->root.u.def.value > addr + && sym_hash->root.u.def.value < toaddr) + { + sym_hash->root.u.def.value -= count; + } + } + + return TRUE; +} + +/* This is a version of bfd_generic_get_relocated_section_contents + which uses elf32_avr_relocate_section. + + For avr it's essentially a cut and paste taken from the H8300 port. + The author of the relaxation support patch for avr had absolutely no + clue what is happening here but found out that this part of the code + seems to be important. */ + +static bfd_byte * +elf32_avr_get_relocated_section_contents (bfd *output_bfd, + struct bfd_link_info *link_info, + struct bfd_link_order *link_order, + bfd_byte *data, + bfd_boolean relocatable, + asymbol **symbols) +{ + Elf_Internal_Shdr *symtab_hdr; + asection *input_section = link_order->u.indirect.section; + bfd *input_bfd = input_section->owner; + asection **sections = NULL; + Elf_Internal_Rela *internal_relocs = NULL; + Elf_Internal_Sym *isymbuf = NULL; + + /* We only need to handle the case of relaxing, or of having a + particular set of section contents, specially. */ + if (relocatable + || elf_section_data (input_section)->this_hdr.contents == NULL) + return bfd_generic_get_relocated_section_contents (output_bfd, link_info, + link_order, data, + relocatable, + symbols); + symtab_hdr = &elf_tdata (input_bfd)->symtab_hdr; + + memcpy (data, elf_section_data (input_section)->this_hdr.contents, + (size_t) input_section->size); + + if ((input_section->flags & SEC_RELOC) != 0 + && input_section->reloc_count > 0) + { + asection **secpp; + Elf_Internal_Sym *isym, *isymend; + bfd_size_type amt; + + internal_relocs = (_bfd_elf_link_read_relocs + (input_bfd, input_section, (PTR) NULL, + (Elf_Internal_Rela *) NULL, FALSE)); + if (internal_relocs == NULL) + goto error_return; + + if (symtab_hdr->sh_info != 0) + { + isymbuf = (Elf_Internal_Sym *) symtab_hdr->contents; + if (isymbuf == NULL) + isymbuf = bfd_elf_get_elf_syms (input_bfd, symtab_hdr, + symtab_hdr->sh_info, 0, + NULL, NULL, NULL); + if (isymbuf == NULL) + goto error_return; + } + + amt = symtab_hdr->sh_info; + amt *= sizeof (asection *); + sections = (asection **) bfd_malloc (amt); + if (sections == NULL && amt != 0) + goto error_return; + + isymend = isymbuf + symtab_hdr->sh_info; + for (isym = isymbuf, secpp = sections; isym < isymend; ++isym, ++secpp) + { + asection *isec; + + if (isym->st_shndx == SHN_UNDEF) + isec = bfd_und_section_ptr; + else if (isym->st_shndx == SHN_ABS) + isec = bfd_abs_section_ptr; + else if (isym->st_shndx == SHN_COMMON) + isec = bfd_com_section_ptr; + else + isec = bfd_section_from_elf_index (input_bfd, isym->st_shndx); + + *secpp = isec; + } + + if (! elf32_avr_relocate_section (output_bfd, link_info, input_bfd, + input_section, data, internal_relocs, + isymbuf, sections)) + goto error_return; + + if (sections != NULL) + free (sections); + if (isymbuf != NULL + && symtab_hdr->contents != (unsigned char *) isymbuf) + free (isymbuf); + if (elf_section_data (input_section)->relocs != internal_relocs) + free (internal_relocs); + } + + return data; + + error_return: + if (sections != NULL) + free (sections); + if (isymbuf != NULL + && symtab_hdr->contents != (unsigned char *) isymbuf) + free (isymbuf); + if (internal_relocs != NULL + && elf_section_data (input_section)->relocs != internal_relocs) + free (internal_relocs); + return NULL; +} + + #define ELF_ARCH bfd_arch_avr #define ELF_MACHINE_CODE EM_AVR #define ELF_MACHINE_ALT1 EM_AVR_OLD @@ -1004,4 +2025,8 @@ elf32_avr_object_p (abfd) bfd_elf_avr_final_write_processing #define elf_backend_object_p elf32_avr_object_p +#define bfd_elf32_bfd_relax_section elf32_avr_relax_section +#define bfd_elf32_bfd_get_relocated_section_contents \ + elf32_avr_get_relocated_section_contents + #include "elf32-target.h" |