From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31314 invoked by alias); 29 Mar 2005 21:26:37 -0000 Mailing-List: contact binutils-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: binutils-owner@sources.redhat.com Received: (qmail 31094 invoked from network); 29 Mar 2005 21:26:22 -0000 Received: from unknown (HELO mail.codesourcery.com) (65.74.133.9) by sourceware.org with SMTP; 29 Mar 2005 21:26:22 -0000 Received: (qmail 17867 invoked from network); 29 Mar 2005 21:26:14 -0000 Received: from localhost (HELO ?192.168.0.149?) (julian@127.0.0.1) by mail.codesourcery.com with SMTP; 29 Mar 2005 21:26:14 -0000 Message-ID: <4249C7E9.8000100@codesourcery.com> Date: Wed, 30 Mar 2005 15:31:00 -0000 From: Julian Brown User-Agent: Debian Thunderbird 1.0 (X11/20050116) MIME-Version: 1.0 To: Richard Earnshaw CC: binutils@sources.redhat.com, julian@codesourcery.com Subject: Re: [PATCH] Fix type and alignment of ARM/Thumb EABI mapping symbols References: <424716CD.5030909@codesourcery.com> <1112111047.12337.7.camel@pc960.cambridge.arm.com> In-Reply-To: <1112111047.12337.7.camel@pc960.cambridge.arm.com> Content-Type: multipart/mixed; boundary="------------040600080605070303060404" X-SW-Source: 2005-03/txt/msg00889.txt.bz2 This is a multi-part message in MIME format. --------------040600080605070303060404 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-length: 3016 Richard Earnshaw wrote: > On Sun, 2005-03-27 at 21:25, Julian Brown wrote: > >>Hi, >> >>This patch fixes two problems: the type of mapping symbols is made >>STT_NOTYPE (from STT_FUNC or STT_OBJECT from ARM/Thumb or data >>respectively), and the alignment is corrected to not have the low bit >>set for Thumb mapping symbols, in accordance with the latest version of >>the ARM AAELF spec. >> >>Unfortunately altering the symbol type to STT_NOTYPE for mapping symbols >>affects the output of disassembly from objdump. $a and $t were >>previously treated as functions. When objdump tried to find the closest >>symbol for possibly-symbol-relative offsets previously, it found those >>mapping symbols since compare_symbols places functions first in a sorted >>version of the symbol table. They were then rejected by the >>symbol_is_valid hook (arm_symbol_is_valid) from the disassemble_info >>struct, and the section name was printed instead. >> >>When the type of mapping symbols is changed to STT_NOTYPE, they are no >>longer placed first in the sorted symbol list, so another symbol is used >>instead. This causes test regressions, e.g. a symbol-offset address >>which was previously output as: >> >> bl 8224 <.text-0xc> >> >>was output instead as: >> >> bl 8224 <_start-0xc> >> >>In the interest of preserving existing behaviour, I have fixed this by >>adding a new disassemble_info hook which allows the symbol table used >>for disassembly to have a target-specific hook for altering each symbol >>(or remove it) in the remove_useless_symbols function. This sets the >>BSF_FUNCTION flag for mapping symbols, which makes things behave the way >>they used to, and possibly provides useful functionality for other >>platforms as well. >> >>It may be better to just change the expected test output instead. Thoughts? >> > > > I think the tests should be fixed. Other targets (those that don't have > mapping symbols) would almost certainly output _start in the example > above, so the existing behaviour should be considered undesirable at > best and probably just buggy. > > That should allow you to simplify your patch so that you don't need to > touch MI parts. OK, this is a simpler version of the patch which alters the expected test output instead (only ARM-specific code is now touched). Tested with cross to arm-none-eabi and arm-none-symbianelf, and with all targets on i686-pc-linux-gnu. OK to apply? ChangeLog: * bfd/elf32-arm.c (arm_elf_find_function): Include STT_NOTYPE in test for mapping symbols. * gas/config/tc-arm.c (mapping_state): Update documentation in function comment. Change type of mapping symbols to BSF_NO_TYPE. (is_arm_mapping_symbol_name): New function. (arm_adjust_symtab): Don't change type of mapping symbols here. * gas/testsuite/gas/arm/mapping.d: Update expected output. * ld/testsuite/ld-arm/arm-app-abs32.d: Likewise. * ld/testsuite/ld-arm/arm-app.d: Likewise. * ld/testsuite/ld-arm/mixed-app.d: Likewise. --------------040600080605070303060404 Content-Type: text/plain; name="patch-4" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="patch-4" Content-length: 15332 ? bfd/doc/bfd.info ? bfd/doc/bfd.info-1 ? gas/doc/as.info ? gas/doc/as.info-1 Index: bfd/elf32-arm.c =================================================================== RCS file: /cvs/src/src/bfd/elf32-arm.c,v retrieving revision 1.28 diff -c -p -r1.28 elf32-arm.c *** bfd/elf32-arm.c 29 Mar 2005 16:54:19 -0000 1.28 --- bfd/elf32-arm.c 29 Mar 2005 21:13:42 -0000 *************** arm_elf_find_function (bfd * abf *** 4754,4765 **** break; case STT_FUNC: case STT_ARM_TFUNC: /* Skip $a and $t symbols. */ if ((q->symbol.flags & BSF_LOCAL) && is_arm_mapping_symbol_name (q->symbol.name)) continue; /* Fall through. */ - case STT_NOTYPE: if (bfd_get_section (&q->symbol) == section && q->symbol.value >= low_func && q->symbol.value <= offset) --- 4754,4765 ---- break; case STT_FUNC: case STT_ARM_TFUNC: + case STT_NOTYPE: /* Skip $a and $t symbols. */ if ((q->symbol.flags & BSF_LOCAL) && is_arm_mapping_symbol_name (q->symbol.name)) continue; /* Fall through. */ if (bfd_get_section (&q->symbol) == section && q->symbol.value >= low_func && q->symbol.value <= offset) Index: gas/config/tc-arm.c =================================================================== RCS file: /cvs/src/src/gas/config/tc-arm.c,v retrieving revision 1.199 diff -c -p -r1.199 tc-arm.c *** gas/config/tc-arm.c 29 Mar 2005 16:54:21 -0000 1.199 --- gas/config/tc-arm.c 29 Mar 2005 21:13:47 -0000 *************** validate_offset_imm (unsigned int val, i *** 1243,1316 **** #ifdef OBJ_ELF /* This code is to handle mapping symbols as defined in the ARM ELF spec. ! (This text is taken from version B-02 of the spec): ! 4.4.7 Mapping and tagging symbols ! A section of an ARM ELF file can contain a mixture of ARM code, ! Thumb code, and data. There are inline transitions between code ! and data at literal pool boundaries. There can also be inline ! transitions between ARM code and Thumb code, for example in ! ARM-Thumb inter-working veneers. Linkers, machine-level ! debuggers, profiling tools, and disassembly tools need to map ! images accurately. For example, setting an ARM breakpoint on a ! Thumb location, or in a literal pool, can crash the program ! being debugged, ruining the debugging session. ! ! ARM ELF entities are mapped (see section 4.4.7.1 below) and ! tagged (see section 4.4.7.2 below) using local symbols (with ! binding STB_LOCAL). To assist consumers, mapping and tagging ! symbols should be collated first in the symbol table, before ! other symbols with binding STB_LOCAL. ! ! To allow properly collated mapping and tagging symbols to be ! skipped by consumers that have no interest in them, the first ! such symbol should have the name $m and its st_value field equal ! to the total number of mapping and tagging symbols (including ! the $m) in the symbol table. ! ! 4.4.7.1 Mapping symbols ! ! $a Labels the first byte of a sequence of ARM instructions. ! Its type is STT_FUNC. ! ! $d Labels the first byte of a sequence of data items. ! Its type is STT_OBJECT. ! ! $t Labels the first byte of a sequence of Thumb instructions. ! Its type is STT_FUNC. ! ! This list of mapping symbols may be extended in the future. ! ! Section-relative mapping symbols ! ! Mapping symbols defined in a section define a sequence of ! half-open address intervals that cover the address range of the ! section. Each interval starts at the address defined by a ! mapping symbol, and continues up to, but not including, the ! address defined by the next (in address order) mapping symbol or ! the end of the section. A corollary is that there must be a ! mapping symbol defined at the beginning of each section. ! Consumers can ignore the size of a section-relative mapping ! symbol. Producers can set it to 0. ! ! Absolute mapping symbols ! ! Because of the need to crystallize a Thumb address with the ! Thumb-bit set, absolute symbol of type STT_FUNC (symbols of type ! STT_FUNC defined in section SHN_ABS) need to be mapped with $a ! or $t. ! ! The extent of a mapping symbol defined in SHN_ABS is [st_value, ! st_value + st_size), or [st_value, st_value + 1) if st_size = 0, ! where [x, y) denotes the half-open address range from x, ! inclusive, to y, exclusive. ! ! In the absence of a mapping symbol, a consumer can interpret a ! function symbol with an odd value as the Thumb code address ! obtained by clearing the least significant bit of the ! value. This interpretation is deprecated, and it may not work in ! the future. Note - the Tagging symbols ($b, $f, $p $m) have been dropped from the EABI (which is still under development), so they are not --- 1243,1308 ---- #ifdef OBJ_ELF /* This code is to handle mapping symbols as defined in the ARM ELF spec. ! (This text is taken from version 0.62 RC 2 of the spec): ! 4.5.7 Mapping symbols ! A section of an ELF file can contain a mixture of ARM code, Thumb code ! and data. ! ! There are inline transitions between code and data at literal pool ! boundaries. There can also be inline transitions between ARM code and ! Thumb code, for example in ARM-Thumb inter-working veneers. ! ! Linkers, and potentially other tools, need to map images correctly (for ! example, to support byte swapping to produce a BE-8 image from a BE-32 ! object file). To support this, a number of symbols, termed mapping ! symbols appear in the symbol table to denote the start of a sequence of ! bytes of the appropriate type. All mapping symbols have type STT_NOTYPE ! and binding STB_LOCAL. The st_size field is unused and must be zero. ! ! The mapping symbols are defined in Table 4-6, Mapping symbols. It is an ! error for a relocation to reference a mapping symbol. Two forms of ! mapping symbol are supported: ! ! * a short form, that uses a dollar character and a single letter ! denoting the class. This form can be used when an object producer ! creates mapping symbols automatically, and minimizes symbol table ! space ! ! * a longer form, where the short form is extended with a period and ! then any sequence of characters that are legal for a symbol. This ! form can be used when assembler files have to be annotated manually ! and the assembler does not support multiple definitions of symbols. ! ! Table 4-6, Mapping symbols ! ! Name Meaning ! ! $a Start of a sequence of ARM instructions ! $a. ! ! $d Start of a sequence of data items (for example, a literal ! $d. pool) ! ! $t Start of a sequence of Thumb instructions ! $t. ! ! 4.5.7.1 Section-relative mapping symbols ! ! Mapping symbols defined in a section define a sequence of half-open ! address intervals that cover the address range of the section. Each ! interval starts at the address defined by the mapping symbol, and ! continues up to, but not including, the address defined by the next (in ! address order) mapping symbol or the end of the section. A section must ! have a mapping symbol defined at the beginning of the section; however, ! if the section contains only data then the mapping symbol may be omitted. ! ! 4.5.7.2 Absolute mapping symbols ! ! Mapping symbols are no-longer required for the absolute section. The ! equivalent information is now conveyed by the type of the absolute ! symbol. Note - the Tagging symbols ($b, $f, $p $m) have been dropped from the EABI (which is still under development), so they are not *************** mapping_state (enum mstate state) *** 1336,1350 **** { case MAP_DATA: symname = "$d"; ! type = BSF_OBJECT; break; case MAP_ARM: symname = "$a"; ! type = BSF_FUNCTION; break; case MAP_THUMB: symname = "$t"; ! type = BSF_FUNCTION; break; case MAP_UNDEFINED: return; --- 1328,1342 ---- { case MAP_DATA: symname = "$d"; ! type = BSF_NO_FLAGS; break; case MAP_ARM: symname = "$a"; ! type = BSF_NO_FLAGS; break; case MAP_THUMB: symname = "$t"; ! type = BSF_NO_FLAGS; break; case MAP_UNDEFINED: return; *************** arm_frob_label (symbolS * sym) *** 13678,13683 **** --- 13670,13685 ---- } } + /* Recognize short-form or long-form mapping symbol names. */ + + static bfd_boolean + is_arm_mapping_symbol_name (const char* name) + { + return name && name[0] == '$' + && (name[1] == 'a' || name[1] == 'd' || name[1] == 't') + && (name[2] == '\0' || name[2] == '.'); + } + /* Adjust the symbol table. This marks Thumb symbols as distinct from ARM ones. */ *************** arm_adjust_symtab (void) *** 13738,13751 **** elf_sym = elf_symbol (symbol_get_bfdsym (sym)); bind = ELF_ST_BIND (elf_sym->internal_elf_sym.st_info); ! /* If it's a .thumb_func, declare it as so, ! otherwise tag label as .code 16. */ ! if (THUMB_IS_FUNC (sym)) ! elf_sym->internal_elf_sym.st_info = ! ELF_ST_INFO (bind, STT_ARM_TFUNC); ! else ! elf_sym->internal_elf_sym.st_info = ! ELF_ST_INFO (bind, STT_ARM_16BIT); } } #endif --- 13740,13756 ---- elf_sym = elf_symbol (symbol_get_bfdsym (sym)); bind = ELF_ST_BIND (elf_sym->internal_elf_sym.st_info); ! if (!is_arm_mapping_symbol_name (elf_sym->symbol.name)) ! { ! /* If it's a .thumb_func, declare it as so, ! otherwise tag label as .code 16. */ ! if (THUMB_IS_FUNC (sym)) ! elf_sym->internal_elf_sym.st_info = ! ELF_ST_INFO (bind, STT_ARM_TFUNC); ! else ! elf_sym->internal_elf_sym.st_info = ! ELF_ST_INFO (bind, STT_ARM_16BIT); ! } } } #endif Index: gas/testsuite/gas/arm/mapping.d =================================================================== RCS file: /cvs/src/src/gas/testsuite/gas/arm/mapping.d,v retrieving revision 1.4 diff -c -p -r1.4 mapping.d *** gas/testsuite/gas/arm/mapping.d 11 Dec 2004 04:32:36 -0000 1.4 --- gas/testsuite/gas/arm/mapping.d 29 Mar 2005 21:13:47 -0000 *************** SYMBOL TABLE: *** 9,18 **** 0+00 l d .text 0+0 (|.text) 0+00 l d .data 0+0 (|.data) 0+00 l d .bss 0+0 (|.bss) ! 0+00 l F .text 0+0 \$a ! 0+08 l F .text 0+0 \$t ! 0+00 l O .data 0+0 \$d 0+00 l d foo 0+0 (|foo) ! 0+00 l F foo 0+0 \$t 0+00 g .text 0+0 mapping 0+08 g F .text 0+0 thumb_mapping --- 9,18 ---- 0+00 l d .text 0+0 (|.text) 0+00 l d .data 0+0 (|.data) 0+00 l d .bss 0+0 (|.bss) ! 0+00 l .text 0+0 \$a ! 0+08 l .text 0+0 \$t ! 0+00 l .data 0+0 \$d 0+00 l d foo 0+0 (|foo) ! 0+00 l foo 0+0 \$t 0+00 g .text 0+0 mapping 0+08 g F .text 0+0 thumb_mapping Index: ld/testsuite/ld-arm/arm-app-abs32.d =================================================================== RCS file: /cvs/src/src/ld/testsuite/ld-arm/arm-app-abs32.d,v retrieving revision 1.2 diff -c -p -r1.2 arm-app-abs32.d *** ld/testsuite/ld-arm/arm-app-abs32.d 17 Nov 2004 17:50:27 -0000 1.2 --- ld/testsuite/ld-arm/arm-app-abs32.d 29 Mar 2005 21:14:01 -0000 *************** Disassembly of section .plt: *** 8,14 **** .* <.plt>: .*: e52de004 str lr, \[sp, #-4\]! ! .*: e59fe004 ldr lr, \[pc, #4\] ; .* <.plt\+0x10> .*: e08fe00e add lr, pc, lr .*: e5bef008 ldr pc, \[lr, #8\]! .*: .* .* --- 8,14 ---- .* <.plt>: .*: e52de004 str lr, \[sp, #-4\]! ! .*: e59fe004 ldr lr, \[pc, #4\] ; .* <_start-0x10> .*: e08fe00e add lr, pc, lr .*: e5bef008 ldr pc, \[lr, #8\]! .*: .* .* Index: ld/testsuite/ld-arm/arm-app.d =================================================================== RCS file: /cvs/src/src/ld/testsuite/ld-arm/arm-app.d,v retrieving revision 1.2 diff -c -p -r1.2 arm-app.d *** ld/testsuite/ld-arm/arm-app.d 17 Nov 2004 17:50:27 -0000 1.2 --- ld/testsuite/ld-arm/arm-app.d 29 Mar 2005 21:14:01 -0000 *************** Disassembly of section .plt: *** 8,14 **** .* <.plt>: .*: e52de004 str lr, \[sp, #-4\]! ! .*: e59fe004 ldr lr, \[pc, #4\] ; .* <.plt\+0x10> .*: e08fe00e add lr, pc, lr .*: e5bef008 ldr pc, \[lr, #8\]! .*: .* --- 8,14 ---- .* <.plt>: .*: e52de004 str lr, \[sp, #-4\]! ! .*: e59fe004 ldr lr, \[pc, #4\] ; .* <_start-0x10> .*: e08fe00e add lr, pc, lr .*: e5bef008 ldr pc, \[lr, #8\]! .*: .* *************** Disassembly of section .text: *** 27,33 **** .* : .*: e1a0c00d mov ip, sp .*: e92dd800 stmdb sp!, {fp, ip, lr, pc} ! .*: ebfffff4 bl .* <.text-0xc> .*: e89d6800 ldmia sp, {fp, sp, lr} .*: e12fff1e bx lr --- 27,33 ---- .* : .*: e1a0c00d mov ip, sp .*: e92dd800 stmdb sp!, {fp, ip, lr, pc} ! .*: ebfffff4 bl .* <_start-0xc> .*: e89d6800 ldmia sp, {fp, sp, lr} .*: e12fff1e bx lr Index: ld/testsuite/ld-arm/mixed-app.d =================================================================== RCS file: /cvs/src/src/ld/testsuite/ld-arm/mixed-app.d,v retrieving revision 1.1 diff -c -p -r1.1 mixed-app.d *** ld/testsuite/ld-arm/mixed-app.d 17 Nov 2004 17:50:27 -0000 1.1 --- ld/testsuite/ld-arm/mixed-app.d 29 Mar 2005 21:14:01 -0000 *************** Disassembly of section .plt: *** 8,14 **** .* <.plt>: .*: e52de004 str lr, \[sp, #-4\]! ! .*: e59fe004 ldr lr, \[pc, #4\] ; .* <.plt\+0x10> .*: e08fe00e add lr, pc, lr .*: e5bef008 ldr pc, \[lr, #8\]! .*: .* --- 8,14 ---- .* <.plt>: .*: e52de004 str lr, \[sp, #-4\]! ! .*: e59fe004 ldr lr, \[pc, #4\] ; .* <_start-0x2c> .*: e08fe00e add lr, pc, lr .*: e5bef008 ldr pc, \[lr, #8\]! .*: .* *************** Disassembly of section .text: *** 34,40 **** .* : .*: e1a0c00d mov ip, sp .*: e92dd800 stmdb sp!, {fp, ip, lr, pc} ! .*: ebffffe. bl .* <.text-0x..> .*: e89d6800 ldmia sp, {fp, sp, lr} .*: e12fff1e bx lr .*: e1a00000 nop \(mov r0,r0\) --- 34,40 ---- .* : .*: e1a0c00d mov ip, sp .*: e92dd800 stmdb sp!, {fp, ip, lr, pc} ! .*: ebffffe. bl .* <_start-0x..> .*: e89d6800 ldmia sp, {fp, sp, lr} .*: e12fff1e bx lr .*: e1a00000 nop \(mov r0,r0\) *************** Disassembly of section .text: *** 49,55 **** .* : .*: b500 push {lr} ! .*: (ffc.f7ff|f7ffffc.) bl .* <.text-0x..> .*: bd00 pop {pc} .*: 4770 bx lr .*: 46c0 nop \(mov r8, r8\) --- 49,55 ---- .* : .*: b500 push {lr} ! .*: (ffc.f7ff|f7ffffc.) bl .* <_start-0x..> .*: bd00 pop {pc} .*: 4770 bx lr .*: 46c0 nop \(mov r8, r8\) --------------040600080605070303060404--