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Re: [PATCH 1/3] ftrace/MIPS: Add MIPS64 support for C version of recordm

To: Wu Zhangjin <wuzhangjin@gmail.com>
Subject: Re: [PATCH 1/3] ftrace/MIPS: Add MIPS64 support for C version of recordmcount
From: Steven Rostedt <rostedt@goodmis.org>
Date: Wed, 27 Oct 2010 09:32:46 -0400
Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, John Reiser <jreiser@bitwagon.com>, "Maciej W. Rozycki" <macro@linux-mips.org>, David Daney <ddaney@caviumnetworks.com>
In-reply-to: <910dc2d5ae1ed042df4f96815fe4a433078d1c2a.1288176026.git.wuzhangjin@gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <cover.1288176026.git.wuzhangjin@gmail.com> <910dc2d5ae1ed042df4f96815fe4a433078d1c2a.1288176026.git.wuzhangjin@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
On Wed, 2010-10-27 at 18:59 +0800, Wu Zhangjin wrote:
> From: Wu Zhangjin <wuzhangjin@gmail.com>

The From above states that you wrote this. Did you modify what John and
Maciej did? If so, please state clearly what each author has done, and
how you modified it. If you did not write this, please change the From
to the correct author.

If you did modify it, then state something like this in the change log.

Original version written by John Reiser <jreiser@BitWagon.com>

Usage of "union mips_r_info" and the functions MIPS64_r_sym() and
MIPS64_r_info() written by Maciej W. Rozycki <macro@linux-mips.org>

Then state the changes you made.

> 
> MIPS64 has 'weird' Elf64_Rel.r_info[1,2], which must be used instead of
> the generic Elf64_Rel.r_info, otherwise, the C version of recordmcount
> will not work for "segmentation fault".
> 
> ----
> [1] 
> http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
> [2] arch/mips/include/asm/module.h
> 
> Signed-off-by: John Reiser <jreiser@BitWagon.com>
> Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
> Tested-by: Wu Zhangjin <wuzhangjin@gmail.com>

Again, if you made changes, you need a SoB yourself.

Thanks!

-- Steve


> ---
>  scripts/recordmcount.c |   41 +++++++++++++++++++++++++++++++++++++++++
>  scripts/recordmcount.h |   34 ++++++++++++++++++++++++++++++----
>  2 files changed, 71 insertions(+), 4 deletions(-)
> 
> diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> index 26e1271..2d32b9c 100644
> --- a/scripts/recordmcount.c
> +++ b/scripts/recordmcount.c
> @@ -217,6 +217,39 @@ is_mcounted_section_name(char const *const txtname)
>  #define RECORD_MCOUNT_64
>  #include "recordmcount.h"
>  
> +/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
> + * 
> http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
> + * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
> + * to imply the order of the members; the spec does not say so.
> + *   typedef unsigned char Elf64_Byte;
> + * fails on MIPS64 because their <elf.h> already has it!
> + */
> +
> +typedef uint8_t myElf64_Byte;                /* Type for a 8-bit quantity.  
> */
> +
> +union mips_r_info {
> +     Elf64_Xword r_info;
> +     struct {
> +             Elf64_Word r_sym;               /* Symbol index.  */
> +             myElf64_Byte r_ssym;            /* Special symbol.  */
> +             myElf64_Byte r_type3;           /* Third relocation.  */
> +             myElf64_Byte r_type2;           /* Second relocation.  */
> +             myElf64_Byte r_type;            /* First relocation.  */
> +     } r_mips;
> +};
> +
> +static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
> +{
> +     return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
> +}
> +
> +static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
> +{
> +     rp->r_info = ((union mips_r_info){
> +             .r_mips = { .r_sym = w(sym), .r_type = type }
> +     }).r_info;
> +}
> +
>  static void
>  do_file(char const *const fname)
>  {
> @@ -268,6 +301,7 @@ do_file(char const *const fname)
>       case EM_386:     reltype = R_386_32;                   break;
>       case EM_ARM:     reltype = R_ARM_ABS32;                break;
>       case EM_IA_64:   reltype = R_IA64_IMM64;   gpfx = '_'; break;
> +     case EM_MIPS:    /* reltype: e_class    */ gpfx = '_'; break;
>       case EM_PPC:     reltype = R_PPC_ADDR32;   gpfx = '_'; break;
>       case EM_PPC64:   reltype = R_PPC64_ADDR64; gpfx = '_'; break;
>       case EM_S390:    /* reltype: e_class    */ gpfx = '_'; break;
> @@ -291,6 +325,8 @@ do_file(char const *const fname)
>               }
>               if (EM_S390 == w2(ehdr->e_machine))
>                       reltype = R_390_32;
> +             if (EM_MIPS == w2(ehdr->e_machine))
> +                     reltype = R_MIPS_32;
>               do32(ehdr, fname, reltype);
>       } break;
>       case ELFCLASS64: {
> @@ -303,6 +339,11 @@ do_file(char const *const fname)
>               }
>               if (EM_S390 == w2(ghdr->e_machine))
>                       reltype = R_390_64;
> +             if (EM_MIPS == w2(ghdr->e_machine)) {
> +                     reltype = R_MIPS_64;
> +                     Elf64_r_sym = MIPS64_r_sym;
> +                     Elf64_r_info = MIPS64_r_info;
> +             }
>               do64(ghdr, fname, reltype);
>       } break;
>       }  /* end switch */
> diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
> index 7f39d09..190fd18 100644
> --- a/scripts/recordmcount.h
> +++ b/scripts/recordmcount.h
> @@ -31,8 +31,12 @@
>  #undef Elf_Rela
>  #undef Elf_Sym
>  #undef ELF_R_SYM
> +#undef Elf_r_sym
>  #undef ELF_R_INFO
> +#undef Elf_r_info
>  #undef ELF_ST_BIND
> +#undef fn_ELF_R_SYM
> +#undef fn_ELF_R_INFO
>  #undef uint_t
>  #undef _w
>  #undef _align
> @@ -52,8 +56,12 @@
>  # define Elf_Rela            Elf64_Rela
>  # define Elf_Sym             Elf64_Sym
>  # define ELF_R_SYM           ELF64_R_SYM
> +# define Elf_r_sym           Elf64_r_sym
>  # define ELF_R_INFO          ELF64_R_INFO
> +# define Elf_r_info          Elf64_r_info
>  # define ELF_ST_BIND         ELF64_ST_BIND
> +# define fn_ELF_R_SYM                fn_ELF64_R_SYM
> +# define fn_ELF_R_INFO               fn_ELF64_R_INFO
>  # define uint_t                      uint64_t
>  # define _w                  w8
>  # define _align                      7u
> @@ -72,14 +80,32 @@
>  # define Elf_Rela            Elf32_Rela
>  # define Elf_Sym             Elf32_Sym
>  # define ELF_R_SYM           ELF32_R_SYM
> +# define Elf_r_sym           Elf32_r_sym
>  # define ELF_R_INFO          ELF32_R_INFO
> +# define Elf_r_info          Elf32_r_info
>  # define ELF_ST_BIND         ELF32_ST_BIND
> +# define fn_ELF_R_SYM                fn_ELF32_R_SYM
> +# define fn_ELF_R_INFO               fn_ELF32_R_INFO
>  # define uint_t                      uint32_t
>  # define _w                  w
>  # define _align                      3u
>  # define _size                       4
>  #endif
>  
> +/* Functions and pointers that 64-bit EM_MIPS can override. */
> +static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
> +{
> +     return ELF_R_SYM(_w(rp->r_info));
> +}
> +static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM;
> +
> +static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type)
> +{
> +     rp->r_info = ELF_R_INFO(sym, type);
> +}
> +static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = 
> fn_ELF_R_INFO;
> +
> +
>  /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
>  static void append_func(Elf_Ehdr *const ehdr,
>                       Elf_Shdr *const shstr,
> @@ -197,22 +223,22 @@ static uint_t *sift_rel_mcount(uint_t *mlocp,
>       for (t = nrel; t; --t) {
>               if (!mcountsym) {
>                       Elf_Sym const *const symp =
> -                             &sym0[ELF_R_SYM(_w(relp->r_info))];
> +                             &sym0[Elf_r_sym(relp)];
>                       char const *symname = &str0[w(symp->st_name)];
>  
>                       if ('.' == symname[0])
>                               ++symname;  /* ppc64 hack */
>                       if (0 == strcmp((('_' == gpfx) ? "_mcount" : "mcount"),
>                                       symname))
> -                             mcountsym = ELF_R_SYM(_w(relp->r_info));
> +                             mcountsym = Elf_r_sym(relp);
>               }
>  
> -             if (mcountsym == ELF_R_SYM(_w(relp->r_info))) {
> +             if (mcountsym == Elf_r_sym(relp)) {
>                       uint_t const addend = _w(_w(relp->r_offset) - recval);
>  
>                       mrelp->r_offset = _w(offbase
>                               + ((void *)mlocp - (void *)mloc0));
> -                     mrelp->r_info = _w(ELF_R_INFO(recsym, reltype));
> +                     Elf_r_info(mrelp, recsym, reltype);
>                       if (sizeof(Elf_Rela) == rel_entsize) {
>                               ((Elf_Rela *)mrelp)->r_addend = addend;
>                               *mlocp++ = 0;



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