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

To: rostedt@goodmis.org, Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/3] ftrace/MIPS: Add MIPS64 support for C version of recordmcount
From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Wed, 27 Oct 2010 18:59:07 +0800
Cc: John Reiser <jreiser@bitwagon.com>, "Maciej W. Rozycki" <macro@linux-mips.org>, David Daney <ddaney@caviumnetworks.com>, Wu Zhangjin <wuzhangjin@gmail.com>, John Reiser <jreiser@BitWagon.com>
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In-reply-to: <cover.1288176026.git.wuzhangjin@gmail.com>
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Original-recipient: rfc822;linux-mips@linux-mips.org
References: <cover.1288176026.git.wuzhangjin@gmail.com>
References: <cover.1288176026.git.wuzhangjin@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
From: Wu Zhangjin <wuzhangjin@gmail.com>

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>
---
 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;
-- 
1.7.1


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