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patch v2: [RFC 2/2] ftrace/MIPS: Add support for C version of recordmcou

To: Steven Rostedt <rostedt@goodmis.org>
Subject: patch v2: [RFC 2/2] ftrace/MIPS: Add support for C version of recordmcount
From: John Reiser <jreiser@bitwagon.com>
Date: Mon, 25 Oct 2010 09:46:44 -0700
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>, wu zhangjin <wuzhangjin@gmail.com>, David Daney <ddaney@caviumnetworks.com>, linux-mips@linux-mips.org, Ralf Baechle <ralf@linux-mips.org>
In-reply-to: <alpine.LFD.2.00.1010250435540.15889@eddie.linux-mips.org>
Organization: -
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <AANLkTinwXjLAYACUfhLYaocHD_vBbiErLN3NjwN8JqSy@mail.gmail.com> <4CC49A99.1080601@bitwagon.com> <alpine.LFD.2.00.1010250435540.15889@eddie.linux-mips.org>
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Here's a second try [discard the first] for handling MIPS64 in 
recordmcount.[ch].

Signed-off-by: John Reiser <jreiser@BitWagon.com

diff --git a/recordmcount.c b/recordmcount.c
index 7f7f718..7337ee8 100644
--- a/recordmcount.c
+++ b/recordmcount.c
@@ -212,11 +212,48 @@ is_mcounted_section_name(char const *const txtname)
                0 == strcmp(".text.unlikely", txtname);
 }

+
 /* 32 bit and 64 bit are very similar */
 #include "recordmcount.h"
 #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 unsigned char myElf64_byte;
+typedef struct {
+       Elf64_Addr    r_offset;               /* Address */
+       struct {
+               Elf64_Word r_sym;
+               myElf64_byte r_ssym;  /* Special sym: gp-relative, etc. */
+               myElf64_byte r_type3;
+               myElf64_byte r_type2;
+               myElf64_byte r_type;
+       } r_info;
+       Elf64_Sxword  r_addend;               /* Addend */
+} MIPS64_Rela;
+
+static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
+{
+       return w(((MIPS64_Rela const *)rp)->r_info.r_sym);
+}
+
+static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
+{
+       MIPS64_Rela *const m64rp = (MIPS64_Rela *)rp;
+       m64rp->r_info.r_sym = w(sym);
+       m64rp->r_info.r_ssym = 0;
+       m64rp->r_info.r_type3 = 0;
+       m64rp->r_info.r_type2 = 0;
+       m64rp->r_info.r_type = type;
+}
+
+
 static void
 do_file(char const *const fname)
 {
@@ -268,6 +305,7 @@ 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 +329,8 @@ 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 +343,11 @@ 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/recordmcount.h b/recordmcount.h
index 7f39d09..190fd18 100644
--- a/recordmcount.h
+++ b/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;

-- 
John Reiser, jreiser@BitWagon.com

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