ftrace/MIPS: Add MIPS64 support for C version of recordmcount

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".

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>

----
[1] http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
[2] arch/mips/include/asm/module.h
Tested-by: Wu Zhangjin <wuzhangjin@gmail.com>
Signed-off-by: John Reiser <jreiser@BitWagon.com>
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
LKML-Reference: <AANLkTinwXjLAYACUfhLYaocHD_vBbiErLN3NjwN8JqSy@mail.gmail.com>
LKML-Reference: <910dc2d5ae1ed042df4f96815fe4a433078d1c2a.1288176026.git.wuzhangjin@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

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 */

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;