[RFC PATCH 4/4] objtool/powerpc: Add --mcount specific implementation

[Sathvika Vasireddy <sv@linux.ibm.com>]

This patch enables objtool --mcount on powerpc, and
adds implementation specific to powerpc.

Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
---
 arch/powerpc/Kconfig                |  1 +
 tools/objtool/arch/powerpc/decode.c | 14 ++++++++++++++
 tools/objtool/check.c               | 12 +++++++-----
 tools/objtool/elf.c                 | 13 +++++++++++++
 tools/objtool/include/objtool/elf.h |  1 +
 5 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 732a3f91ee5e..3373d44a1298 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -233,6 +233,7 @@ config PPC
 	select HAVE_NMI				if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
 	select HAVE_OPTPROBES
 	select HAVE_OBJTOOL			if PPC64
+	select HAVE_OBJTOOL_MCOUNT		if HAVE_OBJTOOL
 	select HAVE_PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI		if PPC64
 	select HAVE_PERF_REGS
diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
index e3b77a6ce357..ad3d79fffac2 100644
--- a/tools/objtool/arch/powerpc/decode.c
+++ b/tools/objtool/arch/powerpc/decode.c
@@ -40,12 +40,26 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
 			    struct list_head *ops_list)
 {
 	u32 insn;
+	unsigned int opcode;
 
 	*immediate = 0;
 	memcpy(&insn, sec->data->d_buf+offset, 4);
 	*len = 4;
 	*type = INSN_OTHER;
 
+	opcode = (insn >> 26);
+
+	switch (opcode) {
+	case 18: /* bl */
+		if ((insn & 3) == 1) {
+			*type = INSN_CALL;
+			*immediate = insn & 0x3fffffc;
+			if (*immediate & 0x2000000)
+				*immediate -= 0x4000000;
+		}
+		break;
+	}
+
 	return 0;
 }
 
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 056302d58e23..fd8bad092f89 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -832,7 +832,7 @@ static int create_mcount_loc_sections(struct objtool_file *file)
 
 		if (elf_add_reloc_to_insn(file->elf, sec,
 					  idx * sizeof(unsigned long),
-					  R_X86_64_64,
+					  elf_reloc_type_long(file->elf),
 					  insn->sec, insn->offset))
 			return -1;
 
@@ -2183,7 +2183,7 @@ static int classify_symbols(struct objtool_file *file)
 			if (arch_is_retpoline(func))
 				func->retpoline_thunk = true;
 
-			if (!strcmp(func->name, "__fentry__"))
+			if ((!strcmp(func->name, "__fentry__")) || (!strcmp(func->name, "_mcount")))
 				func->fentry = true;
 
 			if (is_profiling_func(func->name))
@@ -2259,9 +2259,11 @@ static int decode_sections(struct objtool_file *file)
 	 * Must be before add_jump_destinations(), which depends on 'func'
 	 * being set for alternatives, to enable proper sibling call detection.
 	 */
-	ret = add_special_section_alts(file);
-	if (ret)
-		return ret;
+	if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
+		ret = add_special_section_alts(file);
+		if (ret)
+			return ret;
+	}
 
 	ret = add_jump_destinations(file);
 	if (ret)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index c25e957c1e52..95763060d551 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -793,6 +793,19 @@ elf_create_section_symbol(struct elf *elf, struct section *sec)
 	return sym;
 }
 
+int elf_reloc_type_long(struct elf *elf)
+{
+	switch (elf->ehdr.e_machine) {
+	case EM_X86_64:
+		return R_X86_64_64;
+	case EM_PPC64:
+		return R_PPC64_ADDR64;
+	default:
+		WARN("unknown machine...");
+		exit(-1);
+	}
+}
+
 int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
 			  unsigned long offset, unsigned int type,
 			  struct section *insn_sec, unsigned long insn_off)
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index adebfbc2b518..c43e23c0b3c8 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -144,6 +144,7 @@ static inline bool has_multiple_files(struct elf *elf)
 struct elf *elf_open_read(const char *name, int flags);
 struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr);
 
+int elf_reloc_type_long(struct elf *elf);
 int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
 		  unsigned int type, struct symbol *sym, s64 addend);
 int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
-- 
2.25.1