linux-kernel - [RFC 01/16] objtool: Add abstraction for computation of symbols offsets

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Message-Id: <20190516103655.5509-2-raphael.gault@arm.com>
Date:   Thu, 16 May 2019 11:36:40 +0100
From:   Raphael Gault <raphael.gault@....com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     jpoimboe@...hat.com, peterz@...radead.org, catalin.marinas@....com,
        will.deacon@....com, julien.thierry@....com,
        Raphael Gault <raphael.gault@....com>
Subject: [RFC 01/16] objtool: Add abstraction for computation of symbols offsets

The jump destination and relocation offset used previously are only
reliable on x86_64 architecture. We abstract these computations by calling
arch-dependent implementations.

Signed-off-by: Raphael Gault <raphael.gault@....com>
---
 tools/objtool/arch.h            |  6 ++++++
 tools/objtool/arch/x86/decode.c | 11 +++++++++++
 tools/objtool/check.c           | 15 ++++++++++-----
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index 7a111a77b7aa..9897f9f94b29 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -76,6 +76,8 @@ struct stack_op {
 	struct op_src src;
 };
 
+struct instruction;
+
 void arch_initial_func_cfi_state(struct cfi_state *state);
 
 int arch_decode_instruction(struct elf *elf, struct section *sec,
@@ -85,4 +87,8 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 
 bool arch_callee_saved_reg(unsigned char reg);
 
+unsigned long arch_jump_destination(struct instruction *insn);
+
+unsigned long arch_dest_rela_offset(int addend);
+
 #endif /* _ARCH_H */
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 472e991f6512..c1b95ea447c0 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -23,6 +23,7 @@
 #include "lib/inat.c"
 #include "lib/insn.c"
 
+#include "../../check.h"
 #include "../../elf.h"
 #include "../../arch.h"
 #include "../../warn.h"
@@ -78,6 +79,11 @@ bool arch_callee_saved_reg(unsigned char reg)
 	}
 }
 
+unsigned long arch_dest_rela_offset(int addend)
+{
+	return addend + 4;
+}
+
 int arch_decode_instruction(struct elf *elf, struct section *sec,
 			    unsigned long offset, unsigned int maxlen,
 			    unsigned int *len, unsigned char *type,
@@ -509,3 +515,8 @@ void arch_initial_func_cfi_state(struct cfi_state *state)
 	state->regs[16].base = CFI_CFA;
 	state->regs[16].offset = -8;
 }
+
+unsigned long arch_jump_destination(struct instruction *insn)
+{
+	return insn->offset + insn->len + insn->immediate;
+}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 38b0517dc49e..2a803ab4d5b7 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -574,7 +574,7 @@ static int add_jump_destinations(struct objtool_file *file)
 					       insn->len);
 		if (!rela) {
 			dest_sec = insn->sec;
-			dest_off = insn->offset + insn->len + insn->immediate;
+			dest_off = arch_jump_destination(insn);
 		} else if (rela->sym->type == STT_SECTION) {
 			dest_sec = rela->sym->sec;
 			dest_off = rela->addend + 4;
@@ -668,7 +668,7 @@ static int add_call_destinations(struct objtool_file *file)
 		rela = find_rela_by_dest_range(insn->sec, insn->offset,
 					       insn->len);
 		if (!rela) {
-			dest_off = insn->offset + insn->len + insn->immediate;
+			dest_off = arch_jump_destination(insn);
 			insn->call_dest = find_symbol_by_offset(insn->sec,
 								dest_off);
 
@@ -681,14 +681,19 @@ static int add_call_destinations(struct objtool_file *file)
 			}
 
 		} else if (rela->sym->type == STT_SECTION) {
+			/*
+			 * the original x86_64 code adds 4 to the rela->addend
+			 * which is not needed on arm64 architecture.
+			 */
+			dest_off = arch_dest_rela_offset(rela->addend);
 			insn->call_dest = find_symbol_by_offset(rela->sym->sec,
-								rela->addend+4);
+								dest_off);
 			if (!insn->call_dest ||
 			    insn->call_dest->type != STT_FUNC) {
-				WARN_FUNC("can't find call dest symbol at %s+0x%x",
+				WARN_FUNC("can't find call dest symbol at %s+0x%lx",
 					  insn->sec, insn->offset,
 					  rela->sym->sec->name,
-					  rela->addend + 4);
+					  dest_off);
 				return -1;
 			}
 		} else
-- 
2.17.1