linux-kernel - [RFC 21/31] objtool: Fix x86 addend calcuation

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Message-ID: <43433a745f6db5afb513d015a6181bc40be12b4f.1725334260.git.jpoimboe@kernel.org>
Date: Mon,  2 Sep 2024 21:00:04 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: live-patching@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	x86@...nel.org,
	Miroslav Benes <mbenes@...e.cz>,
	Petr Mladek <pmladek@...e.com>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Song Liu <song@...nel.org>
Subject: [RFC 21/31] objtool: Fix x86 addend calcuation

arch_dest_reloc_offset() hard-codes the addend adjustment to 4, which
isn't always true.  In fact it's dependent on the instruction itself.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 tools/objtool/arch/loongarch/decode.c |  4 ++--
 tools/objtool/arch/powerpc/decode.c   |  4 ++--
 tools/objtool/arch/x86/decode.c       | 15 +++++++++++++--
 tools/objtool/check.c                 | 13 ++++---------
 tools/objtool/include/objtool/arch.h  |  2 +-
 5 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/tools/objtool/arch/loongarch/decode.c b/tools/objtool/arch/loongarch/decode.c
index ef09996c772e..b5d44d7bce4e 100644
--- a/tools/objtool/arch/loongarch/decode.c
+++ b/tools/objtool/arch/loongarch/decode.c
@@ -20,9 +20,9 @@ unsigned long arch_jump_destination(struct instruction *insn)
 	return insn->offset + (insn->immediate << 2);
 }
 
-unsigned long arch_dest_reloc_offset(int addend)
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
 {
-	return addend;
+	return reloc_addend(addend);
 }
 
 bool arch_pc_relative_reloc(struct reloc *reloc)
diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
index 29e05ad1b8b6..11e59065f1dc 100644
--- a/tools/objtool/arch/powerpc/decode.c
+++ b/tools/objtool/arch/powerpc/decode.c
@@ -14,9 +14,9 @@ int arch_ftrace_match(const char *name)
 	return !strcmp(name, "_mcount");
 }
 
-unsigned long arch_dest_reloc_offset(int addend)
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
 {
-	return addend;
+	return reloc_addend(reloc);
 }
 
 bool arch_callee_saved_reg(unsigned char reg)
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 72d55dcd3d7f..afebd67d9b9d 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -67,9 +67,20 @@ bool arch_callee_saved_reg(unsigned char reg)
 	}
 }
 
-unsigned long arch_dest_reloc_offset(int addend)
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
 {
-	return addend + 4;
+	s64 addend = reloc_addend(reloc);
+
+	switch (reloc_type(reloc)) {
+	case R_X86_64_PC32:
+	case R_X86_64_PLT32:
+		addend += insn->offset + insn->len - reloc_offset(reloc);
+		break;
+	default:
+		break;
+	}
+
+	return addend;
 }
 
 unsigned long arch_jump_destination(struct instruction *insn)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 236dc7871f01..3c8d0903dfa7 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1461,7 +1461,7 @@ static void add_jump_destinations(struct objtool_file *file)
 		} else if (sym_has_section(reloc->sym)) {
 			dest_sec = reloc->sym->sec;
 			dest_off = reloc->sym->sym.st_value +
-				   arch_dest_reloc_offset(reloc_addend(reloc));
+				   arch_insn_adjusted_addend(insn, reloc);
 		} else {
 			/* External symbol (UNDEF) */
 			dest_sec = NULL;
@@ -1609,7 +1609,7 @@ static void add_call_destinations(struct objtool_file *file)
 				ERROR_INSN(insn, "unsupported call to non-function");
 
 		} else if (is_section_symbol(reloc->sym)) {
-			dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
+			dest_off = arch_insn_adjusted_addend(insn, reloc);
 			dest = find_call_destination(reloc->sym->sec, dest_off);
 			if (!dest)
 				ERROR_INSN(insn, "can't find call dest symbol at %s+0x%lx",
@@ -3119,7 +3119,7 @@ static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
 	if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
 		return false;
 
-	idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
+	idx = (arch_insn_adjusted_addend(insn, reloc) / sizeof(void *));
 
 	if (file->pv_ops[idx].clean)
 		return true;
@@ -4070,12 +4070,7 @@ static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn
 		if (reloc->sym->static_call_tramp)
 			continue;
 
-		off = reloc->sym->offset;
-		if (reloc_type(reloc) == R_X86_64_PC32 ||
-		    reloc_type(reloc) == R_X86_64_PLT32)
-			off += arch_dest_reloc_offset(reloc_addend(reloc));
-		else
-			off += reloc_addend(reloc);
+		off = reloc->sym->offset + arch_insn_adjusted_addend(insn, reloc);
 
 		dest = find_insn(file, reloc->sym->sec, off);
 		if (!dest)
diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
index f48f5109abb1..14911fdfdc8f 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -81,7 +81,7 @@ bool arch_callee_saved_reg(unsigned char reg);
 
 unsigned long arch_jump_destination(struct instruction *insn);
 
-unsigned long arch_dest_reloc_offset(int addend);
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc);
 
 const char *arch_nop_insn(int len);
 const char *arch_ret_insn(int len);
-- 
2.45.2