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[PATCH v2 18/62] objtool: Fix x86 addend calculation

Josh Poimboeuf posted 62 patches 7 months, 1 week ago
There is a newer version of this series
[PATCH v2 18/62] objtool: Fix x86 addend calculation
Posted by Josh Poimboeuf 7 months, 1 week ago 
On x86, arch_dest_reloc_offset() hardcodes the addend adjustment to
four, but the actual adjustment depends on the relocation type.  Fix
that.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.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 b6fdc68053cc..330671d88c59 100644
--- a/tools/objtool/arch/loongarch/decode.c
+++ b/tools/objtool/arch/loongarch/decode.c
@@ -17,9 +17,9 @@ 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(reloc);
 }
 
 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 c851c51d4bd3..9b17885e6cba 100644
--- a/tools/objtool/arch/powerpc/decode.c
+++ b/tools/objtool/arch/powerpc/decode.c
@@ -14,9 +14,9 @@ int arch_ftrace_match(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 331b9a744410..771ad24e49ee 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -68,9 +68,20 @@ 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 3a411064fa34..ea4e0facd21b 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1502,7 +1502,7 @@ static int add_jump_destinations(struct objtool_file *file)
 			dest_off = arch_jump_destination(insn);
 		} else if (reloc->sym->type == STT_SECTION) {
 			dest_sec = reloc->sym->sec;
-			dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
+			dest_off = arch_insn_adjusted_addend(insn, reloc);
 		} else if (reloc->sym->retpoline_thunk) {
 			ret = add_retpoline_call(file, insn);
 			if (ret)
@@ -1672,7 +1672,7 @@ static int add_call_destinations(struct objtool_file *file)
 			}
 
 		} else if (reloc->sym->type == STT_SECTION) {
-			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",
@@ -3348,7 +3348,7 @@ 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;
@@ -4396,12 +4396,7 @@ static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn
 					      reloc_offset(reloc) + 1,
 					      (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
 
-		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 01ef6f415adf..cd1776c35b13 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -83,7 +83,7 @@ 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);
-- 
2.49.0
Re: [PATCH v2 18/62] objtool: Fix x86 addend calculation
Posted by Peter Zijlstra 6 months, 3 weeks ago 
On Fri, May 09, 2025 at 01:16:42PM -0700, Josh Poimboeuf wrote:
> On x86, arch_dest_reloc_offset() hardcodes the addend adjustment to
> four, but the actual adjustment depends on the relocation type.  Fix
> that.

> +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;
>  }

Should this not be something like:

s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
{
	s64 addend = reloc_addend(reloc);

	if (arch_pc_relative_reloc(reloc))
		addend += insn->offset + insn->len - reloc_offset(reloc);

	return addend;
}

instead?

AFAIU arch_pc_relative_reloc() is the exact same set of relocations.
Re: [PATCH v2 18/62] objtool: Fix x86 addend calculation
Posted by Josh Poimboeuf 6 months, 2 weeks ago 
On Mon, May 26, 2025 at 12:23:15PM +0200, Peter Zijlstra wrote:
> On Fri, May 09, 2025 at 01:16:42PM -0700, Josh Poimboeuf wrote:
> > On x86, arch_dest_reloc_offset() hardcodes the addend adjustment to
> > four, but the actual adjustment depends on the relocation type.  Fix
> > that.
> 
> > +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;
> >  }
> 
> Should this not be something like:
> 
> s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
> {
> 	s64 addend = reloc_addend(reloc);
> 
> 	if (arch_pc_relative_reloc(reloc))
> 		addend += insn->offset + insn->len - reloc_offset(reloc);
> 
> 	return addend;
> }
> 
> instead?
> 
> AFAIU arch_pc_relative_reloc() is the exact same set of relocations.

Yeah that's better, thanks.

-- 
Josh

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