[PATCH 0/3] objtool: Generate ORC data for __pfx code

[PATCH 0/3] objtool: Generate ORC data for __pfx code

[Josh Poimboeuf]

Josh Poimboeuf (3):
  objtool: Separate prefix code from stack validation code
  x86/linkage: Fix padding for typed functions
  objtool: Generate ORC data for __pfx code

 arch/x86/include/asm/linkage.h |   2 +-
 tools/objtool/check.c          | 102 +++++++++++++++++++++------------
 2 files changed, 65 insertions(+), 39 deletions(-)

-- 
2.39.2

[PATCH 1/3] objtool: Separate prefix code from stack validation code

[Josh Poimboeuf]

Simplify the prefix code and make it a standalone feature.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/check.c | 88 ++++++++++++++++++++++++-------------------
 1 file changed, 50 insertions(+), 38 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 53940e2ac632..2f3136145b2e 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4120,54 +4120,61 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	return false;
 }
 
-static int add_prefix_symbol(struct objtool_file *file, struct symbol *func,
-			     struct instruction *insn)
+static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 {
-	if (!opts.prefix)
-		return 0;
+	struct instruction *insn, *prev;
 
-	for (;;) {
-		struct instruction *prev = prev_insn_same_sec(file, insn);
-		u64 offset;
+	insn = find_insn(file, func->sec, func->offset);
+	if (!insn)
+		return -1;
 
-		if (!prev)
-			break;
+	for (prev = prev_insn_same_sec(file, insn);
+	     prev;
+	     prev = prev_insn_same_sec(file, prev)) {
+		u64 offset;
 
 		if (prev->type != INSN_NOP)
-			break;
+			return -1;
 
 		offset = func->offset - prev->offset;
-		if (offset >= opts.prefix) {
-			if (offset == opts.prefix) {
-				/*
-				 * Since the sec->symbol_list is ordered by
-				 * offset (see elf_add_symbol()) the added
-				 * symbol will not be seen by the iteration in
-				 * validate_section().
-				 *
-				 * Hence the lack of list_for_each_entry_safe()
-				 * there.
-				 *
-				 * The direct concequence is that prefix symbols
-				 * don't get visited (because pointless), except
-				 * for the logic in ignore_unreachable_insn()
-				 * that needs the terminating insn to be visited
-				 * otherwise it will report the hole.
-				 *
-				 * Hence mark the first instruction of the
-				 * prefix symbol as visisted.
-				 */
-				prev->visited |= VISITED_BRANCH;
-				elf_create_prefix_symbol(file->elf, func, opts.prefix);
-			}
-			break;
-		}
-		insn = prev;
+
+		if (offset > opts.prefix)
+			return -1;
+
+		if (offset < opts.prefix)
+			continue;
+
+		elf_create_prefix_symbol(file->elf, func, opts.prefix);
+		break;
 	}
 
+	if (!prev)
+		return -1;
+
 	return 0;
 }
 
+static int add_prefix_symbols(struct objtool_file *file)
+{
+	struct section *sec;
+	struct symbol *func;
+	int ret, warnings = 0;
+
+	for_each_sec(file, sec) {
+		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
+			continue;
+
+		list_for_each_entry(func, &sec->symbol_list, list) {
+			if (func->type != STT_FUNC)
+				continue;
+
+			add_prefix_symbol(file, func);
+		}
+	}
+
+	return warnings;
+}
+
 static int validate_symbol(struct objtool_file *file, struct section *sec,
 			   struct symbol *sym, struct insn_state *state)
 {
@@ -4186,8 +4193,6 @@ static int validate_symbol(struct objtool_file *file, struct section *sec,
 	if (!insn || insn->ignore || insn->visited)
 		return 0;
 
-	add_prefix_symbol(file, sym, insn);
-
 	state->uaccess = sym->uaccess_safe;
 
 	ret = validate_branch(file, insn_func(insn), insn, *state);
@@ -4744,6 +4749,13 @@ int check(struct objtool_file *file)
 		warnings += ret;
 	}
 
+	if (opts.prefix) {
+		ret = add_prefix_symbols(file);
+		if (ret < 0)
+			return ret;
+		warnings += ret;
+	}
+
 	if (opts.ibt) {
 		ret = create_ibt_endbr_seal_sections(file);
 		if (ret < 0)
-- 
2.39.2

Re: [PATCH 1/3] objtool: Separate prefix code from stack validation code

[Peter Zijlstra]

On Wed, Apr 12, 2023 at 01:26:13PM -0700, Josh Poimboeuf wrote:
> Simplify the prefix code and make it a standalone feature.

The main thing being that you moved it all after
validate_reachable_instructions() ?


> +static int add_prefix_symbols(struct objtool_file *file)
> +{
> +	struct section *sec;
> +	struct symbol *func;
> +	int ret, warnings = 0;
> +
> +	for_each_sec(file, sec) {
> +		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
> +			continue;
> +
> +		list_for_each_entry(func, &sec->symbol_list, list) {

One of the other patches did a sec_for_each_symbol() thing.

> +			if (func->type != STT_FUNC)
> +				continue;
> +
> +			add_prefix_symbol(file, func);
> +		}
> +	}
> +
> +	return warnings;
> +}

Re: [PATCH 1/3] objtool: Separate prefix code from stack validation code

[Josh Poimboeuf]

On Thu, Apr 13, 2023 at 11:30:31AM +0200, Peter Zijlstra wrote:
> On Wed, Apr 12, 2023 at 01:26:13PM -0700, Josh Poimboeuf wrote:
> > Simplify the prefix code and make it a standalone feature.
> 
> The main thing being that you moved it all after
> validate_reachable_instructions() ?

The main thing being that I extricated it from validate_symbol() so it's
a proper independent feature.

> > +static int add_prefix_symbols(struct objtool_file *file)
> > +{
> > +	struct section *sec;
> > +	struct symbol *func;
> > +	int ret, warnings = 0;
> > +
> > +	for_each_sec(file, sec) {
> > +		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
> > +			continue;
> > +
> > +		list_for_each_entry(func, &sec->symbol_list, list) {
> 
> One of the other patches did a sec_for_each_symbol() thing.

Too many patch sets floating around ;-)

-- 
Josh

[tip: objtool/core] objtool: Separate prefix code from stack validation code

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     bd456a1bedd20cebd37493f8cb0291294a7356ea
Gitweb:        https://git.kernel.org/tip/bd456a1bedd20cebd37493f8cb0291294a7356ea
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Wed, 12 Apr 2023 13:26:13 -07:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 14 Apr 2023 16:08:29 +02:00

objtool: Separate prefix code from stack validation code

Simplify the prefix code by moving it after
validate_reachable_instructions().

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/d7f31ac2de462d0cd7b1db01b7ecb525c057c8f6.1681331135.git.jpoimboe@kernel.org
---
 tools/objtool/check.c | 88 +++++++++++++++++++++++-------------------
 1 file changed, 50 insertions(+), 38 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 1cf2e28..8ee4d51 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4114,54 +4114,61 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	return false;
 }
 
-static int add_prefix_symbol(struct objtool_file *file, struct symbol *func,
-			     struct instruction *insn)
+static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 {
-	if (!opts.prefix)
-		return 0;
+	struct instruction *insn, *prev;
 
-	for (;;) {
-		struct instruction *prev = prev_insn_same_sec(file, insn);
-		u64 offset;
+	insn = find_insn(file, func->sec, func->offset);
+	if (!insn)
+		return -1;
 
-		if (!prev)
-			break;
+	for (prev = prev_insn_same_sec(file, insn);
+	     prev;
+	     prev = prev_insn_same_sec(file, prev)) {
+		u64 offset;
 
 		if (prev->type != INSN_NOP)
-			break;
+			return -1;
 
 		offset = func->offset - prev->offset;
-		if (offset >= opts.prefix) {
-			if (offset == opts.prefix) {
-				/*
-				 * Since the sec->symbol_list is ordered by
-				 * offset (see elf_add_symbol()) the added
-				 * symbol will not be seen by the iteration in
-				 * validate_section().
-				 *
-				 * Hence the lack of list_for_each_entry_safe()
-				 * there.
-				 *
-				 * The direct concequence is that prefix symbols
-				 * don't get visited (because pointless), except
-				 * for the logic in ignore_unreachable_insn()
-				 * that needs the terminating insn to be visited
-				 * otherwise it will report the hole.
-				 *
-				 * Hence mark the first instruction of the
-				 * prefix symbol as visisted.
-				 */
-				prev->visited |= VISITED_BRANCH;
-				elf_create_prefix_symbol(file->elf, func, opts.prefix);
-			}
-			break;
-		}
-		insn = prev;
+
+		if (offset > opts.prefix)
+			return -1;
+
+		if (offset < opts.prefix)
+			continue;
+
+		elf_create_prefix_symbol(file->elf, func, opts.prefix);
+		break;
 	}
 
+	if (!prev)
+		return -1;
+
 	return 0;
 }
 
+static int add_prefix_symbols(struct objtool_file *file)
+{
+	struct section *sec;
+	struct symbol *func;
+	int warnings = 0;
+
+	for_each_sec(file, sec) {
+		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
+			continue;
+
+		sec_for_each_sym(sec, func) {
+			if (func->type != STT_FUNC)
+				continue;
+
+			add_prefix_symbol(file, func);
+		}
+	}
+
+	return warnings;
+}
+
 static int validate_symbol(struct objtool_file *file, struct section *sec,
 			   struct symbol *sym, struct insn_state *state)
 {
@@ -4180,8 +4187,6 @@ static int validate_symbol(struct objtool_file *file, struct section *sec,
 	if (!insn || insn->ignore || insn->visited)
 		return 0;
 
-	add_prefix_symbol(file, sym, insn);
-
 	state->uaccess = sym->uaccess_safe;
 
 	ret = validate_branch(file, insn_func(insn), insn, *state);
@@ -4621,6 +4626,13 @@ int check(struct objtool_file *file)
 		warnings += ret;
 	}
 
+	if (opts.prefix) {
+		ret = add_prefix_symbols(file);
+		if (ret < 0)
+			return ret;
+		warnings += ret;
+	}
+
 	if (opts.ibt) {
 		ret = create_ibt_endbr_seal_sections(file);
 		if (ret < 0)

[PATCH 2/3] x86/linkage: Fix padding for typed functions

[Josh Poimboeuf]

CFI typed functions are failing to get padded properly for
CONFIG_CALL_PADDING.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/linkage.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index dd9b8118f784..0953aa32a324 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -99,7 +99,7 @@
 
 /* SYM_TYPED_FUNC_START -- use for indirectly called globals, w/ CFI type */
 #define SYM_TYPED_FUNC_START(name)				\
-	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)	\
+	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)	\
 	ENDBR
 
 /* SYM_FUNC_START -- use for global functions */
-- 
2.39.2

[tip: objtool/core] x86/linkage: Fix padding for typed functions

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     4a2c3448ed3d362431c249ec0eb0f90281804ea8
Gitweb:        https://git.kernel.org/tip/4a2c3448ed3d362431c249ec0eb0f90281804ea8
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Wed, 12 Apr 2023 13:26:14 -07:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 14 Apr 2023 16:08:30 +02:00

x86/linkage: Fix padding for typed functions

CFI typed functions are failing to get padded properly for
CONFIG_CALL_PADDING.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/721f0da48d2a49fe907225711b8b76a2b787f9a8.1681331135.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/linkage.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index dd9b811..0953aa3 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -99,7 +99,7 @@
 
 /* SYM_TYPED_FUNC_START -- use for indirectly called globals, w/ CFI type */
 #define SYM_TYPED_FUNC_START(name)				\
-	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)	\
+	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)	\
 	ENDBR
 
 /* SYM_FUNC_START -- use for global functions */

[PATCH 3/3] objtool: Generate ORC data for __pfx code

[Josh Poimboeuf]

Allow unwinding from prefix code by copying the CFI from the starting
instruction of the corresponding function.  Even when the NOPs are
replaced, they're still stack-invariant instructions so the same ORC
entry can be reused everywhere.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/check.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 2f3136145b2e..3f27a0278bf8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4123,6 +4123,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 {
 	struct instruction *insn, *prev;
+	struct cfi_state *cfi;
 
 	insn = find_insn(file, func->sec, func->offset);
 	if (!insn)
@@ -4151,6 +4152,19 @@ static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 	if (!prev)
 		return -1;
 
+	if (!insn->cfi) {
+		/*
+		 * This can happen if stack validation isn't enabled or the
+		 * function is annotated with STACK_FRAME_NON_STANDARD.
+		 */
+		return 0;
+	}
+
+	/* Propagate insn->cfi to the prefix code */
+	cfi = cfi_hash_find_or_add(insn->cfi);
+	for (; prev != insn; prev = next_insn_same_sec(file, prev))
+		prev->cfi = cfi;
+
 	return 0;
 }
 
@@ -4158,7 +4172,7 @@ static int add_prefix_symbols(struct objtool_file *file)
 {
 	struct section *sec;
 	struct symbol *func;
-	int ret, warnings = 0;
+	int warnings = 0;
 
 	for_each_sec(file, sec) {
 		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
-- 
2.39.2

Re: [PATCH 3/3] objtool: Generate ORC data for __pfx code

[Peter Zijlstra]

On Wed, Apr 12, 2023 at 01:26:15PM -0700, Josh Poimboeuf wrote:

> @@ -4158,7 +4172,7 @@ static int add_prefix_symbols(struct objtool_file *file)
>  {
>  	struct section *sec;
>  	struct symbol *func;
> -	int ret, warnings = 0;
> +	int warnings = 0;
>  
>  	for_each_sec(file, sec) {
>  		if (!(sec->sh.sh_flags & SHF_EXECINSTR))

Stray hunk that should go in the first patch I suppose.

Re: [PATCH 3/3] objtool: Generate ORC data for __pfx code

[Peter Zijlstra]

On Wed, Apr 12, 2023 at 01:26:15PM -0700, Josh Poimboeuf wrote:
> Allow unwinding from prefix code by copying the CFI from the starting
> instruction of the corresponding function.  Even when the NOPs are
> replaced, they're still stack-invariant instructions so the same ORC
> entry can be reused everywhere.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
>  tools/objtool/check.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 2f3136145b2e..3f27a0278bf8 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -4123,6 +4123,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
>  static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
>  {
>  	struct instruction *insn, *prev;
> +	struct cfi_state *cfi;
>  
>  	insn = find_insn(file, func->sec, func->offset);
>  	if (!insn)
> @@ -4151,6 +4152,19 @@ static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
>  	if (!prev)
>  		return -1;
>  
> +	if (!insn->cfi) {
> +		/*
> +		 * This can happen if stack validation isn't enabled or the
> +		 * function is annotated with STACK_FRAME_NON_STANDARD.
> +		 */
> +		return 0;
> +	}
> +
> +	/* Propagate insn->cfi to the prefix code */
> +	cfi = cfi_hash_find_or_add(insn->cfi);
> +	for (; prev != insn; prev = next_insn_same_sec(file, prev))
> +		prev->cfi = cfi;
> +
>  	return 0;
>  }

FWIW, this makes the whole thing hard rely on the prefix being single
byte NOPs -- which they are, but perhaps we should assert this?

Re: [PATCH 3/3] objtool: Generate ORC data for __pfx code

[Josh Poimboeuf]

On Thu, Apr 13, 2023 at 01:24:26PM +0200, Peter Zijlstra wrote:
> > +	if (!insn->cfi) {
> > +		/*
> > +		 * This can happen if stack validation isn't enabled or the
> > +		 * function is annotated with STACK_FRAME_NON_STANDARD.
> > +		 */
> > +		return 0;
> > +	}
> > +
> > +	/* Propagate insn->cfi to the prefix code */
> > +	cfi = cfi_hash_find_or_add(insn->cfi);
> > +	for (; prev != insn; prev = next_insn_same_sec(file, prev))
> > +		prev->cfi = cfi;
> > +
> >  	return 0;
> >  }
> 
> FWIW, this makes the whole thing hard rely on the prefix being single
> byte NOPs -- which they are, but perhaps we should assert this?

Couldn't they be any stack-invariant instructions?

-- 
Josh

Re: [PATCH 3/3] objtool: Generate ORC data for __pfx code

[Peter Zijlstra]

On Thu, Apr 13, 2023 at 08:29:33AM -0700, Josh Poimboeuf wrote:
> On Thu, Apr 13, 2023 at 01:24:26PM +0200, Peter Zijlstra wrote:
> > > +	if (!insn->cfi) {
> > > +		/*
> > > +		 * This can happen if stack validation isn't enabled or the
> > > +		 * function is annotated with STACK_FRAME_NON_STANDARD.
> > > +		 */
> > > +		return 0;
> > > +	}
> > > +
> > > +	/* Propagate insn->cfi to the prefix code */
> > > +	cfi = cfi_hash_find_or_add(insn->cfi);
> > > +	for (; prev != insn; prev = next_insn_same_sec(file, prev))
> > > +		prev->cfi = cfi;
> > > +
> > >  	return 0;
> > >  }
> > 
> > FWIW, this makes the whole thing hard rely on the prefix being single
> > byte NOPs -- which they are, but perhaps we should assert this?
> 
> Couldn't they be any stack-invariant instructions?

Hmm, I was thikning that since we don't know the size of the
instructions being written, we need CFI for all offsets. But perhaps,
since we do a left-match on IP, only one entry at the __pfx+0 location
would work?

Re: [PATCH 3/3] objtool: Generate ORC data for __pfx code

[Josh Poimboeuf]

On Thu, Apr 13, 2023 at 09:24:49PM +0200, Peter Zijlstra wrote:
> On Thu, Apr 13, 2023 at 08:29:33AM -0700, Josh Poimboeuf wrote:
> > On Thu, Apr 13, 2023 at 01:24:26PM +0200, Peter Zijlstra wrote:
> > > > +	if (!insn->cfi) {
> > > > +		/*
> > > > +		 * This can happen if stack validation isn't enabled or the
> > > > +		 * function is annotated with STACK_FRAME_NON_STANDARD.
> > > > +		 */
> > > > +		return 0;
> > > > +	}
> > > > +
> > > > +	/* Propagate insn->cfi to the prefix code */
> > > > +	cfi = cfi_hash_find_or_add(insn->cfi);
> > > > +	for (; prev != insn; prev = next_insn_same_sec(file, prev))
> > > > +		prev->cfi = cfi;
> > > > +
> > > >  	return 0;
> > > >  }
> > > 
> > > FWIW, this makes the whole thing hard rely on the prefix being single
> > > byte NOPs -- which they are, but perhaps we should assert this?
> > 
> > Couldn't they be any stack-invariant instructions?
> 
> Hmm, I was thikning that since we don't know the size of the
> instructions being written, we need CFI for all offsets. But perhaps,
> since we do a left-match on IP, only one entry at the __pfx+0 location
> would work?

Right, while in objtool (almost) every insn has insn->cfi, the actual
ORC entries only get created at the boundaries of change.

-- 
Josh

[tip: objtool/core] objtool: Generate ORC data for __pfx code

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     5743654f5e2ebd56df99f56fca5ba4b23fe3c815
Gitweb:        https://git.kernel.org/tip/5743654f5e2ebd56df99f56fca5ba4b23fe3c815
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Wed, 12 Apr 2023 13:26:15 -07:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 14 Apr 2023 16:08:30 +02:00

objtool: Generate ORC data for __pfx code

Allow unwinding from prefix code by copying the CFI from the starting
instruction of the corresponding function.  Even when the NOPs are
replaced, they're still stack-invariant instructions so the same ORC
entry can be reused everywhere.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/bc3344e51f3e87102f1301a0be0f72a7689ea4a4.1681331135.git.jpoimboe@kernel.org
---
 tools/objtool/check.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8ee4d51..df634da 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4117,6 +4117,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 {
 	struct instruction *insn, *prev;
+	struct cfi_state *cfi;
 
 	insn = find_insn(file, func->sec, func->offset);
 	if (!insn)
@@ -4145,6 +4146,19 @@ static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 	if (!prev)
 		return -1;
 
+	if (!insn->cfi) {
+		/*
+		 * This can happen if stack validation isn't enabled or the
+		 * function is annotated with STACK_FRAME_NON_STANDARD.
+		 */
+		return 0;
+	}
+
+	/* Propagate insn->cfi to the prefix code */
+	cfi = cfi_hash_find_or_add(insn->cfi);
+	for (; prev != insn; prev = next_insn_same_sec(file, prev))
+		prev->cfi = cfi;
+
 	return 0;
 }