* [PATCH v2 1/9] compiler_types.h: Move __nocfi out of compiler-specific header
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 18:28 ` Nathan Chancellor
2025-09-04 3:46 ` [PATCH v2 2/9] x86/traps: Clarify KCFI instruction layout Kees Cook
` (8 subsequent siblings)
9 siblings, 1 reply; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, Nathan Chancellor, Nick Desaulniers, Bill Wendling,
Justin Stitt, Miguel Ojeda, Marco Elver, Przemek Kitszel,
Ramon de C Valle, llvm, Vegard Nossum, Linus Walleij,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Jonathan Corbet, Paul E. McKenney,
Nicolas Schier, Masahiro Yamada, Arnd Bergmann,
Krzysztof Kozlowski, Sami Tolvanen, Mark Rutland, linux-kernel,
linux-doc, linux-kbuild, linux-arm-kernel, x86, linux-hardening
Prepare for GCC KCFI support and move the __nocfi attribute from
compiler-clang.h to compiler_types.h. This was already gated by
CONFIG_CFI_CLANG, so this remains safe for non-KCFI GCC builds.
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Marco Elver <elver@google.com>
Cc: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Cc: Ramon de C Valle <rcvalle@google.com>
Cc: <llvm@lists.linux.dev>
---
include/linux/compiler-clang.h | 5 -----
include/linux/compiler_types.h | 4 +++-
2 files changed, 3 insertions(+), 6 deletions(-)
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index fa4ffe037bc7..7a4568e421dc 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -96,11 +96,6 @@
# define __noscs __attribute__((__no_sanitize__("shadow-call-stack")))
#endif
-#if __has_feature(kcfi)
-/* Disable CFI checking inside a function. */
-#define __nocfi __attribute__((__no_sanitize__("kcfi")))
-#endif
-
/*
* Turn individual warnings and errors on and off locally, depending
* on version.
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 16755431fc11..a910f9fa5341 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -432,7 +432,9 @@ struct ftrace_likely_data {
# define __noscs
#endif
-#ifndef __nocfi
+#if defined(CONFIG_CFI_CLANG)
+# define __nocfi __attribute__((__no_sanitize__("kcfi")))
+#else
# define __nocfi
#endif
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* Re: [PATCH v2 1/9] compiler_types.h: Move __nocfi out of compiler-specific header
2025-09-04 3:46 ` [PATCH v2 1/9] compiler_types.h: Move __nocfi out of compiler-specific header Kees Cook
@ 2025-09-04 18:28 ` Nathan Chancellor
0 siblings, 0 replies; 20+ messages in thread
From: Nathan Chancellor @ 2025-09-04 18:28 UTC (permalink / raw)
To: Kees Cook
Cc: Peter Zijlstra, Nick Desaulniers, Bill Wendling, Justin Stitt,
Miguel Ojeda, Marco Elver, Przemek Kitszel, Ramon de C Valle,
llvm, Vegard Nossum, Linus Walleij, Jeff Johnson, Randy Dunlap,
David Woodhouse, Russell King (Oracle), Jonathan Corbet,
Paul E. McKenney, Nicolas Schier, Masahiro Yamada, Arnd Bergmann,
Krzysztof Kozlowski, Sami Tolvanen, Mark Rutland, linux-kernel,
linux-doc, linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Wed, Sep 03, 2025 at 08:46:40PM -0700, Kees Cook wrote:
> Prepare for GCC KCFI support and move the __nocfi attribute from
> compiler-clang.h to compiler_types.h. This was already gated by
> CONFIG_CFI_CLANG, so this remains safe for non-KCFI GCC builds.
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
I reviewed this on v1:
https://lore.kernel.org/20250827194657.GA3572128@ax162/
but just to make sure it sticks :)
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> ---
> include/linux/compiler-clang.h | 5 -----
> include/linux/compiler_types.h | 4 +++-
> 2 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index fa4ffe037bc7..7a4568e421dc 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -96,11 +96,6 @@
> # define __noscs __attribute__((__no_sanitize__("shadow-call-stack")))
> #endif
>
> -#if __has_feature(kcfi)
> -/* Disable CFI checking inside a function. */
> -#define __nocfi __attribute__((__no_sanitize__("kcfi")))
> -#endif
> -
> /*
> * Turn individual warnings and errors on and off locally, depending
> * on version.
> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> index 16755431fc11..a910f9fa5341 100644
> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -432,7 +432,9 @@ struct ftrace_likely_data {
> # define __noscs
> #endif
>
> -#ifndef __nocfi
> +#if defined(CONFIG_CFI_CLANG)
> +# define __nocfi __attribute__((__no_sanitize__("kcfi")))
> +#else
> # define __nocfi
> #endif
>
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 20+ messages in thread
* [PATCH v2 2/9] x86/traps: Clarify KCFI instruction layout
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
2025-09-04 3:46 ` [PATCH v2 1/9] compiler_types.h: Move __nocfi out of compiler-specific header Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 3:46 ` [PATCH v2 3/9] x86/cfi: Document the "cfi=" bootparam options Kees Cook
` (7 subsequent siblings)
9 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, Nathan Chancellor, Vegard Nossum, Miguel Ojeda,
Linus Walleij, Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
Just a nit-picky change to the KCFI indirect call check instruction
documentation. The addl offset isn't always -4 (it depends on patchable
function entry configuration).
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Peter Zijlstra <peterz@infradead.org>
---
arch/x86/kernel/cfi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cfi.c b/arch/x86/kernel/cfi.c
index 77086cf565ec..638eb5c933e0 100644
--- a/arch/x86/kernel/cfi.c
+++ b/arch/x86/kernel/cfi.c
@@ -27,7 +27,7 @@ static bool decode_cfi_insn(struct pt_regs *regs, unsigned long *target,
* for indirect call checks:
*
* movl -<id>, %r10d ; 6 bytes
- * addl -4(%reg), %r10d ; 4 bytes
+ * addl -<pos>(%reg), %r10d; 4 bytes
* je .Ltmp1 ; 2 bytes
* ud2 ; <- regs->ip
* .Ltmp1:
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* [PATCH v2 3/9] x86/cfi: Document the "cfi=" bootparam options
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
2025-09-04 3:46 ` [PATCH v2 1/9] compiler_types.h: Move __nocfi out of compiler-specific header Kees Cook
2025-09-04 3:46 ` [PATCH v2 2/9] x86/traps: Clarify KCFI instruction layout Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 18:32 ` Nathan Chancellor
2025-09-04 3:46 ` [PATCH v2 4/9] x86/cfi: Standardize on common "CFI:" prefix for CFI reports Kees Cook
` (6 subsequent siblings)
9 siblings, 1 reply; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, Jonathan Corbet, Paul E. McKenney, Randy Dunlap,
linux-doc, Nathan Chancellor, Vegard Nossum, Miguel Ojeda,
Linus Walleij, Jeff Johnson, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Nicolas Schier, Masahiro Yamada, Arnd Bergmann,
Krzysztof Kozlowski, Sami Tolvanen, Mark Rutland, linux-kernel,
llvm, linux-kbuild, linux-arm-kernel, x86, linux-hardening
The kernel-parameters.txt didn't have a section for the cfi= options.
Add it.
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <linux-doc@vger.kernel.org>
---
Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 747a55abf494..8bbffbb334ab 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -608,6 +608,23 @@
ccw_timeout_log [S390]
See Documentation/arch/s390/common_io.rst for details.
+ cfi= [X86-64] Set Control Flow Integrity checking features
+ when CONFIG_FINEIBT is enabled.
+ Format: feature[,feature...]
+ Default: auto
+
+ auto: Use FineIBT if IBT available, otherwise kCFI.
+ Under FineIBT, enable "paranoid" mode when
+ FRED is not available.
+ off: Turn off CFI checking.
+ kcfi: Use kCFI (disable FineIBT).
+ fineibt: Use FineIBT (even if IBT not available).
+ norand: Do not re-randomize CFI hashes.
+ paranoid: Add caller hash checking under FineIBT.
+ bhi: Enable register poisoning to stop speculation
+ across FineIBT. (Disabled by default.)
+ warn: Do not enforce CFI checking: warn only.
+
cgroup_disable= [KNL] Disable a particular controller or optional feature
Format: {name of the controller(s) or feature(s) to disable}
The effects of cgroup_disable=foo are:
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* Re: [PATCH v2 3/9] x86/cfi: Document the "cfi=" bootparam options
2025-09-04 3:46 ` [PATCH v2 3/9] x86/cfi: Document the "cfi=" bootparam options Kees Cook
@ 2025-09-04 18:32 ` Nathan Chancellor
0 siblings, 0 replies; 20+ messages in thread
From: Nathan Chancellor @ 2025-09-04 18:32 UTC (permalink / raw)
To: Kees Cook
Cc: Peter Zijlstra, Jonathan Corbet, Paul E. McKenney, Randy Dunlap,
linux-doc, Vegard Nossum, Miguel Ojeda, Linus Walleij,
Jeff Johnson, David Woodhouse, Russell King (Oracle),
Nick Desaulniers, Bill Wendling, Justin Stitt, Marco Elver,
Przemek Kitszel, Ramon de C Valle, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-kbuild,
linux-arm-kernel, x86, linux-hardening
On Wed, Sep 03, 2025 at 08:46:42PM -0700, Kees Cook wrote:
> The kernel-parameters.txt didn't have a section for the cfi= options.
> Add it.
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 747a55abf494..8bbffbb334ab 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -608,6 +608,23 @@
> ccw_timeout_log [S390]
> See Documentation/arch/s390/common_io.rst for details.
>
> + cfi= [X86-64] Set Control Flow Integrity checking features
> + when CONFIG_FINEIBT is enabled.
> + Format: feature[,feature...]
> + Default: auto
> +
> + auto: Use FineIBT if IBT available, otherwise kCFI.
> + Under FineIBT, enable "paranoid" mode when
> + FRED is not available.
> + off: Turn off CFI checking.
> + kcfi: Use kCFI (disable FineIBT).
> + fineibt: Use FineIBT (even if IBT not available).
> + norand: Do not re-randomize CFI hashes.
> + paranoid: Add caller hash checking under FineIBT.
> + bhi: Enable register poisoning to stop speculation
> + across FineIBT. (Disabled by default.)
> + warn: Do not enforce CFI checking: warn only.
> +
> cgroup_disable= [KNL] Disable a particular controller or optional feature
> Format: {name of the controller(s) or feature(s) to disable}
> The effects of cgroup_disable=foo are:
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 20+ messages in thread
* [PATCH v2 4/9] x86/cfi: Standardize on common "CFI:" prefix for CFI reports
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
` (2 preceding siblings ...)
2025-09-04 3:46 ` [PATCH v2 3/9] x86/cfi: Document the "cfi=" bootparam options Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 18:40 ` Nathan Chancellor
2025-09-04 3:46 ` [PATCH v2 5/9] x86/cfi: Add "debug" option to "cfi=" bootparam Kees Cook
` (5 subsequent siblings)
9 siblings, 1 reply; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, Nathan Chancellor, Vegard Nossum, Miguel Ojeda,
Linus Walleij, Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
Use a regular "CFI:" prefix for CFI reports during alternatives setup,
including reporting when nothing has happened (i.e. CONFIG_FINEIBT=n).
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Peter Zijlstra <peterz@infradead.org>
---
arch/x86/kernel/alternative.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 7bde68247b5f..d8f4ac95b4df 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1266,26 +1266,26 @@ static __init int cfi_parse_cmdline(char *str)
} else if (!strcmp(str, "norand")) {
cfi_rand = false;
} else if (!strcmp(str, "warn")) {
- pr_alert("CFI mismatch non-fatal!\n");
+ pr_alert("CFI: mismatch non-fatal!\n");
cfi_warn = true;
} else if (!strcmp(str, "paranoid")) {
if (cfi_mode == CFI_FINEIBT) {
cfi_paranoid = true;
} else {
- pr_err("Ignoring paranoid; depends on fineibt.\n");
+ pr_err("CFI: ignoring paranoid; depends on fineibt.\n");
}
} else if (!strcmp(str, "bhi")) {
#ifdef CONFIG_FINEIBT_BHI
if (cfi_mode == CFI_FINEIBT) {
cfi_bhi = true;
} else {
- pr_err("Ignoring bhi; depends on fineibt.\n");
+ pr_err("CFI: ignoring bhi; depends on fineibt.\n");
}
#else
- pr_err("Ignoring bhi; depends on FINEIBT_BHI=y.\n");
+ pr_err("CFI: ignoring bhi; depends on FINEIBT_BHI=y.\n");
#endif
} else {
- pr_err("Ignoring unknown cfi option (%s).", str);
+ pr_err("CFI: Ignoring unknown option (%s).", str);
}
str = next;
@@ -1757,7 +1757,7 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
switch (cfi_mode) {
case CFI_OFF:
if (builtin)
- pr_info("Disabling CFI\n");
+ pr_info("CFI: disabled\n");
return;
case CFI_KCFI:
@@ -1766,7 +1766,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
goto err;
if (builtin)
- pr_info("Using kCFI\n");
+ pr_info("CFI: Using %sretpoline kCFI\n",
+ cfi_rand ? "rehashed " : "");
return;
case CFI_FINEIBT:
@@ -2005,6 +2006,8 @@ bool decode_fineibt_insn(struct pt_regs *regs, unsigned long *target, u32 *type)
static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
s32 *start_cfi, s32 *end_cfi, bool builtin)
{
+ if (IS_ENABLED(CONFIG_CFI) && builtin)
+ pr_info("CFI: Using standard kCFI\n");
}
#ifdef CONFIG_X86_KERNEL_IBT
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* Re: [PATCH v2 4/9] x86/cfi: Standardize on common "CFI:" prefix for CFI reports
2025-09-04 3:46 ` [PATCH v2 4/9] x86/cfi: Standardize on common "CFI:" prefix for CFI reports Kees Cook
@ 2025-09-04 18:40 ` Nathan Chancellor
2025-09-05 0:40 ` Kees Cook
0 siblings, 1 reply; 20+ messages in thread
From: Nathan Chancellor @ 2025-09-04 18:40 UTC (permalink / raw)
To: Kees Cook
Cc: Peter Zijlstra, Vegard Nossum, Miguel Ojeda, Linus Walleij,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Wed, Sep 03, 2025 at 08:46:43PM -0700, Kees Cook wrote:
> Use a regular "CFI:" prefix for CFI reports during alternatives setup,
> including reporting when nothing has happened (i.e. CONFIG_FINEIBT=n).
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Obviously minor but I had pointed out on v1 that there appears to be
some inconsistency within the diff around capitalization, "ignoring" vs.
"Ignoring".
> ---
> arch/x86/kernel/alternative.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 7bde68247b5f..d8f4ac95b4df 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -1266,26 +1266,26 @@ static __init int cfi_parse_cmdline(char *str)
> } else if (!strcmp(str, "norand")) {
> cfi_rand = false;
> } else if (!strcmp(str, "warn")) {
> - pr_alert("CFI mismatch non-fatal!\n");
> + pr_alert("CFI: mismatch non-fatal!\n");
> cfi_warn = true;
> } else if (!strcmp(str, "paranoid")) {
> if (cfi_mode == CFI_FINEIBT) {
> cfi_paranoid = true;
> } else {
> - pr_err("Ignoring paranoid; depends on fineibt.\n");
> + pr_err("CFI: ignoring paranoid; depends on fineibt.\n");
> }
> } else if (!strcmp(str, "bhi")) {
> #ifdef CONFIG_FINEIBT_BHI
> if (cfi_mode == CFI_FINEIBT) {
> cfi_bhi = true;
> } else {
> - pr_err("Ignoring bhi; depends on fineibt.\n");
> + pr_err("CFI: ignoring bhi; depends on fineibt.\n");
> }
> #else
> - pr_err("Ignoring bhi; depends on FINEIBT_BHI=y.\n");
> + pr_err("CFI: ignoring bhi; depends on FINEIBT_BHI=y.\n");
> #endif
> } else {
> - pr_err("Ignoring unknown cfi option (%s).", str);
> + pr_err("CFI: Ignoring unknown option (%s).", str);
> }
>
> str = next;
> @@ -1757,7 +1757,7 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
> switch (cfi_mode) {
> case CFI_OFF:
> if (builtin)
> - pr_info("Disabling CFI\n");
> + pr_info("CFI: disabled\n");
> return;
>
> case CFI_KCFI:
> @@ -1766,7 +1766,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
> goto err;
>
> if (builtin)
> - pr_info("Using kCFI\n");
> + pr_info("CFI: Using %sretpoline kCFI\n",
> + cfi_rand ? "rehashed " : "");
> return;
>
> case CFI_FINEIBT:
> @@ -2005,6 +2006,8 @@ bool decode_fineibt_insn(struct pt_regs *regs, unsigned long *target, u32 *type)
> static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
> s32 *start_cfi, s32 *end_cfi, bool builtin)
> {
> + if (IS_ENABLED(CONFIG_CFI) && builtin)
> + pr_info("CFI: Using standard kCFI\n");
> }
>
> #ifdef CONFIG_X86_KERNEL_IBT
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 20+ messages in thread* Re: [PATCH v2 4/9] x86/cfi: Standardize on common "CFI:" prefix for CFI reports
2025-09-04 18:40 ` Nathan Chancellor
@ 2025-09-05 0:40 ` Kees Cook
0 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2025-09-05 0:40 UTC (permalink / raw)
To: Nathan Chancellor
Cc: Peter Zijlstra, Vegard Nossum, Miguel Ojeda, Linus Walleij,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Thu, Sep 04, 2025 at 11:40:04AM -0700, Nathan Chancellor wrote:
> On Wed, Sep 03, 2025 at 08:46:43PM -0700, Kees Cook wrote:
> > Use a regular "CFI:" prefix for CFI reports during alternatives setup,
> > including reporting when nothing has happened (i.e. CONFIG_FINEIBT=n).
> >
> > Signed-off-by: Kees Cook <kees@kernel.org>
> > ---
>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
>
> Obviously minor but I had pointed out on v1 that there appears to be
> some inconsistency within the diff around capitalization, "ignoring" vs.
> "Ignoring".
Oops! Sorry, I've fixed that locally now.
--
Kees Cook
^ permalink raw reply [flat|nested] 20+ messages in thread
* [PATCH v2 5/9] x86/cfi: Add "debug" option to "cfi=" bootparam
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
` (3 preceding siblings ...)
2025-09-04 3:46 ` [PATCH v2 4/9] x86/cfi: Standardize on common "CFI:" prefix for CFI reports Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 7:00 ` Peter Zijlstra
2025-09-04 3:46 ` [PATCH v2 6/9] x86/cfi: Remove __noinitretpoline and __noretpoline Kees Cook
` (4 subsequent siblings)
9 siblings, 1 reply; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, Nathan Chancellor, Vegard Nossum, Miguel Ojeda,
Linus Walleij, Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
Add "debug" option for "cfi=" bootparam to get details on early CFI
initialization steps so future Kees can find breakage easier.
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Peter Zijlstra <peterz@infradead.org>
---
.../admin-guide/kernel-parameters.txt | 1 +
arch/x86/kernel/alternative.c | 23 +++++++++++++++++++
2 files changed, 24 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 8bbffbb334ab..c8337d0e6ba3 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -624,6 +624,7 @@
bhi: Enable register poisoning to stop speculation
across FineIBT. (Disabled by default.)
warn: Do not enforce CFI checking: warn only.
+ debug: Report CFI initialization details.
cgroup_disable= [KNL] Disable a particular controller or optional feature
Format: {name of the controller(s) or feature(s) to disable}
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index d8f4ac95b4df..b311e31a9056 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1177,6 +1177,7 @@ void __init_or_module apply_seal_endbr(s32 *start, s32 *end) { }
#endif
enum cfi_mode cfi_mode __ro_after_init = __CFI_DEFAULT;
+static bool cfi_debug __ro_after_init;
#ifdef CONFIG_FINEIBT_BHI
bool cfi_bhi __ro_after_init = false;
@@ -1259,6 +1260,8 @@ static __init int cfi_parse_cmdline(char *str)
} else if (!strcmp(str, "off")) {
cfi_mode = CFI_OFF;
cfi_rand = false;
+ } else if (!strcmp(str, "debug")) {
+ cfi_debug = true;
} else if (!strcmp(str, "kcfi")) {
cfi_mode = CFI_KCFI;
} else if (!strcmp(str, "fineibt")) {
@@ -1734,6 +1737,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
* rewrite them. This disables all CFI. If this succeeds but any of the
* later stages fails, we're without CFI.
*/
+ if (cfi_debug)
+ pr_info("CFI: disabling all indirect call checking\n");
ret = cfi_disable_callers(start_retpoline, end_retpoline);
if (ret)
goto err;
@@ -1744,14 +1749,23 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
cfi_bpf_hash = cfi_rehash(cfi_bpf_hash);
cfi_bpf_subprog_hash = cfi_rehash(cfi_bpf_subprog_hash);
}
+ if (cfi_debug)
+ pr_info("CFI: cfi_seed: 0x%08x\n", cfi_seed);
+ if (cfi_debug)
+ pr_info("CFI: rehashing all preambles\n");
ret = cfi_rand_preamble(start_cfi, end_cfi);
if (ret)
goto err;
+ if (cfi_debug)
+ pr_info("CFI: rehashing all indirect calls\n");
ret = cfi_rand_callers(start_retpoline, end_retpoline);
if (ret)
goto err;
+ } else {
+ if (cfi_debug)
+ pr_info("CFI: rehashing disabled\n");
}
switch (cfi_mode) {
@@ -1761,6 +1775,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
return;
case CFI_KCFI:
+ if (cfi_debug)
+ pr_info("CFI: enabling all indirect call checking\n");
ret = cfi_enable_callers(start_retpoline, end_retpoline);
if (ret)
goto err;
@@ -1771,17 +1787,23 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
return;
case CFI_FINEIBT:
+ if (cfi_debug)
+ pr_info("CFI: adding FineIBT to all preambles\n");
/* place the FineIBT preamble at func()-16 */
ret = cfi_rewrite_preamble(start_cfi, end_cfi);
if (ret)
goto err;
/* rewrite the callers to target func()-16 */
+ if (cfi_debug)
+ pr_info("CFI: rewriting indirect call sites to use FineIBT\n");
ret = cfi_rewrite_callers(start_retpoline, end_retpoline);
if (ret)
goto err;
/* now that nobody targets func()+0, remove ENDBR there */
+ if (cfi_debug)
+ pr_info("CFI: removing old endbr insns\n");
cfi_rewrite_endbr(start_cfi, end_cfi);
if (builtin) {
@@ -2324,6 +2346,7 @@ void __init alternative_instructions(void)
__apply_fineibt(__retpoline_sites, __retpoline_sites_end,
__cfi_sites, __cfi_sites_end, true);
+ cfi_debug = false;
/*
* Rewrite the retpolines, must be done before alternatives since
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* Re: [PATCH v2 5/9] x86/cfi: Add "debug" option to "cfi=" bootparam
2025-09-04 3:46 ` [PATCH v2 5/9] x86/cfi: Add "debug" option to "cfi=" bootparam Kees Cook
@ 2025-09-04 7:00 ` Peter Zijlstra
0 siblings, 0 replies; 20+ messages in thread
From: Peter Zijlstra @ 2025-09-04 7:00 UTC (permalink / raw)
To: Kees Cook
Cc: Nathan Chancellor, Vegard Nossum, Miguel Ojeda, Linus Walleij,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Wed, Sep 03, 2025 at 08:46:44PM -0700, Kees Cook wrote:
> @@ -1734,6 +1737,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
> * rewrite them. This disables all CFI. If this succeeds but any of the
> * later stages fails, we're without CFI.
> */
> + if (cfi_debug)
> + pr_info("CFI: disabling all indirect call checking\n");
> ret = cfi_disable_callers(start_retpoline, end_retpoline);
> if (ret)
> goto err;
> @@ -1744,14 +1749,23 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
> cfi_bpf_hash = cfi_rehash(cfi_bpf_hash);
> cfi_bpf_subprog_hash = cfi_rehash(cfi_bpf_subprog_hash);
> }
> + if (cfi_debug)
> + pr_info("CFI: cfi_seed: 0x%08x\n", cfi_seed);
>
> + if (cfi_debug)
> + pr_info("CFI: rehashing all preambles\n");
So this repeated if() bugs the heck out of me ... :-)
What would you prefer, this:
if (cfi_debug) {
pr_info("CFI: cfi_seed: 0x%08x\n", cfi_seed);
pr_info("CFI: rehashing all preambles\n");
}
or something like:
#define pr_cfi_debug(X...) if (cfi_debug) pr_info(X)
pr_cfi_debug("CFI: cfi_seed: 0x%08x\n", cfi_seed);
pr_cfi_debug("CFI: rehashing all preambles\n");
?
> ret = cfi_rand_preamble(start_cfi, end_cfi);
> if (ret)
> goto err;
>
> + if (cfi_debug)
> + pr_info("CFI: rehashing all indirect calls\n");
> ret = cfi_rand_callers(start_retpoline, end_retpoline);
> if (ret)
> goto err;
> + } else {
> + if (cfi_debug)
> + pr_info("CFI: rehashing disabled\n");
> }
>
> switch (cfi_mode) {
> @@ -1761,6 +1775,8 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
> return;
>
> case CFI_KCFI:
> + if (cfi_debug)
> + pr_info("CFI: enabling all indirect call checking\n");
This should be "CFI: re-enabling all..." I suppose, to better match the
earlier "CFI: disabling all ..." message.
> ret = cfi_enable_callers(start_retpoline, end_retpoline);
> if (ret)
> goto err;
> @@ -1771,17 +1787,23 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
> return;
>
> case CFI_FINEIBT:
> + if (cfi_debug)
> + pr_info("CFI: adding FineIBT to all preambles\n");
> /* place the FineIBT preamble at func()-16 */
> ret = cfi_rewrite_preamble(start_cfi, end_cfi);
> if (ret)
> goto err;
>
> /* rewrite the callers to target func()-16 */
> + if (cfi_debug)
> + pr_info("CFI: rewriting indirect call sites to use FineIBT\n");
> ret = cfi_rewrite_callers(start_retpoline, end_retpoline);
> if (ret)
> goto err;
>
> /* now that nobody targets func()+0, remove ENDBR there */
> + if (cfi_debug)
> + pr_info("CFI: removing old endbr insns\n");
> cfi_rewrite_endbr(start_cfi, end_cfi);
>
> if (builtin) {
> @@ -2324,6 +2346,7 @@ void __init alternative_instructions(void)
>
> __apply_fineibt(__retpoline_sites, __retpoline_sites_end,
> __cfi_sites, __cfi_sites_end, true);
> + cfi_debug = false;
>
> /*
> * Rewrite the retpolines, must be done before alternatives since
^ permalink raw reply [flat|nested] 20+ messages in thread
* [PATCH v2 6/9] x86/cfi: Remove __noinitretpoline and __noretpoline
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
` (4 preceding siblings ...)
2025-09-04 3:46 ` [PATCH v2 5/9] x86/cfi: Add "debug" option to "cfi=" bootparam Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 3:46 ` [PATCH v2 7/9] kconfig: Add transitional symbol attribute for migration support Kees Cook
` (3 subsequent siblings)
9 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, David Woodhouse, Nathan Chancellor, Vegard Nossum,
Miguel Ojeda, Linus Walleij, Jeff Johnson, Randy Dunlap,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
Commit 66f793099a63 ("x86/retpoline: Avoid retpolines for built-in __init
functions") disabled retpolines in __init sections (__noinitretpoline)
as a precaution against potential issues with retpolines in early boot,
but it has not been a problem in practice (i.e. see Clang below).
Commit 87358710c1fb ("x86/retpoline: Support retpoline builds with Clang")
narrowed this to only GCC, as Clang doesn't have per-function control
over retpoline emission. As such, Clang has been booting with retpolines
in __init since retpoline support was introduced.
Clang KCFI has been instrumenting __init since CFI was introduced.
With the introduction of KCFI for GCC, KCFI instrumentation with
retpolines disabled means that objtool does not construct .retpoline_sites
section entries for the non-retpoline KCFI calls. At boot, the KCFI
rehashing code, via __apply_fineibt(), misses all __init KCFI calls
(since they are not retpolines), resulting in immediate hash mismatches:
all preambles are rehashed (via .cfi_sites) and none of the __init call
sites are rehashed.
Remove __noinitretpoline since it provides no meaningful utility and
creates problems with CFI. Additionally remove __noretpoline since it
is now unused.
Alternatively, cfi_rand_callers() could walk the .kcfi_traps section which
is exactly the list of KCFI instrumentation sites. But it seems better to
have as few differences in common instruction sequences between compilers
as possible, so better to remove the special handling of retpolines in
__init for GCC.
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Woodhouse <dwmw2@infradead.org>
---
include/linux/compiler-gcc.h | 4 ----
include/linux/init.h | 8 --------
2 files changed, 12 deletions(-)
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 5d07c469b571..5de824a0b3d7 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -35,10 +35,6 @@
(typeof(ptr)) (__ptr + (off)); \
})
-#ifdef CONFIG_MITIGATION_RETPOLINE
-#define __noretpoline __attribute__((__indirect_branch__("keep")))
-#endif
-
#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
#define __latent_entropy __attribute__((latent_entropy))
#endif
diff --git a/include/linux/init.h b/include/linux/init.h
index a60d32d227ee..17c1bc712e23 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -7,13 +7,6 @@
#include <linux/stringify.h>
#include <linux/types.h>
-/* Built-in __init functions needn't be compiled with retpoline */
-#if defined(__noretpoline) && !defined(MODULE)
-#define __noinitretpoline __noretpoline
-#else
-#define __noinitretpoline
-#endif
-
/* These macros are used to mark some functions or
* initialized data (doesn't apply to uninitialized data)
* as `initialization' functions. The kernel can take this
@@ -50,7 +43,6 @@
/* These are for everybody (although not all archs will actually
discard it in modules) */
#define __init __section(".init.text") __cold __latent_entropy \
- __noinitretpoline \
__no_kstack_erase
#define __initdata __section(".init.data")
#define __initconst __section(".init.rodata")
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* [PATCH v2 7/9] kconfig: Add transitional symbol attribute for migration support
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
` (5 preceding siblings ...)
2025-09-04 3:46 ` [PATCH v2 6/9] x86/cfi: Remove __noinitretpoline and __noretpoline Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 3:46 ` [PATCH v2 8/9] kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI Kees Cook
` (2 subsequent siblings)
9 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, Nathan Chancellor, Nicolas Schier, Vegard Nossum,
Jonathan Corbet, Masahiro Yamada, Randy Dunlap, Arnd Bergmann,
Krzysztof Kozlowski, linux-kbuild, linux-doc, Miguel Ojeda,
Linus Walleij, Jeff Johnson, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Paul E. McKenney, Sami Tolvanen, Mark Rutland, linux-kernel, llvm,
linux-arm-kernel, x86, linux-hardening
During kernel option migrations (e.g. CONFIG_CFI_CLANG to CONFIG_CFI),
existing .config files need to maintain backward compatibility while
preventing deprecated options from appearing in newly generated
configurations. This is challenging with existing Kconfig mechanisms
because:
1. Simply removing old options breaks existing .config files.
2. Manually listing an option as "deprecated" leaves it needlessly
visible and still writes them to new .config files.
3. Using any method to remove visibility (.e.g no 'prompt', 'if n',
etc) prevents the option from being processed at all.
Add a "transitional" attribute that creates symbols which are:
- Processed during configuration (can influence other symbols' defaults)
- Hidden from user menus (no prompts appear)
- Omitted from newly written .config files (gets migrated)
- Restricted to only having help sections (no defaults, selects, etc)
making it truly just a "prior value pass-through" option.
The transitional syntax requires a type argument and prevents type
redefinition:
config NEW_OPTION
bool "New option"
default OLD_OPTION
config OLD_OPTION
bool
transitional
help
Transitional config for OLD_OPTION migration.
This allows seamless migration: olddefconfig processes existing
CONFIG_OLD_OPTION=y settings to enable CONFIG_NEW_OPTION=y, while
CONFIG_OLD_OPTION is omitted from newly generated .config files.
Implementation details:
- Parser validates transitional symbols can only have help sections
- Symbol visibility logic updated: usable = (visible != no || transitional)
- Transitional symbols preserve user values during configuration
- Documentation added to show the usage
- Added positive and negative testing via "testconfig" target
Signed-off-by: Kees Cook <kees@kernel.org>
---
With help from Claude Code to show me how to navigate the kconfig parser.
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas.schier@linux.dev>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: <linux-kbuild@vger.kernel.org>
Cc: <linux-doc@vger.kernel.org>
---
.../kconfig/tests/err_transitional/Kconfig | 52 +++++++++
scripts/kconfig/tests/transitional/Kconfig | 100 ++++++++++++++++++
scripts/kconfig/expr.h | 1 +
scripts/kconfig/lexer.l | 1 +
scripts/kconfig/parser.y | 47 ++++++++
scripts/kconfig/symbol.c | 16 ++-
.../tests/err_transitional/__init__.py | 14 +++
.../tests/err_transitional/expected_stderr | 7 ++
.../kconfig/tests/transitional/__init__.py | 18 ++++
.../tests/transitional/expected_config | 12 +++
.../kconfig/tests/transitional/initial_config | 16 +++
Documentation/kbuild/kconfig-language.rst | 32 ++++++
12 files changed, 313 insertions(+), 3 deletions(-)
create mode 100644 scripts/kconfig/tests/err_transitional/Kconfig
create mode 100644 scripts/kconfig/tests/transitional/Kconfig
create mode 100644 scripts/kconfig/tests/err_transitional/__init__.py
create mode 100644 scripts/kconfig/tests/err_transitional/expected_stderr
create mode 100644 scripts/kconfig/tests/transitional/__init__.py
create mode 100644 scripts/kconfig/tests/transitional/expected_config
create mode 100644 scripts/kconfig/tests/transitional/initial_config
diff --git a/scripts/kconfig/tests/err_transitional/Kconfig b/scripts/kconfig/tests/err_transitional/Kconfig
new file mode 100644
index 000000000000..a75ed3b2fe5e
--- /dev/null
+++ b/scripts/kconfig/tests/err_transitional/Kconfig
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-2.0
+# Test that transitional symbols cannot have properties other than help
+
+config BAD_DEFAULT
+ bool
+ transitional
+ default y
+ help
+ This transitional symbol illegally has a default property.
+
+config BAD_PROMPT
+ bool
+ transitional
+ prompt "Bad prompt"
+ help
+ This transitional symbol illegally has a prompt.
+
+config BAD_SELECT
+ bool
+ transitional
+ select OTHER_SYMBOL
+ help
+ This transitional symbol illegally has a select.
+
+config BAD_IMPLY
+ bool
+ transitional
+ imply OTHER_SYMBOL
+ help
+ This transitional symbol illegally has an imply.
+
+config BAD_DEPENDS
+ bool
+ transitional
+ depends on OTHER_SYMBOL
+ help
+ This transitional symbol illegally has a depends.
+
+config BAD_RANGE
+ int
+ transitional
+ range 1 10
+ help
+ This transitional symbol illegally has a range.
+
+config BAD_NO_TYPE
+ transitional
+ help
+ This transitional symbol illegally has no type specified.
+
+config OTHER_SYMBOL
+ bool
diff --git a/scripts/kconfig/tests/transitional/Kconfig b/scripts/kconfig/tests/transitional/Kconfig
new file mode 100644
index 000000000000..62c3b24665b9
--- /dev/null
+++ b/scripts/kconfig/tests/transitional/Kconfig
@@ -0,0 +1,100 @@
+# SPDX-License-Identifier: GPL-2.0
+# Test transitional symbols for config migration with all Kconfig types
+
+# Enable module support for tristate testing
+config MODULES
+ bool "Enable loadable module support"
+ modules
+ default y
+
+# Basic migration tests for all types
+config NEW_BOOL
+ bool "New bool option"
+ default OLD_BOOL
+
+config OLD_BOOL
+ bool
+ transitional
+
+config NEW_TRISTATE
+ tristate "New tristate option"
+ default OLD_TRISTATE
+
+config OLD_TRISTATE
+ tristate
+ transitional
+
+config NEW_STRING
+ string "New string option"
+ default OLD_STRING
+
+config OLD_STRING
+ string
+ transitional
+
+config NEW_HEX
+ hex "New hex option"
+ default OLD_HEX
+
+config OLD_HEX
+ hex
+ transitional
+
+config NEW_INT
+ int "New int option"
+ default OLD_INT
+
+config OLD_INT
+ int
+ transitional
+
+# Precedence tests for all types
+config NEW_BOOL_PRECEDENCE
+ bool "New bool option with precedence"
+ default OLD_BOOL_PRECEDENCE
+
+config OLD_BOOL_PRECEDENCE
+ bool
+ transitional
+
+config NEW_STRING_PRECEDENCE
+ string "New string option with precedence"
+ default OLD_STRING_PRECEDENCE
+
+config OLD_STRING_PRECEDENCE
+ string
+ transitional
+
+config NEW_TRISTATE_PRECEDENCE
+ tristate "New tristate option with precedence"
+ default OLD_TRISTATE_PRECEDENCE
+
+config OLD_TRISTATE_PRECEDENCE
+ tristate
+ transitional
+
+config NEW_HEX_PRECEDENCE
+ hex "New hex option with precedence"
+ default OLD_HEX_PRECEDENCE
+
+config OLD_HEX_PRECEDENCE
+ hex
+ transitional
+
+config NEW_INT_PRECEDENCE
+ int "New int option with precedence"
+ default OLD_INT_PRECEDENCE
+
+config OLD_INT_PRECEDENCE
+ int
+ transitional
+
+# Test that help sections are allowed for transitional symbols
+config OLD_WITH_HELP
+ bool
+ transitional
+ help
+ This transitional symbol has a help section to validate that help is allowed.
+
+config REGULAR_OPTION
+ bool "Regular option"
diff --git a/scripts/kconfig/expr.h b/scripts/kconfig/expr.h
index fe2231e0e6a4..5e7cdabc029c 100644
--- a/scripts/kconfig/expr.h
+++ b/scripts/kconfig/expr.h
@@ -145,6 +145,7 @@ struct symbol {
#define SYMBOL_CONST 0x0001 /* symbol is const */
#define SYMBOL_CHECK 0x0008 /* used during dependency checking */
#define SYMBOL_VALID 0x0080 /* set when symbol.curr is calculated */
+#define SYMBOL_HIDDEN 0x0100 /* symbol is hidden (usable but invisible) */
#define SYMBOL_WRITE 0x0200 /* write symbol to file (KCONFIG_CONFIG) */
#define SYMBOL_WRITTEN 0x0800 /* track info to avoid double-write to .config */
#define SYMBOL_CHECKED 0x2000 /* used during dependency checking */
diff --git a/scripts/kconfig/lexer.l b/scripts/kconfig/lexer.l
index 9c2cdfc33c6f..6d2c92c6095d 100644
--- a/scripts/kconfig/lexer.l
+++ b/scripts/kconfig/lexer.l
@@ -126,6 +126,7 @@ n [A-Za-z0-9_-]
"select" return T_SELECT;
"source" return T_SOURCE;
"string" return T_STRING;
+"transitional" return T_TRANSITIONAL;
"tristate" return T_TRISTATE;
"visible" return T_VISIBLE;
"||" return T_OR;
diff --git a/scripts/kconfig/parser.y b/scripts/kconfig/parser.y
index e9c3c664e925..c95271c22183 100644
--- a/scripts/kconfig/parser.y
+++ b/scripts/kconfig/parser.y
@@ -75,6 +75,7 @@ struct menu *current_menu, *current_entry, *current_choice;
%token T_SELECT
%token T_SOURCE
%token T_STRING
+%token T_TRANSITIONAL
%token T_TRISTATE
%token T_VISIBLE
%token T_EOL
@@ -205,6 +206,12 @@ config_option: T_PROMPT T_WORD_QUOTE if_expr T_EOL
printd(DEBUG_PARSE, "%s:%d:prompt\n", cur_filename, cur_lineno);
};
+config_option: T_TRANSITIONAL T_EOL
+{
+ current_entry->sym->flags |= SYMBOL_HIDDEN;
+ printd(DEBUG_PARSE, "%s:%d:transitional\n", cur_filename, cur_lineno);
+};
+
config_option: default expr if_expr T_EOL
{
menu_add_expr(P_DEFAULT, $2, $3);
@@ -482,6 +489,43 @@ assign_val:
%%
+/**
+ * transitional_check_sanity - check transitional symbols have no other
+ * properties
+ *
+ * @menu: menu of the potentially transitional symbol
+ *
+ * Return: -1 if an error is found, 0 otherwise.
+ */
+static int transitional_check_sanity(const struct menu *menu)
+{
+ struct property *prop;
+
+ if (!menu->sym || !(menu->sym->flags & SYMBOL_HIDDEN))
+ return 0;
+
+ /* Check for depends and visible conditions. */
+ if ((menu->dep && !expr_is_yes(menu->dep)) ||
+ (menu->visibility && !expr_is_yes(menu->visibility))) {
+ fprintf(stderr, "%s:%d: error: %s",
+ menu->filename, menu->lineno,
+ "transitional symbols can only have help sections\n");
+ return -1;
+ }
+
+ /* Check for any property other than "help". */
+ for (prop = menu->sym->prop; prop; prop = prop->next) {
+ if (prop->type != P_COMMENT) {
+ fprintf(stderr, "%s:%d: error: %s",
+ prop->filename, prop->lineno,
+ "transitional symbols can only have help sections\n");
+ return -1;
+ }
+ }
+
+ return 0;
+}
+
/**
* choice_check_sanity - check sanity of a choice member
*
@@ -558,6 +602,9 @@ void conf_parse(const char *name)
if (menu->sym && sym_check_deps(menu->sym))
yynerrs++;
+ if (transitional_check_sanity(menu))
+ yynerrs++;
+
if (menu->sym && sym_is_choice(menu->sym)) {
menu_for_each_sub_entry(child, menu)
if (child->sym && choice_check_sanity(child))
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 26ab10c0fd76..b2686dba05ec 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -408,6 +408,7 @@ void sym_calc_value(struct symbol *sym)
struct symbol_value newval, oldval;
struct property *prop;
struct menu *choice_menu;
+ bool usable;
if (!sym)
return;
@@ -447,6 +448,13 @@ void sym_calc_value(struct symbol *sym)
if (sym->visible != no)
sym->flags |= SYMBOL_WRITE;
+ /*
+ * For a symbol to be processed during configuration it needs to
+ * be either visible or a transitional symbol that is hidden from
+ * menus and omitted from newly written .config files.
+ */
+ usable = (sym->visible != no || (sym->flags & SYMBOL_HIDDEN));
+
/* set default if recursively called */
sym->curr = newval;
@@ -459,13 +467,15 @@ void sym_calc_value(struct symbol *sym)
sym_calc_choice(choice_menu);
newval.tri = sym->curr.tri;
} else {
- if (sym->visible != no) {
+ if (usable) {
/* if the symbol is visible use the user value
* if available, otherwise try the default value
*/
if (sym_has_value(sym)) {
+ tristate value = (sym->flags & SYMBOL_HIDDEN) ?
+ sym->def[S_DEF_USER].tri : sym->visible;
newval.tri = EXPR_AND(sym->def[S_DEF_USER].tri,
- sym->visible);
+ value);
goto calc_newval;
}
}
@@ -497,7 +507,7 @@ void sym_calc_value(struct symbol *sym)
case S_STRING:
case S_HEX:
case S_INT:
- if (sym->visible != no && sym_has_value(sym)) {
+ if (usable && sym_has_value(sym)) {
newval.val = sym->def[S_DEF_USER].val;
break;
}
diff --git a/scripts/kconfig/tests/err_transitional/__init__.py b/scripts/kconfig/tests/err_transitional/__init__.py
new file mode 100644
index 000000000000..7dffb5b0833f
--- /dev/null
+++ b/scripts/kconfig/tests/err_transitional/__init__.py
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0
+"""
+Test that transitional symbols with invalid properties are rejected.
+
+Transitional symbols can only have help sections. Any other properties
+(default, select, depends, etc.) should cause a parser error.
+"""
+
+def test(conf):
+ # This should fail with exit code 1 due to invalid transitional symbol
+ assert conf.olddefconfig() == 1
+
+ # Check that the error message is about transitional symbols
+ assert conf.stderr_contains('expected_stderr')
diff --git a/scripts/kconfig/tests/err_transitional/expected_stderr b/scripts/kconfig/tests/err_transitional/expected_stderr
new file mode 100644
index 000000000000..b52db4f680f4
--- /dev/null
+++ b/scripts/kconfig/tests/err_transitional/expected_stderr
@@ -0,0 +1,7 @@
+Kconfig:46:warning: config symbol defined without type
+Kconfig:7: error: transitional symbols can only have help sections
+Kconfig:14: error: transitional symbols can only have help sections
+Kconfig:21: error: transitional symbols can only have help sections
+Kconfig:28: error: transitional symbols can only have help sections
+Kconfig:32: error: transitional symbols can only have help sections
+Kconfig:42: error: transitional symbols can only have help sections
diff --git a/scripts/kconfig/tests/transitional/__init__.py b/scripts/kconfig/tests/transitional/__init__.py
new file mode 100644
index 000000000000..61937d10edf1
--- /dev/null
+++ b/scripts/kconfig/tests/transitional/__init__.py
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0
+"""
+Test transitional symbol migration functionality for all Kconfig types.
+
+This tests that:
+- OLD_* options in existing .config cause NEW_* options to be set
+- OLD_* options are not written to the new .config file
+- NEW_* options appear in the new .config file with correct values
+- All Kconfig types work correctly: bool, tristate, string, hex, int
+- User-set NEW values take precedence over conflicting OLD transitional values
+"""
+
+def test(conf):
+ # Run olddefconfig to process the migration with the initial config
+ assert conf.olddefconfig(dot_config='initial_config') == 0
+
+ # Check that the configuration matches expected output
+ assert conf.config_contains('expected_config')
diff --git a/scripts/kconfig/tests/transitional/expected_config b/scripts/kconfig/tests/transitional/expected_config
new file mode 100644
index 000000000000..846e9ddcab91
--- /dev/null
+++ b/scripts/kconfig/tests/transitional/expected_config
@@ -0,0 +1,12 @@
+CONFIG_MODULES=y
+CONFIG_NEW_BOOL=y
+CONFIG_NEW_TRISTATE=m
+CONFIG_NEW_STRING="test string"
+CONFIG_NEW_HEX=0x1234
+CONFIG_NEW_INT=42
+# CONFIG_NEW_BOOL_PRECEDENCE is not set
+CONFIG_NEW_STRING_PRECEDENCE="user value"
+CONFIG_NEW_TRISTATE_PRECEDENCE=y
+CONFIG_NEW_HEX_PRECEDENCE=0xABCD
+CONFIG_NEW_INT_PRECEDENCE=100
+# CONFIG_REGULAR_OPTION is not set
diff --git a/scripts/kconfig/tests/transitional/initial_config b/scripts/kconfig/tests/transitional/initial_config
new file mode 100644
index 000000000000..e648a65e504c
--- /dev/null
+++ b/scripts/kconfig/tests/transitional/initial_config
@@ -0,0 +1,16 @@
+CONFIG_MODULES=y
+CONFIG_OLD_BOOL=y
+CONFIG_OLD_TRISTATE=m
+CONFIG_OLD_STRING="test string"
+CONFIG_OLD_HEX=0x1234
+CONFIG_OLD_INT=42
+# CONFIG_NEW_BOOL_PRECEDENCE is not set
+CONFIG_OLD_BOOL_PRECEDENCE=y
+CONFIG_NEW_STRING_PRECEDENCE="user value"
+CONFIG_OLD_STRING_PRECEDENCE="old value"
+CONFIG_NEW_TRISTATE_PRECEDENCE=y
+CONFIG_OLD_TRISTATE_PRECEDENCE=m
+CONFIG_NEW_HEX_PRECEDENCE=0xABCD
+CONFIG_OLD_HEX_PRECEDENCE=0x5678
+CONFIG_NEW_INT_PRECEDENCE=100
+CONFIG_OLD_INT_PRECEDENCE=200
diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst
index a91abb8f6840..abce88f15d7c 100644
--- a/Documentation/kbuild/kconfig-language.rst
+++ b/Documentation/kbuild/kconfig-language.rst
@@ -232,6 +232,38 @@ applicable everywhere (see syntax).
enables the third modular state for all config symbols.
At most one symbol may have the "modules" option set.
+- transitional attribute: "transitional"
+ This declares the symbol as transitional, meaning it should be processed
+ during configuration but omitted from newly written .config files.
+ Transitional symbols are useful for backward compatibility during config
+ option migrations - they allow olddefconfig to process existing .config
+ files while ensuring the old option doesn't appear in new configurations.
+
+ A transitional symbol:
+ - Has no prompt (is not visible to users in menus)
+ - Is processed normally during configuration (values are read and used)
+ - Can be referenced in default expressions of other symbols
+ - Is not written to new .config files
+ - Cannot have any other properties (it is a pass-through option)
+
+ Example migration from OLD_NAME to NEW_NAME::
+
+ config NEW_NAME
+ bool "New option name"
+ default OLD_NAME
+ help
+ This replaces the old CONFIG_OLD_NAME option.
+
+ config OLD_NAME
+ bool
+ transitional
+ help
+ Transitional config for OLD_NAME to NEW_NAME migration.
+
+ With this setup, existing .config files with "CONFIG_OLD_NAME=y" will
+ result in "CONFIG_NEW_NAME=y" being set, while CONFIG_OLD_NAME will be
+ omitted from newly written .config files.
+
Menu dependencies
-----------------
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* [PATCH v2 8/9] kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
` (6 preceding siblings ...)
2025-09-04 3:46 ` [PATCH v2 7/9] kconfig: Add transitional symbol attribute for migration support Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 3:46 ` [PATCH v2 9/9] ARM: traps: Implement KCFI trap handler for ARM32 Kees Cook
2025-09-04 7:04 ` [PATCH v2 0/9] kcfi: Prepare for GCC support Peter Zijlstra
9 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, Linus Walleij, Sami Tolvanen, Mark Rutland,
Puranjay Mohan, Nathan Chancellor, Vegard Nossum, Miguel Ojeda,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski, linux-kernel,
llvm, linux-doc, linux-kbuild, linux-arm-kernel, x86,
linux-hardening
The kernel's CFI implementation uses the KCFI ABI specifically, and is
not strictly tied to a particular compiler. In preparation for GCC
supporting KCFI, rename CONFIG_CFI_CLANG to CONFIG_CFI (along with
associated options).
Use new "transitional" Kconfig option for old CONFIG_CFI_CLANG that will
enable CONFIG_CFI during olddefconfig.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Puranjay Mohan <puranjay@kernel.org>
---
arch/Kconfig | 36 ++++++++++++++++---------
arch/arm/Kconfig | 2 +-
arch/arm64/Kconfig | 4 +--
arch/riscv/Kconfig | 6 ++---
arch/x86/Kconfig | 12 ++++-----
init/Kconfig | 4 +--
kernel/module/Kconfig | 2 +-
lib/Kconfig.debug | 2 +-
Makefile | 2 +-
arch/arm/mm/Makefile | 2 +-
arch/riscv/kernel/Makefile | 2 +-
arch/riscv/purgatory/Makefile | 2 +-
arch/x86/kernel/Makefile | 2 +-
arch/x86/purgatory/Makefile | 2 +-
kernel/Makefile | 2 +-
arch/riscv/include/asm/cfi.h | 4 +--
arch/x86/include/asm/cfi.h | 4 +--
include/asm-generic/vmlinux.lds.h | 2 +-
include/linux/cfi.h | 6 ++---
include/linux/cfi_types.h | 8 +++---
include/linux/compiler.h | 2 +-
include/linux/compiler_types.h | 2 +-
tools/include/linux/cfi_types.h | 6 ++---
tools/perf/util/include/linux/linkage.h | 2 +-
arch/arm/mm/cache-fa.S | 2 +-
arch/arm/mm/cache-v4.S | 2 +-
arch/arm/mm/cache-v4wb.S | 4 +--
arch/arm/mm/cache-v4wt.S | 2 +-
arch/arm/mm/cache-v6.S | 2 +-
arch/arm/mm/cache-v7.S | 2 +-
arch/arm/mm/cache-v7m.S | 2 +-
arch/arm/mm/proc-arm1020.S | 2 +-
arch/arm/mm/proc-arm1020e.S | 2 +-
arch/arm/mm/proc-arm1022.S | 2 +-
arch/arm/mm/proc-arm1026.S | 2 +-
arch/arm/mm/proc-arm920.S | 2 +-
arch/arm/mm/proc-arm922.S | 2 +-
arch/arm/mm/proc-arm925.S | 2 +-
arch/arm/mm/proc-arm926.S | 2 +-
arch/arm/mm/proc-arm940.S | 2 +-
arch/arm/mm/proc-arm946.S | 2 +-
arch/arm/mm/proc-feroceon.S | 2 +-
arch/arm/mm/proc-mohawk.S | 2 +-
arch/arm/mm/proc-xsc3.S | 2 +-
arch/arm/mm/tlb-v4.S | 2 +-
arch/arm/kernel/hw_breakpoint.c | 2 +-
arch/arm64/kernel/debug-monitors.c | 2 +-
arch/arm64/kernel/traps.c | 4 +--
arch/arm64/kvm/handle_exit.c | 2 +-
arch/arm64/net/bpf_jit_comp.c | 2 +-
arch/riscv/net/bpf_jit_comp64.c | 4 +--
arch/x86/kernel/alternative.c | 4 +--
arch/x86/kernel/kprobes/core.c | 2 +-
drivers/misc/lkdtm/cfi.c | 2 +-
kernel/module/tree_lookup.c | 2 +-
kernel/configs/hardening.config | 2 +-
56 files changed, 100 insertions(+), 90 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index d1b4ffd6e085..97642c08a124 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -867,22 +867,26 @@ config PROPELLER_CLANG
If unsure, say N.
-config ARCH_SUPPORTS_CFI_CLANG
+config ARCH_SUPPORTS_CFI
bool
help
- An architecture should select this option if it can support Clang's
- Control-Flow Integrity (CFI) checking.
+ An architecture should select this option if it can support Kernel
+ Control-Flow Integrity (CFI) checking (-fsanitize=kcfi).
config ARCH_USES_CFI_TRAPS
bool
+ help
+ An architecture should select this option if it requires the
+ .kcfi_traps section for KCFI trap handling.
-config CFI_CLANG
- bool "Use Clang's Control Flow Integrity (CFI)"
- depends on ARCH_SUPPORTS_CFI_CLANG
+config CFI
+ bool "Use Kernel Control Flow Integrity (kCFI)"
+ default CFI_CLANG
+ depends on ARCH_SUPPORTS_CFI
depends on $(cc-option,-fsanitize=kcfi)
help
- This option enables Clang's forward-edge Control Flow Integrity
- (CFI) checking, where the compiler injects a runtime check to each
+ This option enables forward-edge Control Flow Integrity (CFI)
+ checking, where the compiler injects a runtime check to each
indirect function call to ensure the target is a valid function with
the correct static type. This restricts possible call targets and
makes it more difficult for an attacker to exploit bugs that allow
@@ -891,10 +895,16 @@ config CFI_CLANG
https://clang.llvm.org/docs/ControlFlowIntegrity.html
+config CFI_CLANG
+ bool
+ transitional
+ help
+ Transitional config for CFI_CLANG to CFI migration.
+
config CFI_ICALL_NORMALIZE_INTEGERS
bool "Normalize CFI tags for integers"
- depends on CFI_CLANG
- depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
+ depends on CFI
+ depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS
help
This option normalizes the CFI tags for integer types so that all
integer types of the same size and signedness receive the same CFI
@@ -907,7 +917,7 @@ config CFI_ICALL_NORMALIZE_INTEGERS
This option is necessary for using CFI with Rust. If unsure, say N.
-config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
+config HAVE_CFI_ICALL_NORMALIZE_INTEGERS
def_bool y
depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers)
# With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826
@@ -915,7 +925,7 @@ config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
def_bool y
- depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
+ depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS
depends on RUSTC_VERSION >= 107900
# With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373
depends on (RUSTC_LLVM_VERSION >= 190103 && RUSTC_VERSION >= 108200) || \
@@ -923,7 +933,7 @@ config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
config CFI_PERMISSIVE
bool "Use CFI in permissive mode"
- depends on CFI_CLANG
+ depends on CFI
help
When selected, Control Flow Integrity (CFI) violations result in a
warning instead of a kernel panic. This option should only be used
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b1f3df39ed40..36ab8625be72 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -38,7 +38,7 @@ config ARM
select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
select ARCH_NEED_CMPXCHG_1_EMU if CPU_V6
select ARCH_SUPPORTS_ATOMIC_RMW
- select ARCH_SUPPORTS_CFI_CLANG
+ select ARCH_SUPPORTS_CFI
select ARCH_SUPPORTS_HUGETLBFS if ARM_LPAE
select ARCH_SUPPORTS_PER_VMA_LOCK
select ARCH_USE_BUILTIN_BSWAP
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index e9bbfacc35a6..1e38b8885a46 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -100,7 +100,7 @@ config ARM64
select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
select ARCH_SUPPORTS_LTO_CLANG if CPU_LITTLE_ENDIAN
select ARCH_SUPPORTS_LTO_CLANG_THIN
- select ARCH_SUPPORTS_CFI_CLANG
+ select ARCH_SUPPORTS_CFI
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
select ARCH_SUPPORTS_NUMA_BALANCING
@@ -212,7 +212,7 @@ config ARM64
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS \
if DYNAMIC_FTRACE_WITH_ARGS && DYNAMIC_FTRACE_WITH_CALL_OPS
select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS \
- if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG && \
+ if (DYNAMIC_FTRACE_WITH_ARGS && !CFI && \
(CC_IS_CLANG || !CC_OPTIMIZE_FOR_SIZE))
select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \
if DYNAMIC_FTRACE_WITH_ARGS
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a4b233a0659e..6043ad82b73c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -60,7 +60,7 @@ config RISCV
select ARCH_STACKWALK
select ARCH_SUPPORTS_ATOMIC_RMW
# clang >= 17: https://github.com/llvm/llvm-project/commit/62fa708ceb027713b386c7e0efda994f8bdc27e2
- select ARCH_SUPPORTS_CFI_CLANG if CLANG_VERSION >= 170000
+ select ARCH_SUPPORTS_CFI if (!CC_IS_CLANG || CLANG_VERSION >= 170000)
select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
select ARCH_SUPPORTS_HUGETLBFS if MMU
@@ -76,7 +76,7 @@ config RISCV
select ARCH_USE_MEMTEST
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_SYM_ANNOTATIONS
- select ARCH_USES_CFI_TRAPS if CFI_CLANG
+ select ARCH_USES_CFI_TRAPS if CFI
select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH if MMU
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
select ARCH_WANT_FRAME_POINTERS
@@ -154,7 +154,7 @@ config RISCV
select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && (CLANG_SUPPORTS_DYNAMIC_FTRACE || GCC_SUPPORTS_DYNAMIC_FTRACE)
select FUNCTION_ALIGNMENT_4B if HAVE_DYNAMIC_FTRACE && RISCV_ISA_C
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS if HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
- select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG)
+ select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS if (DYNAMIC_FTRACE_WITH_ARGS && !CFI)
select HAVE_DYNAMIC_FTRACE_WITH_ARGS if HAVE_DYNAMIC_FTRACE
select HAVE_FTRACE_GRAPH_FUNC
select HAVE_FUNCTION_GRAPH_TRACER if HAVE_DYNAMIC_FTRACE_WITH_ARGS
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 58d890fe2100..b6da2d37cfd1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -127,8 +127,8 @@ config X86
select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
- select ARCH_SUPPORTS_CFI_CLANG if X86_64
- select ARCH_USES_CFI_TRAPS if X86_64 && CFI_CLANG
+ select ARCH_SUPPORTS_CFI if X86_64
+ select ARCH_USES_CFI_TRAPS if X86_64 && CFI
select ARCH_SUPPORTS_LTO_CLANG
select ARCH_SUPPORTS_LTO_CLANG_THIN
select ARCH_SUPPORTS_RT
@@ -2396,11 +2396,11 @@ config FUNCTION_PADDING_CFI
default 3 if FUNCTION_ALIGNMENT_8B
default 0
-# Basically: FUNCTION_ALIGNMENT - 5*CFI_CLANG
+# Basically: FUNCTION_ALIGNMENT - 5*CFI
# except Kconfig can't do arithmetic :/
config FUNCTION_PADDING_BYTES
int
- default FUNCTION_PADDING_CFI if CFI_CLANG
+ default FUNCTION_PADDING_CFI if CFI
default FUNCTION_ALIGNMENT
config CALL_PADDING
@@ -2410,7 +2410,7 @@ config CALL_PADDING
config FINEIBT
def_bool y
- depends on X86_KERNEL_IBT && CFI_CLANG && MITIGATION_RETPOLINE
+ depends on X86_KERNEL_IBT && CFI && MITIGATION_RETPOLINE
select CALL_PADDING
config FINEIBT_BHI
@@ -2427,7 +2427,7 @@ config CALL_THUNKS
config PREFIX_SYMBOLS
def_bool y
- depends on CALL_PADDING && !CFI_CLANG
+ depends on CALL_PADDING && !CFI
menuconfig CPU_MITIGATIONS
bool "Mitigations for CPU vulnerabilities"
diff --git a/init/Kconfig b/init/Kconfig
index 836320251219..67f10d8a33b7 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -2063,8 +2063,8 @@ config RUST
depends on !GCC_PLUGIN_RANDSTRUCT
depends on !RANDSTRUCT
depends on !DEBUG_INFO_BTF || (PAHOLE_HAS_LANG_EXCLUDE && !LTO)
- depends on !CFI_CLANG || HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
- select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG
+ depends on !CFI || HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
+ select CFI_ICALL_NORMALIZE_INTEGERS if CFI
depends on !CALL_PADDING || RUSTC_VERSION >= 108100
depends on !KASAN_SW_TAGS
depends on !(MITIGATION_RETHUNK && KASAN) || RUSTC_VERSION >= 108300
diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index 39278737bb68..2a1beebf1d37 100644
--- a/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -460,6 +460,6 @@ config UNUSED_KSYMS_WHITELIST
config MODULES_TREE_LOOKUP
def_bool y
- depends on PERF_EVENTS || TRACING || CFI_CLANG
+ depends on PERF_EVENTS || TRACING || CFI
endif # MODULES
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index dc0e0c6ed075..e3e69df19e78 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2894,7 +2894,7 @@ config FORTIFY_KUNIT_TEST
config LONGEST_SYM_KUNIT_TEST
tristate "Test the longest symbol possible" if !KUNIT_ALL_TESTS
depends on KUNIT && KPROBES
- depends on !PREFIX_SYMBOLS && !CFI_CLANG && !GCOV_KERNEL
+ depends on !PREFIX_SYMBOLS && !CFI && !GCOV_KERNEL
default KUNIT_ALL_TESTS
help
Tests the longest symbol possible
diff --git a/Makefile b/Makefile
index d1adb78c3596..437989d6e0be 100644
--- a/Makefile
+++ b/Makefile
@@ -1020,7 +1020,7 @@ KBUILD_AFLAGS += -fno-lto
export CC_FLAGS_LTO
endif
-ifdef CONFIG_CFI_CLANG
+ifdef CONFIG_CFI
CC_FLAGS_CFI := -fsanitize=kcfi
ifdef CONFIG_CFI_ICALL_NORMALIZE_INTEGERS
CC_FLAGS_CFI += -fsanitize-cfi-icall-experimental-normalize-integers
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index a195cd1d3e6d..1e2201013371 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -89,7 +89,7 @@ obj-$(CONFIG_CPU_V6) += proc-v6.o
obj-$(CONFIG_CPU_V6K) += proc-v6.o
obj-$(CONFIG_CPU_V7) += proc-v7.o proc-v7-bugs.o
obj-$(CONFIG_CPU_V7M) += proc-v7m.o
-obj-$(CONFIG_CFI_CLANG) += proc.o
+obj-$(CONFIG_CFI) += proc.o
obj-$(CONFIG_OUTER_CACHE) += l2c-common.o
obj-$(CONFIG_CACHE_B15_RAC) += cache-b15-rac.o
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index c7b542573407..f60fce69b725 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -113,7 +113,7 @@ obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o
obj-$(CONFIG_JUMP_LABEL) += jump_label.o
-obj-$(CONFIG_CFI_CLANG) += cfi.o
+obj-$(CONFIG_CFI) += cfi.o
obj-$(CONFIG_EFI) += efi.o
obj-$(CONFIG_COMPAT) += compat_syscall_table.o
diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile
index 240592e3f5c2..530e497ca2f9 100644
--- a/arch/riscv/purgatory/Makefile
+++ b/arch/riscv/purgatory/Makefile
@@ -71,7 +71,7 @@ ifdef CONFIG_STACKPROTECTOR_STRONG
PURGATORY_CFLAGS_REMOVE += -fstack-protector-strong
endif
-ifdef CONFIG_CFI_CLANG
+ifdef CONFIG_CFI
PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_CFI)
endif
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 0d2a6d953be9..bc184dd38d99 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -148,7 +148,7 @@ obj-$(CONFIG_UNWINDER_ORC) += unwind_orc.o
obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o
obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o
-obj-$(CONFIG_CFI_CLANG) += cfi.o
+obj-$(CONFIG_CFI) += cfi.o
obj-$(CONFIG_CALL_THUNKS) += callthunks.o
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index e0a607a14e7e..5ce1d4263000 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -57,7 +57,7 @@ ifdef CONFIG_MITIGATION_RETPOLINE
PURGATORY_CFLAGS_REMOVE += $(RETPOLINE_CFLAGS)
endif
-ifdef CONFIG_CFI_CLANG
+ifdef CONFIG_CFI
PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_CFI)
endif
diff --git a/kernel/Makefile b/kernel/Makefile
index c60623448235..27e0e6a33610 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -122,7 +122,7 @@ obj-$(CONFIG_KCSAN) += kcsan/
obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o
obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call_inline.o
-obj-$(CONFIG_CFI_CLANG) += cfi.o
+obj-$(CONFIG_CFI) += cfi.o
obj-$(CONFIG_PERF_EVENTS) += events/
diff --git a/arch/riscv/include/asm/cfi.h b/arch/riscv/include/asm/cfi.h
index 4508aaa7a2fd..710aa8192edd 100644
--- a/arch/riscv/include/asm/cfi.h
+++ b/arch/riscv/include/asm/cfi.h
@@ -11,7 +11,7 @@
struct pt_regs;
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
enum bug_trap_type handle_cfi_failure(struct pt_regs *regs);
#define __bpfcall
#else
@@ -19,6 +19,6 @@ static inline enum bug_trap_type handle_cfi_failure(struct pt_regs *regs)
{
return BUG_TRAP_TYPE_NONE;
}
-#endif /* CONFIG_CFI_CLANG */
+#endif /* CONFIG_CFI */
#endif /* _ASM_RISCV_CFI_H */
diff --git a/arch/x86/include/asm/cfi.h b/arch/x86/include/asm/cfi.h
index 1751f1eb95ef..976b90a3d190 100644
--- a/arch/x86/include/asm/cfi.h
+++ b/arch/x86/include/asm/cfi.h
@@ -113,7 +113,7 @@ extern bhi_thunk __bhi_args_end[];
struct pt_regs;
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
enum bug_trap_type handle_cfi_failure(struct pt_regs *regs);
#define __bpfcall
@@ -157,7 +157,7 @@ static inline int cfi_get_func_arity(void *func)
{
return 0;
}
-#endif /* CONFIG_CFI_CLANG */
+#endif /* CONFIG_CFI */
#if HAS_KERNEL_IBT == 1
#define CFI_NOSEAL(x) asm(IBT_NOSEAL(__stringify(x)))
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index ae2d2359b79e..a65a87366c48 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -157,7 +157,7 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
#define PATCHABLE_DISCARDS *(__patchable_function_entries)
#endif
-#ifndef CONFIG_ARCH_SUPPORTS_CFI_CLANG
+#ifndef CONFIG_ARCH_SUPPORTS_CFI
/*
* Simply points to ftrace_stub, but with the proper protocol.
* Defined by the linker script in linux/vmlinux.lds.h
diff --git a/include/linux/cfi.h b/include/linux/cfi.h
index 52a98886a455..1fd22ea6eba4 100644
--- a/include/linux/cfi.h
+++ b/include/linux/cfi.h
@@ -11,7 +11,7 @@
#include <linux/module.h>
#include <asm/cfi.h>
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
extern bool cfi_warn;
enum bug_trap_type report_cfi_failure(struct pt_regs *regs, unsigned long addr,
@@ -52,7 +52,7 @@ static inline u32 cfi_get_func_hash(void *func)
extern u32 cfi_bpf_hash;
extern u32 cfi_bpf_subprog_hash;
-#else /* CONFIG_CFI_CLANG */
+#else /* CONFIG_CFI */
static inline int cfi_get_offset(void) { return 0; }
static inline u32 cfi_get_func_hash(void *func) { return 0; }
@@ -60,7 +60,7 @@ static inline u32 cfi_get_func_hash(void *func) { return 0; }
#define cfi_bpf_hash 0U
#define cfi_bpf_subprog_hash 0U
-#endif /* CONFIG_CFI_CLANG */
+#endif /* CONFIG_CFI */
#ifdef CONFIG_ARCH_USES_CFI_TRAPS
bool is_cfi_trap(unsigned long addr);
diff --git a/include/linux/cfi_types.h b/include/linux/cfi_types.h
index 685f7181780f..a86af9bc8bdc 100644
--- a/include/linux/cfi_types.h
+++ b/include/linux/cfi_types.h
@@ -8,7 +8,7 @@
#ifdef __ASSEMBLY__
#include <linux/linkage.h>
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
/*
* Use the __kcfi_typeid_<function> type identifier symbol to
* annotate indirectly called assembly functions. The compiler emits
@@ -29,12 +29,12 @@
#define SYM_TYPED_START(name, linkage, align...) \
SYM_TYPED_ENTRY(name, linkage, align)
-#else /* CONFIG_CFI_CLANG */
+#else /* CONFIG_CFI */
#define SYM_TYPED_START(name, linkage, align...) \
SYM_START(name, linkage, align)
-#endif /* CONFIG_CFI_CLANG */
+#endif /* CONFIG_CFI */
#ifndef SYM_TYPED_FUNC_START
#define SYM_TYPED_FUNC_START(name) \
@@ -43,7 +43,7 @@
#else /* __ASSEMBLY__ */
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
#define DEFINE_CFI_TYPE(name, func) \
/* \
* Force a reference to the function so the compiler generates \
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 6f04a1d8c720..fb27da2221ee 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -248,7 +248,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
#endif /* __KERNEL__ */
-#if defined(CONFIG_CFI_CLANG) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO)
+#if defined(CONFIG_CFI) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO)
/*
* Force a reference to the external symbol so the compiler generates
* __kcfi_typid.
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index a910f9fa5341..27026752aec8 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -432,7 +432,7 @@ struct ftrace_likely_data {
# define __noscs
#endif
-#if defined(CONFIG_CFI_CLANG)
+#if defined(CONFIG_CFI)
# define __nocfi __attribute__((__no_sanitize__("kcfi")))
#else
# define __nocfi
diff --git a/tools/include/linux/cfi_types.h b/tools/include/linux/cfi_types.h
index 6b8713675765..2e098274e45c 100644
--- a/tools/include/linux/cfi_types.h
+++ b/tools/include/linux/cfi_types.h
@@ -8,7 +8,7 @@
#ifdef __ASSEMBLY__
#include <linux/linkage.h>
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
/*
* Use the __kcfi_typeid_<function> type identifier symbol to
* annotate indirectly called assembly functions. The compiler emits
@@ -29,12 +29,12 @@
#define SYM_TYPED_START(name, linkage, align...) \
SYM_TYPED_ENTRY(name, linkage, align)
-#else /* CONFIG_CFI_CLANG */
+#else /* CONFIG_CFI */
#define SYM_TYPED_START(name, linkage, align...) \
SYM_START(name, linkage, align)
-#endif /* CONFIG_CFI_CLANG */
+#endif /* CONFIG_CFI */
#ifndef SYM_TYPED_FUNC_START
#define SYM_TYPED_FUNC_START(name) \
diff --git a/tools/perf/util/include/linux/linkage.h b/tools/perf/util/include/linux/linkage.h
index 89979ca23c3f..34e2fdfe7300 100644
--- a/tools/perf/util/include/linux/linkage.h
+++ b/tools/perf/util/include/linux/linkage.h
@@ -120,7 +120,7 @@
#endif
// In the kernel sources (include/linux/cfi_types.h), this has a different
-// definition when CONFIG_CFI_CLANG is used, for tools/ just use the !clang
+// definition when CONFIG_CFI is used, for tools/ just use the !cfi
// definition:
#ifndef SYM_TYPED_START
#define SYM_TYPED_START(name, linkage, align...) \
diff --git a/arch/arm/mm/cache-fa.S b/arch/arm/mm/cache-fa.S
index 4a3668b52a2d..e1641799569b 100644
--- a/arch/arm/mm/cache-fa.S
+++ b/arch/arm/mm/cache-fa.S
@@ -112,7 +112,7 @@ SYM_FUNC_END(fa_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(fa_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b fa_coherent_user_range
#endif
SYM_FUNC_END(fa_coherent_kern_range)
diff --git a/arch/arm/mm/cache-v4.S b/arch/arm/mm/cache-v4.S
index 0e94e5193dbd..001d7042bd46 100644
--- a/arch/arm/mm/cache-v4.S
+++ b/arch/arm/mm/cache-v4.S
@@ -104,7 +104,7 @@ SYM_FUNC_END(v4_coherent_user_range)
* - size - region size
*/
SYM_TYPED_FUNC_START(v4_flush_kern_dcache_area)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b v4_dma_flush_range
#endif
SYM_FUNC_END(v4_flush_kern_dcache_area)
diff --git a/arch/arm/mm/cache-v4wb.S b/arch/arm/mm/cache-v4wb.S
index ce55a2eef5da..874fe5310f9a 100644
--- a/arch/arm/mm/cache-v4wb.S
+++ b/arch/arm/mm/cache-v4wb.S
@@ -136,7 +136,7 @@ SYM_FUNC_END(v4wb_flush_user_cache_range)
*/
SYM_TYPED_FUNC_START(v4wb_flush_kern_dcache_area)
add r1, r0, r1
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b v4wb_coherent_user_range
#endif
SYM_FUNC_END(v4wb_flush_kern_dcache_area)
@@ -152,7 +152,7 @@ SYM_FUNC_END(v4wb_flush_kern_dcache_area)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(v4wb_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b v4wb_coherent_user_range
#endif
SYM_FUNC_END(v4wb_coherent_kern_range)
diff --git a/arch/arm/mm/cache-v4wt.S b/arch/arm/mm/cache-v4wt.S
index a97dc267b3b0..2ee62e4b2b07 100644
--- a/arch/arm/mm/cache-v4wt.S
+++ b/arch/arm/mm/cache-v4wt.S
@@ -108,7 +108,7 @@ SYM_FUNC_END(v4wt_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(v4wt_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b v4wt_coherent_user_range
#endif
SYM_FUNC_END(v4wt_coherent_kern_range)
diff --git a/arch/arm/mm/cache-v6.S b/arch/arm/mm/cache-v6.S
index 9f415476e218..5ceea8965ea1 100644
--- a/arch/arm/mm/cache-v6.S
+++ b/arch/arm/mm/cache-v6.S
@@ -117,7 +117,7 @@ SYM_FUNC_END(v6_flush_user_cache_range)
* - the Icache does not read data from the write buffer
*/
SYM_TYPED_FUNC_START(v6_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b v6_coherent_user_range
#endif
SYM_FUNC_END(v6_coherent_kern_range)
diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
index 201ca05436fa..726681fb7d4d 100644
--- a/arch/arm/mm/cache-v7.S
+++ b/arch/arm/mm/cache-v7.S
@@ -261,7 +261,7 @@ SYM_FUNC_END(v7_flush_user_cache_range)
* - the Icache does not read data from the write buffer
*/
SYM_TYPED_FUNC_START(v7_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b v7_coherent_user_range
#endif
SYM_FUNC_END(v7_coherent_kern_range)
diff --git a/arch/arm/mm/cache-v7m.S b/arch/arm/mm/cache-v7m.S
index 14d719eba729..7f9cfad2ea21 100644
--- a/arch/arm/mm/cache-v7m.S
+++ b/arch/arm/mm/cache-v7m.S
@@ -286,7 +286,7 @@ SYM_FUNC_END(v7m_flush_user_cache_range)
* - the Icache does not read data from the write buffer
*/
SYM_TYPED_FUNC_START(v7m_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b v7m_coherent_user_range
#endif
SYM_FUNC_END(v7m_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm1020.S b/arch/arm/mm/proc-arm1020.S
index d0ce3414a13e..4612a4961e81 100644
--- a/arch/arm/mm/proc-arm1020.S
+++ b/arch/arm/mm/proc-arm1020.S
@@ -203,7 +203,7 @@ SYM_FUNC_END(arm1020_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm1020_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm1020_coherent_user_range
#endif
SYM_FUNC_END(arm1020_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm1020e.S b/arch/arm/mm/proc-arm1020e.S
index 64f031bf6eff..b4a8a3a8eda3 100644
--- a/arch/arm/mm/proc-arm1020e.S
+++ b/arch/arm/mm/proc-arm1020e.S
@@ -200,7 +200,7 @@ SYM_FUNC_END(arm1020e_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm1020e_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm1020e_coherent_user_range
#endif
SYM_FUNC_END(arm1020e_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm1022.S b/arch/arm/mm/proc-arm1022.S
index 42ed5ed07252..709870e99e19 100644
--- a/arch/arm/mm/proc-arm1022.S
+++ b/arch/arm/mm/proc-arm1022.S
@@ -199,7 +199,7 @@ SYM_FUNC_END(arm1022_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm1022_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm1022_coherent_user_range
#endif
SYM_FUNC_END(arm1022_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm1026.S b/arch/arm/mm/proc-arm1026.S
index b3ae62cd553a..02f7370a8c5c 100644
--- a/arch/arm/mm/proc-arm1026.S
+++ b/arch/arm/mm/proc-arm1026.S
@@ -194,7 +194,7 @@ SYM_FUNC_END(arm1026_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm1026_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm1026_coherent_user_range
#endif
SYM_FUNC_END(arm1026_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm920.S b/arch/arm/mm/proc-arm920.S
index a30df54ad5fa..4727f4b5b6e8 100644
--- a/arch/arm/mm/proc-arm920.S
+++ b/arch/arm/mm/proc-arm920.S
@@ -180,7 +180,7 @@ SYM_FUNC_END(arm920_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm920_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm920_coherent_user_range
#endif
SYM_FUNC_END(arm920_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm922.S b/arch/arm/mm/proc-arm922.S
index aac4e048100d..5a4a3f4f2683 100644
--- a/arch/arm/mm/proc-arm922.S
+++ b/arch/arm/mm/proc-arm922.S
@@ -182,7 +182,7 @@ SYM_FUNC_END(arm922_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm922_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm922_coherent_user_range
#endif
SYM_FUNC_END(arm922_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm925.S b/arch/arm/mm/proc-arm925.S
index 035941faeb2e..1c4830afe1d3 100644
--- a/arch/arm/mm/proc-arm925.S
+++ b/arch/arm/mm/proc-arm925.S
@@ -229,7 +229,7 @@ SYM_FUNC_END(arm925_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm925_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm925_coherent_user_range
#endif
SYM_FUNC_END(arm925_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm926.S b/arch/arm/mm/proc-arm926.S
index 6f43d6af2d9a..a09cc3e02efd 100644
--- a/arch/arm/mm/proc-arm926.S
+++ b/arch/arm/mm/proc-arm926.S
@@ -192,7 +192,7 @@ SYM_FUNC_END(arm926_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm926_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm926_coherent_user_range
#endif
SYM_FUNC_END(arm926_coherent_kern_range)
diff --git a/arch/arm/mm/proc-arm940.S b/arch/arm/mm/proc-arm940.S
index 0d30bb25c42b..545c076c36d2 100644
--- a/arch/arm/mm/proc-arm940.S
+++ b/arch/arm/mm/proc-arm940.S
@@ -153,7 +153,7 @@ SYM_FUNC_END(arm940_coherent_kern_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm940_coherent_user_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm940_flush_kern_dcache_area
#endif
SYM_FUNC_END(arm940_coherent_user_range)
diff --git a/arch/arm/mm/proc-arm946.S b/arch/arm/mm/proc-arm946.S
index 27750ace2ced..f3d4e18c3fba 100644
--- a/arch/arm/mm/proc-arm946.S
+++ b/arch/arm/mm/proc-arm946.S
@@ -173,7 +173,7 @@ SYM_FUNC_END(arm946_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(arm946_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b arm946_coherent_user_range
#endif
SYM_FUNC_END(arm946_coherent_kern_range)
diff --git a/arch/arm/mm/proc-feroceon.S b/arch/arm/mm/proc-feroceon.S
index f67b2ffac854..7f08d06c9625 100644
--- a/arch/arm/mm/proc-feroceon.S
+++ b/arch/arm/mm/proc-feroceon.S
@@ -208,7 +208,7 @@ SYM_FUNC_END(feroceon_flush_user_cache_range)
*/
.align 5
SYM_TYPED_FUNC_START(feroceon_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b feroceon_coherent_user_range
#endif
SYM_FUNC_END(feroceon_coherent_kern_range)
diff --git a/arch/arm/mm/proc-mohawk.S b/arch/arm/mm/proc-mohawk.S
index 8e9f38da863a..4669c63e3121 100644
--- a/arch/arm/mm/proc-mohawk.S
+++ b/arch/arm/mm/proc-mohawk.S
@@ -163,7 +163,7 @@ SYM_FUNC_END(mohawk_flush_user_cache_range)
* - end - virtual end address
*/
SYM_TYPED_FUNC_START(mohawk_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b mohawk_coherent_user_range
#endif
SYM_FUNC_END(mohawk_coherent_kern_range)
diff --git a/arch/arm/mm/proc-xsc3.S b/arch/arm/mm/proc-xsc3.S
index 14927b380452..fd25634a2ed5 100644
--- a/arch/arm/mm/proc-xsc3.S
+++ b/arch/arm/mm/proc-xsc3.S
@@ -223,7 +223,7 @@ SYM_FUNC_END(xsc3_flush_user_cache_range)
* it also trashes the mini I-cache used by JTAG debuggers.
*/
SYM_TYPED_FUNC_START(xsc3_coherent_kern_range)
-#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
b xsc3_coherent_user_range
#endif
SYM_FUNC_END(xsc3_coherent_kern_range)
diff --git a/arch/arm/mm/tlb-v4.S b/arch/arm/mm/tlb-v4.S
index 09ff69008d94..079774a02be6 100644
--- a/arch/arm/mm/tlb-v4.S
+++ b/arch/arm/mm/tlb-v4.S
@@ -52,7 +52,7 @@ SYM_FUNC_END(v4_flush_user_tlb_range)
* - start - virtual address (may not be aligned)
* - end - virtual address (may not be aligned)
*/
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
SYM_TYPED_FUNC_START(v4_flush_kern_tlb_range)
b .v4_flush_kern_tlb_range
SYM_FUNC_END(v4_flush_kern_tlb_range)
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index a12efd0f43e8..cd4b34c96e35 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -904,7 +904,7 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
watchpoint_single_step_handler(addr);
}
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
static void hw_breakpoint_cfi_handler(struct pt_regs *regs)
{
/*
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 110d9ff54174..ebf010443e22 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -212,7 +212,7 @@ static int call_el1_break_hook(struct pt_regs *regs, unsigned long esr)
if (esr_brk_comment(esr) == BUG_BRK_IMM)
return bug_brk_handler(regs, esr);
- if (IS_ENABLED(CONFIG_CFI_CLANG) && esr_is_cfi_brk(esr))
+ if (IS_ENABLED(CONFIG_CFI) && esr_is_cfi_brk(esr))
return cfi_brk_handler(regs, esr);
if (esr_brk_comment(esr) == FAULT_BRK_IMM)
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index f528b6041f6a..5041817af267 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -1015,7 +1015,7 @@ int bug_brk_handler(struct pt_regs *regs, unsigned long esr)
return DBG_HOOK_HANDLED;
}
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
int cfi_brk_handler(struct pt_regs *regs, unsigned long esr)
{
unsigned long target;
@@ -1039,7 +1039,7 @@ int cfi_brk_handler(struct pt_regs *regs, unsigned long esr)
arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
return DBG_HOOK_HANDLED;
}
-#endif /* CONFIG_CFI_CLANG */
+#endif /* CONFIG_CFI */
int reserved_fault_brk_handler(struct pt_regs *regs, unsigned long esr)
{
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index a598072f36d2..8bdb1eed090a 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -545,7 +545,7 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr,
kvm_err("nVHE hyp BUG at: %s:%u!\n", file, line);
else
print_nvhe_hyp_panic("BUG", panic_addr);
- } else if (IS_ENABLED(CONFIG_CFI_CLANG) && esr_is_cfi_brk(esr)) {
+ } else if (IS_ENABLED(CONFIG_CFI) && esr_is_cfi_brk(esr)) {
kvm_nvhe_report_cfi_failure(panic_addr);
} else if (IS_ENABLED(CONFIG_UBSAN_KVM_EL2) &&
ESR_ELx_EC(esr) == ESR_ELx_EC_BRK64 &&
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 52ffe115a8c4..28996e0a9b00 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -185,7 +185,7 @@ static inline void emit_bti(u32 insn, struct jit_ctx *ctx)
static inline void emit_kcfi(u32 hash, struct jit_ctx *ctx)
{
- if (IS_ENABLED(CONFIG_CFI_CLANG))
+ if (IS_ENABLED(CONFIG_CFI))
emit_u32_data(hash, ctx);
}
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 10e01ff06312..24ba546a1c0e 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -18,7 +18,7 @@
#define RV_MAX_REG_ARGS 8
#define RV_FENTRY_NINSNS 2
#define RV_FENTRY_NBYTES (RV_FENTRY_NINSNS * 4)
-#define RV_KCFI_NINSNS (IS_ENABLED(CONFIG_CFI_CLANG) ? 1 : 0)
+#define RV_KCFI_NINSNS (IS_ENABLED(CONFIG_CFI) ? 1 : 0)
/* imm that allows emit_imm to emit max count insns */
#define RV_MAX_COUNT_IMM 0x7FFF7FF7FF7FF7FF
@@ -469,7 +469,7 @@ static int emit_call(u64 addr, bool fixed_addr, struct rv_jit_context *ctx)
static inline void emit_kcfi(u32 hash, struct rv_jit_context *ctx)
{
- if (IS_ENABLED(CONFIG_CFI_CLANG))
+ if (IS_ENABLED(CONFIG_CFI))
emit(hash, ctx);
}
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index b311e31a9056..9afd765873ca 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1170,7 +1170,7 @@ void __init_or_module apply_seal_endbr(s32 *start, s32 *end) { }
#ifdef CONFIG_CFI_AUTO_DEFAULT
# define __CFI_DEFAULT CFI_AUTO
-#elif defined(CONFIG_CFI_CLANG)
+#elif defined(CONFIG_CFI)
# define __CFI_DEFAULT CFI_KCFI
#else
# define __CFI_DEFAULT CFI_OFF
@@ -1183,7 +1183,7 @@ static bool cfi_debug __ro_after_init;
bool cfi_bhi __ro_after_init = false;
#endif
-#ifdef CONFIG_CFI_CLANG
+#ifdef CONFIG_CFI
u32 cfi_get_func_hash(void *func)
{
u32 hash;
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 6079d15dab8c..3863d7709386 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -339,7 +339,7 @@ static bool can_probe(unsigned long paddr)
if (is_exception_insn(&insn))
return false;
- if (IS_ENABLED(CONFIG_CFI_CLANG)) {
+ if (IS_ENABLED(CONFIG_CFI)) {
/*
* The compiler generates the following instruction sequence
* for indirect call checks and cfi.c decodes this;
diff --git a/drivers/misc/lkdtm/cfi.c b/drivers/misc/lkdtm/cfi.c
index 6a33889d0902..c3971f7caa65 100644
--- a/drivers/misc/lkdtm/cfi.c
+++ b/drivers/misc/lkdtm/cfi.c
@@ -43,7 +43,7 @@ static void lkdtm_CFI_FORWARD_PROTO(void)
lkdtm_indirect_call((void *)lkdtm_increment_int);
pr_err("FAIL: survived mismatched prototype function call!\n");
- pr_expected_config(CONFIG_CFI_CLANG);
+ pr_expected_config(CONFIG_CFI);
}
/*
diff --git a/kernel/module/tree_lookup.c b/kernel/module/tree_lookup.c
index d3204c5c74eb..f8e8c126705c 100644
--- a/kernel/module/tree_lookup.c
+++ b/kernel/module/tree_lookup.c
@@ -14,7 +14,7 @@
* Use a latched RB-tree for __module_address(); this allows us to use
* RCU lookups of the address from any context.
*
- * This is conditional on PERF_EVENTS || TRACING || CFI_CLANG because those can
+ * This is conditional on PERF_EVENTS || TRACING || CFI because those can
* really hit __module_address() hard by doing a lot of stack unwinding;
* potentially from NMI context.
*/
diff --git a/kernel/configs/hardening.config b/kernel/configs/hardening.config
index 64caaf997fc0..94a3d023e15e 100644
--- a/kernel/configs/hardening.config
+++ b/kernel/configs/hardening.config
@@ -94,7 +94,7 @@ CONFIG_SECCOMP_FILTER=y
CONFIG_SYN_COOKIES=y
# Enable Kernel Control Flow Integrity (currently Clang only).
-CONFIG_CFI_CLANG=y
+CONFIG_CFI=y
# CONFIG_CFI_PERMISSIVE is not set
# Attack surface reduction: do not autoload TTY line disciplines.
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* [PATCH v2 9/9] ARM: traps: Implement KCFI trap handler for ARM32
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
` (7 preceding siblings ...)
2025-09-04 3:46 ` [PATCH v2 8/9] kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI Kees Cook
@ 2025-09-04 3:46 ` Kees Cook
2025-09-04 7:04 ` [PATCH v2 0/9] kcfi: Prepare for GCC support Peter Zijlstra
9 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2025-09-04 3:46 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Kees Cook, Russell King (Oracle), Zhen Lei, Arnd Bergmann,
Michał Pecio, Sebastian Andrzej Siewior, Sami Tolvanen,
linux-arm-kernel, Nathan Chancellor, Vegard Nossum, Miguel Ojeda,
Linus Walleij, Jeff Johnson, Randy Dunlap, David Woodhouse,
Nick Desaulniers, Bill Wendling, Justin Stitt, Marco Elver,
Przemek Kitszel, Ramon de C Valle, Jonathan Corbet,
Paul E. McKenney, Nicolas Schier, Masahiro Yamada,
Krzysztof Kozlowski, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, x86, linux-hardening
ARM32 KCFI violations currently show as generic "Oops - undefined
instruction" errors, making debugging CFI failures difficult. Add a
proper KCFI trap handler similar to the aarch64 implementation to
provide clear CFI error messages.
The GCC ARM32 KCFI implementation uses UDF instructions with a specific
encoding pattern:
- UDF instruction format: cccc 0111 1111 imm12 1111 imm4
- 16-bit immediate reconstructed from bits 19-8 and 3-0
- KCFI encoding: 0x8000 | (type_reg_num << 5) | (target_reg_num & 31)
- Bit 15: KCFI trap identifier (0x8000)
- Bits 9-5: Type ID register field (0x1F when unavailable)
- Bits 4-0: Target address register number
When the type register field is 0x1F (unavailable due to stack
spilling), the handler walks back up to 5 preceding instructions to
locate the movw/movt instruction pair that loads the 32-bit type ID,
similar to x86 CFI trap reconstruction.
The undef_hook pattern matching includes the KCFI bit requirement to
ensure the handler is only called for KCFI violations, not arbitrary
UDF instructions.
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Michał Pecio" <michal.pecio@gmail.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: <linux-arm-kernel@lists.infradead.org>
---
arch/arm/kernel/traps.c | 102 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 102 insertions(+)
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index afbd2ebe5c39..f2e4e18541e0 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -27,6 +27,7 @@
#include <linux/sched/task_stack.h>
#include <linux/irq.h>
#include <linux/vmalloc.h>
+#include <linux/cfi.h>
#include <linux/atomic.h>
#include <asm/cacheflush.h>
@@ -40,6 +41,7 @@
#include <asm/stacktrace.h>
#include <asm/system_misc.h>
#include <asm/opcodes.h>
+#include <linux/bitfield.h>
static const char *handler[]= {
@@ -685,6 +687,106 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
return 0;
}
+#ifdef CONFIG_CFI
+/*
+ * ARM32 KCFI trap handler.
+ * UDF instruction format: cccc 0111 1111 imm12 1111 imm4
+ * Immediate is reconstructed from bits 19-8 (12 bits) and bits 3-0 (4 bits)
+ * KCFI immediate encoding: 0x8000 | (0x1F << 5) | (target_reg_num & 31)
+ * - Bit 15: KCFI trap identifier (0x8000)
+ * - Bits 9-5: Type ID register field (0x1F when invalid due to stack spilling)
+ * - Bits 4-0: Target address register number
+ */
+#define CFI_UDF_KCFI_BIT BIT(15) /* KCFI identifier bit (0x8000) */
+#define CFI_UDF_IMM_TARGET GENMASK(4, 0) /* Target register (bits 4:0) */
+#define CFI_UDF_IMM_TYPE GENMASK(9, 5) /* Type register (bits 9:5) */
+
+/* UDF base pattern with KCFI bit: cond=0xe, 0x7f, xxxx, 1xxx, 0xf, xxxx */
+#define CFI_UDF_IMM_BASE 0xe7f008f0
+#define CFI_UDF_IMM_MASK 0xfff008f0 /* Mask for UDF + KCFI bit matching */
+
+static int cfi_udf_handler(struct pt_regs *regs, unsigned int instr)
+{
+ unsigned long target;
+ u32 target_reg, type_reg, type, imm16;
+
+ /* Reconstruct 16-bit immediate from bits 19-8 and 3-0 */
+ imm16 = ((instr >> 4) & 0xfff0) | (instr & 0x0f);
+
+ target_reg = FIELD_GET(CFI_UDF_IMM_TARGET, imm16);
+ type_reg = FIELD_GET(CFI_UDF_IMM_TYPE, imm16);
+
+ if (target_reg >= 16) {
+ pr_err("CFI UDF handler: invalid target register %u\n", target_reg);
+ return 1;
+ }
+
+ target = regs->uregs[target_reg];
+
+ /* Type register field is set to all 1s (0x1F) when invalid due to stack spilling */
+ if (type_reg == 0x1F) {
+ u32 *pc = (u32 *)regs->ARM_pc;
+ int i;
+
+ type = 0;
+ /* Walk back up to 5 instructions to find movw/movt pair for type ID */
+ for (i = 1; i <= 5; i++) {
+ u32 instr_prev = __mem_to_opcode_arm(pc[-i]);
+
+ /* Check for movw: cccc 0011 0000 imm4 Rd imm12 */
+ if ((instr_prev & 0x0ff00000) == 0x03000000) {
+ u32 imm16 = ((instr_prev >> 4) & 0xf000) | (instr_prev & 0xfff);
+ type |= imm16;
+ }
+ /* Check for movt: cccc 0011 0100 imm4 Rd imm12 */
+ else if ((instr_prev & 0x0ff00000) == 0x03400000) {
+ u32 imm16 = ((instr_prev >> 4) & 0xf000) | (instr_prev & 0xfff);
+ type |= (imm16 << 16);
+ }
+ }
+ if (type == 0)
+ pr_err("CFI UDF handler: failed to find type value\n");
+ } else {
+ if (type_reg >= 16) {
+ pr_err("CFI UDF handler: invalid type register %u\n", type_reg);
+ return 1;
+ }
+
+ type = regs->uregs[type_reg];
+ }
+
+ switch (report_cfi_failure(regs, regs->ARM_pc, &target, type)) {
+ case BUG_TRAP_TYPE_BUG:
+ die("Oops - CFI", regs, 0);
+ break;
+ case BUG_TRAP_TYPE_WARN:
+ break;
+ default:
+ return 1;
+ }
+
+ /* Skip the UDF instruction */
+ regs->ARM_pc += 4;
+ return 0;
+}
+
+static struct undef_hook cfi_undef_hook = {
+ .instr_mask = CFI_UDF_IMM_MASK,
+ .instr_val = CFI_UDF_IMM_BASE,
+ .cpsr_mask = 0,
+ .cpsr_val = 0,
+ .fn = cfi_udf_handler,
+};
+
+static int __init arm_cfi_init(void)
+{
+ register_undef_hook(&cfi_undef_hook);
+ return 0;
+}
+
+early_initcall(arm_cfi_init);
+#endif /* CONFIG_CFI */
+
#ifdef CONFIG_TLS_REG_EMUL
/*
--
2.34.1
^ permalink raw reply related [flat|nested] 20+ messages in thread* Re: [PATCH v2 0/9] kcfi: Prepare for GCC support
2025-09-04 3:46 [PATCH v2 0/9] kcfi: Prepare for GCC support Kees Cook
` (8 preceding siblings ...)
2025-09-04 3:46 ` [PATCH v2 9/9] ARM: traps: Implement KCFI trap handler for ARM32 Kees Cook
@ 2025-09-04 7:04 ` Peter Zijlstra
2025-09-04 16:37 ` Kees Cook
9 siblings, 1 reply; 20+ messages in thread
From: Peter Zijlstra @ 2025-09-04 7:04 UTC (permalink / raw)
To: Kees Cook
Cc: Nathan Chancellor, Vegard Nossum, Miguel Ojeda, Linus Walleij,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Wed, Sep 03, 2025 at 08:46:39PM -0700, Kees Cook wrote:
> Kees Cook (9):
> compiler_types.h: Move __nocfi out of compiler-specific header
> x86/traps: Clarify KCFI instruction layout
> x86/cfi: Document the "cfi=" bootparam options
> x86/cfi: Standardize on common "CFI:" prefix for CFI reports
> x86/cfi: Add "debug" option to "cfi=" bootparam
> x86/cfi: Remove __noinitretpoline and __noretpoline
So I can take these first 6 patches (and edit that debug patch to
un-annoy myself ;-), but I'm thinking this Kconfig stuff:
> kconfig: Add transitional symbol attribute for migration support
> kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI
Should perhaps go through the kbuild tree? A
Leaving this:
> ARM: traps: Implement KCFI trap handler for ARM32
Can that go independently through the arm tree, or are there
dependencies?
^ permalink raw reply [flat|nested] 20+ messages in thread* Re: [PATCH v2 0/9] kcfi: Prepare for GCC support
2025-09-04 7:04 ` [PATCH v2 0/9] kcfi: Prepare for GCC support Peter Zijlstra
@ 2025-09-04 16:37 ` Kees Cook
2025-09-04 20:01 ` Peter Zijlstra
0 siblings, 1 reply; 20+ messages in thread
From: Kees Cook @ 2025-09-04 16:37 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Nathan Chancellor, Vegard Nossum, Miguel Ojeda, Linus Walleij,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Thu, Sep 04, 2025 at 09:04:10AM +0200, Peter Zijlstra wrote:
> On Wed, Sep 03, 2025 at 08:46:39PM -0700, Kees Cook wrote:
>
> > Kees Cook (9):
> > compiler_types.h: Move __nocfi out of compiler-specific header
> > x86/traps: Clarify KCFI instruction layout
> > x86/cfi: Document the "cfi=" bootparam options
> > x86/cfi: Standardize on common "CFI:" prefix for CFI reports
> > x86/cfi: Add "debug" option to "cfi=" bootparam
> > x86/cfi: Remove __noinitretpoline and __noretpoline
>
> So I can take these first 6 patches (and edit that debug patch to
> un-annoy myself ;-), but I'm thinking this Kconfig stuff:
Sure, yeah. Do you want a v3 for the debug stuff that uses your proposed
helper?
> > kconfig: Add transitional symbol attribute for migration support
> > kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI
>
> Should perhaps go through the kbuild tree? A
I had chatted offline with Nathan about this series, and he'd suggested
the kconfig change could go with it's first user (the rename). So if you
don't want to put it in -tip, I can take it in the hardening tree.
(There's no dependencies between these 2 and the first 6.)
> Leaving this:
>
> > ARM: traps: Implement KCFI trap handler for ARM32
>
> Can that go independently through the arm tree, or are there
> dependencies?
I can take this too, assuming ARM folks don't want to snag it. I may,
however, wait on it, just to avoid implementing the kernel support
before the GCC folks are happy with the arm32 KCFI backend and its UDF
encoding, etc.
Thanks for looking at these! :)
-Kees
--
Kees Cook
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: [PATCH v2 0/9] kcfi: Prepare for GCC support
2025-09-04 16:37 ` Kees Cook
@ 2025-09-04 20:01 ` Peter Zijlstra
2025-09-05 0:42 ` Kees Cook
0 siblings, 1 reply; 20+ messages in thread
From: Peter Zijlstra @ 2025-09-04 20:01 UTC (permalink / raw)
To: Kees Cook
Cc: Nathan Chancellor, Vegard Nossum, Miguel Ojeda, Linus Walleij,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Thu, Sep 04, 2025 at 09:37:14AM -0700, Kees Cook wrote:
> On Thu, Sep 04, 2025 at 09:04:10AM +0200, Peter Zijlstra wrote:
> > On Wed, Sep 03, 2025 at 08:46:39PM -0700, Kees Cook wrote:
> >
> > > Kees Cook (9):
> > > compiler_types.h: Move __nocfi out of compiler-specific header
> > > x86/traps: Clarify KCFI instruction layout
> > > x86/cfi: Document the "cfi=" bootparam options
> > > x86/cfi: Standardize on common "CFI:" prefix for CFI reports
> > > x86/cfi: Add "debug" option to "cfi=" bootparam
> > > x86/cfi: Remove __noinitretpoline and __noretpoline
> >
> > So I can take these first 6 patches (and edit that debug patch to
> > un-annoy myself ;-), but I'm thinking this Kconfig stuff:
>
> Sure, yeah. Do you want a v3 for the debug stuff that uses your proposed
> helper?
Nah, already done :-) I just pushed out these 6 and my UDB hackery to
queue.git/x86/core. If the robots don't complain, I'll stuff it into tip
in a few days.
> > > kconfig: Add transitional symbol attribute for migration support
> > > kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI
> >
> > Should perhaps go through the kbuild tree? A
>
> I had chatted offline with Nathan about this series, and he'd suggested
> the kconfig change could go with it's first user (the rename). So if you
> don't want to put it in -tip, I can take it in the hardening tree.
> (There's no dependencies between these 2 and the first 6.)
So I suppose I can carry them, just to keep the lot together, but then I
need an ack from someone that actually knows this Kconfig language stuff
:-)
You taking them through the hardening tree also works for em.
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: [PATCH v2 0/9] kcfi: Prepare for GCC support
2025-09-04 20:01 ` Peter Zijlstra
@ 2025-09-05 0:42 ` Kees Cook
2025-09-05 7:44 ` Miguel Ojeda
0 siblings, 1 reply; 20+ messages in thread
From: Kees Cook @ 2025-09-05 0:42 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Nathan Chancellor, Vegard Nossum, Miguel Ojeda, Linus Walleij,
Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Thu, Sep 04, 2025 at 10:01:34PM +0200, Peter Zijlstra wrote:
> Nah, already done :-) I just pushed out these 6 and my UDB hackery to
> queue.git/x86/core. If the robots don't complain, I'll stuff it into tip
> in a few days.
Okay, thanks!
> So I suppose I can carry them, just to keep the lot together, but then I
> need an ack from someone that actually knows this Kconfig language stuff
> :-)
>
> You taking them through the hardening tree also works for em.
Assuming Nathan (and Vegard? or other folks from the other thread?) are
okay with the kconfig changes, I'll take it via hardening.
Wheee
--
Kees Cook
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: [PATCH v2 0/9] kcfi: Prepare for GCC support
2025-09-05 0:42 ` Kees Cook
@ 2025-09-05 7:44 ` Miguel Ojeda
0 siblings, 0 replies; 20+ messages in thread
From: Miguel Ojeda @ 2025-09-05 7:44 UTC (permalink / raw)
To: Kees Cook
Cc: Peter Zijlstra, Nathan Chancellor, Vegard Nossum, Miguel Ojeda,
Linus Walleij, Jeff Johnson, Randy Dunlap, David Woodhouse,
Russell King (Oracle), Nick Desaulniers, Bill Wendling,
Justin Stitt, Marco Elver, Przemek Kitszel, Ramon de C Valle,
Jonathan Corbet, Paul E. McKenney, Nicolas Schier,
Masahiro Yamada, Arnd Bergmann, Krzysztof Kozlowski,
Sami Tolvanen, Mark Rutland, linux-kernel, llvm, linux-doc,
linux-kbuild, linux-arm-kernel, x86, linux-hardening
On Fri, Sep 5, 2025 at 2:42 AM Kees Cook <kees@kernel.org> wrote:
>
> Assuming Nathan (and Vegard? or other folks from the other thread?) are
> okay with the kconfig changes, I'll take it via hardening.
I haven't had time to take a proper look, test it etc., so I didn't
reply, sorry -- but I am following the thread and I am glad if we have
something to easily/properly support this, so thanks for this.
(And sorry for having triggered all this discussion/work -- at least
if we get this done it will have been worth it :)
I will leave a quick message about the commit message.
Cheers,
Miguel
^ permalink raw reply [flat|nested] 20+ messages in thread