[PATCH 0/3] arm64: trivial constification patches

[PATCH 0/3] arm64: trivial constification patches

[Mark Rutland]

I spotted a few arrays under arm64 that we can mark const, as their
contents are never intentionally modified at runtime. Doing this will
make it a bit easier to spot bugs, and (in the case of sys64_hook) will
make it marginally harder to get the kernel to execute the wrong thing.

Our crypto algorithm and undef_hook arrays all have runtime-modified state, so
these cannot be made const.

Thanks,
Mark.

Mark Rutland (3):
  arm64: constify icache_policy_str[]
  arm64: constify aarch64_insn_encoding_class[]
  arm64: constify sys64_hook instances

 arch/arm64/kernel/cpuinfo.c |  2 +-
 arch/arm64/kernel/insn.c    |  2 +-
 arch/arm64/kernel/traps.c   | 10 +++++-----
 3 files changed, 7 insertions(+), 7 deletions(-)

-- 
2.11.0


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[PATCH 1/3] arm64: constify icache_policy_str[]

[Mark Rutland]

The icache_policy_str[] array contains compile-time constant data, and
is never intentionally modified, so let's mark it as const.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/kernel/cpuinfo.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 876055e37352..05933c065732 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -33,7 +33,7 @@
 DEFINE_PER_CPU(struct cpuinfo_arm64, cpu_data);
 static struct cpuinfo_arm64 boot_cpu_data;
 
-static char *icache_policy_str[] = {
+static const char *icache_policy_str[] = {
 	[0 ... ICACHE_POLICY_PIPT]	= "RESERVED/UNKNOWN",
 	[ICACHE_POLICY_VIPT]		= "VIPT",
 	[ICACHE_POLICY_PIPT]		= "PIPT",
-- 
2.11.0


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[PATCH 2/3] arm64: constify aarch64_insn_encoding_class[]

[Mark Rutland]

The aarch64_insn_encoding_class[] array contains compile-time constant
data, and is never intentionally modified, so let's mark it as const.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/kernel/insn.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 84b059ed04fc..d801a7094076 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -26,7 +26,7 @@
 #define AARCH64_INSN_N_BIT	BIT(22)
 #define AARCH64_INSN_LSL_12	BIT(22)
 
-static int aarch64_insn_encoding_class[] = {
+static const int aarch64_insn_encoding_class[] = {
 	AARCH64_INSN_CLS_UNKNOWN,
 	AARCH64_INSN_CLS_UNKNOWN,
 	AARCH64_INSN_CLS_UNKNOWN,
-- 
2.11.0


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[PATCH 3/3] arm64: constify sys64_hook instances

[Mark Rutland]

All instances of struct sys64_hook contain compile-time constant data,
and are never inentionally modified, so let's make them all const.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/kernel/traps.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 42c8422cdf4a..a5d7ce4297b0 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -511,7 +511,7 @@ struct sys64_hook {
 	void (*handler)(unsigned int esr, struct pt_regs *regs);
 };
 
-static struct sys64_hook sys64_hooks[] = {
+static const struct sys64_hook sys64_hooks[] = {
 	{
 		.esr_mask = ESR_ELx_SYS64_ISS_EL0_CACHE_OP_MASK,
 		.esr_val = ESR_ELx_SYS64_ISS_EL0_CACHE_OP_VAL,
@@ -636,7 +636,7 @@ static void compat_cntfrq_read_handler(unsigned int esr, struct pt_regs *regs)
 	arm64_compat_skip_faulting_instruction(regs, 4);
 }
 
-static struct sys64_hook cp15_32_hooks[] = {
+static const struct sys64_hook cp15_32_hooks[] = {
 	{
 		.esr_mask = ESR_ELx_CP15_32_ISS_SYS_MASK,
 		.esr_val = ESR_ELx_CP15_32_ISS_SYS_CNTFRQ,
@@ -656,7 +656,7 @@ static void compat_cntvct_read_handler(unsigned int esr, struct pt_regs *regs)
 	arm64_compat_skip_faulting_instruction(regs, 4);
 }
 
-static struct sys64_hook cp15_64_hooks[] = {
+static const struct sys64_hook cp15_64_hooks[] = {
 	{
 		.esr_mask = ESR_ELx_CP15_64_ISS_SYS_MASK,
 		.esr_val = ESR_ELx_CP15_64_ISS_SYS_CNTVCT,
@@ -667,7 +667,7 @@ static struct sys64_hook cp15_64_hooks[] = {
 
 asmlinkage void __exception do_cp15instr(unsigned int esr, struct pt_regs *regs)
 {
-	struct sys64_hook *hook, *hook_base;
+	const struct sys64_hook *hook, *hook_base;
 
 	if (!cp15_cond_valid(esr, regs)) {
 		/*
@@ -707,7 +707,7 @@ asmlinkage void __exception do_cp15instr(unsigned int esr, struct pt_regs *regs)
 
 asmlinkage void __exception do_sysinstr(unsigned int esr, struct pt_regs *regs)
 {
-	struct sys64_hook *hook;
+	const struct sys64_hook *hook;
 
 	for (hook = sys64_hooks; hook->handler; hook++)
 		if ((hook->esr_mask & esr) == hook->esr_val) {
-- 
2.11.0


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Re: [PATCH 1/3] arm64: constify icache_policy_str[]

[Dave Martin]

On Tue, Aug 13, 2019 at 03:16:37PM +0100, Mark Rutland wrote:
> The icache_policy_str[] array contains compile-time constant data, and
> is never intentionally modified, so let's mark it as const.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
>  arch/arm64/kernel/cpuinfo.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 876055e37352..05933c065732 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -33,7 +33,7 @@
>  DEFINE_PER_CPU(struct cpuinfo_arm64, cpu_data);
>  static struct cpuinfo_arm64 boot_cpu_data;
>  
> -static char *icache_policy_str[] = {
> +static const char *icache_policy_str[] = {

Can this be const char *const ?

The strings will be in .rodata and can't be modified anyway, but I
presume we don't modify the array elements either...

>  	[0 ... ICACHE_POLICY_PIPT]	= "RESERVED/UNKNOWN",
>  	[ICACHE_POLICY_VIPT]		= "VIPT",
>  	[ICACHE_POLICY_PIPT]		= "PIPT",

[...]

Cheers
---Dave

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Re: [PATCH 2/3] arm64: constify aarch64_insn_encoding_class[]

[Dave Martin]

On Tue, Aug 13, 2019 at 03:16:38PM +0100, Mark Rutland wrote:
> The aarch64_insn_encoding_class[] array contains compile-time constant
> data, and is never intentionally modified, so let's mark it as const.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
>  arch/arm64/kernel/insn.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
> index 84b059ed04fc..d801a7094076 100644
> --- a/arch/arm64/kernel/insn.c
> +++ b/arch/arm64/kernel/insn.c
> @@ -26,7 +26,7 @@
>  #define AARCH64_INSN_N_BIT	BIT(22)
>  #define AARCH64_INSN_LSL_12	BIT(22)
>  
> -static int aarch64_insn_encoding_class[] = {
> +static const int aarch64_insn_encoding_class[] = {
>  	AARCH64_INSN_CLS_UNKNOWN,
>  	AARCH64_INSN_CLS_UNKNOWN,
>  	AARCH64_INSN_CLS_UNKNOWN,

This is an implementation detail of aarch64_get_insn_class(), so it
could be moved inside there, or rewritten as a switch.  It works as-is
though.

Either way,

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

Cheers
---Dave

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Re: [PATCH 3/3] arm64: constify sys64_hook instances

[Dave Martin]

On Tue, Aug 13, 2019 at 03:16:39PM +0100, Mark Rutland wrote:
> All instances of struct sys64_hook contain compile-time constant data,
> and are never inentionally modified, so let's make them all const.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
>  arch/arm64/kernel/traps.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 42c8422cdf4a..a5d7ce4297b0 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -511,7 +511,7 @@ struct sys64_hook {
>  	void (*handler)(unsigned int esr, struct pt_regs *regs);
>  };
>  
> -static struct sys64_hook sys64_hooks[] = {
> +static const struct sys64_hook sys64_hooks[] = {
>  	{
>  		.esr_mask = ESR_ELx_SYS64_ISS_EL0_CACHE_OP_MASK,
>  		.esr_val = ESR_ELx_SYS64_ISS_EL0_CACHE_OP_VAL,
> @@ -636,7 +636,7 @@ static void compat_cntfrq_read_handler(unsigned int esr, struct pt_regs *regs)
>  	arm64_compat_skip_faulting_instruction(regs, 4);
>  }
>  
> -static struct sys64_hook cp15_32_hooks[] = {
> +static const struct sys64_hook cp15_32_hooks[] = {
>  	{
>  		.esr_mask = ESR_ELx_CP15_32_ISS_SYS_MASK,
>  		.esr_val = ESR_ELx_CP15_32_ISS_SYS_CNTFRQ,
> @@ -656,7 +656,7 @@ static void compat_cntvct_read_handler(unsigned int esr, struct pt_regs *regs)
>  	arm64_compat_skip_faulting_instruction(regs, 4);
>  }
>  
> -static struct sys64_hook cp15_64_hooks[] = {
> +static const struct sys64_hook cp15_64_hooks[] = {
>  	{
>  		.esr_mask = ESR_ELx_CP15_64_ISS_SYS_MASK,
>  		.esr_val = ESR_ELx_CP15_64_ISS_SYS_CNTVCT,
> @@ -667,7 +667,7 @@ static struct sys64_hook cp15_64_hooks[] = {
>  
>  asmlinkage void __exception do_cp15instr(unsigned int esr, struct pt_regs *regs)
>  {
> -	struct sys64_hook *hook, *hook_base;
> +	const struct sys64_hook *hook, *hook_base;
>  
>  	if (!cp15_cond_valid(esr, regs)) {
>  		/*
> @@ -707,7 +707,7 @@ asmlinkage void __exception do_cp15instr(unsigned int esr, struct pt_regs *regs)
>  
>  asmlinkage void __exception do_sysinstr(unsigned int esr, struct pt_regs *regs)
>  {
> -	struct sys64_hook *hook;
> +	const struct sys64_hook *hook;
>  
>  	for (hook = sys64_hooks; hook->handler; hook++)
>  		if ((hook->esr_mask & esr) == hook->esr_val) {

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

Cheers
---Dave

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