1. Patchew
  2. linux
  3. [PATCH v12 00/28] riscv control-flow integrity for usermode
  4. View patch

[PATCH v12 23/28] riscv: kernel command line option to opt out of user cfi

Deepak Gupta posted 28 patches 2 weeks, 6 days ago
[PATCH v12 23/28] riscv: kernel command line option to opt out of user cfi
Posted by Deepak Gupta 2 weeks, 6 days ago 
This commit adds a kernel command line option using which user cfi can be
disabled.

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
---
 arch/riscv/kernel/usercfi.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c
index d31d89618763..813162ce4f15 100644
--- a/arch/riscv/kernel/usercfi.c
+++ b/arch/riscv/kernel/usercfi.c
@@ -17,6 +17,8 @@
 #include <asm/csr.h>
 #include <asm/usercfi.h>
 
+bool disable_riscv_usercfi;
+
 #define SHSTK_ENTRY_SIZE sizeof(void *)
 
 bool is_shstk_enabled(struct task_struct *task)
@@ -396,6 +398,9 @@ int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status)
 	unsigned long size = 0, addr = 0;
 	bool enable_shstk = false;
 
+	if (disable_riscv_usercfi)
+		return 0;
+
 	if (!cpu_supports_shadow_stack())
 		return -EINVAL;
 
@@ -475,6 +480,9 @@ int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status)
 {
 	bool enable_indir_lp = false;
 
+	if (disable_riscv_usercfi)
+		return 0;
+
 	if (!cpu_supports_indirect_br_lp_instr())
 		return -EINVAL;
 
@@ -507,3 +515,16 @@ int arch_lock_indir_br_lp_status(struct task_struct *task,
 
 	return 0;
 }
+
+static int __init setup_global_riscv_enable(char *str)
+{
+	if (strcmp(str, "true") == 0)
+		disable_riscv_usercfi = true;
+
+	pr_info("Setting riscv usercfi to be %s\n",
+		(disable_riscv_usercfi ? "disabled" : "enabled"));
+
+	return 1;
+}
+
+__setup("disable_riscv_usercfi=", setup_global_riscv_enable);

-- 
2.34.1
Re: [PATCH v12 23/28] riscv: kernel command line option to opt out of user cfi
Posted by Radim Krčmář 2 weeks ago 
2025-03-14T14:39:42-07:00, Deepak Gupta <debug@rivosinc.com>:
> This commit adds a kernel command line option using which user cfi can be
> disabled.
>
> Signed-off-by: Deepak Gupta <debug@rivosinc.com>
> ---
>  arch/riscv/kernel/usercfi.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c
> index d31d89618763..813162ce4f15 100644
> --- a/arch/riscv/kernel/usercfi.c
> +++ b/arch/riscv/kernel/usercfi.c
> @@ -17,6 +17,8 @@
>  #include <asm/csr.h>
>  #include <asm/usercfi.h>
>  
> +bool disable_riscv_usercfi;
> +
>  #define SHSTK_ENTRY_SIZE sizeof(void *)
>  
>  bool is_shstk_enabled(struct task_struct *task)
> @@ -396,6 +398,9 @@ int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status)
>  	unsigned long size = 0, addr = 0;
>  	bool enable_shstk = false;
>  
> +	if (disable_riscv_usercfi)
> +		return 0;
> +
>  	if (!cpu_supports_shadow_stack())
>  		return -EINVAL;
>  
> @@ -475,6 +480,9 @@ int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status)
>  {
>  	bool enable_indir_lp = false;
>  
> +	if (disable_riscv_usercfi)
> +		return 0;
> +
>  	if (!cpu_supports_indirect_br_lp_instr())
>  		return -EINVAL;
>  
> @@ -507,3 +515,16 @@ int arch_lock_indir_br_lp_status(struct task_struct *task,
>  
>  	return 0;
>  }
> +
> +static int __init setup_global_riscv_enable(char *str)
> +{
> +	if (strcmp(str, "true") == 0)
> +		disable_riscv_usercfi = true;
> +
> +	pr_info("Setting riscv usercfi to be %s\n",
> +		(disable_riscv_usercfi ? "disabled" : "enabled"));
> +
> +	return 1;
> +}
> +
> +__setup("disable_riscv_usercfi=", setup_global_riscv_enable);

I'd prefer two command line options instead.

In any case, I think we still document params in kernel-parameters.txt.
Re: [PATCH v12 23/28] riscv: kernel command line option to opt out of user cfi
Posted by Deepak Gupta 1 week, 6 days ago 
On Thu, Mar 20, 2025 at 2:35 PM Radim Krčmář <rkrcmar@ventanamicro.com> wrote:
>
> 2025-03-14T14:39:42-07:00, Deepak Gupta <debug@rivosinc.com>:
> > This commit adds a kernel command line option using which user cfi can be
> > disabled.
> >
> > Signed-off-by: Deepak Gupta <debug@rivosinc.com>
> > ---
> >  arch/riscv/kernel/usercfi.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> >
> > diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c
> > index d31d89618763..813162ce4f15 100644
> > --- a/arch/riscv/kernel/usercfi.c
> > +++ b/arch/riscv/kernel/usercfi.c
> > @@ -17,6 +17,8 @@
> >  #include <asm/csr.h>
> >  #include <asm/usercfi.h>
> >
> > +bool disable_riscv_usercfi;
> > +
> >  #define SHSTK_ENTRY_SIZE sizeof(void *)
> >
> >  bool is_shstk_enabled(struct task_struct *task)
> > @@ -396,6 +398,9 @@ int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status)
> >       unsigned long size = 0, addr = 0;
> >       bool enable_shstk = false;
> >
> > +     if (disable_riscv_usercfi)
> > +             return 0;
> > +
> >       if (!cpu_supports_shadow_stack())
> >               return -EINVAL;
> >
> > @@ -475,6 +480,9 @@ int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status)
> >  {
> >       bool enable_indir_lp = false;
> >
> > +     if (disable_riscv_usercfi)
> > +             return 0;
> > +
> >       if (!cpu_supports_indirect_br_lp_instr())
> >               return -EINVAL;
> >
> > @@ -507,3 +515,16 @@ int arch_lock_indir_br_lp_status(struct task_struct *task,
> >
> >       return 0;
> >  }
> > +
> > +static int __init setup_global_riscv_enable(char *str)
> > +{
> > +     if (strcmp(str, "true") == 0)
> > +             disable_riscv_usercfi = true;
> > +
> > +     pr_info("Setting riscv usercfi to be %s\n",
> > +             (disable_riscv_usercfi ? "disabled" : "enabled"));
> > +
> > +     return 1;
> > +}
> > +
> > +__setup("disable_riscv_usercfi=", setup_global_riscv_enable);
>
> I'd prefer two command line options instead.

One for zicfilp and one for zicfiss ?
>
> In any case, I think we still document params in kernel-parameters.txt.

Noted, will do that.
Re: [PATCH v12 23/28] riscv: kernel command line option to opt out of user cfi
Posted by Radim Krčmář 1 week, 6 days ago 
2025-03-20T15:31:09-07:00, Deepak Gupta <debug@rivosinc.com>:
> On Thu, Mar 20, 2025 at 2:35 PM Radim Krčmář <rkrcmar@ventanamicro.com> wrote:
>> 2025-03-14T14:39:42-07:00, Deepak Gupta <debug@rivosinc.com>:
>> > +__setup("disable_riscv_usercfi=", setup_global_riscv_enable);
>>
>> I'd prefer two command line options instead.
>
> One for zicfilp and one for zicfiss ?

Yes.  I don't want to suggest the naming, because I would have used
"nousercfi" without an argument for the current one.

Patchew 2.1-devel-b67e4c2

© 2016 - 2025 Red Hat, Inc.