[PATCH v2] riscv: add icache flush for nommu sigreturn trampoline

[PATCH v2] riscv: add icache flush for nommu sigreturn trampoline

[Mathis Salmen]

In a NOMMU kernel, sigreturn trampolines are generated on the user
stack by setup_rt_frame. Currently, these trampolines are not instruction
fenced, thus their visibility to ifetch is not guaranteed.

This patch adds a flush_icache_range in setup_rt_frame to fix this
problem.

Signed-off-by: Mathis Salmen <mathis.salmen@matsal.de>
---
V1 -> V2: Added local variable for readability.

 arch/riscv/kernel/signal.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index bfb2afa41..dee66c929 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -19,6 +19,7 @@
 #include <asm/signal32.h>
 #include <asm/switch_to.h>
 #include <asm/csr.h>
+#include <asm/cacheflush.h>
 
 extern u32 __user_rt_sigreturn[2];
 
@@ -181,6 +182,7 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 {
 	struct rt_sigframe __user *frame;
 	long err = 0;
+	unsigned long __maybe_unused addr;
 
 	frame = get_sigframe(ksig, regs, sizeof(*frame));
 	if (!access_ok(frame, sizeof(*frame)))
@@ -209,7 +211,12 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 	if (copy_to_user(&frame->sigreturn_code, __user_rt_sigreturn,
 			 sizeof(frame->sigreturn_code)))
 		return -EFAULT;
-	regs->ra = (unsigned long)&frame->sigreturn_code;
+
+	addr = (unsigned long)&frame->sigreturn_code;
+	/* Make sure the two instructions are pushed to icache. */
+	flush_icache_range(addr, addr + sizeof(frame->sigreturn_code));
+
+	regs->ra = addr;
 #endif /* CONFIG_MMU */
 
 	/*
-- 
2.40.0


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v2] riscv: add icache flush for nommu sigreturn trampoline

[Conor Dooley]

[-- Attachment #1.1: Type: text/plain, Size: 2095 bytes --]

Hey Mathis,

On Thu, Apr 06, 2023 at 12:11:31PM +0200, Mathis Salmen wrote:
> In a NOMMU kernel, sigreturn trampolines are generated on the user
> stack by setup_rt_frame. Currently, these trampolines are not instruction
> fenced, thus their visibility to ifetch is not guaranteed.
> 
> This patch adds a flush_icache_range in setup_rt_frame to fix this
> problem.
> 

I assume that this is then
Fixes: 6bd33e1ece52 ("riscv: add nommu support")
yeah?

Cheers,
Conor.

> Signed-off-by: Mathis Salmen <mathis.salmen@matsal.de>
> ---
> V1 -> V2: Added local variable for readability.
> 
>  arch/riscv/kernel/signal.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
> index bfb2afa41..dee66c929 100644
> --- a/arch/riscv/kernel/signal.c
> +++ b/arch/riscv/kernel/signal.c
> @@ -19,6 +19,7 @@
>  #include <asm/signal32.h>
>  #include <asm/switch_to.h>
>  #include <asm/csr.h>
> +#include <asm/cacheflush.h>
>  
>  extern u32 __user_rt_sigreturn[2];
>  
> @@ -181,6 +182,7 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
>  {
>  	struct rt_sigframe __user *frame;
>  	long err = 0;
> +	unsigned long __maybe_unused addr;
>  
>  	frame = get_sigframe(ksig, regs, sizeof(*frame));
>  	if (!access_ok(frame, sizeof(*frame)))
> @@ -209,7 +211,12 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
>  	if (copy_to_user(&frame->sigreturn_code, __user_rt_sigreturn,
>  			 sizeof(frame->sigreturn_code)))
>  		return -EFAULT;
> -	regs->ra = (unsigned long)&frame->sigreturn_code;
> +
> +	addr = (unsigned long)&frame->sigreturn_code;
> +	/* Make sure the two instructions are pushed to icache. */
> +	flush_icache_range(addr, addr + sizeof(frame->sigreturn_code));
> +
> +	regs->ra = addr;
>  #endif /* CONFIG_MMU */
>  
>  	/*
> -- 
> 2.40.0
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

[-- Attachment #2: Type: text/plain, Size: 161 bytes --]

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v2] riscv: add icache flush for nommu sigreturn trampoline

[Palmer Dabbelt]

On Thu, 06 Apr 2023 12:11:31 +0200, Mathis Salmen wrote:
> In a NOMMU kernel, sigreturn trampolines are generated on the user
> stack by setup_rt_frame. Currently, these trampolines are not instruction
> fenced, thus their visibility to ifetch is not guaranteed.
> 
> This patch adds a flush_icache_range in setup_rt_frame to fix this
> problem.
> 
> [...]

Applied, thanks!

[1/1] riscv: add icache flush for nommu sigreturn trampoline
      https://git.kernel.org/palmer/c/8d736482749f

Best regards,
-- 
Palmer Dabbelt <palmer@rivosinc.com>


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v2] riscv: add icache flush for nommu sigreturn trampoline

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Thu,  6 Apr 2023 12:11:31 +0200 you wrote:
> In a NOMMU kernel, sigreturn trampolines are generated on the user
> stack by setup_rt_frame. Currently, these trampolines are not instruction
> fenced, thus their visibility to ifetch is not guaranteed.
> 
> This patch adds a flush_icache_range in setup_rt_frame to fix this
> problem.
> 
> [...]

Here is the summary with links:
  - [v2] riscv: add icache flush for nommu sigreturn trampoline
    https://git.kernel.org/riscv/c/8d736482749f

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html



_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv