Re: [PATCH v4 3/7] powerpc/64: Sanitise common exit code for interrupts

[Nicholas Piggin]

On Tue Nov 29, 2022 at 2:43 PM AEST, Rohan McLure wrote:
> Interrupt code is shared between Book3E/S 64-bit systems for interrupt
> handlers. Ensure that exit code correctly restores non-volatile gprs on
> each system when CONFIG_INTERRUPT_SANITIZE_REGISTERS is enabled.
>
> Also introduce macros for clearing/restoring registers on interrupt
> entry for when this configuration option is either disabled or enabled.
>
> Signed-off-by: Rohan McLure 
> ---
> v4: New patch
> ---
>  arch/powerpc/kernel/interrupt_64.S | 6 ++
>  1 file changed, 6 insertions(+)
>
> diff --git a/arch/powerpc/kernel/interrupt_64.S 
> b/arch/powerpc/kernel/interrupt_64.S
> index 978a173eb339..1ef4fdef74fb 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -408,9 +408,11 @@ interrupt_return_\srr\()_user: /* make backtraces match 
> the _kernel variant */
>  _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
>   addir3,r1,STACK_FRAME_OVERHEAD
>   bl  interrupt_exit_user_prepare
> +#ifndef CONFIG_INTERRUPT_SANITIZE_REGISTERS
>   cmpdi   r3,0
>   bne-.Lrestore_nvgprs_\srr
>  .Lrestore_nvgprs_\srr\()_cont:
> +#endif

Looks pretty good. You might add a comment here to say nvgprs are always
restored, in the sanitize case. Not that it's hard to grep for.

Reviewed-by: Nicholas Piggin 

Thanks,
Nick

[PATCH v4 3/7] powerpc/64: Sanitise common exit code for interrupts

[Rohan McLure]

Interrupt code is shared between Book3E/S 64-bit systems for interrupt
handlers. Ensure that exit code correctly restores non-volatile gprs on
each system when CONFIG_INTERRUPT_SANITIZE_REGISTERS is enabled.

Also introduce macros for clearing/restoring registers on interrupt
entry for when this configuration option is either disabled or enabled.

Signed-off-by: Rohan McLure 
---
v4: New patch
---
 arch/powerpc/kernel/interrupt_64.S | 6 ++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/kernel/interrupt_64.S 
b/arch/powerpc/kernel/interrupt_64.S
index 978a173eb339..1ef4fdef74fb 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -408,9 +408,11 @@ interrupt_return_\srr\()_user: /* make backtraces match 
the _kernel variant */
 _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
addir3,r1,STACK_FRAME_OVERHEAD
bl  interrupt_exit_user_prepare
+#ifndef CONFIG_INTERRUPT_SANITIZE_REGISTERS
cmpdi   r3,0
bne-.Lrestore_nvgprs_\srr
 .Lrestore_nvgprs_\srr\()_cont:
+#endif
std r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
 #ifdef CONFIG_PPC_BOOK3S
 .Linterrupt_return_\srr\()_user_rst_start:
@@ -424,6 +426,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
stb r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
 
 .Lfast_user_interrupt_return_\srr\():
+   SANITIZE_RESTORE_NVGPRS()
 #ifdef CONFIG_PPC_BOOK3S
.ifc \srr,srr
lbz r4,PACASRR_VALID(r13)
@@ -493,9 +496,11 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
b   .   /* prevent speculative execution */
 .Linterrupt_return_\srr\()_user_rst_end:
 
+#ifndef CONFIG_INTERRUPT_SANITIZE_REGISTERS
 .Lrestore_nvgprs_\srr\():
REST_NVGPRS(r1)
b   .Lrestore_nvgprs_\srr\()_cont
+#endif
 
 #ifdef CONFIG_PPC_BOOK3S
 interrupt_return_\srr\()_user_restart:
@@ -576,6 +581,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_kernel)
stb r11,PACAIRQHAPPENED(r13) // clear the possible HARD_DIS
 
 .Lfast_kernel_interrupt_return_\srr\():
+   SANITIZE_RESTORE_NVGPRS()
cmpdi   cr1,r3,0
 #ifdef CONFIG_PPC_BOOK3S
.ifc \srr,srr
-- 
2.37.2