From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Rohan McLure" <rmclure@linux.ibm.com>, <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH 20/23] powerpc/64s: Clear/restore caller gprs in syscall interrupt/return
Date: Tue, 20 Sep 2022 12:07:23 +1000 [thread overview]
Message-ID: <CN0V19K4UC47.3NKT93DAEOX2I@bobo> (raw)
In-Reply-To: <20220916053300.786330-21-rmclure@linux.ibm.com>
On Fri Sep 16, 2022 at 3:32 PM AEST, Rohan McLure wrote:
> Clear user state in gprs (assign to zero) to reduce the influence of user
> registers on speculation within kernel syscall handlers. Clears occur
> at the very beginning of the sc and scv 0 interrupt handlers, with
> restores occurring following the execution of the syscall handler.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Update summary
> V2 -> V3: Remove erroneous summary paragraph on syscall_exit_prepare
> V3 -> V4: Use ZEROIZE instead of NULLIFY. Clear r0 also.
> V4 -> V5: Move to end of patch series.
> ---
Oh I would say change the title more like the interrupt patches to avoid
mentioning the restore/return because that's implicit.
e.g., "Clear user GPRs in syscall interrupt entry"
Could we have the one config option that does both this and the interrupt
zeroing?
Thanks,
Nick
> arch/powerpc/kernel/interrupt_64.S | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
> index 16a1b44088e7..40147558e1a6 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -70,7 +70,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
> ld r2,PACATOC(r13)
> mfcr r12
> li r11,0
> - /* Can we avoid saving r3-r8 in common case? */
> + /* Save syscall parameters in r3-r8 */
> SAVE_GPRS(3, 8, r1)
> /* Zero r9-r12, this should only be required when restoring all GPRs */
> std r11,GPR9(r1)
> @@ -110,6 +110,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
> * Zero user registers to prevent influencing speculative execution
> * state of kernel code.
> */
> + ZEROIZE_GPR(0)
> ZEROIZE_GPRS(5, 12)
> ZEROIZE_NVGPRS()
> bl system_call_exception
> @@ -140,6 +141,7 @@ BEGIN_FTR_SECTION
> HMT_MEDIUM_LOW
> END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>
> + REST_NVGPRS(r1)
> cmpdi r3,0
> bne .Lsyscall_vectored_\name\()_restore_regs
>
> @@ -243,7 +245,7 @@ END_BTB_FLUSH_SECTION
> ld r2,PACATOC(r13)
> mfcr r12
> li r11,0
> - /* Can we avoid saving r3-r8 in common case? */
> + /* Save syscall parameters in r3-r8 */
> SAVE_GPRS(3, 8, r1)
> /* Zero r9-r12, this should only be required when restoring all GPRs */
> std r11,GPR9(r1)
> @@ -295,6 +297,7 @@ END_BTB_FLUSH_SECTION
> * Zero user registers to prevent influencing speculative execution
> * state of kernel code.
> */
> + ZEROIZE_GPR(0)
> ZEROIZE_GPRS(5, 12)
> ZEROIZE_NVGPRS()
> bl system_call_exception
> @@ -337,6 +340,7 @@ BEGIN_FTR_SECTION
> stdcx. r0,0,r1 /* to clear the reservation */
> END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
>
> + REST_NVGPRS(r1)
> cmpdi r3,0
> bne .Lsyscall_restore_regs
> /* Zero volatile regs that may contain sensitive kernel data */
> @@ -364,7 +368,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
> .Lsyscall_restore_regs:
> ld r3,_CTR(r1)
> ld r4,_XER(r1)
> - REST_NVGPRS(r1)
> mtctr r3
> mtspr SPRN_XER,r4
> REST_GPR(0, r1)
> --
> 2.34.1
next prev parent reply other threads:[~2022-09-20 2:08 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-16 5:32 [PATCH 00/23] powerpc: Syscall wrapper and register clearing Rohan McLure
2022-09-16 5:32 ` [PATCH 01/23] powerpc: Remove asmlinkage from syscall handler definitions Rohan McLure
2022-09-16 5:32 ` [PATCH 02/23] powerpc: Save caller r3 prior to system_call_exception Rohan McLure
2022-09-16 5:32 ` [PATCH 03/23] powerpc: Add ZEROIZE_GPRS macros for register clears Rohan McLure
2022-09-16 5:32 ` [PATCH 04/23] powerpc/64s: Use {ZEROIZE,SAVE,REST}_GPRS macros in sc, scv 0 handlers Rohan McLure
2022-09-16 5:32 ` [PATCH 05/23] powerpc/32: Clarify interrupt restores with REST_GPR macro in entry_32.S Rohan McLure
2022-09-20 0:51 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 06/23] powerpc/64e: Clarify register saves and clears with {SAVE,ZEROIZE}_GPRS Rohan McLure
2022-09-20 0:55 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 07/23] powerpc/64s: Fix comment on interrupt handler prologue Rohan McLure
2022-09-20 0:55 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 08/23] powerpc: Fix fallocate and fadvise64_64 compat parameter combination Rohan McLure
2022-09-16 6:54 ` Arnd Bergmann
2022-09-20 1:01 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 09/23] asm-generic: compat: Support BE for long long args in 32-bit ABIs Rohan McLure
2022-09-20 1:06 ` Nicholas Piggin
2022-09-20 7:09 ` Arnd Bergmann
2022-09-16 5:32 ` [PATCH 10/23] powerpc: Use generic fallocate compatibility syscall Rohan McLure
2022-09-16 6:56 ` Arnd Bergmann
2022-09-16 5:32 ` [PATCH 11/23] powerpc/32: Remove powerpc select specialisation Rohan McLure
2022-09-16 5:32 ` [PATCH 12/23] powerpc: Remove direct call to personality syscall handler Rohan McLure
2022-09-16 5:32 ` [PATCH 13/23] powerpc: Remove direct call to mmap2 syscall handlers Rohan McLure
2022-09-16 5:32 ` [PATCH 14/23] powerpc: Provide do_ppc64_personality helper Rohan McLure
2022-09-16 5:32 ` [PATCH 15/23] powerpc: Adopt SYSCALL_DEFINE for arch-specific syscall handlers Rohan McLure
2022-09-16 5:48 ` Rohan McLure
2022-09-20 1:24 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 16/23] powerpc: Include all arch-specific syscall prototypes Rohan McLure
2022-09-20 1:27 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 17/23] powerpc: Enable compile-time check for syscall handlers Rohan McLure
2022-09-20 1:30 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 18/23] powerpc: Use common syscall handler type Rohan McLure
2022-09-20 1:39 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 19/23] powerpc: Provide syscall wrapper Rohan McLure
2022-09-20 1:59 ` Nicholas Piggin
2022-09-21 3:44 ` Rohan McLure
2022-09-16 5:32 ` [PATCH 20/23] powerpc/64s: Clear/restore caller gprs in syscall interrupt/return Rohan McLure
2022-09-20 2:03 ` Nicholas Piggin
2022-09-20 4:54 ` Rohan McLure
2022-09-21 5:33 ` Rohan McLure
2022-09-20 2:07 ` Nicholas Piggin [this message]
2022-09-16 5:32 ` [PATCH 21/23] powerpc/64: Add INTERRUPT_SANITIZE_REGISTERS Kconfig Rohan McLure
2022-09-20 2:10 ` Nicholas Piggin
2022-09-16 5:32 ` [PATCH 22/23] powerpc/64s: Clear gprs on interrupt routine entry in Book3S Rohan McLure
2022-09-20 2:27 ` Nicholas Piggin
2022-09-16 5:33 ` [PATCH 23/23] powerpc/64e: Clear gprs on interrupt routine entry on Book3E Rohan McLure
2022-09-16 5:58 ` [PATCH 00/23] powerpc: Syscall wrapper and register clearing Rohan McLure
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