Clears user state in gprs to reduce the influence of user registers on speculation within kernel syscall handlers.
Remove conditional branches on result of `syscall_exit_prepare` to restore non-volatile gprs, as these registers are always cleared and hence always must be restored. Signed-off-by: Rohan McLure <rmcl...@linux.ibm.com> --- arch/powerpc/kernel/interrupt_64.S | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index b11c2bd84827..e601ed999798 100644 --- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S @@ -108,6 +108,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) * but this is the best we can do. */ + ZERO_GPRS(5, 12) + ZERO_NVGPRS() + /* Calling convention has r3 = orig r0, r4 = regs */ mr r3,r0 bl system_call_exception @@ -138,6 +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 @@ -180,7 +184,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) ld r4,_LINK(r1) ld r5,_XER(r1) - REST_NVGPRS(r1) ld r0,GPR0(r1) mtcr r2 mtctr r3 @@ -308,6 +311,9 @@ END_BTB_FLUSH_SECTION wrteei 1 #endif + ZERO_GPRS(5, 12) + ZERO_NVGPRS() + /* Calling convention has r3 = orig r0, r4 = regs */ mr r3,r0 bl system_call_exception @@ -350,6 +356,7 @@ 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 */ @@ -377,7 +384,6 @@ 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) @@ -445,7 +451,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user) bl interrupt_exit_user_prepare cmpdi r3,0 bne- .Lrestore_nvgprs_\srr -.Lrestore_nvgprs_\srr\()_cont: + .Lrestore_nvgprs_\srr\()_cont: std r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */ #ifdef CONFIG_PPC_BOOK3S .Linterrupt_return_\srr\()_user_rst_start: -- 2.34.1