Re: [PATCH v4 15/20] powerpc/64s: Use {ZEROIZE,SAVE,REST}_GPRS macros in sc, scv 0 handlers
From: "Nicholas Piggin" <npiggin@gmail.com>
Date: 2022-09-12 11:50:03
On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
Use the convenience macros for saving/clearing/restoring gprs in keeping with syscall calling conventions. The plural variants of these macros can store a range of registers for concision. This works well when the user gpr value we are hoping to save is still live. In the syscall interrupt handlers, user register state is sometimes juggled between registers. Hold-off from issuing the SAVE_GPR macro for applicable neighbouring lines to highlight the delicate register save logic.
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
quoted hunk ↗ jump to hunk
Signed-off-by: Rohan McLure <redacted> --- V1 -> V2: Update summary V2 -> V3: Update summary regarding exclusions for the SAVE_GPR marco. Acknowledge new name for ZEROIZE_GPR{,S} macros. --- arch/powerpc/kernel/interrupt_64.S | 43 ++++++---------------------- 1 file changed, 9 insertions(+), 34 deletions(-)diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index a8065209dd8c..ad302ad93433 100644 --- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S@@ -71,12 +71,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name) mfcr r12 li r11,0 /* Save syscall parameters in r3-r8 */ - std r3,GPR3(r1) - std r4,GPR4(r1) - std r5,GPR5(r1) - std r6,GPR6(r1) - std r7,GPR7(r1) - std r8,GPR8(r1) + SAVE_GPRS(3, 8, r1) /* Zero r9-r12, this should only be required when restoring all GPRs */ std r11,GPR9(r1) std r11,GPR10(r1)@@ -157,17 +152,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) /* Could zero these as per ABI, but we may consider a stricter ABI * which preserves these if libc implementations can benefit, so * restore them for now until further measurement is done. */ - ld r0,GPR0(r1) - ld r4,GPR4(r1) - ld r5,GPR5(r1) - ld r6,GPR6(r1) - ld r7,GPR7(r1) - ld r8,GPR8(r1) + REST_GPR(0, r1) + REST_GPRS(4, 8, r1) /* Zero volatile regs that may contain sensitive kernel data */ - li r9,0 - li r10,0 - li r11,0 - li r12,0 + ZEROIZE_GPRS(9, 12) mtspr SPRN_XER,r0 /*@@ -189,7 +177,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) ld r4,_LINK(r1) ld r5,_XER(r1) - ld r0,GPR0(r1) + REST_GPR(0, r1) mtcr r2 mtctr r3 mtlr r4@@ -257,12 +245,7 @@ END_BTB_FLUSH_SECTION mfcr r12 li r11,0 /* Save syscall parameters in r3-r8 */ - std r3,GPR3(r1) - std r4,GPR4(r1) - std r5,GPR5(r1) - std r6,GPR6(r1) - std r7,GPR7(r1) - std r8,GPR8(r1) + SAVE_GPRS(3, 8, r1) /* Zero r9-r12, this should only be required when restoring all GPRs */ std r11,GPR9(r1) std r11,GPR10(r1)@@ -360,16 +343,8 @@ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) cmpdi r3,0 bne .Lsyscall_restore_regs /* Zero volatile regs that may contain sensitive kernel data */ - li r0,0 - li r4,0 - li r5,0 - li r6,0 - li r7,0 - li r8,0 - li r9,0 - li r10,0 - li r11,0 - li r12,0 + ZEROIZE_GPR(0) + ZEROIZE_GPRS(4, 12) mtctr r0 mtspr SPRN_XER,r0 .Lsyscall_restore_regs_cont:@@ -394,7 +369,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) ld r4,_XER(r1) mtctr r3 mtspr SPRN_XER,r4 - ld r0,GPR0(r1) + REST_GPR(0, r1) REST_GPRS(4, 12, r1) b .Lsyscall_restore_regs_cont .Lsyscall_rst_end:-- 2.34.1