Commit 2b1dac4b authored by Rohan McLure's avatar Rohan McLure Committed by Michael Ellerman
Browse files

powerpc/64s: Use {ZEROIZE,SAVE,REST}_GPRS macros in sc, scv 0 handlers 



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.

Signed-off-by: default avatarRohan McLure <rmclure@linux.ibm.com>
Reviewed-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220921065605.1051927-5-rmclure@linux.ibm.com
parent 9d54a5ce

arch/powerpc/kernel/interrupt_64.S

+9 −34
Original line number Diff line number Diff line
@@ -61,12 +61,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name) 
	mfcr	r12

	li	r11,0

	/* Can we avoid saving r3-r8 in common case? */

	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)
@@ -139,17 +134,10 @@ 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



	/*
@@ -172,7 +160,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) 
	ld	r5,_XER(r1)



	REST_NVGPRS(r1)

	ld	r0,GPR0(r1)

	REST_GPR(0, r1)

	mtcr	r2

	mtctr	r3

	mtlr	r4
@@ -240,12 +228,7 @@ END_BTB_FLUSH_SECTION 
	mfcr	r12

	li	r11,0

	/* Can we avoid saving r3-r8 in common case? */

	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)
@@ -335,16 +318,8 @@ 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:
@@ -370,7 +345,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) 
	REST_NVGPRS(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: