Commit 555e2817 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/64: remove support for kernel-mode syscalls 



There is support for the kernel to execute the 'sc 0' instruction and
make a system call to itself. This is a relic that is unused in the
tree, therefore untested. It's also highly questionable for modules to
be doing this.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190827033010.28090-3-npiggin@gmail.com
parent facd04a9

arch/powerpc/kernel/entry_64.S

+6 −15
Original line number Diff line number Diff line
@@ -69,24 +69,20 @@ BEGIN_FTR_SECTION 
	bne	.Ltabort_syscall

END_FTR_SECTION_IFSET(CPU_FTR_TM)

#endif

	andi.	r10,r12,MSR_PR

	mr	r10,r1

	addi	r1,r1,-INT_FRAME_SIZE

	beq-	1f

	ld	r1,PACAKSAVE(r13)

1:	std	r10,0(r1)

	std	r10,0(r1)

	std	r11,_NIP(r1)

	std	r12,_MSR(r1)

	std	r0,GPR0(r1)

	std	r10,GPR1(r1)

	beq	2f			/* if from kernel mode */

#ifdef CONFIG_PPC_FSL_BOOK3E

START_BTB_FLUSH_SECTION

	BTB_FLUSH(r10)

END_BTB_FLUSH_SECTION

#endif

	ACCOUNT_CPU_USER_ENTRY(r13, r10, r11)

2:	std	r2,GPR2(r1)

	std	r2,GPR2(r1)

	std	r3,GPR3(r1)

	mfcr	r2

	std	r4,GPR4(r1)
@@ -122,14 +118,13 @@ END_BTB_FLUSH_SECTION 


#if defined(CONFIG_VIRT_CPU_ACCOUNTING_NATIVE) && defined(CONFIG_PPC_SPLPAR)

BEGIN_FW_FTR_SECTION

	beq	33f

	/* if from user, see if there are any DTL entries to process */

	/* see if there are any DTL entries to process */

	ld	r10,PACALPPACAPTR(r13)	/* get ptr to VPA */

	ld	r11,PACA_DTL_RIDX(r13)	/* get log read index */

	addi	r10,r10,LPPACA_DTLIDX

	LDX_BE	r10,0,r10		/* get log write index */

	cmpd	cr1,r11,r10

	beq+	cr1,33f

	cmpd	r11,r10

	beq+	33f

	bl	accumulate_stolen_time

	REST_GPR(0,r1)

	REST_4GPRS(3,r1)
@@ -203,6 +198,7 @@ system_call: /* label this so stack traces look sane */ 
	mtctr   r12

	bctrl			/* Call handler */



	/* syscall_exit can exit to kernel mode, via ret_from_kernel_thread */

.Lsyscall_exit:

	std	r3,RESULT(r1)
@@ -216,11 +212,6 @@ system_call: /* label this so stack traces look sane */ 
	ld	r12, PACA_THREAD_INFO(r13)



	ld	r8,_MSR(r1)

#ifdef CONFIG_PPC_BOOK3S

	/* No MSR:RI on BookE */

	andi.	r10,r8,MSR_RI

	beq-	.Lunrecov_restore

#endif



/*

 * This is a few instructions into the actual syscall exit path (which actually

arch/powerpc/kernel/exceptions-64s.S

+0 −2
Original line number Diff line number Diff line
@@ -1522,8 +1522,6 @@ EXC_COMMON(trap_0b_common, 0xb00, unknown_exception) 
 * system call / hypercall (0xc00, 0x4c00)

 *

 * The system call exception is invoked with "sc 0" and does not alter HV bit.

 * There is support for kernel code to invoke system calls but there are no

 * in-tree users.

 *

 * The hypercall is invoked with "sc 1" and sets HV=1.

 *

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