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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: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190827033010.28090-3-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2019-08-27 13:30:07 +10:00 committed by Michael Ellerman
parent facd04a904
commit 555e28179d
2 changed files with 6 additions and 17 deletions
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21
arch/powerpc/kernel/entry_64.S
View File

@ -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

2
arch/powerpc/kernel/exceptions-64s.S
View File

@ -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.
*