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powerpc: Change system_call_exception calling convention

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Change system_call_exception arguments to pass a pointer to a stack
frame container caller state, as well as the original r0, which
determines the number of the syscall. This has been observed to yield
improved performance to passing them by registers, circumventing the
need to allocate a stack frame.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Retain clearing of high bits of args for compat tasks]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220921065605.1051927-21-rmclure@linux.ibm.com
This commit is contained in:
Rohan McLure 2022-09-21 16:56:00 +10:00 committed by Michael Ellerman
parent 8640de0dee
commit f8971c627b
4 changed files with 23 additions and 24 deletions
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3
arch/powerpc/include/asm/interrupt.h
View file

@ -665,8 +665,7 @@ static inline void interrupt_cond_local_irq_enable(struct pt_regs *regs)
local_irq_enable();
}
long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
unsigned long r0, struct pt_regs *regs);
long system_call_exception(struct pt_regs *regs, unsigned long r0);
notrace unsigned long syscall_exit_prepare(unsigned long r3, struct pt_regs *regs, long scv);
notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs);
notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs);

6
arch/powerpc/kernel/entry_32.S
View file

@ -122,9 +122,9 @@ transfer_to_syscall:
SAVE_NVGPRS(r1)
kuep_lock
/* Calling convention has r9 = orig r0, r10 = regs */
addi r10,r1,STACK_FRAME_OVERHEAD
mr r9,r0
/* Calling convention has r3 = regs, r4 = orig r0 */
addi r3,r1,STACK_FRAME_OVERHEAD
mr r4,r0
bl system_call_exception
ret_from_syscall:

20
arch/powerpc/kernel/interrupt_64.S
View file

@ -60,7 +60,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
ld r2,PACATOC(r13)
mfcr r12
li r11,0
/* Can we avoid saving r3-r8 in common case? */
/* Save syscall parameters in r3-r8 */
SAVE_GPRS(3, 8, r1)
/* Zero r9-r12, this should only be required when restoring all GPRs */
std r11,GPR9(r1)
@ -77,9 +77,11 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
std r11,_TRAP(r1)
std r12,_CCR(r1)
std r3,ORIG_GPR3(r1)
addi r10,r1,STACK_FRAME_OVERHEAD
/* Calling convention has r3 = regs, r4 = orig r0 */
addi r3,r1,STACK_FRAME_OVERHEAD
mr r4,r0
ld r11,exception_marker@toc(r2)
std r11,-16(r10) /* "regshere" marker */
std r11,-16(r3) /* "regshere" marker */
BEGIN_FTR_SECTION
HMT_MEDIUM
@ -94,8 +96,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
* but this is the best we can do.
*/
/* Calling convention has r9 = orig r0, r10 = regs */
mr r9,r0
bl system_call_exception
.Lsyscall_vectored_\name\()_exit:
@ -227,7 +227,7 @@ END_BTB_FLUSH_SECTION
ld r2,PACATOC(r13)
mfcr r12
li r11,0
/* Can we avoid saving r3-r8 in common case? */
/* Save syscall parameters in r3-r8 */
SAVE_GPRS(3, 8, r1)
/* Zero r9-r12, this should only be required when restoring all GPRs */
std r11,GPR9(r1)
@ -250,9 +250,11 @@ END_BTB_FLUSH_SECTION
std r11,_TRAP(r1)
std r12,_CCR(r1)
std r3,ORIG_GPR3(r1)
addi r10,r1,STACK_FRAME_OVERHEAD
/* Calling convention has r3 = regs, r4 = orig r0 */
addi r3,r1,STACK_FRAME_OVERHEAD
mr r4,r0
ld r11,exception_marker@toc(r2)
std r11,-16(r10) /* "regshere" marker */
std r11,-16(r3) /* "regshere" marker */
#ifdef CONFIG_PPC_BOOK3S
li r11,1
@ -273,8 +275,6 @@ END_BTB_FLUSH_SECTION
wrteei 1
#endif
/* Calling convention has r9 = orig r0, r10 = regs */
mr r9,r0
bl system_call_exception
.Lsyscall_exit:

18
arch/powerpc/kernel/syscall.c
View file

@ -13,10 +13,9 @@
/* Has to run notrace because it is entered not completely "reconciled" */
notrace long system_call_exception(long r3, long r4, long r5,
long r6, long r7, long r8,
unsigned long r0, struct pt_regs *regs)
notrace long system_call_exception(struct pt_regs *regs, unsigned long r0)
{
unsigned long r3, r4, r5, r6, r7, r8;
long ret;
syscall_fn f;
@ -136,12 +135,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
r0 = do_syscall_trace_enter(regs);
if (unlikely(r0 >= NR_syscalls))
return regs->gpr[3];
r3 = regs->gpr[3];
r4 = regs->gpr[4];
r5 = regs->gpr[5];
r6 = regs->gpr[6];
r7 = regs->gpr[7];
r8 = regs->gpr[8];
} else if (unlikely(r0 >= NR_syscalls)) {
if (unlikely(trap_is_unsupported_scv(regs))) {
@ -152,6 +145,13 @@ notrace long system_call_exception(long r3, long r4, long r5,
return -ENOSYS;
}
r3 = regs->gpr[3];
r4 = regs->gpr[4];
r5 = regs->gpr[5];
r6 = regs->gpr[6];
r7 = regs->gpr[7];
r8 = regs->gpr[8];
/* May be faster to do array_index_nospec? */
barrier_nospec();