Re: [PATCH v4 20/23] powerpc/syscall: Do not check unsupported scv vector on PPC32

[Christophe Leroy]

Le 26/01/2021 à 11:16, Nicholas Piggin a écrit :

Excerpts from Christophe Leroy's message of January 26, 2021 12:48 am:

Only PPC64 has scv. No need to check the 0x7ff0 trap on PPC32.

And ignore the scv parameter in syscall_exit_prepare (Save 14 cycles
346 => 332 cycles)

Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
  arch/powerpc/kernel/entry_32.S | 1 -
  arch/powerpc/kernel/syscall.c  | 7 +++++--
  2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 9922a04650f7..6ae9c7bcb06c 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -343,7 +343,6 @@ transfer_to_syscall:

ret_from_syscall:

        addi    r4,r1,STACK_FRAME_OVERHEAD
-       li      r5,0
        bl      syscall_exit_prepare
  #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
        /* If the process has its own DBCR0 value, load it up.  The internal
diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
index 476909b11051..30f8a397a522 100644
--- a/arch/powerpc/kernel/syscall.c
+++ b/arch/powerpc/kernel/syscall.c
@@ -86,7 +86,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
        local_irq_enable();

if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {

-               if (unlikely(regs->trap == 0x7ff0)) {
+               if (IS_ENABLED(CONFIG_PPC64) && unlikely(regs->trap == 0x7ff0)) 
{
                        /* Unsupported scv vector */
                        _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
                        return regs->gpr[3];
@@ -109,7 +109,7 @@ notrace long system_call_exception(long r3, long r4, long 
r5,
                r8 = regs->gpr[8];

} else if (unlikely(r0 >= NR_syscalls)) {

-               if (unlikely(regs->trap == 0x7ff0)) {
+               if (IS_ENABLED(CONFIG_PPC64) && unlikely(regs->trap == 0x7ff0)) 
{

Perhaps this could be hidden behind a function like trap_is_scv()?

trap_is_unsupported_scv() ?

Ok, I did that in v5

Thanks
Christophe