From: Linus Torvalds <torva...@linux-foundation.org>

We have it in a register in the low-level asm, just pass it in as an
argument rather than have do_syscall_64() load it back in from the
ptregs pointer.

Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: Andi Kleen <a...@linux.intel.com>
Cc: x...@kernel.org
Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net>
---
 arch/x86/entry/common.c   | 12 ++++++------
 arch/x86/entry/entry_64.S |  3 ++-
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 74f6eee15179..a8b066dbbf48 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -266,14 +266,13 @@ __visible inline void syscall_return_slowpath(struct 
pt_regs *regs)
 }
 
 #ifdef CONFIG_X86_64
-__visible void do_syscall_64(struct pt_regs *regs)
+__visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
 {
-       struct thread_info *ti = current_thread_info();
-       unsigned long nr = regs->orig_ax;
+       struct thread_info *ti;
 
        enter_from_user_mode();
        local_irq_enable();
-
+       ti = current_thread_info();
        if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
                nr = syscall_trace_enter(regs);
 
@@ -282,8 +281,9 @@ __visible void do_syscall_64(struct pt_regs *regs)
         * table.  The only functional difference is the x32 bit in
         * regs->orig_ax, which changes the behavior of some syscalls.
         */
-       if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) {
-               nr = array_index_nospec(nr & __SYSCALL_MASK, NR_syscalls);
+       nr &= __SYSCALL_MASK;
+       if (likely(nr < NR_syscalls)) {
+               nr = array_index_nospec(nr, NR_syscalls);
                regs->ax = sys_call_table[nr](
                        regs->di, regs->si, regs->dx,
                        regs->r10, regs->r8, regs->r9);
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 936e19642eab..6cfe38665f3c 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -233,7 +233,8 @@ GLOBAL(entry_SYSCALL_64_after_hwframe)
        TRACE_IRQS_OFF
 
        /* IRQs are off. */
-       movq    %rsp, %rdi
+       movq    %rax, %rdi
+       movq    %rsp, %rsi
        call    do_syscall_64           /* returns with IRQs disabled */
 
        TRACE_IRQS_IRETQ                /* we're about to change IF */
-- 
2.16.3

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