x86/entry/64/compat: Migrate the body of the syscall entry to C

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/a2f0fce68feeba798a24339b5a7ec1ec2dd9eaf7.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 83ad95877570c1f3f469e39f9ca1e5f9dd9be1ea..53616ca0324440d6cba482c3855433b5a63b4ef9 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -582,7 +582,7 @@ retint_kernel:
  * At this label, code paths which return to kernel and to user,
  * which come from interrupts/exception and from syscalls, merge.
  */
-restore_regs_and_iret:
+GLOBAL(restore_regs_and_iret)
        RESTORE_EXTRA_REGS
 restore_c_regs_and_iret:
        RESTORE_C_REGS

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 2c2aac577b3ccc61af94f3b2c9a778b3b33befea..63ef9fa290028018b8698f017178a2c62fc0feb4 100644 (file)
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -202,14 +202,17 @@ END(entry_SYSCALL_compat)
 ENTRY(entry_INT80_compat)
        /*
         * Interrupts are off on entry.
-        * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
-        * it is too small to ever cause noticeable irq latency.
         */
        PARAVIRT_ADJUST_EXCEPTION_FRAME
        SWAPGS
-       ENABLE_INTERRUPTS(CLBR_NONE)
 
-       /* Zero-extending 32-bit regs, do not remove */
+       /*
+        * User tracing code (ptrace or signal handlers) might assume that
+        * the saved RAX contains a 32-bit number when we're invoking a 32-bit
+        * syscall.  Just in case the high bits are nonzero, zero-extend
+        * the syscall number.  (This could almost certainly be deleted
+        * with no ill effects.)
+        */
        movl    %eax, %eax
 
        /* Construct struct pt_regs on stack (iret frame is already on stack) */
@@ -232,42 +235,19 @@ ENTRY(entry_INT80_compat)
        pushq   %r15                    /* pt_regs->r15 */
        cld
 
-       orl     $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
-       testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
-       jnz     ia32_tracesys
-
-ia32_do_call:
-       /* 32-bit syscall -> 64-bit C ABI argument conversion */
-       movl    %edi, %r8d              /* arg5 */
-       movl    %ebp, %r9d              /* arg6 */
-       xchg    %ecx, %esi              /* rsi:arg2, rcx:arg4 */
-       movl    %ebx, %edi              /* arg1 */
-       movl    %edx, %edx              /* arg3 (zero extension) */
-       cmpq    $(IA32_NR_syscalls-1), %rax
-       ja      1f
-
-       call    *ia32_sys_call_table(, %rax, 8)
-       movq    %rax, RAX(%rsp)
-1:
-       RESTORE_EXTRA_REGS
-       jmp     int_ret_from_sys_call
-
-ia32_tracesys:
-       movq    %rsp, %rdi                      /* &pt_regs -> arg1 */
-       call    syscall_trace_enter
        /*
-        * Reload arg registers from stack in case ptrace changed them.
-        * Don't reload %eax because syscall_trace_enter() returned
-        * the %rax value we should see.  But do truncate it to 32 bits.
-        * If it's -1 to make us punt the syscall, then (u32)-1 is still
-        * an appropriately invalid value.
+        * User mode is traced as though IRQs are on, and the interrupt
+        * gate turned them off.
         */
-       movl    RCX(%rsp), %ecx
-       movl    RDX(%rsp), %edx
-       movl    RSI(%rsp), %esi
-       movl    RDI(%rsp), %edi
-       movl    %eax, %eax              /* zero extension */
-       jmp     ia32_do_call
+       TRACE_IRQS_OFF
+
+       movq    %rsp, %rdi
+       call    do_int80_syscall_32
+
+       /* Go back to user mode. */
+       TRACE_IRQS_ON
+       SWAPGS
+       jmp     restore_regs_and_iret
 END(entry_INT80_compat)
 
        ALIGN