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Message-Id: <a2f0fce68feeba798a24339b5a7ec1ec2dd9eaf7.1444091585.git.luto@kernel.org> Date: Mon, 5 Oct 2015 17:48:09 -0700 From: Andy Lutomirski <luto@...nel.org> To: x86@...nel.org, linux-kernel@...r.kernel.org Cc: Brian Gerst <brgerst@...il.com>, Denys Vlasenko <dvlasenk@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org> Subject: [PATCH v2 21/36] x86/entry/64/compat: Migrate the body of the syscall entry to C Signed-off-by: Andy Lutomirski <luto@...nel.org> --- arch/x86/entry/entry_64.S | 2 +- arch/x86/entry/entry_64_compat.S | 56 +++++++++++++--------------------------- 2 files changed, 19 insertions(+), 39 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 4f8c25eb3437..f9067d610e50 100644 --- 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 2c2aac577b3c..63ef9fa29002 100644 --- 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 -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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