x86/entry/32: Re-implement SYSENTER using the new C path (5f310f73) · Commits · e / devices / android_kernel_teracube_2e

arch/x86/entry/common.c

+15 −2

Original line number	Diff line number	Diff line
		@@ -363,7 +363,7 @@ __visible void do_int80_syscall_32(struct pt_regs *regs)
		syscall_return_slowpath(regs);
		}

		/* Returns 0 to return using IRET or 1 to return using SYSRETL. */
		/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
		__visible long do_fast_syscall_32(struct pt_regs *regs)
		{
		/*
		@@ -417,7 +417,20 @@ __visible long do_fast_syscall_32(struct pt_regs *regs)
		regs->ip == landing_pad &&
		(regs->flags & (X86_EFLAGS_RF \| X86_EFLAGS_TF)) == 0;
		#else
		return 0;
		/*
		* Opportunistic SYSEXIT: if possible, try to return using SYSEXIT.
		*
		* Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
		* because the ECX fixup above will ensure that this is essentially
		* never the case.
		*
		* We don't allow syscalls at all from VM86 mode, but we still
		* need to check VM, because we might be returning from sys_vm86.
		*/
		return static_cpu_has(X86_FEATURE_SEP) &&
		regs->cs == __USER_CS && regs->ss == __USER_DS &&
		regs->ip == landing_pad &&
		(regs->flags & (X86_EFLAGS_RF \| X86_EFLAGS_TF \| X86_EFLAGS_VM)) == 0;
		#endif
		}
		#endif

arch/x86/entry/entry_32.S

+34 −98

Original line number	Diff line number	Diff line
		@@ -287,76 +287,47 @@ need_resched:
		END(resume_kernel)
		#endif

		/*
		* SYSENTER_RETURN points to after the SYSENTER instruction
		* in the vsyscall page. See vsyscall-sysentry.S, which defines
		* the symbol.
		*/

		# SYSENTER call handler stub
		ENTRY(entry_SYSENTER_32)
		movl TSS_sysenter_sp0(%esp), %esp
		sysenter_past_esp:
		/*
		* Interrupts are disabled here, but we can't trace it until
		* enough kernel state to call TRACE_IRQS_OFF can be called - but
		* we immediately enable interrupts at that point anyway.
		*/
		pushl $__USER_DS
		pushl %ebp
		pushfl
		orl $X86_EFLAGS_IF, (%esp)
		pushl $__USER_CS
		/*
		* Push current_thread_info()->sysenter_return to the stack.
		* A tiny bit of offset fixup is necessary: TI_sysenter_return
		* is relative to thread_info, which is at the bottom of the
		* kernel stack page. 4*4 means the 4 words pushed above;
		* TOP_OF_KERNEL_STACK_PADDING takes us to the top of the stack;
		* and THREAD_SIZE takes us to the bottom.
		*/
		pushl ((TI_sysenter_return) - THREAD_SIZE + TOP_OF_KERNEL_STACK_PADDING + 4*4)(%esp)

		pushl %eax
		SAVE_ALL
		ENABLE_INTERRUPTS(CLBR_NONE)
		pushl $__USER_DS /* pt_regs->ss */
		pushl %ecx /* pt_regs->cx */
		pushfl /* pt_regs->flags (except IF = 0) */
		orl $X86_EFLAGS_IF, (%esp) /* Fix IF */
		pushl $__USER_CS /* pt_regs->cs */
		pushl $0 /* pt_regs->ip = 0 (placeholder) */
		pushl %eax /* pt_regs->orig_ax */
		SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */

		/*
		* Load the potential sixth argument from user stack.
		* Careful about security.
		* User mode is traced as though IRQs are on, and SYSENTER
		* turned them off.
		*/
		cmpl $__PAGE_OFFSET-3, %ebp
		jae syscall_fault
		ASM_STAC
		1: movl (%ebp), %ebp
		ASM_CLAC
		movl %ebp, PT_EBP(%esp)
		_ASM_EXTABLE(1b, syscall_fault)

		GET_THREAD_INFO(%ebp)

		testl $_TIF_WORK_SYSCALL_ENTRY, TI_flags(%ebp)
		jnz syscall_trace_entry
		sysenter_do_call:
		cmpl $(NR_syscalls), %eax
		jae sysenter_badsys
		call *sys_call_table(, %eax, 4)
		sysenter_after_call:
		movl %eax, PT_EAX(%esp)
		LOCKDEP_SYS_EXIT
		DISABLE_INTERRUPTS(CLBR_ANY)
		TRACE_IRQS_OFF
		movl TI_flags(%ebp), %ecx
		testl $_TIF_ALLWORK_MASK, %ecx
		jnz syscall_exit_work_irqs_off
		sysenter_exit:
		/* if something modifies registers it must also disable sysexit */
		movl PT_EIP(%esp), %edx
		movl PT_OLDESP(%esp), %ecx
		xorl %ebp, %ebp
		TRACE_IRQS_ON

		movl %esp, %eax
		call do_fast_syscall_32
		testl %eax, %eax
		jz .Lsyscall_32_done

		/* Opportunistic SYSEXIT */
		TRACE_IRQS_ON /* User mode traces as IRQs on. */
		movl PT_EIP(%esp), %edx /* pt_regs->ip */
		movl PT_OLDESP(%esp), %ecx /* pt_regs->sp */
		popl %ebx /* pt_regs->bx */
		addl $24, %esp / skip pt_regs->cx and pt_regs->dx */
		popl %esi /* pt_regs->si */
		popl %edi /* pt_regs->di */
		popl %ebp /* pt_regs->bp */
		popl %eax /* pt_regs->ax */
		1: mov PT_FS(%esp), %fs
		PTGS_TO_GS

		/*
		* Return back to the vDSO, which will pop ecx and edx.
		* Don't bother with DS and ES (they already contain __USER_DS).
		*/
		ENABLE_INTERRUPTS_SYSEXIT

		.pushsection .fixup, "ax"
		@@ -371,7 +342,7 @@ ENDPROC(entry_SYSENTER_32)
		ENTRY(entry_INT80_32)
		ASM_CLAC
		pushl %eax /* pt_regs->orig_ax */
		SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest, load -ENOSYS into ax */
		SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */

		/*
		* User mode is traced as though IRQs are on, and the interrupt gate
		@@ -381,6 +352,7 @@ ENTRY(entry_INT80_32)

		movl %esp, %eax
		call do_int80_syscall_32
		.Lsyscall_32_done:

		restore_all:
		TRACE_IRQS_IRET
		@@ -457,42 +429,6 @@ ldt_ss:
		#endif
		ENDPROC(entry_INT80_32)

		# perform syscall exit tracing
		ALIGN
		syscall_trace_entry:
		movl $-ENOSYS, PT_EAX(%esp)
		movl %esp, %eax
		call syscall_trace_enter
		/* What it returned is what we'll actually use. */
		cmpl $(NR_syscalls), %eax
		jnae syscall_call
		jmp syscall_exit
		END(syscall_trace_entry)

		# perform syscall exit tracing
		ALIGN
		syscall_exit_work_irqs_off:
		TRACE_IRQS_ON
		ENABLE_INTERRUPTS(CLBR_ANY)

		syscall_exit_work:
		movl %esp, %eax
		call syscall_return_slowpath
		jmp restore_all
		END(syscall_exit_work)

		syscall_fault:
		ASM_CLAC
		GET_THREAD_INFO(%ebp)
		movl $-EFAULT, PT_EAX(%esp)
		jmp resume_userspace
		END(syscall_fault)

		sysenter_badsys:
		movl $-ENOSYS, %eax
		jmp sysenter_after_call
		END(sysenter_badsys)

		.macro FIXUP_ESPFIX_STACK
		/*
		* Switch back for ESPFIX stack to the normal zerobased stack

arch/x86/entry/vdso/vdso32/system_call.S

+2 −0

Original line number	Diff line number	Diff line
		@@ -34,6 +34,8 @@ __kernel_vsyscall:
		/* If SYSENTER (Intel) or SYSCALL32 (AMD) is available, use it. */
		ALTERNATIVE_2 "", "sysenter", X86_FEATURE_SYSENTER32, \
		"syscall", X86_FEATURE_SYSCALL32
		#else
		ALTERNATIVE "", "sysenter", X86_FEATURE_SEP
		#endif

		/* Enter using int $0x80 */