Commit d1721250 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Thomas Gleixner
Browse files

x86/entry: Move SYSENTER's regs->sp and regs->flags fixups into C 



The SYSENTER asm (32-bit and compat) contains fixups for regs->sp and
regs->flags.  Move the fixups into C and fix some comments while at it.

This is a valid cleanup all by itself, and it also simplifies the
subsequent patch that will fix Xen PV SYSENTER.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/fe62bef67eda7fac75b8f3dbafccf571dc4ece6b.1593191971.git.luto@kernel.org
parent c9c26150

arch/x86/entry/common.c

+12 −0
Original line number Diff line number Diff line
@@ -522,6 +522,18 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs) 
		(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0;

#endif

}



/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */

__visible noinstr long do_SYSENTER_32(struct pt_regs *regs)

{

	/* SYSENTER loses RSP, but the vDSO saved it in RBP. */

	regs->sp = regs->bp;



	/* SYSENTER clobbers EFLAGS.IF.  Assume it was set in usermode. */

	regs->flags |= X86_EFLAGS_IF;



	return do_fast_syscall_32(regs);

}

#endif



SYSCALL_DEFINE0(ni_syscall)

arch/x86/entry/entry_32.S

+2 −3
Original line number Diff line number Diff line
@@ -933,9 +933,8 @@ SYM_FUNC_START(entry_SYSENTER_32) 


.Lsysenter_past_esp:

	pushl	$__USER_DS		/* pt_regs->ss */

	pushl	%ebp			/* pt_regs->sp (stashed in bp) */

	pushl	$0			/* pt_regs->sp (placeholder) */

	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 */
@@ -965,7 +964,7 @@ SYM_FUNC_START(entry_SYSENTER_32) 
.Lsysenter_flags_fixed:



	movl	%esp, %eax

	call	do_fast_syscall_32

	call	do_SYSENTER_32

	/* XEN PV guests always use IRET path */

	ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \

		    "jmp .Lsyscall_32_done", X86_FEATURE_XENPV

arch/x86/entry/entry_64_compat.S

+5 −6
Original line number Diff line number Diff line
@@ -68,16 +68,15 @@ SYM_CODE_START(entry_SYSENTER_compat) 


	/* Construct struct pt_regs on stack */

	pushq	$__USER32_DS		/* pt_regs->ss */

	pushq	%rbp			/* pt_regs->sp (stashed in bp) */

	pushq	$0			/* pt_regs->sp = 0 (placeholder) */



	/*

	 * Push flags.  This is nasty.  First, interrupts are currently

	 * off, but we need pt_regs->flags to have IF set.  Second, even

	 * if TF was set when SYSENTER started, it's clear by now.  We fix

	 * that later using TIF_SINGLESTEP.

	 * off, but we need pt_regs->flags to have IF set.  Second, if TS

	 * was set in usermode, it's still set, and we're singlestepping

	 * through this code.  do_SYSENTER_32() will fix up IF.

	 */

	pushfq				/* pt_regs->flags (except IF = 0) */

	orl	$X86_EFLAGS_IF, (%rsp)	/* Fix saved flags */

	pushq	$__USER32_CS		/* pt_regs->cs */

	pushq	$0			/* pt_regs->ip = 0 (placeholder) */

	pushq	%rax			/* pt_regs->orig_ax */
@@ -135,7 +134,7 @@ SYM_CODE_START(entry_SYSENTER_compat) 
.Lsysenter_flags_fixed:



	movq	%rsp, %rdi

	call	do_fast_syscall_32

	call	do_SYSENTER_32

	/* XEN PV guests always use IRET path */

	ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \

		    "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV

CRA Git | Maintained and supported by SUSTech CRA and CCSE