The following commit has been merged into the x86/urgent branch of tip: Commit-ID: d1721250f3ffed9afba3e1fb729947cec64c5a8a Gitweb: https://git.kernel.org/tip/d1721250f3ffed9afba3e1fb729947cec64c5a8a Author: Andy Lutomirski <[email protected]> AuthorDate: Fri, 26 Jun 2020 10:21:12 -07:00 Committer: Thomas Gleixner <[email protected]> CommitterDate: Wed, 01 Jul 2020 10:00:25 +02:00
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: Andy Lutomirski <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Link: https://lkml.kernel.org/r/fe62bef67eda7fac75b8f3dbafccf571dc4ece6b.1593191971.git.l...@kernel.org --- arch/x86/entry/common.c | 12 ++++++++++++ arch/x86/entry/entry_32.S | 5 ++--- arch/x86/entry/entry_64_compat.S | 11 +++++------ 3 files changed, 19 insertions(+), 9 deletions(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index ed8ccc8..f392a8b 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -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) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 024d7d2..2d0bd5d 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -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 diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 0f974ae..7b9d815 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -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
