Merging upstream version 6.7.7.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 9 insertions, 75 deletions

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 43606de22..de6469dff 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -18,6 +18,7 @@
  * - SYM_FUNC_START/END:Define functions in the symbol table.
  * - idtentry:		Define exception entry points.
  */
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/segment.h>
 #include <asm/cache.h>
@@ -34,7 +35,6 @@
 #include <asm/asm.h>
 #include <asm/smap.h>
 #include <asm/pgtable_types.h>
-#include <asm/export.h>
 #include <asm/frame.h>
 #include <asm/trapnr.h>
 #include <asm/nospec-branch.h>
@@ -126,70 +126,8 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe, SYM_L_GLOBAL)
 	 * In the Xen PV case we must use iret anyway.
 	 */
 
-	ALTERNATIVE "", "jmp	swapgs_restore_regs_and_return_to_usermode", \
-		X86_FEATURE_XENPV
-
-	movq	RCX(%rsp), %rcx
-	movq	RIP(%rsp), %r11
-
-	cmpq	%rcx, %r11	/* SYSRET requires RCX == RIP */
-	jne	swapgs_restore_regs_and_return_to_usermode
-
-	/*
-	 * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP
-	 * in kernel space.  This essentially lets the user take over
-	 * the kernel, since userspace controls RSP.
-	 *
-	 * If width of "canonical tail" ever becomes variable, this will need
-	 * to be updated to remain correct on both old and new CPUs.
-	 *
-	 * Change top bits to match most significant bit (47th or 56th bit
-	 * depending on paging mode) in the address.
-	 */
-#ifdef CONFIG_X86_5LEVEL
-	ALTERNATIVE "shl $(64 - 48), %rcx; sar $(64 - 48), %rcx", \
-		"shl $(64 - 57), %rcx; sar $(64 - 57), %rcx", X86_FEATURE_LA57
-#else
-	shl	$(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
-	sar	$(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
-#endif
-
-	/* If this changed %rcx, it was not canonical */
-	cmpq	%rcx, %r11
-	jne	swapgs_restore_regs_and_return_to_usermode
-
-	cmpq	$__USER_CS, CS(%rsp)		/* CS must match SYSRET */
-	jne	swapgs_restore_regs_and_return_to_usermode
-
-	movq	R11(%rsp), %r11
-	cmpq	%r11, EFLAGS(%rsp)		/* R11 == RFLAGS */
-	jne	swapgs_restore_regs_and_return_to_usermode
-
-	/*
-	 * SYSCALL clears RF when it saves RFLAGS in R11 and SYSRET cannot
-	 * restore RF properly. If the slowpath sets it for whatever reason, we
-	 * need to restore it correctly.
-	 *
-	 * SYSRET can restore TF, but unlike IRET, restoring TF results in a
-	 * trap from userspace immediately after SYSRET.  This would cause an
-	 * infinite loop whenever #DB happens with register state that satisfies
-	 * the opportunistic SYSRET conditions.  For example, single-stepping
-	 * this user code:
-	 *
-	 *           movq	$stuck_here, %rcx
-	 *           pushfq
-	 *           popq %r11
-	 *   stuck_here:
-	 *
-	 * would never get past 'stuck_here'.
-	 */
-	testq	$(X86_EFLAGS_RF|X86_EFLAGS_TF), %r11
-	jnz	swapgs_restore_regs_and_return_to_usermode
-
-	/* nothing to check for RSP */
-
-	cmpq	$__USER_DS, SS(%rsp)		/* SS must match SYSRET */
-	jne	swapgs_restore_regs_and_return_to_usermode
+	ALTERNATIVE "testb %al, %al; jz swapgs_restore_regs_and_return_to_usermode", \
+		"jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV
 
 	/*
 	 * We win! This label is here just for ease of understanding
@@ -1163,8 +1101,8 @@ SYM_CODE_START(asm_exc_nmi)
 	 * anyway.
 	 *
 	 * To handle this case we do the following:
-	 *  Check the a special location on the stack that contains
-	 *  a variable that is set when NMIs are executing.
+	 *  Check a special location on the stack that contains a
+	 *  variable that is set when NMIs are executing.
 	 *  The interrupted task's stack is also checked to see if it
 	 *  is an NMI stack.
 	 *  If the variable is not set and the stack is not the NMI
@@ -1237,7 +1175,6 @@ SYM_CODE_START(asm_exc_nmi)
 	 */
 
 	movq	%rsp, %rdi
-	movq	$-1, %rsi
 	call	exc_nmi
 
 	/*
@@ -1295,8 +1232,8 @@ SYM_CODE_START(asm_exc_nmi)
 	 * end_repeat_nmi, then we are a nested NMI.  We must not
 	 * modify the "iret" frame because it's being written by
 	 * the outer NMI.  That's okay; the outer NMI handler is
-	 * about to about to call exc_nmi() anyway, so we can just
-	 * resume the outer NMI.
+	 * about to call exc_nmi() anyway, so we can just resume
+	 * the outer NMI.
 	 */
 
 	movq	$repeat_nmi, %rdx
@@ -1451,7 +1388,6 @@ end_repeat_nmi:
 	UNWIND_HINT_REGS
 
 	movq	%rsp, %rdi
-	movq	$-1, %rsi
 	call	exc_nmi
 
 	/* Always restore stashed SPEC_CTRL value (see paranoid_entry) */
@@ -1511,18 +1447,16 @@ nmi_restore:
 	iretq
 SYM_CODE_END(asm_exc_nmi)
 
-#ifndef CONFIG_IA32_EMULATION
 /*
  * This handles SYSCALL from 32-bit code.  There is no way to program
  * MSRs to fully disable 32-bit SYSCALL.
  */
-SYM_CODE_START(ignore_sysret)
+SYM_CODE_START(entry_SYSCALL32_ignore)
 	UNWIND_HINT_END_OF_STACK
 	ENDBR
 	mov	$-ENOSYS, %eax
 	sysretl
-SYM_CODE_END(ignore_sysret)
-#endif
+SYM_CODE_END(entry_SYSCALL32_ignore)
 
 .pushsection .text, "ax"
 	__FUNC_ALIGN