Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 pti fixes from Thomas Gleixner:
 "A set of updates for the x86/pti related code:

   - Preserve r8-r11 in int $0x80. r8-r11 need to be preserved, but the
     int$80 entry code removed that quite some time ago. Make it correct
     again.

   - A set of fixes for the Global Bit work which went into 4.17 and
     caused a bunch of interesting regressions:

      - Triggering a BUG in the page attribute code due to a missing
        check for early boot stage

      - Warnings in the page attribute code about holes in the kernel
        text mapping which are caused by the freeing of the init code.
        Handle such holes gracefully.

      - Reduce the amount of kernel memory which is set global to the
        actual text and do not incidentally overlap with data.

      - Disable the global bit when RANDSTRUCT is enabled as it
        partially defeats the hardening.

      - Make the page protection setup correct for vma->page_prot
        population again. The adjustment of the protections fell through
        the crack during the Global bit rework and triggers warnings on
        machines which do not support certain features, e.g. NX"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/entry/64/compat: Preserve r8-r11 in int $0x80
  x86/pti: Filter at vma->vm_page_prot population
  x86/pti: Disallow global kernel text with RANDSTRUCT
  x86/pti: Reduce amount of kernel text allowed to be Global
  x86/pti: Fix boot warning from Global-bit setting
  x86/pti: Fix boot problems from Global-bit setting

1 files changed, 21 insertions, 14 deletions

diff --git a/tools/testing/selftests/x86/test_syscall_vdso.c b/tools/testing/selftests/x86/test_syscall_vdso.c
index 40370354d4c1..c9c3281077bc 100644
--- a/tools/testing/selftests/x86/test_syscall_vdso.c
+++ b/tools/testing/selftests/x86/test_syscall_vdso.c
@@ -100,12 +100,19 @@ asm (
 	"	shl	$32, %r8\n"
 	"	orq	$0x7f7f7f7f, %r8\n"
 	"	movq	%r8, %r9\n"
-	"	movq	%r8, %r10\n"
-	"	movq	%r8, %r11\n"
-	"	movq	%r8, %r12\n"
-	"	movq	%r8, %r13\n"
-	"	movq	%r8, %r14\n"
-	"	movq	%r8, %r15\n"
+	"	incq	%r9\n"
+	"	movq	%r9, %r10\n"
+	"	incq	%r10\n"
+	"	movq	%r10, %r11\n"
+	"	incq	%r11\n"
+	"	movq	%r11, %r12\n"
+	"	incq	%r12\n"
+	"	movq	%r12, %r13\n"
+	"	incq	%r13\n"
+	"	movq	%r13, %r14\n"
+	"	incq	%r14\n"
+	"	movq	%r14, %r15\n"
+	"	incq	%r15\n"
 	"	ret\n"
 	"	.code32\n"
 	"	.popsection\n"
@@ -128,12 +135,13 @@ int check_regs64(void)
 	int err = 0;
 	int num = 8;
 	uint64_t *r64 = &regs64.r8;
+	uint64_t expected = 0x7f7f7f7f7f7f7f7fULL;
 
 	if (!kernel_is_64bit)
 		return 0;
 
 	do {
-		if (*r64 == 0x7f7f7f7f7f7f7f7fULL)
+		if (*r64 == expected++)
 			continue; /* register did not change */
 		if (syscall_addr != (long)&int80) {
 			/*
@@ -147,18 +155,17 @@ int check_regs64(void)
 				continue;
 			}
 		} else {
-			/* INT80 syscall entrypoint can be used by
+			/*
+			 * INT80 syscall entrypoint can be used by
 			 * 64-bit programs too, unlike SYSCALL/SYSENTER.
 			 * Therefore it must preserve R12+
 			 * (they are callee-saved registers in 64-bit C ABI).
 			 *
-			 * This was probably historically not intended,
-			 * but R8..11 are clobbered (cleared to 0).
-			 * IOW: they are the only registers which aren't
-			 * preserved across INT80 syscall.
+			 * Starting in Linux 4.17 (and any kernel that
+			 * backports the change), R8..11 are preserved.
+			 * Historically (and probably unintentionally), they
+			 * were clobbered or zeroed.
 			 */
-			if (*r64 == 0 && num <= 11)
-				continue;
 		}
 		printf("[FAIL]\tR%d has changed:%016llx\n", num, *r64);
 		err++;