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

Pull x86 fixes from Ingo Molnar:
 "The biggest diffstat comes from self-test updates, plus there's entry
  code fixes, 5-level paging related fixes, console debug output fixes,
  and misc fixes"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mm: Clean up the printk()s in show_fault_oops()
  x86/mm: Drop unneeded __always_inline for p4d page table helpers
  x86/efi: Fix efi_call_phys_epilog() with CONFIG_X86_5LEVEL=y
  selftests/x86/sigreturn: Do minor cleanups
  selftests/x86/sigreturn/64: Fix spurious failures on AMD CPUs
  x86/entry/64/compat: Fix "x86/entry/64/compat: Preserve r8-r11 in int $0x80"
  x86/mm: Don't free P4D table when it is folded at runtime
  x86/entry/32: Add explicit 'l' instruction suffix
  x86/mm: Get rid of KERN_CONT in show_fault_oops()

1 files changed, 36 insertions, 23 deletions

diff --git a/tools/testing/selftests/x86/sigreturn.c b/tools/testing/selftests/x86/sigreturn.c
index 246145b84a12..4d9dc3f2fd70 100644
--- a/tools/testing/selftests/x86/sigreturn.c
+++ b/tools/testing/selftests/x86/sigreturn.c
@@ -610,21 +610,41 @@ static int test_valid_sigreturn(int cs_bits, bool use_16bit_ss, int force_ss)
 	 */
 	for (int i = 0; i < NGREG; i++) {
 		greg_t req = requested_regs[i], res = resulting_regs[i];
+
 		if (i == REG_TRAPNO || i == REG_IP)
 			continue;	/* don't care */
-		if (i == REG_SP) {
-			printf("\tSP: %llx -> %llx\n", (unsigned long long)req,
-			       (unsigned long long)res);
 
+		if (i == REG_SP) {
 			/*
-			 * In many circumstances, the high 32 bits of rsp
-			 * are zeroed.  For example, we could be a real
-			 * 32-bit program, or we could hit any of a number
-			 * of poorly-documented IRET or segmented ESP
-			 * oddities.  If this happens, it's okay.
+			 * If we were using a 16-bit stack segment, then
+			 * the kernel is a bit stuck: IRET only restores
+			 * the low 16 bits of ESP/RSP if SS is 16-bit.
+			 * The kernel uses a hack to restore bits 31:16,
+			 * but that hack doesn't help with bits 63:32.
+			 * On Intel CPUs, bits 63:32 end up zeroed, and, on
+			 * AMD CPUs, they leak the high bits of the kernel
+			 * espfix64 stack pointer.  There's very little that
+			 * the kernel can do about it.
+			 *
+			 * Similarly, if we are returning to a 32-bit context,
+			 * the CPU will often lose the high 32 bits of RSP.
 			 */
-			if (res == (req & 0xFFFFFFFF))
-				continue;  /* OK; not expected to work */
+
+			if (res == req)
+				continue;
+
+			if (cs_bits != 64 && ((res ^ req) & 0xFFFFFFFF) == 0) {
+				printf("[NOTE]\tSP: %llx -> %llx\n",
+				       (unsigned long long)req,
+				       (unsigned long long)res);
+				continue;
+			}
+
+			printf("[FAIL]\tSP mismatch: requested 0x%llx; got 0x%llx\n",
+			       (unsigned long long)requested_regs[i],
+			       (unsigned long long)resulting_regs[i]);
+			nerrs++;
+			continue;
 		}
 
 		bool ignore_reg = false;
@@ -654,25 +674,18 @@ static int test_valid_sigreturn(int cs_bits, bool use_16bit_ss, int force_ss)
 #endif
 
 		/* Sanity check on the kernel */
-		if (i == REG_CX && requested_regs[i] != resulting_regs[i]) {
+		if (i == REG_CX && req != res) {
 			printf("[FAIL]\tCX (saved SP) mismatch: requested 0x%llx; got 0x%llx\n",
-			       (unsigned long long)requested_regs[i],
-			       (unsigned long long)resulting_regs[i]);
+			       (unsigned long long)req,
+			       (unsigned long long)res);
 			nerrs++;
 			continue;
 		}
 
-		if (requested_regs[i] != resulting_regs[i] && !ignore_reg) {
-			/*
-			 * SP is particularly interesting here.  The
-			 * usual cause of failures is that we hit the
-			 * nasty IRET case of returning to a 16-bit SS,
-			 * in which case bits 16:31 of the *kernel*
-			 * stack pointer persist in ESP.
-			 */
+		if (req != res && !ignore_reg) {
 			printf("[FAIL]\tReg %d mismatch: requested 0x%llx; got 0x%llx\n",
-			       i, (unsigned long long)requested_regs[i],
-			       (unsigned long long)resulting_regs[i]);
+			       i, (unsigned long long)req,
+			       (unsigned long long)res);
 			nerrs++;
 		}
 	}