Merge tag 'v5.9-rc4' into patchwork

Linux 5.9-rc4

* tag 'v5.9-rc4': (1001 commits)
  Linux 5.9-rc4
  io_uring: fix linked deferred ->files cancellation
  io_uring: fix cancel of deferred reqs with ->files
  include/linux/log2.h: add missing () around n in roundup_pow_of_two()
  mm/khugepaged.c: fix khugepaged's request size in collapse_file
  mm/hugetlb: fix a race between hugetlb sysctl handlers
  mm/hugetlb: try preferred node first when alloc gigantic page from cma
  mm/migrate: preserve soft dirty in remove_migration_pte()
  mm/migrate: remove unnecessary is_zone_device_page() check
  mm/rmap: fixup copying of soft dirty and uffd ptes
  mm/migrate: fixup setting UFFD_WP flag
  mm: madvise: fix vma user-after-free
  checkpatch: fix the usage of capture group ( ... )
  fork: adjust sysctl_max_threads definition to match prototype
  ipc: adjust proc_ipc_sem_dointvec definition to match prototype
  mm: track page table modifications in __apply_to_page_range()
  MAINTAINERS: IA64: mark Status as Odd Fixes only
  MAINTAINERS: add LLVM maintainers
  MAINTAINERS: update Cavium/Marvell entries
  mm: slub: fix conversion of freelist_corrupted()
  ...

1 files changed, 20 insertions, 2 deletions

diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
index c41f24b517f4..65c141ebfbbd 100644
--- a/tools/testing/selftests/x86/test_vsyscall.c
+++ b/tools/testing/selftests/x86/test_vsyscall.c
@@ -462,6 +462,17 @@ static int test_vsys_x(void)
 	return 0;
 }
 
+/*
+ * Debuggers expect ptrace() to be able to peek at the vsyscall page.
+ * Use process_vm_readv() as a proxy for ptrace() to test this.  We
+ * want it to work in the vsyscall=emulate case and to fail in the
+ * vsyscall=xonly case.
+ *
+ * It's worth noting that this ABI is a bit nutty.  write(2) can't
+ * read from the vsyscall page on any kernel version or mode.  The
+ * fact that ptrace() ever worked was a nice courtesy of old kernels,
+ * but the code to support it is fairly gross.
+ */
 static int test_process_vm_readv(void)
 {
 #ifdef __x86_64__
@@ -477,8 +488,12 @@ static int test_process_vm_readv(void)
 	remote.iov_len = 4096;
 	ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
 	if (ret != 4096) {
-		printf("[OK]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", ret, errno);
-		return 0;
+		/*
+		 * We expect process_vm_readv() to work if and only if the
+		 * vsyscall page is readable.
+		 */
+		printf("[%s]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", vsyscall_map_r ? "FAIL" : "OK", ret, errno);
+		return vsyscall_map_r ? 1 : 0;
 	}
 
 	if (vsyscall_map_r) {
@@ -488,6 +503,9 @@ static int test_process_vm_readv(void)
 			printf("[FAIL]\tIt worked but returned incorrect data\n");
 			return 1;
 		}
+	} else {
+		printf("[FAIL]\tprocess_rm_readv() succeeded, but it should have failed in this configuration\n");
+		return 1;
 	}
 #endif