[PATCH 1/2] linux-user: Implement finer grained madivse() syscall

[Helge Deller <deller@kernel.org>]

From: Helge Deller <deller@gmx.de>

Although most madvise() values are hints, some are important and are
checked by userspace, especially by security-relevant applications like
BoringSLL.  So, return -EINVAL for those functions which we don't emulate.

Signed-off-by: Helge Deller <deller@gmx.de>
Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3489
---
 linux-user/mmap.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index b4b7b3e5cc..50916c29a5 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -1282,7 +1282,7 @@ abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice)
     case TARGET_MADV_KEEPONFORK:    /* parisc */
         advice = MADV_KEEPONFORK;
         break;
-    /* we do not care about the other MADV_xxx values yet */
+    /* all other MADV_xxx values are the same across architectures */
     }
 
     /*
@@ -1307,6 +1307,19 @@ abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice)
      */
     mmap_lock();
     switch (advice) {
+    case MADV_NORMAL:
+    case MADV_RANDOM:
+    case MADV_SEQUENTIAL:
+    case MADV_WILLNEED:
+    case MADV_DOFORK:
+    case MADV_FREE:
+    case MADV_COLD:
+    case MADV_PAGEOUT:
+        ret = 0; /* OK */
+        break;
+    case MADV_REMOVE:
+        ret = -EOPNOTSUPP;
+        break;
     case MADV_DONTDUMP:
         page_set_flags(start, start + len - 1, PAGE_DONTDUMP, 0);
         break;
@@ -1324,6 +1337,23 @@ abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice)
                 page_reset_target_data(start, start + len - 1);
             }
         }
+        break;
+    case MADV_DONTFORK:
+    case MADV_MERGEABLE:
+    case MADV_UNMERGEABLE:
+    case MADV_HWPOISON:
+    case MADV_HUGEPAGE:
+    case MADV_NOHUGEPAGE:
+    case MADV_COLLAPSE:
+    case MADV_POPULATE_READ:
+    case MADV_POPULATE_WRITE:
+    case -1:    /* BoringSSL uses -1 to check if the environment is broken */
+        ret = -EINVAL;
+        break;
+    default:
+        qemu_log_mask(LOG_UNIMP, "Unhandled madvise(%d) call.\n", advice);
+        ret = -EINVAL; /* not yet known advise */
+        break;
     }
     mmap_unlock();
 
-- 
2.54.0