Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-5.1-pull-request' into staging

linux-user 20200728

Fix "pgb_reserved_va: Assertion `guest_base != 0' failed." error
Fix rt_sigtimedwait() errno
Fix getcwd() errno

# gpg: Signature made Tue 28 Jul 2020 13:34:11 BST
# gpg:                using RSA key CD2F75DDC8E3A4DC2E4F5173F30C38BD3F2FBE3C
# gpg:                issuer "laurent@vivier.eu"
# gpg: Good signature from "Laurent Vivier <lvivier@redhat.com>" [full]
# gpg:                 aka "Laurent Vivier <laurent@vivier.eu>" [full]
# gpg:                 aka "Laurent Vivier (Red Hat) <lvivier@redhat.com>" [full]
# Primary key fingerprint: CD2F 75DD C8E3 A4DC 2E4F  5173 F30C 38BD 3F2F BE3C

* remotes/vivier2/tags/linux-user-for-5.1-pull-request:
  linux-user: Use getcwd syscall directly
  linux-user: Fix syscall rt_sigtimedwait() implementation
  linux-user: Ensure mmap_min_addr is non-zero

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 14 insertions, 2 deletions

diff --git a/linux-user/main.c b/linux-user/main.c
index 3597e99bb1..75c9785157 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -758,15 +758,27 @@ int main(int argc, char **argv, char **envp)
 
         if ((fp = fopen("/proc/sys/vm/mmap_min_addr", "r")) != NULL) {
             unsigned long tmp;
-            if (fscanf(fp, "%lu", &tmp) == 1) {
+            if (fscanf(fp, "%lu", &tmp) == 1 && tmp != 0) {
                 mmap_min_addr = tmp;
-                qemu_log_mask(CPU_LOG_PAGE, "host mmap_min_addr=0x%lx\n", mmap_min_addr);
+                qemu_log_mask(CPU_LOG_PAGE, "host mmap_min_addr=0x%lx\n",
+                              mmap_min_addr);
             }
             fclose(fp);
         }
     }
 
     /*
+     * We prefer to not make NULL pointers accessible to QEMU.
+     * If we're in a chroot with no /proc, fall back to 1 page.
+     */
+    if (mmap_min_addr == 0) {
+        mmap_min_addr = qemu_host_page_size;
+        qemu_log_mask(CPU_LOG_PAGE,
+                      "host mmap_min_addr=0x%lx (fallback)\n",
+                      mmap_min_addr);
+    }
+
+    /*
      * Prepare copy of argv vector for target.
      */
     target_argc = argc - optind;