[PATCH 0/1] MR10925: ntdll: Avoid MAP_PRIVATE when recording with rr-debugger.

[Bernhard Übelacker (＠bernhardu)]

Followup of 07160a23fa2, 9e006e94c9c, 8fd49c4d8e9, d9d012965de.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=58332

rr-debugger-Bug: https://github.com/rr-debugger/rr/issues/3972

Since above commits Wine uses for some mappings at Linux MAP_PRIVATE.

Unfortunately this is not fully supported by rr, at least with the flags for the session mapping.
And if I understood it correctly, adding support in rr would come with a general performance penalty.

Probably we can use the fallback path of non-linux systems for rr, too?

This patch should not change behaviour, except for session mapping when running below rr, which is detected by the environment `RUNNING_UNDER_RR`.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10925

[PATCH 1/1] ntdll: Avoid MAP_PRIVATE when recording with rr-debugger.

[Bernhard Übelacker]

From: Bernhard Übelacker <[e-mail]>

Followup of 07160a23fa2, 9e006e94c9c, 8fd49c4d8e9, d9d012965de.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=58332
rr-debugger-Bug: https://github.com/rr-debugger/rr/issues/3972
---
 dlls/ntdll/unix/virtual.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/dlls/ntdll/unix/virtual.c b/dlls/ntdll/unix/virtual.c
index a2ea5244b9f..62f143d6c4f 100644
--- a/dlls/ntdll/unix/virtual.c
+++ b/dlls/ntdll/unix/virtual.c
@@ -2364,7 +2364,16 @@ static NTSTATUS map_file_into_view( struct file_view *view, int fd, size_t start
         /* changes to the file are not guaranteed to be visible in read-only MAP_PRIVATE mappings,
          * but they are on Linux so we take advantage of it */
 #ifdef __linux__
-        flags |= MAP_PRIVATE;
+        static int use_map_private = -1;
+        if (use_map_private == -1)
+            use_map_private = getenv("RUNNING_UNDER_RR") ? FALSE : TRUE;
+        if (vprot & SEC_FILE || use_map_private)
+            flags |= MAP_PRIVATE;
+        else
+        {
+            flags |= MAP_SHARED;
+            prot &= ~PROT_WRITE;
+        }
 #else
         flags |= MAP_SHARED;
         prot &= ~PROT_WRITE;
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/10925

[Alexandre Julliard (＠julliard)]

I don't think we want the mapping behavior to change when running inside a debugger, that can affect the application.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10925#note_142548