Recording Wine no longer works, shows `.../loader/wine: failed to read ELF header`.

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
43/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
cpp, linux
Domain
operating-systems

Research direction

Start with the Wine change to loader/preloader.c linked in the report, then trace how rr uses FIXED_SCRATCH_PTR and librrpage.so during recording. Compare the suggested preload ranges with rr's current assumptions and reproduce the reported failed to read ELF header error. Done means recording works with the affected Wine change; the report notes replay also needs a workaround for #4124.

Written by the indexing model from the issue text.

Description

Since this Wine commit, specifically the changes to loader/preloader.c, it looks like Wine unmaps the first 8G,
therefore the scratch memory at FIXED_SCRATCH_PTR no longer works,
the librrpage.so gets removed, which seems to make the wld_read in loader/preloader.c to fail.

Just reverting those two lines in loader/preloader.c makes recording work again,
or following lines may be closer to what the current wine unmapping wants to achieve:

--- a/loader/preloader.c
+++ b/loader/preloader.c
@@ -117,7 +117,11 @@ static struct wine_preload_info preload_info[] =
     { (void *)0x7f000000, 0x00ff0000 },  /* top-down allocations + shared user data */
 #else
     { (void *)0x00010000, 0x00100000 },  /* DOS area */
-    { (void *)0x00110000, 0x1ffef0000 }, /* low 8G */
+    { (void *)0x00110000, 0x67ef0000 },  /* low memory area */
+    /*        0x68000000, 0x00200000        rr's FIXED_SCRATCH_PTR */
+    { (void *)0x68200000, 0x07df0000 },  /* */
+    /*        0x6fffd000, 0x00004000        rr's librrpage.so */
+    { (void *)0x70010000, 0x18fff0000 }, /* */
 #endif
     { 0, 0 },                            /* PE exe range set with WINEPRELOADRESERVE */
     { 0, 0 }                             /* end of list */

Unfortunately, I guess, this is the second issue with Wine besides #3972, that looks quite hard to fix?
Replaying currently needs some workaround for #4124.

I have not yet reported this in Wine's bugtracker.

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