Bug 386427

Summary: Valgrind unsupported clone on Android
Product: [Developer tools] valgrind Reporter: Tamara Vlahovic <tamara.vlahovic>
Component: generalAssignee: Julian Seward <jseward>
Status: REPORTED ---    
Severity: normal CC: mips32r2, njn, philippe.waroquiers, yituohe
Priority: NOR    
Version First Reported In: unspecified   
Target Milestone: ---   
Platform: Android   
OS: Linux   
Latest Commit: Version Fixed In:
Sentry Crash Report:
Attachments: Clone thread without CLONE_FILES and CLONE_FS flags set
fd_clone_test

Description Tamara Vlahovic 2017-11-01 13:41:16 UTC 
When program crashes from one of following signals: SIGILL, SIGABRT, SIGBUS, SIGFPE, SIGSEGV,SIGSTKFLT, SIGPIPE, on Android, debuggerd handler is called to handle it. Inside that handler clone is called with following flags:
 CLONE_THREAD, CLONE_SIGHAND, CLONE_VM, CLONE_CHILD_SETTID, CLONE_CHILD_CLEARTID.

When such program is run under Valgrind, Valgrind will report that such clone isn't supported, as Valgrind supports only NPTL clone, vfork and fork. To check for a clone kind Valgrind checks for  VKI_CLONE_VM, VKI_CLONE_FS, CLONE_FILES, CLONE_VFORK flags. This allows for clone with set CLONE_VM, CLONE_FS, CLONE_FILES, and without set CLONE_THREAD, to pass as a clone which creates new thread, which isn't the case.

On the other hand there is no problem in allowing program to clone a thread without CLONE_FS flag set.
As for the missing CLONE_FILES, problem only occurs when Valgrind is run with --track-fds=yes option. Patch in next comment should fix this.
Comment 1 Tamara Vlahovic 2017-11-01 13:43:30 UTC 
Created attachment 108666 [details]
Clone thread without CLONE_FILES and CLONE_FS flags set

This patch adds support for cloning a thread without set CLONE_FS and CLONE_FILES, and changing fds trackinng system to allow for Valgrind to run programs which such clone calls with --track-fds=yes option.   
It was tested on x86, mips32, and mips64 linux.
Comment 2 Tamara Vlahovic 2017-11-01 13:44:40 UTC 
Created attachment 108667 [details]
fd_clone_test

This patch adds tests in none/tests/linux which check Valgrind behevior during thread creation with different combination of CLONE_FS, and CLONE_FILES set flags.
Comment 3 Tamara Vlahovic 2017-11-14 10:25:36 UTC 
Can somebody take a look at these patches?