Bug 449309

Created attachment 146027 [details]
Patch to add missing loop ioctls

SUMMARY
A Linux program using loopback device interface, when instrumented with valgrind, reports missing IOCTLS and routes the user to https://valgrind.org/docs/manual/dist.readme-missing.html. This bug-report is meant to bring the missing functionality into valgrind developers knowledge and to supply a supporting patch.


STEPS TO REPRODUCE
1. Sample C program with steps to build and run is available at: https://gist.github.com/fsheikh/cd184450338f750af9e1a79f40b78419
2. Build above program with a C compiler e.g. "clang-10 -Wall -Werror loop_ioctls.c -o loop_ioctl"
3. Running the program with valgrind " valgrind ./loop_ioctl"

OBSERVED RESULT
==28554== Memcheck, a memory error detector
==28554== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==28554== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==28554== Command: ./loop_ioctl
==28554== 
Valgrind loopback test starting...
==28554== Warning: noted but unhandled ioctl 0x4c82 with no size/direction hints.
==28554==    This could cause spurious value errors to appear.
==28554==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
Free loopback device /dev/loop32 found
==28554== Warning: noted but unhandled ioctl 0x4c01 with no size/direction hints.
==28554==    This could cause spurious value errors to appear.
==28554==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==28554== Warning: noted but unhandled ioctl 0x4c09 with no size/direction hints.
==28554==    This could cause spurious value errors to appear.
==28554==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==28554== Warning: noted but unhandled ioctl 0x4c05 with no size/direction hints.
==28554==    This could cause spurious value errors to appear.
==28554==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
Valgrind loopback test done!
==28554== 
==28554== HEAP SUMMARY:
==28554==     in use at exit: 0 bytes in 0 blocks
==28554==   total heap usage: 1 allocs, 1 frees, 1,024 bytes allocated
==28554== 
==28554== All heap blocks were freed -- no leaks are possible
==28554== 
==28554== For counts of detected and suppressed errors, rerun with: -v
==28554== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

EXPECTED RESULT
valgrind does not generates warnings and memcheck tools is able to process a program containing loopback IOCTL(s)

SOFTWARE/OS VERSIONS
Ubuntu Linux (5.4.0-96-generic)

ADDITIONAL INFORMATION
Please see attachment for a proposed fix. Please do let me know if the patch needs to be sent to a mailing-list for review/approval or if it should be pushed to a public repository. Thanks!