qemu-user -g xxx -E LD_PROFILE=xxx segfault

Here is two simple steps to reproduce the bug:

$ qemu-x86_64 -E LD_PROFILE=libc.so.6 -E LD_PROFILE_OUTPUT=. -g 12345 -L / /bin/ls

(libc.so and /bin/ls might change on your system, in this case we just need a binary with a profilable needed library)

In a other window launch:

$ gdb
(gdb) target remote :12345
(gdb) c

At this point qemu will segfault.

It seems this problem is appends when sigprof passed to gdb.
One way I have found to bypass this:
patch gdbstub.c gdb_handlesig and ignore sig if
sig == TARGET_SIGPROF
(which means now I can't catch sigprof on gdb anymore)

We were mis-parsing the 'vCont' packet in the gdb protocol, so when gdb told us "send a SIGPROF (0x1b)" we skipped the first digit in the hex signal number and interpreted it as "send an 0xb", which happens to be SIGSEGV.

Should be fixed by this:
https://<email address hidden>/


https://gitlab.com/qemu-project/qemu/-/commit/3ddd9036389f5f577e09