Richard Henderson <richard.henderson@linaro.org> writes:
> There are at least 4 separate bugs preventing clone from working.
>
> (1) cpu_copy left both cpus sharing the same register window (!)
>
> (2) cpu_clone_regs did not initialize %o1, so the new thread path
> in the guest __clone was always taken, even for the parent
> (old %o1 value was newsp, and so non-zero).
>
> (3) cpu_clone_regs did not advance the pc past the syscall in the
> child, which meant that the child re-executed the syscall
> (and because of (1), with essentially random inputs).
>
> (4) clone did not flush register windows, which would cause the
> parent stack to be clobbered by the child writing out old
> windows in order to allocate a new one.
>
> This is enough for Alex's atomic-test to make progress, but not
> quite enough for it to actually work. What I'm seeing now is a
> legitimate SEGV for a write to a r-xp memory segment. I'll need
> to examine the testcase further to see why that is happening.
Hmm and testthread now reliably bombs with:
thread2: 10 hello2
testthread: allocatestack.c:384: advise_stack_range: Assertion `freesize < size' failed.
fish: “./qemu-sparc64 -d trace:user_qu…” terminated by signal SIGABRT (Abort)
However the behaviour of the atomic test now looks similar to the
occasional failure I was seeing in testthread before, i.e. a crash
during atomic operations.
>
>
> r~
>
>
> Richard Henderson (4):
> linux-user: Disallow setting newsp for fork
> linux-user: Pass the parent env to cpu_clone_regs
> linux-user/sparc: Fix cpu_clone_regs
> linux-user/sparc: Flush register windows before clone
>
> linux-user/aarch64/target_cpu.h | 3 ++-
> linux-user/alpha/target_cpu.h | 3 ++-
> linux-user/arm/target_cpu.h | 3 ++-
> linux-user/cris/target_cpu.h | 3 ++-
> linux-user/hppa/target_cpu.h | 3 ++-
> linux-user/i386/target_cpu.h | 3 ++-
> linux-user/m68k/target_cpu.h | 3 ++-
> linux-user/microblaze/target_cpu.h | 3 ++-
> linux-user/mips/target_cpu.h | 3 ++-
> linux-user/nios2/target_cpu.h | 3 ++-
> linux-user/openrisc/target_cpu.h | 4 +++-
> linux-user/ppc/target_cpu.h | 3 ++-
> linux-user/riscv/target_cpu.h | 3 ++-
> linux-user/s390x/target_cpu.h | 3 ++-
> linux-user/sh4/target_cpu.h | 3 ++-
> linux-user/sparc/target_cpu.h | 23 ++++++++++++++++++++---
> linux-user/tilegx/target_cpu.h | 3 ++-
> linux-user/xtensa/target_cpu.h | 3 ++-
> linux-user/sparc/cpu_loop.c | 3 +++
> linux-user/syscall.c | 9 ++++++---
> 20 files changed, 64 insertions(+), 23 deletions(-)
--
Alex Bennée