[libc-dev] Linux powerpc new system call instruction and ABI

[Dmitry V. Levin via libc-dev]

Hi,

On Thu, Jun 11, 2020 at 06:12:01PM +1000, Nicholas Piggin wrote:
[...]
> - Error handling: The consensus among kernel, glibc, and musl is to move to
>   using negative return values in r3 rather than CR0[SO]=1 to indicate error,
>   which matches most other architectures, and is closer to a function call.

Apparently, the patchset merged by commit v5.9-rc1~100^2~164 was
incomplete: all functions defined in arch/powerpc/include/asm/ptrace.h and
arch/powerpc/include/asm/syscall.h that use ccr are broken when scv is used.
This includes syscall_get_error() and all its users including
PTRACE_GET_SYSCALL_INFO API, which in turn makes strace unusable
when scv is used.

See also https://bugzilla.redhat.com/1929836


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ldv