arm64/sve: Disentangle <uapi/asm/ptrace.h> from <uapi/asm/sigcontext.h>
This fixes issues with building strace on aarch64 e.g.
/usr/include/asm/sigcontext.h: error: redefinition of 'struct sigcontextCurrently, <uapi/asm/sigcontext.h> provides common definitions for describing SVE context structures that are also used by the ptrace definitions in <uapi/asm/ptrace.h>.
For this reason, a #include of <asm/sigcontext.h> was added in ptrace.h, but it this turns out that this can interact badly with userspace code that tries to include ptrace.h on top of the libc headers (which may provide their own shadow definitions for sigcontext.h).
To make the headers easier for userspace to consume, this patch bounces the common definitions into an _SVE* namespace and moves them to a backend header <uapi/asm/sve_context.h> that can be included by the other headers as appropriate. This should allow ptrace.h to be used alongside libc's sigcontext.h (if any) without ill effects.
This should make the situation unambiguous: <asm/sigcontext.h> is the header to include for the sigframe-specific definitions, while <asm/ptrace.h> is the header to include for ptrace-specific definitions.
To avoid conflicting with existing usage, <asm/sigcontext.h> remains the canonical way to get the common definitions for SVE_VQ_MIN, sve_vq_from_vl() etc., both in userspace and in the kernel: relying on these being defined as a side effect of including just <asm/ptrace.h> was never intended to be safe.
Signed-off-by: Dave Martin Dave.Martin@arm.com Signed-off-by: Will Deacon will.deacon@arm.com