1 Commits

Author	SHA1	Message	Date
Sean Christopherson	6b6f71484b	KVM: selftests: Implement memcmp(), memcpy(), and memset() for guest use ... Implement memcmp(), memcpy(), and memset() to override the compiler's built-in versions in order to guarantee that the compiler won't generate out-of-line calls to external functions via the PLT. This allows the helpers to be safely used in guest code, as KVM selftests don't support dynamic loading of guest code. Steal the implementations from the kernel's generic versions, sans the optimizations in memcmp() for unaligned accesses. Put the utilities in a separate compilation unit and build with -ffreestanding to fudge around a gcc "feature" where it will optimize memset(), memcpy(), etc... by generating a recursive call. I.e. the compiler optimizes itself into infinite recursion. Alternatively, the individual functions could be tagged with optimize("no-tree-loop-distribute-patterns"), but using "optimize" for anything but debug is discouraged, and Linus NAK'd the use of the flag in the kernel proper[*]. https://lore.kernel.org/lkml/CAHk-=wik-oXnUpfZ6Hw37uLykc-_P0Apyn2XuX-odh-3Nzop8w@mail.gmail.com Cc: Andrew Jones <andrew.jones@linux.dev> Cc: Anup Patel <anup@brainfault.org> Cc: Atish Patra <atishp@atishpatra.org> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Janosch Frank <frankja@linux.ibm.com> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20220928233652.783504-2-seanjc@google.com> Reviewed-by: Andrew Jones <andrew.jones@linux.dev> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>	2022-09-30 06:38:02 -04:00