x86/x86_64: fix compatibility with bionic headers

glibc and musl use a static block of memory for storing floating-point
registers, while bionic uses a structure instead.

no functional change

ref #78
ref termux/termux-packages#27605

Signed-off-by: Ariadne Conill <ariadne@ariadne.space>

Author: kaniini

arch/x86/makecontext.c

@@ -36,7 +36,7 @@ libucontext_makecontext(libucontext_ucontext_t *ucp, void (*func)(void), int arg
 	sp -= uc_link;
 	sp = (libucontext_greg_t *) (((uintptr_t) sp & -16L) - 8);
 
-	ucp->uc_mcontext.fpregs = (void *) &ucp->__fpregs_mem[0];
+	ucp->uc_mcontext.fpregs = (void *) &ucp->__fpregs_mem;
 	ucp->uc_mcontext.gregs[REG_EIP] = (uintptr_t) func;
 	ucp->uc_mcontext.gregs[REG_EBX] = (uintptr_t) argc;
 	ucp->uc_mcontext.gregs[REG_ESP] = (uintptr_t) sp;

arch/x86_64/makecontext.c

@@ -36,7 +36,7 @@ libucontext_makecontext(libucontext_ucontext_t *ucp, void (*func)(void), int arg
 	sp -= uc_link;
 	sp = (libucontext_greg_t *) (((uintptr_t) sp & -16L) - 8);
 
-	ucp->uc_mcontext.fpregs = (void *) &ucp->__fpregs_mem[0];
+	ucp->uc_mcontext.fpregs = (void *) &ucp->__fpregs_mem;
 	ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t) func;
 	ucp->uc_mcontext.gregs[REG_RBX] = (uintptr_t) &sp[uc_link];
 	ucp->uc_mcontext.gregs[REG_RSP] = (uintptr_t) sp;