#include "miscfuncs.h"
#include <imagehlp.h>
#include <stdlib.h>
+#include <stdarg.h>
#include <syslog.h>
#include <wchar.h>
#include <ucontext.h>
ResumeThread (th);
}
}
+
+#ifdef __x86_64__
+static inline void
+__unwind_single_frame (PCONTEXT ctx)
+{
+ /* Amazing, but true: On 32 bit, RtlCaptureContext returns the context
+ matching the caller of getcontext, so all we have to do is call it.
+ On 64 bit, RtlCaptureContext returns the exact context of its own
+ caller, so we have to unwind virtually by a single frame to get the
+ context of the caller of getcontext. */
+ PRUNTIME_FUNCTION f;
+ ULONG64 imagebase;
+ UNWIND_HISTORY_TABLE hist;
+ DWORD64 establisher;
+ PVOID hdl;
+
+ f = RtlLookupFunctionEntry (ctx->Rip, &imagebase, &hist);
+ if (f)
+ RtlVirtualUnwind (0, imagebase, ctx->Rip, f, ctx, &hdl, &establisher,
+ NULL);
+ else
+ {
+ ctx->Rip = *(ULONG_PTR *) ctx->Rsp;
+ ctx->Rsp += 8;
+ }
+}
+#endif
+
+extern "C" int
+setcontext (const ucontext_t *ucp)
+{
+ PCONTEXT ctx = (PCONTEXT) &ucp->uc_mcontext;
+ _my_tls.sigmask = ucp->uc_sigmask;
+#ifdef __x86_64__
+ /* Apparently a call to NtContinue works on 64 bit as well, but using
+ RtlRestoreContext is the blessed way. */
+ RtlRestoreContext (ctx, NULL);
+#else
+ NtContinue (ctx, FALSE);
+#endif
+ /* If we got here, something was wrong. */
+ set_errno (EINVAL);
+ return -1;
+}
+
+#ifdef __x86_64__
+
+extern "C" int
+getcontext (ucontext_t *ucp)
+{
+ PCONTEXT ctx = (PCONTEXT) &ucp->uc_mcontext;
+ ctx->ContextFlags = CONTEXT_FULL;
+ RtlCaptureContext (ctx);
+ __unwind_single_frame (ctx);
+ /* Successful getcontext is supposed to return 0. If we don't set rax to 0
+ here, there's a chance that code like this:
+
+ if (getcontext (&ctx) != 0)
+
+ assumes that getcontext failed after calling setcontext (&ctx).
+ Same goes for eax on 32 bit, see assembler implementation below. */
+ ucp->uc_mcontext.rax = 0;
+ ucp->uc_sigmask = ucp->uc_mcontext.oldmask = _my_tls.sigmask;
+ /* Do not touch any other member of ucontext_t. */
+ return 0;
+}
+
+extern "C" int
+swapcontext (ucontext_t *oucp, const ucontext_t *ucp)
+{
+ PCONTEXT ctx = (PCONTEXT) &oucp->uc_mcontext;
+ ctx->ContextFlags = CONTEXT_FULL;
+ RtlCaptureContext (ctx);
+ __unwind_single_frame (ctx);
+ /* See above. */
+ oucp->uc_mcontext.rax = 0;
+ oucp->uc_sigmask = oucp->uc_mcontext.oldmask = _my_tls.sigmask;
+ return setcontext (ucp);
+}
+
+/* Trampoline function to set the context to uc_link. The pointer to the
+ address of uc_link is stored in the callee-saved register $rbx. If uc_link
+ is NULL, call exit. */
+__asm__ (" \n\
+ .global __cont_link_context \n\
+__cont_link_context: \n\
+ movq %rbx, %rsp \n\
+ popq %rcx \n\
+ testq %rcx, %rcx \n\
+ je 1f \n\
+ call setcontext \n\
+ movq $0xff, %rcx \n\
+1: \n\
+ call cygwin_exit \n\
+ nop \n\
+ ");
+
+#else
+
+/* On 32 bit it's crucial to call RtlCaptureContext in a way which makes sure
+ the callee-saved registers, especially $ebx, are not changed by the calling
+ function. If so, makecontext/__cont_link_context would be broken.
+
+ Both functions are split into the first half in assembler, and the second
+ half in C to allow easy access to _my_tls. */
+
+extern "C" int
+__getcontext (ucontext_t *ucp)
+{
+ ucp->uc_mcontext.eax = 0;
+ ucp->uc_sigmask = ucp->uc_mcontext.oldmask = _my_tls.sigmask;
+ return 0;
+}
+
+__asm__ (" \n\
+ .global _getcontext \n\
+_getcontext: \n\
+ pushl %ebp \n\
+ movl %esp, %ebp \n\
+ movl 8(%esp), %eax \n\
+ pushl %eax \n\
+ call _RtlCaptureContext@4 \n\
+ popl %ebp \n\
+ jmp ___getcontext \n\
+ nop \n\
+ ");
+
+extern "C" int
+__swapcontext (ucontext_t *oucp, const ucontext_t *ucp)
+{
+ oucp->uc_mcontext.eax = 0;
+ oucp->uc_sigmask = oucp->uc_mcontext.oldmask = _my_tls.sigmask;
+ return setcontext (ucp);
+}
+
+__asm__ (" \n\
+ .global _swapcontext \n\
+_swapcontext: \n\
+ pushl %ebp \n\
+ movl %esp, %ebp \n\
+ movl 8(%esp), %eax \n\
+ pushl %eax \n\
+ call _RtlCaptureContext@4 \n\
+ popl %ebp \n\
+ jmp ___swapcontext \n\
+ nop \n\
+ ");
+
+/* Trampoline function to set the context to uc_link. The pointer to the
+ address of uc_link is stored in the callee-saved register $ebx. If uc_link
+ is NULL, call exit. */
+__asm__ (" \n\
+ .global ___cont_link_context \n\
+___cont_link_context: \n\
+ movl %ebx, %esp \n\
+ movl (%esp), %eax \n\
+ testl %eax, %eax \n\
+ je 1f \n\
+ call _setcontext \n\
+ movl $0xff, (%esp) \n\
+1: \n\
+ call _cygwin_exit \n\
+ nop \n\
+ ");
+#endif
+
+/* makecontext is modelled after GLibc's makecontext. The stack from uc_stack
+ is prepared so that it starts with a pointer to the linked context uc_link,
+ followed by the arguments to func, and finally at the bottom the "return"
+ address set to __cont_link_context. In the ucp context, rbx/ebx is set to
+ point to the stack address where the pointer to uc_link is stored. The
+ requirement to make this work is that rbx/ebx are callee-saved registers
+ per the ABI. If any function is called which doesn't follow the ABI
+ conventions, e.g. assembler code, this method will break. But that's ok. */
+extern "C" void
+makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
+{
+ extern void __cont_link_context (void);
+ uintptr_t *sp;
+ va_list ap;
+
+ sp = (uintptr_t *) ((uintptr_t) ucp->uc_stack.ss_sp
+ + ucp->uc_stack.ss_size);
+ sp -= (argc + 1);
+ sp = (uintptr_t *) ((uintptr_t) sp & ~0xf);
+ --sp;
+ sp[0] = (uintptr_t) __cont_link_context;
+ sp[argc + 1] = (uintptr_t) ucp->uc_link;
+#ifdef __x86_64__
+ ucp->uc_mcontext.rip = (uint64_t) func;
+ ucp->uc_mcontext.rbx = (uint64_t) (sp + argc + 1);
+ ucp->uc_mcontext.rsp = (uint64_t) sp;
+#else
+ ucp->uc_mcontext.eip = (uint32_t) func;
+ ucp->uc_mcontext.ebx = (uint32_t) (sp + argc + 1);
+ ucp->uc_mcontext.esp = (uint32_t) sp;
+#endif
+ va_start (ap, argc);
+ for (int i = 0; i < argc; ++i)
+#ifdef __x86_64__
+ switch (i)
+ {
+ case 0:
+ ucp->uc_mcontext.rcx = va_arg (ap, uintptr_t);
+ break;
+ case 1:
+ ucp->uc_mcontext.rdx = va_arg (ap, uintptr_t);
+ break;
+ case 2:
+ ucp->uc_mcontext.r8 = va_arg (ap, uintptr_t);
+ break;
+ case 3:
+ ucp->uc_mcontext.r9 = va_arg (ap, uintptr_t);
+ break;
+ default:
+ sp[i + 1] = va_arg (ap, uintptr_t);
+ break;
+ }
+#else
+ sp[i + 1] = va_arg (ap, uintptr_t);
+#endif
+ va_end (ap);
+}
git://sourceware.org / newlib-cygwin.git / commitdiff