[glibc] mach: Define MACHINE_THREAD_STATE_SETUP_CALL

[Samuel Thibault <sthibaul@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4a373ea7d677c69dc95903dbb542237ab1380eb5

commit 4a373ea7d677c69dc95903dbb542237ab1380eb5
Author: Sergey Bugaev <bugaevc@gmail.com>
Date:   Wed May 17 22:14:28 2023 +0300

    mach: Define MACHINE_THREAD_STATE_SETUP_CALL
    
    The existing two macros, MACHINE_THREAD_STATE_SET_PC and
    MACHINE_THREAD_STATE_SET_SP, can be used to set program counter and the
    stack pointer registers in a machine-specific thread state structure.
    
    Useful as it is, this may not be enough to set up the thread to make a
    function call, because the machine-specific ABI may impose additional
    requirements. In particular, x86_64 ABI requires that upon function
    entry, the stack pointer is 8 less than 16-byte aligned (sp & 15 == 8).
    
    To deal with this, introduce a new macro,
    MACHINE_THREAD_STATE_SETUP_CALL (), which sets both stack and
    instruction pointers, and also applies any machine-specific requirements
    to make a valid function call. The default implementation simply
    forwards to MACHINE_THREAD_STATE_SET_PC and MACHINE_THREAD_STATE_SET_SP,
    but on x86_64 we additionally align the stack pointer.
    
    Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
    Message-Id: <20230517191436.73636-3-bugaevc@gmail.com>

Diff:
---
 sysdeps/mach/thread_state.h     |  9 +++++++++
 sysdeps/mach/x86/thread_state.h | 13 +++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/sysdeps/mach/thread_state.h b/sysdeps/mach/thread_state.h
index 9fa3d4e161..431aaf82ed 100644
--- a/sysdeps/mach/thread_state.h
+++ b/sysdeps/mach/thread_state.h
@@ -38,6 +38,15 @@
 #endif
 #endif
 
+/* Set up the thread state to call the given function on the given state.
+   Dependning on architecture, this may imply more than just setting PC
+   and SP.  */
+#ifndef MACHINE_THREAD_STATE_SETUP_CALL
+#define MACHINE_THREAD_STATE_SETUP_CALL(ts, stack, size, func) \
+  (MACHINE_THREAD_STATE_SET_PC (ts, func), \
+   MACHINE_THREAD_STATE_SET_SP (ts, stack, size))
+#endif
+
 /* This copies architecture-specific bits from the current thread to the new
    thread state.  */
 #ifndef MACHINE_THREAD_STATE_FIX_NEW
diff --git a/sysdeps/mach/x86/thread_state.h b/sysdeps/mach/x86/thread_state.h
index 5be0bec150..8c419515f9 100644
--- a/sysdeps/mach/x86/thread_state.h
+++ b/sysdeps/mach/x86/thread_state.h
@@ -20,6 +20,7 @@
 #define _MACH_X86_THREAD_STATE_H 1
 
 #include <mach/machine/thread_status.h>
+#include <libc-pointer-arith.h>
 
 /* This lets the kernel define segments for a new thread.  */
 #define MACHINE_NEW_THREAD_STATE_FLAVOR	i386_THREAD_STATE
@@ -54,6 +55,18 @@ struct machine_thread_all_state
     struct i386_float_state fpu;
   };
 
+#ifdef __x86_64__
+/* We're setting up the stack to perform a function call.  On function entry,
+   the stack pointer must be 8 bytes less than 16-aligned.  */
+#define PTR_ALIGN_DOWN_8_16(ptr)					      \
+ ({ uintptr_t __ptr = PTR_ALIGN_DOWN (ptr, 8);				      \
+    PTR_IS_ALIGNED (__ptr, 16) ? (__ptr - 8) : __ptr; })
+
+#define MACHINE_THREAD_STATE_SETUP_CALL(ts, stack, size, func)		      \
+  ((ts)->SP = PTR_ALIGN_DOWN_8_16 ((uintptr_t) (stack) + (size)),	      \
+   (ts)->PC = (uintptr_t) func)
+#endif
+
 #include <sysdeps/mach/thread_state.h>
 
 #endif /* mach/x86/thread_state.h */