From 4a373ea7d677c69dc95903dbb542237ab1380eb5 Mon Sep 17 00:00:00 2001 From: Sergey Bugaev Date: Wed, 17 May 2023 22:14:28 +0300 Subject: [PATCH] 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 Message-Id: <20230517191436.73636-3-bugaevc@gmail.com> --- 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 9fa3d4e..431aaf8 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 5be0bec..8c41951 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 +#include /* 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 #endif /* mach/x86/thread_state.h */ -- 2.7.4