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zephyr/arch/xtensa/include/xtensa_context.h
Mazen NEIFER 01e9646638 xtensa port: Clear the CP descriptor of new created thread. 
This commit should fix the concern about uninitialized memory of main
thread that was raised in https://gerrit.zephyrproject.org/r/#/c/12920/

The issue is more general, if it happens that the content of the
CPENABLE flag of any thread is set then any other thread using the CP
may cause a memory corruption.

I'd prefer to avoid the issue by initializing the CP descriptor to 0.
The descriptor itself is few words. We set them to 0 up to CP_ASA, which
is set to a real value.

As the dummy thread instantiated at the kernel startup does not use CP,
there is no CP area in its thread memory buffer. However it is mandatory
that it have the CP descriptor and that cpEnable in that descripot is
set to null. This is ensured by adding XT_CP_DESCR_SIZE to
_K_THREAD_NO_FLOAT_SIZEOF.

Change-Id: I6a36b5b363600ea1e6d98ab679981182b2b5a236
Signed-off-by: Mazen NEIFER <mazen@nestwave.com>
2017-04-20 16:01:55 +00:00

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/*
* Copyright (c) 2016 Cadence Design Systems, Inc.
* SPDX-License-Identifier: Apache-2.0
*/
/*
* XTENSA CONTEXT FRAMES AND MACROS FOR RTOS ASSEMBLER SOURCES
*
* This header contains definitions and macros for use primarily by Xtensa RTOS
* assembly coded source files. It includes and uses the Xtensa hardware
* abstraction layer (HAL) to deal with config specifics. It may also be
* included in C source files.
*
* Supports only Xtensa Exception Architecture 2 (XEA2). XEA1 not supported.
*
* NOTE: The Xtensa architecture requires stack pointer alignment to 16 bytes.
*/
#ifndef XTENSA_CONTEXT_H
#define XTENSA_CONTEXT_H
#ifdef __ASSEMBLER__
#include <xtensa/coreasm.h>
#endif
#include <xtensa/config/tie.h>
#include <xtensa/corebits.h>
#include <xtensa/config/system.h>
#include <xtensa/xtruntime-frames.h>
/* Align a value up to nearest n-byte boundary, where n is a power of 2. */
#define ALIGNUP(n, val) (((val) + (n)-1) & -(n))
/*
* INTERRUPT/EXCEPTION STACK FRAME FOR A THREAD OR NESTED INTERRUPT
*
* A stack frame of this structure is allocated for any interrupt or exception.
* It goes on the current stack. If the RTOS has a system stack for handling
* interrupts, every thread stack must allow space for just one interrupt stack
* frame, then nested interrupt stack frames go on the system stack.
*
* The frame includes basic registers (explicit) and "extra" registers
* introduced by user TIE or the use of the MAC16 option in the user's Xtensa
* config. The frame size is minimized by omitting regs not applicable to
* user's config.
*
* For Windowed ABI, this stack frame includes the interruptee's base save
* area, another base save area to manage gcc nested functions, and a little
* temporary space to help manage the spilling of the register windows.
*/
STRUCT_BEGIN
STRUCT_FIELD(long, 4, XT_STK_, exit) /* exit point for dispatch */
STRUCT_FIELD(long, 4, XT_STK_, pc) /* return PC */
STRUCT_FIELD(long, 4, XT_STK_, ps) /* return PS */
STRUCT_FIELD(long, 4, XT_STK_, a0)
STRUCT_FIELD(long, 4, XT_STK_, a1) /* stack pointer before irq */
STRUCT_FIELD(long, 4, XT_STK_, a2)
STRUCT_FIELD(long, 4, XT_STK_, a3)
STRUCT_FIELD(long, 4, XT_STK_, a4)
STRUCT_FIELD(long, 4, XT_STK_, a5)
STRUCT_FIELD(long, 4, XT_STK_, a6)
STRUCT_FIELD(long, 4, XT_STK_, a7)
STRUCT_FIELD(long, 4, XT_STK_, a8)
STRUCT_FIELD(long, 4, XT_STK_, a9)
STRUCT_FIELD(long, 4, XT_STK_, a10)
STRUCT_FIELD(long, 4, XT_STK_, a11)
STRUCT_FIELD(long, 4, XT_STK_, a12)
STRUCT_FIELD(long, 4, XT_STK_, a13)
STRUCT_FIELD(long, 4, XT_STK_, a14)
STRUCT_FIELD(long, 4, XT_STK_, a15)
STRUCT_FIELD(long, 4, XT_STK_, sar)
STRUCT_FIELD(long, 4, XT_STK_, exccause)
STRUCT_FIELD(long, 4, XT_STK_, excvaddr)
#if XCHAL_HAVE_LOOPS
STRUCT_FIELD(long, 4, XT_STK_, lbeg)
STRUCT_FIELD(long, 4, XT_STK_, lend)
STRUCT_FIELD(long, 4, XT_STK_, lcount)
#endif
#ifndef __XTENSA_CALL0_ABI__
/* Temporary space for saving stuff during window spill */
STRUCT_FIELD(long, 4, XT_STK_, tmp0)
STRUCT_FIELD(long, 4, XT_STK_, tmp1)
STRUCT_FIELD(long, 4, XT_STK_, tmp2)
#endif
#ifdef XT_USE_SWPRI
/* Storage for virtual priority mask */
STRUCT_FIELD(long, 4, XT_STK_, vpri)
#endif
#ifdef XT_USE_OVLY
/* Storage for overlay state */
STRUCT_FIELD(long, 4, XT_STK_, ovly)
#endif
STRUCT_END(XtExcFrame)
#if defined(_ASMLANGUAGE) || defined(__ASSEMBLER__)
#define XT_STK_NEXT1 XtExcFrameSize
#else
#define XT_STK_NEXT1 sizeof(XtExcFrame)
#endif
/* Allocate extra storage if needed */
#if XCHAL_EXTRA_SA_SIZE != 0
#if XCHAL_EXTRA_SA_ALIGN <= 16
#define XT_STK_EXTRA ALIGNUP(XCHAL_EXTRA_SA_ALIGN, XT_STK_NEXT1)
#else
/* If need more alignment than stack, add space for dynamic alignment */
#define XT_STK_EXTRA (ALIGNUP(XCHAL_EXTRA_SA_ALIGN, XT_STK_NEXT1) \
+ XCHAL_EXTRA_SA_ALIGN)
#endif
#define XT_STK_NEXT2 (XT_STK_EXTRA + XCHAL_EXTRA_SA_SIZE)
#else
#define XT_STK_NEXT2 XT_STK_NEXT1
#endif
/*
* This is the frame size. Add space for 4 registers (interruptee's base save
* area) and some space for gcc nested functions if any.
*/
#define XT_STK_FRMSZ (ALIGNUP(0x10, XT_STK_NEXT2) + 0x20)
/*
* SOLICITED STACK FRAME FOR A THREAD
*
* A stack frame of this structure is allocated whenever a thread enters the
* RTOS kernel intentionally (and synchronously) to submit to thread
* scheduling. It goes on the current thread's stack.
*
* The solicited frame only includes registers that are required to be
* preserved by the callee according to the compiler's ABI conventions, some
* space to save the return address for returning to the caller, and the
* caller's PS register. For Windowed ABI, this stack frame includes the
* caller's base save area.
*
* Note on XT_SOL_EXIT field:
*
* It is necessary to distinguish a solicited from an interrupt stack frame.
* This field corresponds to XT_STK_EXIT in the interrupt stack frame and is
* always at the same offset (0). It can be written with a code (usually 0) to
* distinguish a solicted frame from an interrupt frame. An RTOS port may opt
* to ignore this field if it has another way of distinguishing frames.
*/
STRUCT_BEGIN
STRUCT_FIELD(long, 4, XT_SOL_, exit)
STRUCT_FIELD(long, 4, XT_SOL_, pc)
STRUCT_FIELD(long, 4, XT_SOL_, ps)
STRUCT_FIELD(long, 4, XT_SOL_, next)
#ifdef __XTENSA_CALL0_ABI__
STRUCT_FIELD(long, 4, XT_SOL_, a12) /* should be on 16-byte alignment */
STRUCT_FIELD(long, 4, XT_SOL_, a13)
STRUCT_FIELD(long, 4, XT_SOL_, a14)
STRUCT_FIELD(long, 4, XT_SOL_, a15)
#else
STRUCT_FIELD(long, 4, XT_SOL_, a0) /* should be on 16-byte alignment */
STRUCT_FIELD(long, 4, XT_SOL_, a1)
STRUCT_FIELD(long, 4, XT_SOL_, a2)
STRUCT_FIELD(long, 4, XT_SOL_, a3)
#endif
STRUCT_END(XtSolFrame)
/* Size of solicited stack frame */
#define XT_SOL_FRMSZ ALIGNUP(0x10, XtSolFrameSize)
/*
* CO-PROCESSOR STATE SAVE AREA FOR A THREAD
*
* The RTOS must provide an area per thread to save the state of co-processors
* when that thread does not have control. Co-processors are context-switched
* lazily (on demand) only when a new thread uses a co-processor instruction,
* otherwise a thread retains ownership of the co-processor even when it loses
* control of the processor. An Xtensa co-processor exception is triggered when
* any co-processor instruction is executed by a thread that is not the owner,
* and the context switch of that co-processor is then peformed by the handler.
* Ownership represents which thread's state is currently in the co-processor.
*
* Co-processors may not be used by interrupt or exception handlers. If a
* co-processor instruction is executed by an interrupt or exception handler,
* the co-processor exception handler will trigger a kernel panic and freeze.
* This restriction is introduced to reduce the overhead of saving and
* restoring co-processor state (which can be quite large) and in particular
* remove that overhead from interrupt handlers.
*
* The co-processor state save area may be in any convenient per-thread
* location such as in the thread control block or above the thread stack area.
* It need not be in the interrupt stack frame since interrupts don't use
* co-processors.
*
* Along with the save area for each co-processor, two bitmasks with flags per
* co-processor (laid out as in the CPENABLE reg) help manage context-switching
* co-processors as efficiently as possible:
*
* XT_CPENABLE
*
* The contents of a non-running thread's CPENABLE register. It represents the
* co-processors owned (and whose state is still needed) by the thread. When a
* thread is preempted, its CPENABLE is saved here. When a thread solicits a
* context-swtich, its CPENABLE is cleared - the compiler has saved the
* (caller-saved) co-proc state if it needs to. When a non-running thread
* loses ownership of a CP, its bit is cleared. When a thread runs, it's
* XT_CPENABLE is loaded into the CPENABLE reg. Avoids co-processor exceptions
* when no change of ownership is needed.
*
* XT_CPSTORED
*
* A bitmask with the same layout as CPENABLE, a bit per co-processor.
* Indicates whether the state of each co-processor is saved in the state save
* area. When a thread enters the kernel, only the state of co-procs still
* enabled in CPENABLE is saved. When the co-processor exception handler
* assigns ownership of a co-processor to a thread, it restores the saved state
* only if this bit is set, and clears this bit.
*
* XT_CP_CS_ST
*
* A bitmask with the same layout as CPENABLE, a bit per co-processor.
* Indicates whether callee-saved state is saved in the state save area.
* Callee-saved state is saved by itself on a solicited context switch, and
* restored when needed by the coprocessor exception handler. Unsolicited
* switches will cause the entire coprocessor to be saved when necessary.
*
* XT_CP_ASA
*
* Pointer to the aligned save area. Allows it to be aligned more than the
* overall save area (which might only be stack-aligned or TCB-aligned).
* Especially relevant for Xtensa cores configured with a very large data path
* that requires alignment greater than 16 bytes (ABI stack alignment).
*/
#define XT_CP_DESCR_SIZE 12
#if XCHAL_CP_NUM > 0
/* Offsets of each coprocessor save area within the 'aligned save area': */
#define XT_CP0_SA 0
#define XT_CP1_SA ALIGNUP(XCHAL_CP1_SA_ALIGN, XT_CP0_SA + XCHAL_CP0_SA_SIZE)
#define XT_CP2_SA ALIGNUP(XCHAL_CP2_SA_ALIGN, XT_CP1_SA + XCHAL_CP1_SA_SIZE)
#define XT_CP3_SA ALIGNUP(XCHAL_CP3_SA_ALIGN, XT_CP2_SA + XCHAL_CP2_SA_SIZE)
#define XT_CP4_SA ALIGNUP(XCHAL_CP4_SA_ALIGN, XT_CP3_SA + XCHAL_CP3_SA_SIZE)
#define XT_CP5_SA ALIGNUP(XCHAL_CP5_SA_ALIGN, XT_CP4_SA + XCHAL_CP4_SA_SIZE)
#define XT_CP6_SA ALIGNUP(XCHAL_CP6_SA_ALIGN, XT_CP5_SA + XCHAL_CP5_SA_SIZE)
#define XT_CP7_SA ALIGNUP(XCHAL_CP7_SA_ALIGN, XT_CP6_SA + XCHAL_CP6_SA_SIZE)
#define XT_CP_SA_SIZE ALIGNUP(16, XT_CP7_SA + XCHAL_CP7_SA_SIZE)
/* Offsets within the overall save area: */
/* (2 bytes) coprocessors active for this thread */
#define XT_CPENABLE 0
/* (2 bytes) coprocessors saved for this thread */
#define XT_CPSTORED 2
/* (2 bytes) coprocessor callee-saved regs stored for this thread */
#define XT_CP_CS_ST 4
/* (4 bytes) ptr to aligned save area */
#define XT_CP_ASA 8
/* Overall size allows for dynamic alignment: */
#define XT_CP_SIZE ALIGNUP(XCHAL_TOTAL_SA_ALIGN, \
XT_CP_DESCR_SIZE + XT_CP_SA_SIZE)
#else
#define XT_CP_SIZE 0
#endif
/*
* MACROS TO HANDLE ABI SPECIFICS OF FUNCTION ENTRY AND RETURN
*
* Convenient where the frame size requirements are the same for both ABIs.
* ENTRY(sz), RET(sz) are for framed functions (have locals or make calls).
* ENTRY0, RET0 are for frameless functions (no locals, no calls).
*
* where size = size of stack frame in bytes (must be >0 and aligned to 16).
* For framed functions the frame is created and the return address saved at
* base of frame (Call0 ABI) or as determined by hardware (Windowed ABI). For
* frameless functions, there is no frame and return address remains in
* a0.
*
* Note: Because CPP macros expand to a single line, macros requiring
* multi-line expansions are implemented as assembler macros.
*/
#ifdef __ASSEMBLER__
#ifdef __XTENSA_CALL0_ABI__
/* Call0 */
#define ENTRY(sz) entry1 sz
.macro entry1 size=0x10
addi sp, sp, -\size
s32i a0, sp, 0
.endm
#define ENTRY0
#define RET(sz) ret1 sz
.macro ret1 size=0x10
l32i a0, sp, 0
addi sp, sp, \size
ret
.endm
#define RET0 ret
#else
/* Windowed */
#define ENTRY(sz) entry sp, sz
#define ENTRY0 entry sp, 0x10
#define RET(sz) retw
#define RET0 retw
#endif /* __XTENSA_CALL0_ABI__ */
#endif /* __ASSEMBLER__ */
#endif /* XTENSA_CONTEXT_H */
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