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Re: [PATCH 2/2] [Arm] Stack Pointer and Stack Limit initialization refactored.
Ping
On Fri, 12 Apr 2019 at 16:31, <alfedotov@gmail.com> wrote:
> From: Alexander Fedotov <alfedotov@gmail.com>
>
> SP initialization changes:
> 1. set default value in semihosting case as well
> 2. moved existing SP & SL init code for processor modes in separate
> routine and made it as "hook"
> 3. init SP for processor modes in Thumb mode as well
>
> Add new macro FN_RETURN, FN_EH_START and FN_EH_END.
> ---
> libgloss/arm/arm.h | 26 ++++
> libgloss/arm/crt0.S | 277 ++++++++++++++++++++++++++-----------
> newlib/libc/sys/arm/arm.h | 26 ++++
> newlib/libc/sys/arm/crt0.S | 277 ++++++++++++++++++++++++++-----------
> 4 files changed, 440 insertions(+), 166 deletions(-)
>
> diff --git a/libgloss/arm/arm.h b/libgloss/arm/arm.h
> index 0489f2d92..04b3a5ac7 100644
> --- a/libgloss/arm/arm.h
> +++ b/libgloss/arm/arm.h
> @@ -61,4 +61,30 @@
> # define HAVE_CALL_INDIRECT
> #endif
>
> +/* A and R profiles (and legacy Arm).
> + Current Program Status Register (CPSR)
> + M[4:0] Mode bits. M[4] is always 1 for 32-bit modes.
> + T[5] 1: Thumb, 0: ARM instruction set
> + F[6] 1: disables FIQ
> + I[7] 1: disables IRQ
> + A[8] 1: disables imprecise aborts
> + E[9] 0: Little-endian, 1: Big-endian
> + J[24] 1: Jazelle instruction set
> + */
> +#define CPSR_M_USR 0x00 /* User mode */
> +#define CPSR_M_FIQ 0x01 /* Fast Interrupt mode */
> +#define CPSR_M_IRQ 0x02 /* Interrupt mode */
> +#define CPSR_M_SVR 0x03 /* Supervisor mode */
> +#define CPSR_M_MON 0x06 /* Monitor mode */
> +#define CPSR_M_ABT 0x07 /* Abort mode */
> +#define CPSR_M_HYP 0x0A /* Hypervisor mode */
> +#define CPSR_M_UND 0x0B /* Undefined mode */
> +#define CPSR_M_SYS 0x0F /* System mode */
> +#define CPSR_M_32BIT 0x10 /* 32-bit mode */
> +#define CPSR_T_BIT 0x20 /* Thumb bit */
> +#define CPSR_F_MASK 0x40 /* FIQ bit */
> +#define CPSR_I_MASK 0x80 /* IRQ bit */
> +
> +#define CPSR_M_MASK 0x0F /* Mode mask except M[4] */
> +
> #endif /* _LIBGLOSS_ARM_H */
> diff --git a/libgloss/arm/crt0.S b/libgloss/arm/crt0.S
> index 1deb73aa5..95aa3b578 100644
> --- a/libgloss/arm/crt0.S
> +++ b/libgloss/arm/crt0.S
> @@ -59,6 +59,21 @@
> .endm
> #endif
>
> +/* Annotation for EABI unwinding tables. */
> +.macro FN_EH_START
> +#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
> + .fnstart
> +#endif
> +.endm
> +
> +.macro FN_EH_END
> +#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
> + /* Protect against unhandled exceptions. */
> + .cantunwind
> + .fnend
> +#endif
> +.endm
> +
> .macro indirect_call reg
> #ifdef HAVE_CALL_INDIRECT
> blx \reg
> @@ -68,16 +83,170 @@
> #endif
> .endm
>
> +/* For armv4t and newer, toolchains will transparently convert
> + 'bx lr' to 'mov pc, lr' if needed. GCC has deprecated support
> + for anything older than armv4t, but this should handle that
> + corner case in case anyone needs it anyway */
> +.macro FN_RETURN
> +#if __ARM_ARCH <= 4 && __ARM_ARCH_ISA_THUMB == 0
> + mov pc, lr
> +#else
> + bx lr
> +#endif
> +.endm
> +
> +
> +
>
> +/******************************************************************************
> +* User mode only: This routine makes default target specific
> Stack
> +* +-----+ <- SL_sys, Pointer initialization for different processor
> modes:
> +* | | SL_usr FIQ, Abort, IRQ, Undefined, Supervisor, System
> (User)
> +* | SYS | and setups a default Stack Limit in-case the
> code has
> +* | USR | -=0x10000 been compiled with "-mapcs-stack-check" for FIQ
> and
> +* | | System (User) modes.
> +* | |
> +* +-----+ <- initial SP,
> +* becomes SP_sys Hard-wiring SL value is not ideal, since
> there is
> +* and SL_usr currently no support for checking that the
> heap and
> +* stack have not collided, or that this default
> 64k is
> +* All modes: is enough for the program being executed.
> However,
> +* +-----+ <- SL_sys, it ensures that this simple crt0 world will not
> +* | | SL_usr immediately cause an overflow event.
> +* | SYS |
> +* | USR | -=0x10000 We go through all execution modes and set up
> SP
> +* | | for each of them.
> +* +-----+ <- SP_sys,
> +* | | SP_usr Note:
> +* | SVC | -= 0x8000 Mode switch via CPSR is not allowed once in
> +* | | non-privileged mode, so we take care not to
> enter
> +* +-----+ <- SP_svc "User" to set up its sp, and also skip most
> +* | | operations if already in that mode.
> +* | IRQ | -= 0x2000
> +* | | Input parameters:
> +* ^ +-----+ <- SP_und - sp - Initialized SP
> +* s | | - r2 - May contain SL value from semihosting
> +* t | UND | -= 0x1000 SYS_HEAPINFO call
> +* a | | Scratch registers:
> +* c +-----+ <- SP_und - r1 - new value of CPSR
> +* k | | - r2 - intermediate value (in standalone mode)
> +* | ABT | -= 0x1000 - r3 - new SP value
> +* g | | - r4 - save/restore CPSR on entry/exit
> +* r +-----+ <- SP_abt,
> +* o | | SL_fiq Declared as "weak" so that user can write
> and use
> +* w | FIQ | -= 0x1000 his own implementation if current doesn't fit.
> +* t | |
> +* h +-----+ <- initial SP,
> +* becomes SP_fiq
> +*
>
> +******************************************************************************/
> + .align 0
> + FUNC_START _stack_init
> + .weak FUNCTION (_stack_init)
> + FN_EH_START
> +
> + /* M profile doesn't have CPSR register. */
> +#if (__ARM_ARCH_PROFILE != 'M')
> + /* Following code is compatible for both ARM and Thumb ISA */
> + mrs r4, CPSR
> + /* Test mode bits - in User of all are 0 */
> + tst r4, #(CPSR_M_MASK)
> + /* "eq" means r4 AND #0x0F is 0 */
> + beq .Lskip_cpu_modes
> +
> + mov r3, sp /* save input SP value */
> +
> + /* FIQ mode, interrupts disabled */
> + mov r1, #(CPSR_M_FIQ|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> + sub sl, sp, #0x1000 /* FIQ mode has its own SL */
> +
> + /* Abort mode, interrupts disabled */
> + mov r3, sl
> + mov r1, #(CPSR_M_ABT|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> + sub r3, r3, #0x1000
> +
> + /* Undefined mode, interrupts disabled */
> + mov r1, #(CPSR_M_UND|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> + sub r3, r3, #0x1000
> +
> + /* IRQ mode, interrupts disabled */
> + mov r1, #(CPSR_M_IRQ|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> + sub r3, r3, #0x2000
> +
> + /* Supervisory mode, interrupts disabled */
> + mov r1, #(CPSR_M_SVR|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> +
> + sub r3, r3, #0x8000 /* Min size 32k */
> + bic r3, r3, #0x00FF /* Align with current 64k block */
> + bic r3, r3, #0xFF00
> +
> +# if __ARM_ARCH >= 4
> + /* System (shares regs with User) mode, interrupts disabled */
> + mov r1, #(CPSR_M_SYS|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> +# else
> + /* Keep this for ARMv3, but GCC actually dropped it. */
> + /* Move value into user mode sp without changing modes, */
> + /* via '^' form of ldm */
> + str r3, [r3, #-4]
> + ldmdb r3, {sp}^
> +# endif
> +
> + /* Back to original mode, presumably SVC, with diabled FIQ/IRQ */
> + orr r4, r4, #(CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r4
> +
> +.Lskip_cpu_modes:
> +#endif
> +
> + /* Set SL register */
> +#if defined (ARM_RDI_MONITOR) /* semihosting */
> + cmp r2, #0
> + beq .Lsl_forced_zero
> + /* allow slop for stack overflow handling and small frames */
> +# ifdef THUMB1_ONLY
> + adds r2, #128
> + adds r2, #128
> + mov sl, r2
> +# else
> + add sl, r2, #256
> +# endif
> +.Lsl_forced_zero:
> +
> +#else /* standalone */
> + /* r3 contains SP for System/User mode. Set SL = SP - 0x10000 */
> + #ifdef THUMB1_ONLY
> + movs r2, #64
> + lsls r2, r2, #10
> + subs r2, r3, r2
> + mov sl, r2
> + #else
> + /* Still assumes 256bytes below sl */
> + sub sl, r3, #64 << 10
> + #endif
> +#endif
> +
> + FN_RETURN
> + FN_EH_END
> +
> +
>
> /*******************************************************************************
> * Main library startup code.
>
> *******************************************************************************/
> .align 0
> FUNC_START _mainCRTStartup
> FUNC_START _start
> -#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
> - /* Annotation for EABI unwinding tables. */
> - .fnstart
> -#endif
> + FN_EH_START
>
> /* __ARM_ARCH_PROFILE is defined from GCC 4.8 onwards, however
> __ARM_ARCH_7A
> has been defined since 4.2 onwards, which is when v7-a support was
> added
> @@ -150,36 +319,27 @@
> to skip setting sp/sl to 0 here.
> - Considering M-profile processors, We might want to initialize
> sp by the first entry of vector table and return 0 to
> SYS_HEAPINFO
> - semihosting call, which will be skipped here. */
> + semihosting call, which will be skipped here.
> + - Considering R-profile processors there is no automatic SP
> init by hardware
> + so we need to initialize it by default value. */
> + ldr r3, .Lstack
> cmp r1, #0
> beq .LC26
> - mov sp, r1
> + mov r3, r1
> .LC26:
> - cmp r2, #0
> - beq .LC27
> + mov sp, r3
>
> - /* Allow slop for stack overflow handling and small frames. */
> -#ifdef THUMB1_ONLY
> - adds r2, #128
> - adds r2, #128
> - mov sl, r2
> -#else
> - add sl, r2, #256
> -#endif
> + /* r2 (SL value) will be used in _stack_init */
> + bl FUNCTION (_stack_init)
>
> -.LC27:
> -#else
> - /* Set up the stack pointer to a fixed value. */
> +
> +#else /* standalone */
> + /* Set up the stack pointer to a fixed value. */
> /* Changes by toralf:
> - Allow linker script to provide stack via __stack symbol - see
> defintion of .Lstack
> - Provide "hooks" that may be used by the application to add
> - custom init code - see .Lhwinit and .Lswinit
> - - Go through all execution modes and set up stack for each of
> them.
> - Loosely based on init.s from ARM/Motorola example code.
> - Note: Mode switch via CPSR is not allowed once in
> non-privileged
> - mode, so we take care not to enter "User" to set up
> its sp,
> - and also skip most operations if already in that
> mode. */
> + custom init code - see .Lhwinit and .Lswinit */
>
> ldr r3, .Lstack
> cmp r3, #0
> @@ -198,57 +358,10 @@
> have somehow missed it below (in which case it gets the
> same
> value as FIQ - not ideal, but better than nothing). */
> mov sp, r3
> -#ifdef PREFER_THUMB
> - /* XXX Fill in stack assignments for interrupt modes. */
> -#else
> - mrs r2, CPSR
> - tst r2, #0x0F /* Test mode bits - in User of all are 0.
> */
> - beq .LC23 /* "eq" means r2 AND #0x0F is 0. */
> - msr CPSR_c, #0xD1 /* FIRQ mode, interrupts disabled. */
> - mov sp, r3
> - sub sl, sp, #0x1000 /* This mode also has its own sl (see
> below). */
> -
> - mov r3, sl
> - msr CPSR_c, #0xD7 /* Abort mode, interrupts disabled. */
> - mov sp, r3
> - sub r3, r3, #0x1000
> -
> - msr CPSR_c, #0xDB /* Undefined mode, interrupts disabled. */
> - mov sp, r3
> - sub r3, r3, #0x1000
>
> - msr CPSR_c, #0xD2 /* IRQ mode, interrupts disabled. */
> - mov sp, r3
> - sub r3, r3, #0x2000
> -
> - msr CPSR_c, #0xD3 /* Supervisory mode, interrupts disabled.
> */
> + /* we don't care of r2 value in standalone */
> + bl FUNCTION (_stack_init)
>
> - mov sp, r3
> - sub r3, r3, #0x8000 /* Min size 32k. */
> - bic r3, r3, #0x00FF /* Align with current 64k block. */
> - bic r3, r3, #0xFF00
> -
> - str r3, [r3, #-4] /* Move value into user mode sp without */
> - ldmdb r3, {sp}^ /* changing modes, via '^' form of ldm.
> */
> - orr r2, r2, #0xC0 /* Back to original mode, presumably SVC,
> */
> - msr CPSR_c, r2 /* with FIQ/IRQ disable bits forced to 1.
> */
> -#endif
> -.LC23:
> - /* Setup a default stack-limit in-case the code has been
> - compiled with "-mapcs-stack-check". Hard-wiring this value
> - is not ideal, since there is currently no support for
> - checking that the heap and stack have not collided, or that
> - this default 64k is enough for the program being executed.
> - However, it ensures that this simple crt0 world will not
> - immediately cause an overflow event: */
> -#ifdef THUMB1_ONLY
> - movs r2, #64
> - lsls r2, r2, #10
> - subs r2, r3, r2
> - mov sl, r2
> -#else
> - sub sl, r3, #64 << 10 /* Still assumes 256bytes below
> sl. */
> -#endif
> #endif
> #endif
> /* Zero the memory in the .bss section. */
> @@ -447,6 +560,8 @@ change_back:
> swi SWI_Exit
> #endif
>
> + FN_EH_END
> +
> /* For Thumb, constants must be after the code since only
> positive offsets are supported for PC relative addresses. */
> .align 0
> @@ -464,9 +579,6 @@ change_back:
> #else
> .word 0x80000 /* Top of RAM on the PIE board. */
> #endif
> -
> -.Lstack:
> - .word __stack
> .Lhwinit:
> .word FUNCTION (hardware_init_hook)
> .Lswinit:
> @@ -479,17 +591,16 @@ change_back:
> and only if, a normal version of the same symbol isn't provided
> e.g. by a linker script or another object file.) */
>
> - .weak __stack
> .weak FUNCTION (hardware_init_hook)
> .weak FUNCTION (software_init_hook)
> #endif
>
> #endif
> -#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
> - /* Protect against unhandled exceptions. */
> - .cantunwind
> - .fnend
> -#endif
> +
> +.Lstack:
> + .word __stack
> + .weak __stack
> +
> .LC1:
> .word __bss_start__
> .LC2:
> diff --git a/newlib/libc/sys/arm/arm.h b/newlib/libc/sys/arm/arm.h
> index 0489f2d92..04b3a5ac7 100644
> --- a/newlib/libc/sys/arm/arm.h
> +++ b/newlib/libc/sys/arm/arm.h
> @@ -61,4 +61,30 @@
> # define HAVE_CALL_INDIRECT
> #endif
>
> +/* A and R profiles (and legacy Arm).
> + Current Program Status Register (CPSR)
> + M[4:0] Mode bits. M[4] is always 1 for 32-bit modes.
> + T[5] 1: Thumb, 0: ARM instruction set
> + F[6] 1: disables FIQ
> + I[7] 1: disables IRQ
> + A[8] 1: disables imprecise aborts
> + E[9] 0: Little-endian, 1: Big-endian
> + J[24] 1: Jazelle instruction set
> + */
> +#define CPSR_M_USR 0x00 /* User mode */
> +#define CPSR_M_FIQ 0x01 /* Fast Interrupt mode */
> +#define CPSR_M_IRQ 0x02 /* Interrupt mode */
> +#define CPSR_M_SVR 0x03 /* Supervisor mode */
> +#define CPSR_M_MON 0x06 /* Monitor mode */
> +#define CPSR_M_ABT 0x07 /* Abort mode */
> +#define CPSR_M_HYP 0x0A /* Hypervisor mode */
> +#define CPSR_M_UND 0x0B /* Undefined mode */
> +#define CPSR_M_SYS 0x0F /* System mode */
> +#define CPSR_M_32BIT 0x10 /* 32-bit mode */
> +#define CPSR_T_BIT 0x20 /* Thumb bit */
> +#define CPSR_F_MASK 0x40 /* FIQ bit */
> +#define CPSR_I_MASK 0x80 /* IRQ bit */
> +
> +#define CPSR_M_MASK 0x0F /* Mode mask except M[4] */
> +
> #endif /* _LIBGLOSS_ARM_H */
> diff --git a/newlib/libc/sys/arm/crt0.S b/newlib/libc/sys/arm/crt0.S
> index 7a6b40d9a..0929a435e 100644
> --- a/newlib/libc/sys/arm/crt0.S
> +++ b/newlib/libc/sys/arm/crt0.S
> @@ -59,6 +59,21 @@
> .endm
> #endif
>
> +/* Annotation for EABI unwinding tables. */
> +.macro FN_EH_START
> +#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
> + .fnstart
> +#endif
> +.endm
> +
> +.macro FN_EH_END
> +#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
> + /* Protect against unhandled exceptions. */
> + .cantunwind
> + .fnend
> +#endif
> +.endm
> +
> .macro indirect_call reg
> #ifdef HAVE_CALL_INDIRECT
> blx \reg
> @@ -68,16 +83,170 @@
> #endif
> .endm
>
> +/* For armv4t and newer, toolchains will transparently convert
> + 'bx lr' to 'mov pc, lr' if needed. GCC has deprecated support
> + for anything older than armv4t, but this should handle that
> + corner case in case anyone needs it anyway */
> +.macro FN_RETURN
> +#if __ARM_ARCH <= 4 && __ARM_ARCH_ISA_THUMB == 0
> + mov pc, lr
> +#else
> + bx lr
> +#endif
> +.endm
> +
> +
> +
>
> +/******************************************************************************
> +* User mode only: This routine makes default target specific
> Stack
> +* +-----+ <- SL_sys, Pointer initialization for different processor
> modes:
> +* | | SL_usr FIQ, Abort, IRQ, Undefined, Supervisor, System
> (User)
> +* | SYS | and setups a default Stack Limit in-case the
> code has
> +* | USR | -=0x10000 been compiled with "-mapcs-stack-check" for FIQ
> and
> +* | | System (User) modes.
> +* | |
> +* +-----+ <- initial SP,
> +* becomes SP_sys Hard-wiring SL value is not ideal, since
> there is
> +* and SL_usr currently no support for checking that the
> heap and
> +* stack have not collided, or that this default
> 64k is
> +* All modes: is enough for the program being executed.
> However,
> +* +-----+ <- SL_sys, it ensures that this simple crt0 world will not
> +* | | SL_usr immediately cause an overflow event.
> +* | SYS |
> +* | USR | -=0x10000 We go through all execution modes and set up
> SP
> +* | | for each of them.
> +* +-----+ <- SP_sys,
> +* | | SP_usr Note:
> +* | SVC | -= 0x8000 Mode switch via CPSR is not allowed once in
> +* | | non-privileged mode, so we take care not to
> enter
> +* +-----+ <- SP_svc "User" to set up its sp, and also skip most
> +* | | operations if already in that mode.
> +* | IRQ | -= 0x2000
> +* | | Input parameters:
> +* ^ +-----+ <- SP_und - sp - Initialized SP
> +* s | | - r2 - May contain SL value from semihosting
> +* t | UND | -= 0x1000 SYS_HEAPINFO call
> +* a | | Scratch registers:
> +* c +-----+ <- SP_und - r1 - new value of CPSR
> +* k | | - r2 - intermediate value (in standalone mode)
> +* | ABT | -= 0x1000 - r3 - new SP value
> +* g | | - r4 - save/restore CPSR on entry/exit
> +* r +-----+ <- SP_abt,
> +* o | | SL_fiq Declared as "weak" so that user can write
> and use
> +* w | FIQ | -= 0x1000 his own implementation if current doesn't fit.
> +* t | |
> +* h +-----+ <- initial SP,
> +* becomes SP_fiq
> +*
>
> +******************************************************************************/
> + .align 0
> + FUNC_START _stack_init
> + .weak FUNCTION (_stack_init)
> + FN_EH_START
> +
> + /* M profile doesn't have CPSR register. */
> +#if (__ARM_ARCH_PROFILE != 'M')
> + /* Following code is compatible for both ARM and Thumb ISA */
> + mrs r4, CPSR
> + /* Test mode bits - in User of all are 0 */
> + tst r4, #(CPSR_M_MASK)
> + /* "eq" means r4 AND #0x0F is 0 */
> + beq .Lskip_cpu_modes
> +
> + mov r3, sp /* save input SP value */
> +
> + /* FIQ mode, interrupts disabled */
> + mov r1, #(CPSR_M_FIQ|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> + sub sl, sp, #0x1000 /* FIQ mode has its own SL */
> +
> + /* Abort mode, interrupts disabled */
> + mov r3, sl
> + mov r1, #(CPSR_M_ABT|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> + sub r3, r3, #0x1000
> +
> + /* Undefined mode, interrupts disabled */
> + mov r1, #(CPSR_M_UND|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> + sub r3, r3, #0x1000
> +
> + /* IRQ mode, interrupts disabled */
> + mov r1, #(CPSR_M_IRQ|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> + sub r3, r3, #0x2000
> +
> + /* Supervisory mode, interrupts disabled */
> + mov r1, #(CPSR_M_SVR|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> +
> + sub r3, r3, #0x8000 /* Min size 32k */
> + bic r3, r3, #0x00FF /* Align with current 64k block */
> + bic r3, r3, #0xFF00
> +
> +# if __ARM_ARCH >= 4
> + /* System (shares regs with User) mode, interrupts disabled */
> + mov r1, #(CPSR_M_SYS|CPSR_M_32BIT|CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r1
> + mov sp, r3
> +# else
> + /* Keep this for ARMv3, but GCC actually dropped it. */
> + /* Move value into user mode sp without changing modes, */
> + /* via '^' form of ldm */
> + str r3, [r3, #-4]
> + ldmdb r3, {sp}^
> +# endif
> +
> + /* Back to original mode, presumably SVC, with diabled FIQ/IRQ */
> + orr r4, r4, #(CPSR_I_MASK|CPSR_F_MASK)
> + msr CPSR_c, r4
> +
> +.Lskip_cpu_modes:
> +#endif
> +
> + /* Set SL register */
> +#if defined (ARM_RDI_MONITOR) /* semihosting */
> + cmp r2, #0
> + beq .Lsl_forced_zero
> + /* allow slop for stack overflow handling and small frames */
> +# ifdef THUMB1_ONLY
> + adds r2, #128
> + adds r2, #128
> + mov sl, r2
> +# else
> + add sl, r2, #256
> +# endif
> +.Lsl_forced_zero:
> +
> +#else /* standalone */
> + /* r3 contains SP for System/User mode. Set SL = SP - 0x10000 */
> + #ifdef THUMB1_ONLY
> + movs r2, #64
> + lsls r2, r2, #10
> + subs r2, r3, r2
> + mov sl, r2
> + #else
> + /* Still assumes 256bytes below sl */
> + sub sl, r3, #64 << 10
> + #endif
> +#endif
> +
> + FN_RETURN
> + FN_EH_END
> +
> +
>
> /*******************************************************************************
> * Main library startup code.
>
> *******************************************************************************/
> .align 0
> FUNC_START _mainCRTStartup
> FUNC_START _start
> -#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
> - /* Annotation for EABI unwinding tables. */
> - .fnstart
> -#endif
> + FN_EH_START
>
> /* Start by setting up a stack. */
> #ifdef ARM_RDP_MONITOR
> @@ -130,36 +299,27 @@
> to skip setting sp/sl to 0 here.
> - Considering M-profile processors, We might want to initialize
> sp by the first entry of vector table and return 0 to
> SYS_HEAPINFO
> - semihosting call, which will be skipped here. */
> + semihosting call, which will be skipped here.
> + - Considering R-profile processors there is no automatic SP
> init by hardware
> + so we need to initialize it by default value. */
> + ldr r3, .Lstack
> cmp r1, #0
> beq .LC26
> - mov sp, r1
> + mov r3, r1
> .LC26:
> - cmp r2, #0
> - beq .LC27
> + mov sp, r3
>
> - /* Allow slop for stack overflow handling and small frames. */
> -#ifdef THUMB1_ONLY
> - adds r2, #128
> - adds r2, #128
> - mov sl, r2
> -#else
> - add sl, r2, #256
> -#endif
> + /* r2 (SL value) will be used in _stack_init */
> + bl FUNCTION (_stack_init)
>
> -.LC27:
> -#else
> - /* Set up the stack pointer to a fixed value. */
> +
> +#else /* standalone */
> + /* Set up the stack pointer to a fixed value. */
> /* Changes by toralf:
> - Allow linker script to provide stack via __stack symbol - see
> defintion of .Lstack
> - Provide "hooks" that may be used by the application to add
> - custom init code - see .Lhwinit and .Lswinit
> - - Go through all execution modes and set up stack for each of
> them.
> - Loosely based on init.s from ARM/Motorola example code.
> - Note: Mode switch via CPSR is not allowed once in
> non-privileged
> - mode, so we take care not to enter "User" to set up
> its sp,
> - and also skip most operations if already in that
> mode. */
> + custom init code - see .Lhwinit and .Lswinit */
>
> ldr r3, .Lstack
> cmp r3, #0
> @@ -178,57 +338,10 @@
> have somehow missed it below (in which case it gets the
> same
> value as FIQ - not ideal, but better than nothing). */
> mov sp, r3
> -#ifdef PREFER_THUMB
> - /* XXX Fill in stack assignments for interrupt modes. */
> -#else
> - mrs r2, CPSR
> - tst r2, #0x0F /* Test mode bits - in User of all are 0.
> */
> - beq .LC23 /* "eq" means r2 AND #0x0F is 0. */
> - msr CPSR_c, #0xD1 /* FIRQ mode, interrupts disabled. */
> - mov sp, r3
> - sub sl, sp, #0x1000 /* This mode also has its own sl (see
> below). */
> -
> - mov r3, sl
> - msr CPSR_c, #0xD7 /* Abort mode, interrupts disabled. */
> - mov sp, r3
> - sub r3, r3, #0x1000
> -
> - msr CPSR_c, #0xDB /* Undefined mode, interrupts disabled. */
> - mov sp, r3
> - sub r3, r3, #0x1000
>
> - msr CPSR_c, #0xD2 /* IRQ mode, interrupts disabled. */
> - mov sp, r3
> - sub r3, r3, #0x2000
> -
> - msr CPSR_c, #0xD3 /* Supervisory mode, interrupts disabled.
> */
> + /* we don't care of r2 value in standalone */
> + bl FUNCTION (_stack_init)
>
> - mov sp, r3
> - sub r3, r3, #0x8000 /* Min size 32k. */
> - bic r3, r3, #0x00FF /* Align with current 64k block. */
> - bic r3, r3, #0xFF00
> -
> - str r3, [r3, #-4] /* Move value into user mode sp without */
> - ldmdb r3, {sp}^ /* changing modes, via '^' form of ldm.
> */
> - orr r2, r2, #0xC0 /* Back to original mode, presumably SVC,
> */
> - msr CPSR_c, r2 /* with FIQ/IRQ disable bits forced to 1.
> */
> -#endif
> -.LC23:
> - /* Setup a default stack-limit in-case the code has been
> - compiled with "-mapcs-stack-check". Hard-wiring this value
> - is not ideal, since there is currently no support for
> - checking that the heap and stack have not collided, or that
> - this default 64k is enough for the program being executed.
> - However, it ensures that this simple crt0 world will not
> - immediately cause an overflow event: */
> -#ifdef THUMB1_ONLY
> - movs r2, #64
> - lsls r2, r2, #10
> - subs r2, r3, r2
> - mov sl, r2
> -#else
> - sub sl, r3, #64 << 10 /* Still assumes 256bytes below
> sl. */
> -#endif
> #endif
> #endif
> /* Zero the memory in the .bss section. */
> @@ -421,6 +534,8 @@ change_back:
> swi SWI_Exit
> #endif
>
> + FN_EH_END
> +
> /* For Thumb, constants must be after the code since only
> positive offsets are supported for PC relative addresses. */
> .align 0
> @@ -438,9 +553,6 @@ change_back:
> #else
> .word 0x80000 /* Top of RAM on the PIE board. */
> #endif
> -
> -.Lstack:
> - .word __stack
> .Lhwinit:
> .word FUNCTION (hardware_init_hook)
> .Lswinit:
> @@ -453,17 +565,16 @@ change_back:
> and only if, a normal version of the same symbol isn't provided
> e.g. by a linker script or another object file.) */
>
> - .weak __stack
> .weak FUNCTION (hardware_init_hook)
> .weak FUNCTION (software_init_hook)
> #endif
>
> #endif
> -#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
> - /* Protect against unhandled exceptions. */
> - .cantunwind
> - .fnend
> -#endif
> +
> +.Lstack:
> + .word __stack
> + .weak __stack
> +
> .LC1:
> .word __bss_start__
> .LC2:
> --
> 2.17.1
>
>