Hi,

I have read some sources that contains in the same file, asm, C and
linker instruction.
But when I compile a source file containing pre-processor instruction
like #define and linker instruction like entry(_start) with arm-elf-as
I've an error. Is it really possible to mix asm, C and linker
instruction and how?

thanks in advance for your help,

Best regards,

Stefan wrote:
> I've never seen such a source file. pre-processor instructions mixed
> with assembler code, yes - this are the *.S files, but mixed with linker
> instructions... no. Can you give an example?
>
> Stefan

Here it is : there are linker instruction in this source file whereas
usually I've seen them in a linker script. thanks for your help.

/*
 *  linux/arch/arm/kernel/head-armv.S
 *
 *  Copyright (C) 1994-1999 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  32-bit kernel startup code for all architectures
 *
 * added S3C4510 code by Mac Wang
 * added S3C4530 code by Arcturus Networks Inc.
 * added S3C2500 code by Arcturus Networks Inc.
 * added TI TMS320DM270 code by Chee Tim Loh
<cheetim_loh@innomedia.com.sg>.
 *
 */
#include <linux/config.h>
#include <linux/linkage.h>

#include <asm/assembler.h>
#include <asm/mach-types.h>
#include <asm/mach/arch.h>

#define K(a,b,c)  ((a) << 24 | (b) << 12 | (c))

/*
 * We place the page tables 16K below TEXTADDR.  Therefore, we must make
sure
 * that TEXTADDR is correctly set.  Currently, we expect the least
significant
 * "short" to be 0x8000, but we could probably relax this restriction to
 * TEXTADDR > PAGE_OFFSET + 0x4000
 *
 * Note that swapper_pg_dir is the virtual address of the page tables,
and
 * pgtbl gives us a position-independent reference to these tables.  We
can
 * do this because stext == TEXTADDR
 *
 * swapper_pg_dir, pgtbl and krnladr are all closely related.
 */

/*
 *  Kernel startup entry point.
 *
 * The rules are:
 *  r0      - should be 0
 *  r1      - unique architecture number
 *  MMU     - off
 *  I-cache - on or off
 *  D-cache - off
 *
 * See linux/arch/arm/tools/mach-types for the complete list of numbers
 * for r1.
 */

.section ".text.init",#alloc,#execinstr
    .type  stext, #function
ENTRY(stext)

                mov  r12, r0

/*
 * NOTE!  Any code which is placed here should be done for one of
 * the following reasons:
 *
 *  1. Compatability with old production boot firmware (ie, users
 *     actually have and are booting the kernel with the old firmware)
 *     and therefore will be eventually removed.
 *  2. Cover the case when there is no boot firmware.  This is not
 *     ideal, but in this case, it should ONLY set r0 and r1 to the
 *     appropriate value.
 */


#if defined(CONFIG_ARCH_L7200)
/*
 * FIXME - No bootloader, so manually set 'r1' with our architecture
number.
 */
    mov  r1, #MACH_TYPE_L7200
#elif defined(CONFIG_ARCH_INTEGRATOR)
    mov  r1, #MACH_TYPE_INTEGRATOR
#elif defined(CONFIG_ARCH_P52)
    mov  r1, #MACH_TYPE_P52
#elif defined(CONFIG_ARCH_CX821XX)
    mov  r1, #MACH_TYPE_CX821XX
#elif defined(CONFIG_ARCH_SWARM)
    mov  r1, #MACH_TYPE_SWARM
#elif defined(CONFIG_BOARD_SNDS100)
    mov  r1, #MACH_TYPE_SNDS100
#elif defined (CONFIG_BOARD_SMDK40100)
    mov  r1, #MACH_TYPE_S3C3410
#elif defined (CONFIG_BOARD_MBA44)
    mov  r1, #MACH_TYPE_S3C44B0X
#elif defined(CONFIG_BOARD_SMDK2500)
    mov r1, #MACH_TYPE_SMDK2500
#elif defined(CONFIG_BOARD_S3C2500REFRGP)
    mov  r1, #MACH_TYPE_S3C2500REFRGP
#elif defined(CONFIG_ARCH_LPC)
    mov r1, #MACH_TYPE_LPC22XX & 0xff
    orr r1, r1, #MACH_TYPE_LPC22XX & 0xff00
#endif

    mov  r0, #F_BIT | I_BIT | MODE_SVC  @ make sure svc mode
    msr  cpsr_c, r0      @ and all irqs disabled


#if defined(CONFIG_ARCH_ATMEL)

        adr  r5, LC0
        ldmia  r5, {r5, r6, r8, r9, sp}      @ Setup stack

        /*  Copy data sections to their new home.  */


        /*  Clear BSS */
        mov  r4, #0
1:      cmp  r5, r8
        strcc  r4, [r5],#4
        bcc  1b

/* FIXME */
#if 0
        /*  Put initial values into stack.  This would normally be done
        by sched_init() in kernel/sched.c, but that would overwrite the
        stack we're already using.  That would be bad.
        */
        mov r5, sp
        sub r5, r5, #0x2000
        ldr r4, L_STACK_MAGIC
        str r4, [r5], #4
        ldr r4, L_STACK_UNTOUCHED_MAGIC
1:      cmp r5, sp
        strcc r4, [r5], #4
        bcc 1b
#endif
        /*  Pretend we know what our processor code is (for arm_id)   */

@@@  ldr     r2, =0x41000000
@@@  orr  r2, r2, #0x7000    @ FIXME --> 0x41007000

  ldr  r2, L_AT91_SF_CIDR
  ldr  r2, [r2]    @ read processor id

  str     r2, [r6]
  mov     r2, #MACH_TYPE_ATMEL
  str     r2, [r9]

        mov fp, #0
        b  start_kernel

LC0:  .long  __bss_start
        .long  processor_id
        .long  _end
  .long   __machine_arch_type
        .long  init_task_union+8192
#endif


    adr  lr, __ret      @ return address
    add  pc, r10, #12      @ initialise processor
              @ (return control reg)

__switch_data:  .long  __mmap_switched
    .long  SYMBOL_NAME(compat)
    .long  SYMBOL_NAME(__bss_start)
    .long  SYMBOL_NAME(_end)
    .long  SYMBOL_NAME(processor_id)
    .long  SYMBOL_NAME(__machine_arch_type)
    .long  SYMBOL_NAME(cr_alignment)
    .long  SYMBOL_NAME(init_task_union)+8192

__ret:    ldr  lr, __switch_data

    mov  pc, lr

    /*
     * This code follows on after the page
     * table switch and jump above.
     *
     * r0  = processor control register
     * r1  = machine ID
     * r9  = processor ID
     */
    .align  5

__mmap_switched:
    adr  r3, __switch_data + 4
    ldmia  r3, {r2, r4, r5, r6, r7, r8, sp}@ r2 = compat
              @ sp = stack pointer
    str  r12, [r2]

#ifdef CONFIG_RAM_ATTACHED_ROMFS
# ifdef CONFIG_ARCH_DM270
/*
 *  Move ROM filesystem above bss :-)
 */
    ldr r3, L_DM270_ROMFS      @ Get end of data

    ldr r10, [r3, #8]      @ Get size of ROMFS (big-endian)
#ifndef CONFIG_CPU_BIG_ENDIAN
    mov r2, #0        @ Convert to little-endian
    and fp, r10, #0x000000ff
    orr r2, r2, fp, lsl #24
    and fp, r10, #0x0000ff00
    orr r2, r2, fp, lsl #8
    and fp, r10, #0x00ff0000
    orr r2, r2, fp, lsr #8
    and fp, r10, #0xff000000
    orr r2, r2, fp, lsr #24
    mov r10, r2
#endif
    add r10, r10, #8      @ Allow for rounding
    bic r10, r10, #3      @ Whole words

    ldr fp, L_DM270_ROMFS + 4    @ Set up destination
    mov r2, r3        @ Copy of _edata

    add r3, r3, r10        @ Copy from end
    add fp, fp, r10
    ldr r10, L_DM270_RAMSTART
    str fp, [r10]

_copy_romfs:
    ldr r10, [r3, #-4]!      @ Copy dword
    str r10, [fp, #-4]!
    cmp r3, r2        @ Check if at end
    bne _copy_romfs
# endif
#endif

    mov  fp, #0        @ Clear BSS (and zero fp)
1:    cmp  r4, r5
    strcc  fp, [r4],#4
    bcc  1b

    str  r9, [r6]      @ Save processor ID
    str  r1, [r7]      @ Save machine type
#ifdef CONFIG_ALIGNMENT_TRAP
    orr  r0, r0, #2      @ ...........A.
#endif
    bic  r2, r0, #2      @ Clear 'A' bit
    stmia  r8, {r0, r2}      @ Save control register values
    b  SYMBOL_NAME(start_kernel)


/*
 * Exception handling.  Something went wrong and we can't
 * proceed.  We ought to tell the user, but since we
 * don't have any guarantee that we're even running on
 * the right architecture, we do virtually nothing.
 * r0 = ascii error character:
 *  a = invalid architecture
 *  p = invalid processor
 *  i = invalid calling convention
 *
 * Generally, only serious errors cause this.
 */
__error:
#ifdef CONFIG_DEBUG_LL
    mov  r8, r0        @ preserve r0
    adr  r0, err_str
    bl  printascii
    mov  r0, r8
    bl  printch
#endif
#ifdef CONFIG_ARCH_RPC
/*
 * Turn the screen red on a error - RiscPC only.
 */
    mov  r0, #0x02000000
    mov  r3, #0x11
    orr  r3, r3, r3, lsl #8
    orr  r3, r3, r3, lsl #16
    str  r3, [r0], #4
    str  r3, [r0], #4
    str  r3, [r0], #4
    str  r3, [r0], #4
#endif
1:    mov  r0, r0
    b  1b

#ifdef CONFIG_DEBUG_LL
err_str:  .asciz  "\nError: "
    .align
#endif

/*
 * Read processor ID register (CP#15, CR0), and look up in the
linker-built
 * supported processor list.  Note that we can't use the absolute
addresses
 * for the __proc_info lists since we aren't running with the MMU on
 * (and therefore, we are not in the correct address space).  We have to
 * calculate the offset.
 *
 * Returns:
 *  r5, r6, r7 corrupted
 *  r8  = page table flags
 *  r9  = processor ID
 *  r10 = pointer to processor structure
 */
__lookup_processor_type:
    adr  r5, 2f
    ldmia  r5, {r7, r9, r10}
    sub  r5, r5, r10      @ convert addresses
    add  r7, r7, r5      @ to our address space
    add  r10, r9, r5
#ifdef CONFIG_CPU_WITH_MCR_INSTRUCTION
    mrc  p15, 0, r9, c0, c0    @ get processor id
#else
# warning   "FIXME: Get Processor ID without MCR Instruction"
    @ A possible code
    @ldr  r9, PROCESSOR_ID_MEM_LOCATION
    @ldr  r9, [r9]
#ifdef CONFIG_ARCH_DM270
    ldr  r9, L_DM270_PID
#endif
#endif
1:    ldmia  r10, {r5, r6, r8}    @ value, mask, mmuflags
    and  r6, r6, r9      @ mask wanted bits
    teq  r5, r6
    moveq  pc, lr
    add  r10, r10, #36      @ sizeof(proc_info_list)
    cmp  r10, r7
    blt  1b
    mov  r10, #0        @ unknown processor
    mov  pc, lr

/*
 * Look in include/asm-arm/procinfo.h and arch/arm/kernel/arch.[ch] for
 * more information about the __proc_info and __arch_info structures.
 */
2:    .long  __proc_info_end
    .long  __proc_info_begin
    .long  2b
    .long  __arch_info_begin
    .long  __arch_info_end

/*
 * Lookup machine architecture in the linker-build list of
architectures.
 * Note that we can't use the absolute addresses for the __arch_info
 * lists since we aren't running with the MMU on (and therefore, we are
 * not in the correct address space).  We have to calculate the offset.
 *
 *  r1 = machine architecture number
 * Returns:
 *  r2, r3, r4 corrupted
 *  r5 = physical start address of RAM
 *  r6 = physical address of IO
 *  r7 = byte offset into page tables for IO
 */
__lookup_architecture_type:
    adr  r4, 2b
    ldmia  r4, {r2, r3, r5, r6, r7}  @ throw away r2, r3
    sub  r5, r4, r5      @ convert addresses
    add  r4, r6, r5      @ to our address space
    add  r7, r7, r5
1:    ldr  r5, [r4]      @ get machine type
    teq  r5, r1
    beq  2f
    add  r4, r4, #SIZEOF_MACHINE_DESC
    cmp  r4, r7
    blt  1b
    mov  r7, #0        @ unknown architecture
    mov  pc, lr
2:    ldmib  r4, {r5, r6, r7}    @ found, get results
    mov  r7, r7, lsr #18      @ pagetable byte offset
    mov  pc, lr

L_AT91_SF_CIDR: .long  0xfff00000

#ifdef CONFIG_ARCH_DM270
L_DM270_PID:  .long  0xd2700000

# ifdef CONFIG_RAM_ATTACHED_ROMFS
.global  _ramstart
_ramstart:  .long  0

L_DM270_ROMFS:  .long  _edata
    .long  _ebss

L_DM270_RAMSTART:
    .long  _ramstart
# endif
#endif

You are right.

in the fiel linkage.h, there is the following lines :

#define ENTRY(name) \
  .globl SYMBOL_NAME(name); \
  ALIGN; \
  SYMBOL_NAME_LABEL(name)

and

#define SYMBOL_NAME_LABEL(X) X##:

#define ALIGN __ALIGN

and

#if defined(_i386_) && defined(CONFIG_X86_ALIGNMENT_16)
#define __ALIGN .align 16,0x90
#define __ALIGN_STR ".align 16,0x90"
#else
#define __ALIGN .align 4,0x90
#define __ALIGN_STR ".align 4,0x90"
#endif

so all is clear, it's asm with pre-processor code.

The aim of such a pre-processor code seems to use ENTRY(stext) in the
linker script. isn't it ? because if I understand the precedent lines,

  .globl SYMBOL_NAME(name); \
  ALIGN; \
  SYMBOL_NAME_LABEL(name)

doesn't define an entry point, there still need an ENTRY command in the
linker script.

Thanks, it confirms waht I thought. Things are getting clearer now.

It's really nice to all of you to help me like that.