FreeBSD/Linux Kernel Cross Reference
sys/tools/arm_kernel_boothdr.awk

     #!/usr/bin/awk -f
     #-
     # SPDX-License-Identifier: BSD-2-Clause-FreeBSD
     #
     # Copyright 2019 Ian Lepore <ian@freebsd.org>
     #
     # Redistribution and use in source and binary forms, with or without
     # modification, are permitted provided that the following conditions
     # are met:
    # 1. Redistributions of source code must retain the above copyright
    #    notice, this list of conditions and the following disclaimer.
    # 2. Redistributions in binary form must reproduce the above copyright
    #    notice, this list of conditions and the following disclaimer in the
    #    documentation and/or other materials provided with the distribution.
    #
    # THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
    # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    # ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
    # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    # SUCH DAMAGE.
    #
    # $FreeBSD$
    
    BEGIN {
            # Init global vars.
            gBytesOut = 0;  # How many output bytes we've written so far
            gKernbase = 0;  # Address of first byte of loaded kernel image
            gStart = 0;     # Address of _start symbol
            gStartOff = 0;  # Offset of _start symbol from start of image
            gEnd = 0;       # Address of _end symbol
            gEndOff = 0;    # Offset of _end symbol from start of image
    
            # The type of header we're writing is set using -v hdrtype= on
            # the command line, ensure we got a valid value for it.
            if (hdrtype != "v7jump" &&
                hdrtype != "v8jump" &&
                hdrtype != "v8booti") {
                    print "arm_kernel_boothdr.awk: " \
                        "missing or invalid '-v hdrtype=' argument" >"/dev/stderr"
                    gHdrType = "error_reported"
                    exit 1
            }
    
            gHdrType = hdrtype
    }
    
    function addr_to_offset(addr) {
            # Turn an address into an offset from the start of the loaded image.
            return addr % gKernbase
    }
    
    function hexstr_to_num(str) {
    
            # Prepend a 0x onto the string, then coerce it to a number by doing
            # arithmetic with it, which makes awk run it through strtod(),
            # which handles hex numbers that have a 0x prefix.
    
            return 0 + ("0x" str)
    }
    
    function write_le32(num) {
    
            for (i = 0; i < 4; i++) {
                    printf("%c", num % 256);
                    num /= 256
            }
            gBytesOut += 4
    }
    
    function write_le64(num) {
    
            for (i = 0; i < 8; i++) {
                    printf("%c", num % 256);
                    num /= 256
            }
            gBytesOut += 8
    }
    
    function write_padding() {
    
            # Write enough padding bytes so that the header fills all the
            # remaining space before the _start symbol.
    
            while (gBytesOut++ < gStartOff) {
                    printf("%c", 0);
            }
    }
    
    function write_v7jump() {
    
            # Write the machine code for "b _start"...
            #   0xea is armv7 "branch always" and the low 24 bits is the signed
            #   offset from the current PC, in words.  We know the gStart offset
           #   is in the first 2mb, so it'll fit in 24 bits.
   
           write_le32(hexstr_to_num("ea000000") + (gStartOff / 4) - 2)
   }
   
   function write_v8jump() {
   
           # Write the machine code for "b _start"...
           #   0x14 is armv8 "branch always" and the low 26 bits is the signed
           #   offset from the current PC, in words.  We know the gStart offset
           #   is in the first 2mb, so it'll fit in 26 bits.
   
           write_le32(hexstr_to_num("14000000") + (gStartOff / 4))
   }
   
   function write_v8booti() {
   
           # We are writing this struct...
           #
           # struct Image_header {
           #       uint32_t        code0;          /* Executable code */
           #       uint32_t        code1;          /* Executable code */
           #       uint64_t        text_offset;    /* Image load offset, LE */
           #       uint64_t        image_size;     /* Effective Image size, LE */
           #       uint64_t        flags;          /* Kernel flags, LE */
           #       uint64_t        res1[3];        /* reserved */
           #       uint32_t        magic;          /* Magic number */
           #       uint32_t        res2;
           # };
           #
           # We write 'b _start' into code0.  The image size is everything from
           # the start of the loaded image to the offset given by the _end symbol.
   
           write_v8jump()                        # code0
           write_le32(0)                         # code1
           write_le64(0)                         # text_offset
           write_le64(gEndOff)                   # image_size
           write_le64(0)                         # flags
           write_le64(0)                         # res1[0]
           write_le64(0)                         # res1[1]
           write_le64(0)                         # res1[2]
           write_le32(hexstr_to_num("644d5241")) # magic (LE "ARMd" (d is 0x64))
           write_le32(0)                         # res2
   }
   
   /kernbase/ {
           # If the symbol name is exactly "kernbase" save its address.
           if ($8 == "kernbase") {
                   gKernbase = hexstr_to_num($2)
           }
   }
   
   /_start/ {
           # If the symbol name is exactly "_start" save its address.
           if ($8 == "_start") {
                   gStart = hexstr_to_num($2)
           }
   }
   
   /_end/ {
           # If the symbol name is exactly "_end" remember its value.
           if ($8 == "_end") {
                   gEnd = hexstr_to_num($2)
           }
   }
   
   END {
           # Note that this function runs even if BEGIN calls exit(1)!
           if (gHdrType == "error_reported") {
                   exit 1
           }
   
           # Make sure we got all three required symbols.
           if (gKernbase == 0 || gStart == 0 || gEnd == 0) {
                   print "arm_kernel_boothdr.awk: " \
                       "missing kernbase/_start/_end symbol(s)" >"/dev/stderr"
                       exit 1
           }
   
           gStartOff = addr_to_offset(gStart)
           gEndOff = addr_to_offset(gEnd)
   
           if (gHdrType == "v7jump") {
                   write_v7jump()
           } else if (gHdrType == "v8jump") {
                   write_v8jump()
           } else if (gHdrType == "v8booti") {
                   write_v8booti()
           }
           write_padding()
   }

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