95 lines
2.2 KiB
ArmAsm
95 lines
2.2 KiB
ArmAsm
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#define CBFS_HEADER_PTR 0xfffffffc
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#define CBFS_HEADER_MAGIC 0
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#define CBFS_HEADER_VERSION (CBFS_HEADER_MAGIC + 4)
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#define CBFS_HEADER_ROMSIZE (CBFS_HEADER_VERSION + 4)
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#define CBFS_HEADER_BOOTBLOCKSIZE (CBFS_HEADER_ROMSIZE + 4)
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#define CBFS_HEADER_ALIGN (CBFS_HEADER_BOOTBLOCKSIZE + 4)
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#define CBFS_HEADER_OFFSET (CBFS_HEADER_ALIGN + 4)
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#define CBFS_FILE_MAGIC 0
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#define CBFS_FILE_LEN (CBFS_FILE_MAGIC + 8)
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#define CBFS_FILE_TYPE (CBFS_FILE_LEN + 4)
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#define CBFS_FILE_CHECKSUM (CBFS_FILE_TYPE + 4)
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#define CBFS_FILE_OFFSET (CBFS_FILE_CHECKSUM + 4)
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#define CBFS_FILE_STRUCTSIZE (CBFS_FILE_OFFSET + 4)
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#define CBFS_STAGE_COMPRESSION 0
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#define CBFS_STAGE_ENTRY (CBFS_STAGE_COMPRESSION + 4)
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#define CBFS_STAGE_LOAD (CBFS_STAGE_ENTRY + 8)
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#define CBFS_STAGE_LEN (CBFS_STAGE_LOAD + 8)
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#define CBFS_STAGE_MEMLEN (CBFS_STAGE_LEN + 4)
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/*
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input %esi: filename
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input %esp: return address (not pointer to return address!)
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output %eax: entry point
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clobbers %ebx, %ecx, %edx, %edi, %ebp
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*/
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walkcbfs:
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mov %esi, %ebp /* stash away filename pointer */
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mov $0, %edx
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1:
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cmpb $0, (%edx,%esi)
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jz 2f
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add $1, %edx
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jmp 1b
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2:
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add $1, %edx
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mov CBFS_HEADER_PTR, %eax
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mov CBFS_HEADER_ROMSIZE(%eax), %ecx
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bswap %ecx
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mov $0, %ebx
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sub %ecx, %ebx
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mov CBFS_HEADER_OFFSET(%eax), %ecx
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bswap %ecx
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add %ecx, %ebx
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mov CBFS_HEADER_ALIGN(%eax), %eax
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bswap %eax
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sub $1, %eax
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walker:
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mov %ebp, %esi
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mov %ebx, %edi
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add $CBFS_FILE_STRUCTSIZE, %edi /* edi = address of first byte after struct cbfs_file */
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mov %edx, %ecx
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repe cmpsb
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# zero flag set if strings are equal
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jnz tryharder
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# we found it!
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mov CBFS_FILE_OFFSET(%ebx), %eax
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bswap %eax
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add %ebx, %eax
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add $CBFS_STAGE_ENTRY, %eax /* eax = ((cbfs_stage* (cbfs_file* ebx)->offset)->entry) */
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mov 0(%eax), %eax
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jmp *%esp
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tryharder:
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mov CBFS_FILE_OFFSET(%ebx), %ecx
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bswap %ecx
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add %ebx, %ecx
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mov CBFS_FILE_LEN(%ebx), %edi
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bswap %edi
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add %edi, %ecx
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add %eax, %ecx
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mov %eax, %edi
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not %edi
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and %edi, %ecx
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mov %ecx, %ebx
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/* look if we should exit */
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mov CBFS_HEADER_PTR, %esi
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mov CBFS_HEADER_ROMSIZE(%esi), %ecx
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bswap %ecx
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not %ecx
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add $1, %ecx
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cmp %ebx, %ecx
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/* if we're still inside the ROM area, jump back */
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jbe walker
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mov $0, %eax
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jmp *%esp
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