| 1 | GC on EWS4800
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| 2 | -------------
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| 3 |
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| 4 | 1. About EWS4800
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| 5 | EWS4800 is 32bit/64bit workstation.
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| 6 |
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| 7 | Vender: NEC Corporation
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| 8 | OS: UX/4800 R9.* - R13.* (SystemV R4.2)
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| 9 | CPU: R4000, R4400, R10000 (MIPS)
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| 10 |
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| 11 | 2. Compiler
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| 12 |
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| 13 | 32bit:
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| 14 | Use ANSI C compiler.
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| 15 | CC = /usr/abiccs/bin/cc
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| 16 |
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| 17 | 64bit:
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| 18 | Use 64bit ANSI C compiler.
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| 19 | CC = /usr/ccs64/bin/cc
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| 20 | AR = /usr/ccs64/bin/ar
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| 21 |
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| 22 | 3. ELF file format
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| 23 | *** Caution: The following infomation is empirical. ***
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| 24 |
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| 25 | 32bit:
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| 26 | ELF file has an unique format. (See a.out(4) and end(3C).)
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| 27 |
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| 28 | &_start
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| 29 | : text segment
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| 30 | &etext
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| 31 | DATASTART
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| 32 | : data segment (initialized)
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| 33 | &edata
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| 34 | DATASTART2
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| 35 | : data segment (uninitialized)
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| 36 | &end
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| 37 |
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| 38 | Here, DATASTART and DATASTART2 are macros of GC, and are defined as
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| 39 | the following equations. (See include/private/gcconfig.h.)
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| 40 | The algorithm for DATASTART is similar with the function
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| 41 | GC_SysVGetDataStart() in os_dep.c.
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| 42 |
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| 43 | DATASTART = ((&etext + 0x3ffff) & ~0x3ffff) + (&etext & 0xffff)
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| 44 |
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| 45 | Dynamically linked:
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| 46 | DATASTART2 = (&_gp + 0x8000 + 0x3ffff) & ~0x3ffff
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| 47 |
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| 48 | Statically linked:
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| 49 | DATASTART2 = &edata
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| 50 |
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| 51 | GC has to check addresses both between DATASTART and &edata, and
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| 52 | between DATASTART2 and &end. If a program accesses between &etext
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| 53 | and DATASTART, or between &edata and DATASTART2, the segmentation
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| 54 | error occurs and the program stops.
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| 55 |
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| 56 | If a program is statically linked, there is not a gap between
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| 57 | &edata and DATASTART2. The global symbol &_DYNAMIC_LINKING is used
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| 58 | for the detection.
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| 59 |
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| 60 | 64bit:
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| 61 | ELF file has a simple format. (See end(3C).)
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| 62 |
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| 63 | _ftext
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| 64 | : text segment
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| 65 | _etext
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| 66 | _fdata = DATASTART
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| 67 | : data segment (initialized)
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| 68 | _edata
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| 69 | _fbss
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| 70 | : data segment (uninitialized)
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| 71 | _end = DATAEND
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| 72 |
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| 73 | --
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| 74 | Hironori SAKAMOTO <hsaka@mth.biglobe.ne.jp>
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| 75 |
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