97 lines
2.6 KiB
Groff
97 lines
2.6 KiB
Groff
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.Dd December 2, 2016
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.Dt CVMACH 6
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.Os
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.Sh NAME
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.Nm cvmach
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.Nd convert an executable file from ack.out to Mach-o
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.Sh SYNOPSIS
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.Cm ~em/lib/ack/cvmach
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.Fl m Ns Ar number
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.Oo
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.Ar infile
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.Op Ar outfile
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.Oc
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.Sh DESCRIPTION
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The
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.Nm
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utility converts an executable file from
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.Xr ack.out 5
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format to Mach-object format.
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It can produce Mach-o executables for Mac OS X.
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If the
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.Ar infile
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or
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.Ar outfile
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are not given, then
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.Nm
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reads from standard input or writes to standard output.
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.Pp
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The option is required:
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.Bl -tag -width Ds
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.It Fl m Ns Ar number
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Sets the CPU type in the Mach header.
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This must be
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.Fl m Ns Cm 7
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for Intel i386 or
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.Fl m Ns Cm 18
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for PowerPC.
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.Nm
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doesn't know how to make Mach-o files for other CPU types.
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.El
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.Pp
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The input file must have four segments:
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TEXT, ROM, DATA and BSS, in that order.
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.Nm
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converts them into four Mach sections in two Mach segments.
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TEXT and ROM go in the RX segment (Read and eXecute).
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DATA and BSS go in the RW segment (Read and Write).
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.Nm
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sets the page protection so programs can't write the RX segment,
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and can't execute the RW segment.
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The program will begin execution at the beginning of TEXT.
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.Pp
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.Nm
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also converts the symbol table.
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.Sh DIAGNOSTICS
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.Bl -diag
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.It text segment must have base 0x%lx, not 0x%lx
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TEXT must begin immediately after the Mach header and load commands.
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The message gives the correct
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.Ar base .
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Relinking the program with
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.Cm em_led Fl b Ns 0: Ns Ar base
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would fix it.
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.It the %s segment must follow the %s segment.
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TEXT and ROM must be continuous in memory, because
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.Nm
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maps them in the same Mach segment.
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Likewise, DATA and BSS must be contiguous.
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There may be a small gap between TEXT and ROM, or between DATA and
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BSS, only if the gap is necessary to align ROM or BSS.
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.It the data and rom segments are too close.
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DATA and ROM must not share a page in memory, because
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.Nm
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maps them in different Mach segments, with different page protections.
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The page size for i386 and PowerPC is 4096 or 0x1000 bytes.
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For example, if ROM ends at address 0x2bed,
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then DATA may not begin at 0x2bf0, because
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.Nm
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can't put the page from 0x2000 to 0x2fff in both Mach segments.
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Relinking the program with
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.Cm em_led Fl a Ns 2:4096
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would fix it.
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.It the bss space contains initialized data.
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BSS must not contain initialized data, because
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.Nm
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converts it to a zero-fill section.
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.El
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.Sh CAVEATS
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Mac OS X 10.4 for PowerPC does not protect pages against execution.
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All mapped pages are executable, whether or not the execute bit is set
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in the page protection.
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.Nm
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can't prevent the execution of the RW segment.
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.Sh BUGS
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The symbol conversion preserves the name and value of each symbol, but
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may lose other information, such as the symbol type.
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