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adbgen makes it possible to write adb(1)
scripts that do not contain hard-coded dependencies on structure member offsets. The input to adbgen is a file named filename.adb that contains
header information, then a null line, then the name of a structure, and finally an adb script. adbgen only deals with one structure per file; all member names are assumed
to be in this structure. The output of adbgen is an adb script in filename. adbgen operates by generating a C program
which determines structure member offsets and sizes, which in turn generate the adb script.
The header lines, up to the null line, are copied verbatim into the generated C program. Typically, these are #include statements, which include the headers containing the relevant
structure declarations.
The adb script part may contain any valid adb commands (see adb(1)), and may also contain adbgen requests, each enclosed in braces ({}). Request types are:
- Print a structure member. The request form is {member,format}. member is a member name of the structure given earlier, and format is any valid adb format request or any of the adbgen format specifiers (such as {POINTER}) listed below. For example, to print the p_pid field of the proc structure as a decimal
number, you would write {p_pid,d}.
- Print the appropriate adb format character for the given adbgen format specifier. This action takes the data model into consideration. The
request form is {format specifier}. The valid adbgen format specifiers are:
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{POINTER}
- pointer value in hexadecimal
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{LONGDEC}
- long value in decimal
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{ULONGDEC}
- unsigned long value in decimal
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{ULONGHEX}
- unsigned long value in hexadecimal
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{LONGOCT}
- long value in octal
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{ULONGOCT}
- unsigned long value in octal
- Reference a structure member. The request form is {*member,base}. member is the member name whose value is desired, and base is an adb register name which contains the base address of
the structure. For example, to get the p_pid field of the proc structure, you would get the proc structure address in an adb register, for example <f, and write {*p_pid,<f}.
- Tell adbgen that the offset is valid. The request form is {OFFSETOK}. This is useful after invoking another adb script
which moves the adb dot.
- Get the size of the structure. The request form is {SIZEOF}. adbgen replaces this request with the size of the
structure. This is useful in incrementing a pointer to step through an array of structures.
- Calculate an arbitrary C expression. The request form is {EXPR,expression}. adbgen
replaces this request with the value of the expression. This is useful when more than one structure is involved in the script.
- Get the offset to the end of the structure. The request form is {END}. This is useful at the end of the structure to get adb to align the dot for printing the next structure member.
adbgen keeps track of the movement of the adb dot and generates adb code to move forward or backward as necessary
before printing any structure member in a script. adbgen's model of the behavior of adb's dot is simple: it is assumed that the first line
of the script is of the form struct_address/adb text and that subsequent lines are of the form +/adb text. The adb dot then moves in a sane fashion. adbgen does not check the script to ensure that these limitations are met. adbgen also checks
the size of the structure member against the size of the adb format code and warns if they are not equal.
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