Specifications

Loading an OpenVMS AXP Device Driver
10.3 Loading Sliced Executive Images
10.3.1 Controlling Executive Image Slicing
The system parameter LOAD_SYS_IMAGES is a bitmask and has several bits
defined:
• SGN$V_LOAD_SYS_IMAGES (bit 0)—Enables loading alternate executive
images specified in VMS$SYSTEM_IMAGES.DATA
• SGN$V_EXEC_SLICING (bit 1)—Enables the loading of the executive into
granularity hint regions
• SGN$V_RELEASE_PFNS (bit 2)—Enables releasing unused portions of the
huge pages
These bits are set by default. Use conversational bootstrap to disable exec slicing.
10.3.1.1 XDELTA Support for Executive Image Slicing
The display of the XDELTA ;L command accommodates both normally loaded and
sliced executive images. In Figure 10–2, you can see that EXEC_INIT has only a
single base and end address, it has not been sliced. The other executive images
all have multiple base and end addresses. These executive images have been
sliced. As the boot proceeds, the initialization and fixup sections are deleted; once
deleted, they are no longer displayed.
The ‘‘Seq#’’ field uniquely identifies each executive image. This sequence number
can be used with ;L to get a partial display.
10.3.1.2 Locating Source Modules with Image Slicing Enabled
The following steps describe how to determine what source module a given
program counter (PC) is in:
1. Use XDELTA to get a display of the loaded executive images. Scan the list to
find the executive image and image section which contain the PC.
2. Subtract the base address for the image section listed by XDELTA from the
PC you are trying to identify.
3. Get a linker map for that executive image and look at the ‘‘Image Section
Synopsis’’. Match the image section the PC is in with an image section from
the map.
4. Add the value calculated in step 2 to the base address for the image section
listed in the map.
5. Look at the ‘‘Program Section Synopsis’’ in the map and use the offset
calculated in step 4 to determine the source module.
The following example demonstrates how to determine the source module that
corresponds to address 80026530, using the preceding steps:
1. Use XDELTA to get a display of the loaded executive images. The display
shows that address 80026530 is in SYSTEM_SYNCRONIZATION’s nonpaged
read only image section.
2. Subtract the base address for the image section listed by XDELTA (80024000)
from the PC you are trying to identify (80026530). The difference (2530) is
the offset within the image section.
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