Implement `PerfEventConfig::Breakpoint`, allowing users to attach
hardware breakpoints. Generate `HW_BREAKPOINT_*` and `struct
bpf_perf_event_data` in support of this feature and update the type of
`PerfEventContext` accordingly.
Add a test exercising R, W, RW, and X breakpoints. Note that R
breakpoints are unsupported on x86, and this is asserted in the test.
Extend the VM integration test harness and supporting infrastructure
(e.g. `download_kernel_images.sh`) to download kernel debug packages and
mount `System.map` in initramfs. This is needed (at least) on the aarch
6.1 Debian kernel which was not compiled with `CONFIG_KALLSYMS_ALL=y`
for some reason, and the locations of globals are not available in
kallsyms. To attach breakpoints to these symbols in the test pipeline,
we need to read them from System.map and apply the KASLR offset to get
their real address. The `System.map` file is not provided in the kernel
package by default, so we need to extract it from the corresponding
debug package. The KASLR offset is computed using `gunzip` which appears
in kallsyms on all Debian kernels tested.
Co-authored-by: Tamir Duberstein <tamird@gmail.com>
We're seeing 429 from Github trying to download gen_init_cpio, so cache
it using actions cache. Since I'm here add this for kernel images as
well to save time waiting on slow Debian servers.
