Fix issues when porting alloy/pyroscope to android

[zmj64351508]

I'm porting alloy/pyroscope to the mobile phone running Android 14. And I found some issues:

1. The config CONFIG_PID_NS is not set in standard Android kernel, which means /proc/self/ns/pid is not exist and alloy will exit with failure. The first commit fixed this issue by ignoring error when /proc/self/ns/pid doesn't exist.

2. When kernel modules or bpf programs are dynamic loaded from userspace after kernel boot, the address in /proc/kallsyms may be unordered, which causes the origin code find wrong symbol. The second commit fixed this issue by sorting the symbol by address.
   Here's an example for such /proc/kallsyms:

# cat /proc/kallsyms
...
ffffffd6b60e2140 t cleanup_module       [bootprof]
ffffffd6b60e53c0 d __this_module        [bootprof]  
ffffffc0145a52cc t bpf_prog_98e4c662c49a1bca_xdp_drop_ipv4_u    [bpf]
ffffffc0145ad4a8 t bpf_prog_a06399a1ec0a769e_schedcls_tether    [bpf]
ffffffc012b4b218 t bpf_prog_e814348da2c722a4_schedcls_tether    [bpf]
...

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[korniltsev]

Something looks off here. I would expect this condition to be true if error is ErrExist and I do not expect this error to be returned during pid ns check ( we do not create any files/objects).
The next error check looks suspicious as well. It looks like we rewrite global_config constant here only in case if ErrExist and err==nil which looks impossible to my brain
Did you test this change with PD_NS configured and inside a pid namespace ( a docker container for example)?

We need to change something here.
Let me know if I am missing/misunderstanding something.

[zmj64351508]

PR Updated. I'm new to golang and it's my misunderstanding of os.IsExist. It's now replaced by !os.IsNotExist().

[zmj64351508]

I tested the new patch on WSL and Android Phone, both work fine.

[korniltsev]

nit: It would be nice to add a test, but it is is not required

[zmj64351508]

PR Updated. I add 2 unordered symbols in testdata. I tested it and it will fail without this patch and success with this patch.

[korniltsev]

Thank you for the contribution. I left some comments.

[korniltsev]

Thank you for the contribution!
I've created an issue to add an integration tests for these cases. Feel free to submit a PR if you want to
#3588