Add user function call support #3068
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Function defined by the user can now be called in the same ways as built-in
functions, for example:
fn add($a: int64, $b: int64): int64 {
return $a + $b;
}
BEGIN {
print(add(5, 9));
}
If a function of the same name as an existing built-in is defined, it
overrides the built-in and a warning is printed.
Implementation-wise, the functionality depends on existing relocations
against subprogs implemented in commit d345d06 ("Implement relocations
against .text for subprogs"). Those are extended to also support R_BPF_64_32
relocations used for direct calls in addition to R_BPF_64_64 used for
indirect calls.
Functions are generated as separate LLVM IR functions and translated into
BPF subprogs via the LLVM bpf backend. Inlining of those function is
disabled to prevent aggressive LLVM optimizations turning recursion into
iteration, which could be rejected by the verifier.
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Function defined by the user can now be called in the same ways as built-in functions, for example:
fn add($a: int64, $b: int64): int64 {
return $a + $b;
}
BEGIN {
print(add(5, 9));
}
If a function of the same name as an existing built-in is defined, it overrides the built-in and a warning is printed.
Implementation-wise, the functionality depends on existing relocations against subprogs implemented in commit d345d06 ("Implement relocations against .text for subprogs").
Functions are generated as separate LLVM IR functions and translated into BPF subprogs via the LLVM bpf backend. Relocations make sure the resulting program can be loaded.
Checklist
man/adoc/bpftrace.adocCHANGELOG.md