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Unprivileged objNameAllowsDot, return *btf.Var from Variable{Spec}.Type() #1612

Merged
merged 3 commits into from
Nov 14, 2024
Merged

Unprivileged objNameAllowsDot, return *btf.Var from Variable{Spec}.Type() #1612

merged 3 commits into from
Nov 14, 2024

Commits on Nov 14, 2024

  1. features: tolerate EPERM in haveObjName and objNameAllowsDot 

    When loading ELFs using unprivileged tools or tests, EPERM causes dots and
underscores to be stripped from MapSpec.Name, causing strange results for
maps like .rodata.foo.

Also, only consider ErrNotSupported as conclusive and bubble up any other
errors to the caller. Most callers just check err != nil, but in case
someone indirectly relies on the sentinel, this should result in more
accurate output.

Signed-off-by: Timo Beckers <[email protected]>
    @ti-mo
    ti-mo committed Nov 14, 2024
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  2. variable: return *btf.Var from Variable{Spec}.Type() 

    In the initial design, we decided to return the inner type from .Type(), but
I forgot the outer btf.Var was needed to access decl tags set on the variable.

Returning a *Var here is the most convenient way of accessing the tags, otherwise
the caller would need to find the underlying map and parse the datasec manually,
which goes against what this API aims to solve.

Instead of the initial idea of returning a btf.Var as btf.Type, this now returns
btf.Var directly.

Signed-off-by: Timo Beckers <[email protected]>
    @ti-mo
    ti-mo committed Nov 14, 2024
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  3. variable: add VariableSpec.MapName() and .Offset() methods 

    Cilium's variable inliner needs this information to look up variable contents
based on the offset specified in the instruction stream, and wants to validate
that it's pulling data from the right data section.

It makes for a slightly leaky abstraction, but at least something meaningful
can be accomplished by combining the two, e.g. by accessing the given offset
in the map.

Signed-off-by: Timo Beckers <[email protected]>
    @ti-mo
    ti-mo committed Nov 14, 2024
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