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fix: support bpf_core_type_exists() #655

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merged 1 commit into from May 5, 2022
Merged

fix: support bpf_core_type_exists() #655

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10 changes: 8 additions & 2 deletions internal/btf/core.go
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Expand Up @@ -313,10 +313,16 @@ func coreCalculateFixups(byteOrder binary.ByteOrder, local Type, targets []Type,

if bestFixups == nil {
// Nothing at all matched, probably because there are no suitable
// targets at all. Poison everything!
// targets at all.
//
// Poison everything except checksForExistence.
bestFixups = make([]COREFixup, len(relos))
for i, relo := range relos {
bestFixups[i] = COREFixup{kind: relo.kind, poison: true}
if relo.kind.checksForExistence() {
bestFixups[i] = COREFixup{kind: relo.kind, local: 1, target: 0}
} else {
bestFixups[i] = COREFixup{kind: relo.kind, poison: true}
}
}
}

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Binary file modified internal/btf/testdata/relocs_read-eb.elf
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Binary file modified internal/btf/testdata/relocs_read-el.elf
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15 changes: 15 additions & 0 deletions internal/btf/testdata/relocs_read.c
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Expand Up @@ -26,6 +26,12 @@ struct bits {
u64 f : 16, g : 30;
};

struct nonexist {
int non_exist;
};

enum nonexist_enum { NON_EXIST = 1 };

// Perform a read from a subprog to ensure CO-RE relocations
// occurring there are tracked and executed in the final linked program.
__attribute__((noinline)) int read_subprog() {
Expand Down Expand Up @@ -89,6 +95,15 @@ __attribute__((noinline)) int read_subprog() {
if (BPF_CORE_READ_BITFIELD(&bar, g) != 0x15443322)
return __LINE__;

if (bpf_core_type_exists(struct nonexist) != 0)
return __LINE__;

if (bpf_core_field_exists(((struct nonexist *)0)->non_exist) != 0)
return __LINE__;

if (bpf_core_enum_value_exists(enum nonexist_enum, NON_EXIST) != 0)
return __LINE__;

return 0;
}

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