diff --git a/src/cmd/go/testdata/script/trampoline_reuse_test.txt b/src/cmd/go/testdata/script/trampoline_reuse_test.txt new file mode 100644 index 0000000000000..bca897c16d054 --- /dev/null +++ b/src/cmd/go/testdata/script/trampoline_reuse_test.txt @@ -0,0 +1,100 @@ +# Verify PPC64 does not reuse a trampoline which is too far away. +# This tests an edge case where the direct call relocation addend should +# be ignored when computing the distance from the direct call to the +# already placed trampoline +[short] skip +[!ppc64] [!ppc64le] skip +[aix] skip + +# Note, this program does not run. Presumably, 'DWORD $0' is simpler to +# assembly 2^26 or so times. +# +# We build something which should be laid out as such: +# +# bar.Bar +# main.Func1 +# bar.Bar+400-tramp0 +# main.BigAsm +# main.Func2 +# bar.Bar+400-tramp1 +# +# bar.Bar needs to be placed far enough away to generate relocations +# from main package calls. and main.Func1 and main.Func2 are placed +# a bit more than the direct call limit apart, but not more than 0x400 +# bytes beyond it (to verify the reloc calc). + +go build + +-- go.mod -- + +module foo + +go 1.19 + +-- main.go -- + +package main + +import "foo/bar" + +func Func1() + +func main() { + Func1() + bar.Bar2() +} + +-- foo.s -- + +TEXT main·Func1(SB),0,$0-0 + CALL bar·Bar+0x400(SB) + CALL main·BigAsm(SB) +// A trampoline will be placed here to bar.Bar + +// This creates a gap sufficiently large to prevent trampoline reuse +#define NOP64 DWORD $0; DWORD $0; DWORD $0; DWORD $0; DWORD $0; DWORD $0; DWORD $0; DWORD $0; +#define NOP256 NOP64 NOP64 NOP64 NOP64 +#define NOP2S10 NOP256 NOP256 NOP256 NOP256 +#define NOP2S12 NOP2S10 NOP2S10 NOP2S10 NOP2S10 +#define NOP2S14 NOP2S12 NOP2S12 NOP2S12 NOP2S12 +#define NOP2S16 NOP2S14 NOP2S14 NOP2S14 NOP2S14 +#define NOP2S18 NOP2S16 NOP2S16 NOP2S16 NOP2S16 +#define NOP2S20 NOP2S18 NOP2S18 NOP2S18 NOP2S18 +#define NOP2S22 NOP2S20 NOP2S20 NOP2S20 NOP2S20 +#define NOP2S24 NOP2S22 NOP2S22 NOP2S22 NOP2S22 +#define BIGNOP NOP2S24 NOP2S24 +TEXT main·BigAsm(SB),0,$0-0 + // Fill to the direct call limit so Func2 must generate a new trampoline. + // As the implicit trampoline above is just barely unreachable. + BIGNOP + MOVD $main·Func2(SB), R3 + +TEXT main·Func2(SB),0,$0-0 + CALL bar·Bar+0x400(SB) +// Another trampoline should be placed here. + +-- bar/bar.s -- + +#define NOP64 DWORD $0; DWORD $0; DWORD $0; DWORD $0; DWORD $0; DWORD $0; DWORD $0; DWORD $0; +#define NOP256 NOP64 NOP64 NOP64 NOP64 +#define NOP2S10 NOP256 NOP256 NOP256 NOP256 +#define NOP2S12 NOP2S10 NOP2S10 NOP2S10 NOP2S10 +#define NOP2S14 NOP2S12 NOP2S12 NOP2S12 NOP2S12 +#define NOP2S16 NOP2S14 NOP2S14 NOP2S14 NOP2S14 +#define NOP2S18 NOP2S16 NOP2S16 NOP2S16 NOP2S16 +#define NOP2S20 NOP2S18 NOP2S18 NOP2S18 NOP2S18 +#define NOP2S22 NOP2S20 NOP2S20 NOP2S20 NOP2S20 +#define NOP2S24 NOP2S22 NOP2S22 NOP2S22 NOP2S22 +#define BIGNOP NOP2S24 NOP2S24 NOP2S10 +// A very big not very interesting function. +TEXT bar·Bar(SB),0,$0-0 + BIGNOP + +-- bar/bar.go -- + +package bar + +func Bar() + +func Bar2() { +} diff --git a/src/cmd/link/internal/ppc64/asm.go b/src/cmd/link/internal/ppc64/asm.go index 73c2718a3369f..879adaa965050 100644 --- a/src/cmd/link/internal/ppc64/asm.go +++ b/src/cmd/link/internal/ppc64/asm.go @@ -809,8 +809,9 @@ func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) { if ldr.SymValue(tramp) == 0 { break } - - t = ldr.SymValue(tramp) + r.Add() - (ldr.SymValue(s) + int64(r.Off())) + // Note, the trampoline is always called directly. The addend of the original relocation is accounted for in the + // trampoline itself. + t = ldr.SymValue(tramp) - (ldr.SymValue(s) + int64(r.Off())) // With internal linking, the trampoline can be used if it is not too far. // With external linking, the trampoline must be in this section for it to be reused.