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cmd/link: split text sections for arm 32-bit
This CL is a roll-forward (tweaked slightly) of CL 467715, which turned on text section splitting for GOARCH=arm. The intent is to avoid recurrent problems with external linking where there is a disagreement between the Go linker and the external linker over whether a given branch will reach. In the past our approach has been to tweak the reachability calculations slightly to try to work around potential linker problems, but this hasn't proven to be very robust; section splitting seems to offer a better long term fix. Fixes #58425. Change-Id: I7372d41abce84097906a3d0805b6b9c486f345d6 Reviewed-on: https://go-review.googlesource.com/c/go/+/531795 Reviewed-by: Cherry Mui <[email protected]> Run-TryBot: Than McIntosh <[email protected]> TryBot-Result: Gopher Robot <[email protected]>
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2 files changed

Lines changed: 14 additions & 7 deletions

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‎src/cmd/link/internal/ld/data.go‎

Lines changed: 13 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -2615,15 +2615,22 @@ func assignAddress(ctxt *Link, sect *sym.Section, n int, s loader.Sym, va uint64
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// Return whether we may need to split text sections.
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//
2618-
// On PPC64x whem external linking a text section should not be larger than 2^25 bytes
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// due to the size of call target offset field in the bl instruction. Splitting into
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// smaller text sections smaller than this limit allows the system linker to modify the long
2621-
// calls appropriately. The limit allows for the space needed for tables inserted by the
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// linker.
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// On PPC64x, when external linking, a text section should not be
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// larger than 2^25 bytes due to the size of call target offset field
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// in the 'bl' instruction. Splitting into smaller text sections
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// smaller than this limit allows the system linker to modify the long
2622+
// calls appropriately. The limit allows for the space needed for
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// tables inserted by the linker.
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//
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// The same applies to Darwin/ARM64, with 2^27 byte threshold.
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//
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// Similarly for ARM, we split sections (at 2^25 bytes) to avoid
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// inconsistencies between the Go linker's reachability calculations
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// (e.g. will direct call from X to Y need a trampoline) and similar
2630+
// machinery in the external linker; see #58425 for more on the
2631+
// history here.
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func splitTextSections(ctxt *Link) bool {
2626-
return (ctxt.IsPPC64() || (ctxt.IsARM64() && ctxt.IsDarwin())) && ctxt.IsExternal()
2633+
return (ctxt.IsARM() || ctxt.IsPPC64() || (ctxt.IsARM64() && ctxt.IsDarwin())) && ctxt.IsExternal()
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}
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// On Wasm, we reserve 4096 bytes for zero page, then 8192 bytes for wasm_exec.js

‎src/cmd/link/internal/ld/ld_test.go‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -136,7 +136,7 @@ func TestArchiveBuildInvokeWithExec(t *testing.T) {
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func TestLargeTextSectionSplitting(t *testing.T) {
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switch runtime.GOARCH {
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case "ppc64", "ppc64le":
139+
case "ppc64", "ppc64le", "arm":
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case "arm64":
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if runtime.GOOS == "darwin" {
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break

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