From ca201ad6e92a1924138e83ff966f7a091e3bbe6e Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Thu, 15 Oct 2026 11:40:44 -0400 Subject: [PATCH] ARC: Strip libgcc debug information when generating BTF ARC links against the compiler's libgcc archive. The ARC GNU 2023.03 toolchain ships this library with debug information, including complex floating-point types in integer arithmetic helpers such as __udivdi3. These types reach vmlinux even though the kernel does not use complex floating-point arithmetic. When floating-point BTF encoding is enabled, pahole rejects those types: Complex, interval and imaginary float types are not supported Error while encoding BTF. FAILED: load BTF from .tmp_vmlinux1.BTF.1: No such file or directory KernelCI's upgrade to pahole 1.31 exposed this long-standing problem as failed ARC builds. As of 1.32, pahole still rejects these types, and older versions will stay in use, so the kernel build has to keep them out of vmlinux. Commit f122668ddcce ("ARC: Add eBPF JIT support") documented the same failure along with a workaround of disabling floating-point BTF encoding, but that also discards supported floating-point types from kernel BTF. For CONFIG_DEBUG_INFO_BTF, generate a debug-stripped copy of the selected libgcc archive in the output tree and link that copy. Preserve the archive structure so that only needed helpers are linked, and use the normal Kbuild objcopy rule to track input and command changes. The trade-off is that vmlinux in BTF-enabled builds no longer carries DWARF for the libgcc helpers. Debug information for kernel code, the installed toolchain and non-BTF builds stay unchanged. Reproduced and tested with ARC GCC 12.2.1 and pahole 1.31 and 1.32 using an ARCv2 tinyconfig with BPF_SYSCALL and DWARF4/BTF enabled. Before and after vmlinux.o files are identical after stripping debug information. Fixes: db16c1fe92d7 ("bpf: Generate BTF_KIND_FLOAT when linking vmlinux") Signed-off-by: Sasha Levin Signed-off-by: Alexei Starovoitov Acked-by: Alan Maguire (Oracle) Link: https://github.com/kernelci/kernelci-core/commit/e71b8c9f42253180596e734c18965a5aad80c8c5 Link: https://patch.msgid.link/20261015154044.4058618-1-sashal@kernel.org --- arch/arc/Makefile | 9 ++++++++- arch/arc/lib/Makefile | 8 ++++++++ 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/arc/Makefile b/arch/arc/Makefile index 868805ffcfea..4ea705a331c7 100644 --- a/arch/arc/Makefile +++ b/arch/arc/Makefile @@ -86,7 +86,14 @@ core-$(CONFIG_ARC_PLAT_TB10X) += arch/arc/plat-tb10x/ core-$(CONFIG_ARC_PLAT_AXS10X) += arch/arc/plat-axs10x/ core-$(CONFIG_ARC_SOC_HSDK) += arch/arc/plat-hsdk/ -libs-y += arch/arc/lib/ $(LIBGCC) +libs-y += arch/arc/lib/ + +ifdef CONFIG_DEBUG_INFO_BTF +export LIBGCC := $(LIBGCC) +libs-y += arch/arc/lib/libgcc.a +else +libs-y += $(LIBGCC) +endif boot := arch/arc/boot diff --git a/arch/arc/lib/Makefile b/arch/arc/lib/Makefile index 30158ae69fd4..2807ee24f27e 100644 --- a/arch/arc/lib/Makefile +++ b/arch/arc/lib/Makefile @@ -13,3 +13,11 @@ lib-$(CONFIG_ISA_ARCV2) +=memcpy-archs-unaligned.o else lib-$(CONFIG_ISA_ARCV2) +=memcpy-archs.o endif + +# libgcc can contain complex floating-point debug types unsupported by BTF. +# Strip only the debug information from a local copy of the selected archive. +always-$(CONFIG_DEBUG_INFO_BTF) += libgcc.a +OBJCOPYFLAGS_libgcc.a := --strip-debug + +$(obj)/libgcc.a: $(LIBGCC) FORCE + $(call if_changed,objcopy)