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xdp-tools: Fix embedded BPF objects when linking with lld

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libxdp turns its BPF programs into linkable objects with a relocatable
link of a raw binary input (cc -r -Wl,--format=binary). Because there is
no real object among the inputs, lld on riscv64 writes an object with
e_flags 0 (soft-float ABI) and a GNU property note with every CFI feature
bit set. Linking it then fails with clang:

  ld.lld: error: libxdp.a(xdp-dispatcher.embed.o): file has conflicting
    properties: GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_UNLABELED and
    GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_FUNC_SIG
  ld.lld: error: libxdp.a(xdp-dispatcher.embed.o): cannot link object
    files with different floating-point ABI from Scrt1.o

Build the embed objects from a small .incbin assembly stub instead, so the
compiler driver emits them with the correct target ABI.

AI-Generated: Uses Claude Code
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
This commit is contained in:
Khem Raj committed 2026-10-19 15:08:27 -07:00
1 parent 72127a754d
commit ec72249e3a
2 files changed
+44
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meta-oe/recipes-support/xdp-tools/files/0005-lib-libxdp-Embed-BPF-objects-with-.incbin-instead-of.patch
+43
View File
@@ -0,0 +1,43 @@
From: Khem Raj <raj.khem@gmail.com>
Date: Sun, 18 Oct 2026 18:00:00 -0700
Subject: [PATCH] lib/libxdp: Embed BPF objects with .incbin instead of ld --format=binary
The embedded BPF objects are made with a relocatable link of a raw binary
input (cc -r -Wl,--format=binary). When the only input is a raw binary,
the linker has no real object to take target attributes from. With lld on
riscv64 the result has e_flags 0 (soft-float ABI) and a
.note.gnu.property where every CFI feature bit is set. Linking it into
libxdp users then fails:
ld.lld: error: libxdp.a(xdp-dispatcher.embed.o): file has conflicting
properties: GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_UNLABELED and
GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_FUNC_SIG
ld.lld: error: libxdp.a(xdp-dispatcher.embed.o): cannot link object
files with different floating-point ABI from Scrt1.o
Instead, assemble a small stub that pulls in the BPF object with .incbin.
The compiler driver then emits a normal object for the target ABI. The
_binary_<name>_start/_end symbol names that libxdp.c uses stay the same.
Upstream-Status: Pending
Signed-off-by: Khem Raj <raj.khem@gmail.com>
---
lib/libxdp/Makefile | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/lib/libxdp/Makefile b/lib/libxdp/Makefile
--- a/lib/libxdp/Makefile
+++ b/lib/libxdp/Makefile
@@ -134,8 +134,10 @@
$(QUIET_M4)$(M4) $(DEFINES) $< > $@ || ( ret=$$?; rm -f $@; exit $$ret )
$(EMBEDDED_XDP_OBJS): %.embed.o: %.o
- $(QUIET_CC)$(CC) -r -nostdlib -Wl,-z,noexecstack,--format=binary $(LDFLAGS) -o $@ $<
- $(Q)$(OBJCOPY) --rename-section .data=.rodata,alloc,load,readonly,data,contents $@
+ $(QUIET_CC)SYM=_binary_$$(echo '$<' | sed 's/[^A-Za-z0-9_]/_/g'); \
+ printf '\t.section .rodata,"a"\n\t.balign 8\n\t.globl %s_start\n%s_start:\n\t.incbin "%s"\n\t.globl %s_end\n%s_end:\n' \
+ $$SYM $$SYM '$<' $$SYM $$SYM | \
+ $(CC) -c -x assembler -Wa,--noexecstack -o $@ -
$(XDP_OBJS): %.o: %.c $(BPF_HEADERS) $(LIBMK)
$(QUIET_CLANG)$(CLANG) -target $(BPF_TARGET) $(BPF_CFLAGS) -O2 -c -g -o $@ $<
meta-oe/recipes-support/xdp-tools/xdp-tools_1.6.3.bb
+1
View File
@@ -18,6 +18,7 @@ SRC_URI = " \
file://0002-lib-libxdp-Makefile-use-cp-fRd-to-preserve-symlinks-.patch \
file://0003-lib-util-avoid-struct-ethhdr-redefinition-on-musl.patch \
file://0004-xdp-filter-xdp-dump-avoid-struct-ethhdr-redefinitio.patch \
file://0005-lib-libxdp-Embed-BPF-objects-with-.incbin-instead-of.patch \
"
SRCREV = "8fbad9f0af621a22aa87ff2520b3735915b1f0fd"