[DTrace-devel] [PATCH 2/2] bpf: add check for -mcpu=v3 BPFC option

[Kris Van Hees]

Newer BPF gcc cross compilers emit instructions that older kernels do not
support yet.  Passing -mcpu=v3 disables using those instructions, but older
BPF cross compilers do not support that option.  Fortunately, those compilers
also do not emit the newer instructions.

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
 GNUmakefile | 2 +-
 Makeconfig  | 1 +
 configure   | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/GNUmakefile b/GNUmakefile
index 97d55618..d967134f 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -124,7 +124,7 @@ PREPROCESS = $(CC) -E
 export BPFC = bpf-unknown-none-gcc
 
 BPFCPPFLAGS += -D$(subst sparc64,__sparc,$(subst aarch64,__aarch64__,$(subst x86_64,__amd64,$(ARCH))))
-BPFCFLAGS ?= -O2 -Wall -Wno-unknown-pragmas
+BPFCFLAGS ?= -O2 -Wall -Wno-unknown-pragmas $(if $(HAVE_BPFV3),-mcpu=v3)
 export BPFLD = bpf-unknown-none-ld
 
 all::
diff --git a/Makeconfig b/Makeconfig
index 332e9519..0c1fad1a 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -229,6 +229,7 @@ $(eval $(call check-header-rule,DIS1,disassembler(NULL),dis-asm))
 $(eval $(call check-header-rule,DIS4,disassembler(0,0,0,NULL),dis-asm))
 $(eval $(call check-header-rule,INITDISINFO3,init_disassemble_info(NULL,NULL,NULL),dis-asm))
 $(eval $(call check-header-rule,INITDISINFO4,init_disassemble_info(NULL,NULL,NULL,NULL),dis-asm))
+$(eval $(call check-gcc-option-rule,BPFV3,-mcpu=v3))
 
 help-overrides::
 	printf "\n" >&2
diff --git a/configure b/configure
index d4e71914..312e2aa2 100755
--- a/configure
+++ b/configure
@@ -162,6 +162,7 @@ for option in "$@"; do
         HAVE_FUSE_NUMA=*) write_config_var FUSE_NUMA "$option";;
         HAVE_CLOSE_RANGE=*) write_config_var CLOSE_RANGE "$option";;
         HAVE_GETTID=*) write_config_var GETTID "$option";;
+        HAVE_BPFV3=*) write_config_var BPFV3 "$option";;
 	*) echo "Unknown option $option" >&2
            exit 1;;
     esac
-- 
2.42.0