From: Thomas Huth <thuth@xxxxxxxxxx> In the long run, we want to use parts of the libc like memset() etc., too. However, to be able to link it correctly, we have to provide some stub functions like puts() and exit() to avoid that too much other stuff from the lib folder gets pulled into the binaries, which we cannot provide in the snippets (like the sclp support). Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx> Message-Id: <20211008092649.959956-1-thuth@xxxxxxxxxx> Link: https://lore.kernel.org/kvm/20211008092649.959956-1-thuth@xxxxxxxxxx/ Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx> --- s390x/Makefile | 2 +- s390x/snippets/c/cstart.S | 11 +++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/s390x/Makefile b/s390x/Makefile index 5d1a33a0..d18b08b0 100644 --- a/s390x/Makefile +++ b/s390x/Makefile @@ -81,7 +81,7 @@ asmlib = $(TEST_DIR)/cstart64.o $(TEST_DIR)/cpu.o FLATLIBS = $(libcflat) SNIPPET_DIR = $(TEST_DIR)/snippets -snippet_asmlib = $(SNIPPET_DIR)/c/cstart.o +snippet_asmlib = $(SNIPPET_DIR)/c/cstart.o lib/auxinfo.o # perquisites (=guests) for the snippet hosts. # $(TEST_DIR)/<snippet-host>.elf: snippets = $(SNIPPET_DIR)/<c/asm>/<snippet>.gbin diff --git a/s390x/snippets/c/cstart.S b/s390x/snippets/c/cstart.S index 031a6b83..aaa5380c 100644 --- a/s390x/snippets/c/cstart.S +++ b/s390x/snippets/c/cstart.S @@ -20,6 +20,17 @@ start: lghi %r15, stackptr sam64 brasl %r14, main + /* + * If main() returns, we stop the CPU with the code below. We also + * route some functions that are required by the libc (but not usable + * from snippets) to the CPU stop code below, so that snippets can + * still be linked against the libc code (to use non-related functions + * like memset() etc.) + */ +.global puts +.global exit +puts: +exit: /* For now let's only use cpu 0 in snippets so this will always work. */ xgr %r0, %r0 sigp %r2, %r0, SIGP_STOP -- 2.31.1
