Re: [kvm-unit-tests PATCH 3/6] s390x: Add a linker script to assembly snippets

Steffen Eiden
2022-07-29T14:17:41Z

On 7/29/22 10:26, Janosch Frank wrote:
> A linker script has a few benefits:
> - We can easily define a lowcore and load the snippet from 0x0 instead
> of 0x4000 which makes asm snippets behave like c snippets
> - We can easily define an invalid PGM new PSW to ensure an exit on a
> guest PGM
>
> As we gain another step and file extension by linking, a comment
> explains which file extensions are generated and why.
>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
> lib/s390x/snippet.h | 3 +--
> s390x/Makefile | 16 +++++++++++++---
> s390x/mvpg-sie.c | 2 +-
> s390x/pv-diags.c | 6 +++---
> 4 files changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/lib/s390x/snippet.h b/lib/s390x/snippet.h
> index b17b2a4c..57045994 100644
> --- a/lib/s390x/snippet.h
> +++ b/lib/s390x/snippet.h
> @@ -32,8 +32,7 @@
>
> #define SNIPPET_PV_TWEAK0 0x42UL
> #define SNIPPET_PV_TWEAK1 0UL
> -#define SNIPPET_OFF_C 0
> -#define SNIPPET_OFF_ASM 0x4000
> +#define SNIPPET_UNPACK_OFF 0
>
>
> /*
> diff --git a/s390x/Makefile b/s390x/Makefile
> index ee34a1d7..9a0b48e2 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -122,6 +122,13 @@ else
> snippet-hdr-obj =
> endif
>
> +# Each snippet will generate the following files (in order): \
> + *.o is a snippet that has been compiled \
> + *.ol is a snippet that has been linked \
> + *.gbin is a snippet that has been converted to binary \
> + *.gobj is the final format after converting the binary into a elf file again, \
> + it will be linked into the tests
> +
> # the asm/c snippets %.o have additional generated files as dependencies
> $(SNIPPET_DIR)/asm/%.o: $(SNIPPET_DIR)/asm/%.S $(asm-offsets)
> $(CC) $(CFLAGS) -c -nostdlib -o $@ $<
> @@ -129,8 +136,11 @@ $(SNIPPET_DIR)/asm/%.o: $(SNIPPET_DIR)/asm/%.S $(asm-offsets)
> $(SNIPPET_DIR)/c/%.o: $(SNIPPET_DIR)/c/%.c $(asm-offsets)
> $(CC) $(CFLAGS) -c -nostdlib -o $@ $<
>
> -$(SNIPPET_DIR)/asm/%.gbin: $(SNIPPET_DIR)/asm/%.o
> - $(OBJCOPY) -O binary -j ".rodata" -j ".text" -j ".data" -j ".bss" --set-section-flags .bss=alloc,load,contents $(patsubst %.gbin,%.o,$@) $@
> +$(SNIPPET_DIR)/asm/%.ol: $(SNIPPET_DIR)/asm/%.o
> + $(CC) $(LDFLAGS) -o $@ -T $(SRCDIR)/s390x/snippets/asm/flat.lds $<

I think you forgot to include that linker script in the patch.
Or did I miss anything?

you can also use the $(SNIPPET_DIR) variable instead of searching for
that directory yourself.

> +
> +$(SNIPPET_DIR)/asm/%.gbin: $(SNIPPET_DIR)/asm/%.ol
> + $(OBJCOPY) -O binary -j ".rodata" -j ".lowcore" -j ".text" -j ".data" -j ".bss" --set-section-flags .bss=alloc,load,contents $< $@
> truncate -s '%4096' $@
>
> $(SNIPPET_DIR)/c/%.gbin: $(SNIPPET_DIR)/c/%.o $(snippet_lib) $(FLATLIBS)
> @@ -139,7 +149,7 @@ $(SNIPPET_DIR)/c/%.gbin: $(SNIPPET_DIR)/c/%.o $(snippet_lib) $(FLATLIBS)
> truncate -s '%4096' $@
>
> $(SNIPPET_DIR)/asm/%.hdr: $(SNIPPET_DIR)/asm/%.gbin $(HOST_KEY_DOCUMENT)
> - $(GEN_SE_HEADER) -k $(HOST_KEY_DOCUMENT) -c $<,0x4000,0x00000000000000420000000000000000 --psw-addr 0x4000 -o $@
> + $(GEN_SE_HEADER) -k $(HOST_KEY_DOCUMENT) -c $<,0x0,0x00000000000000420000000000000000 --psw-addr 0x4000 -o $@
>
> $(SNIPPET_DIR)/c/%.hdr: $(SNIPPET_DIR)/c/%.gbin $(HOST_KEY_DOCUMENT)
> $(GEN_SE_HEADER) -k $(HOST_KEY_DOCUMENT) -c $<,0x0,0x00000000000000420000000000000000 --psw-addr 0x4000 -o $@
> diff --git a/s390x/mvpg-sie.c b/s390x/mvpg-sie.c
> index 46a2edb6..99f4859b 100644
> --- a/s390x/mvpg-sie.c
> +++ b/s390x/mvpg-sie.c
> @@ -87,7 +87,7 @@ static void setup_guest(void)
>
> snippet_setup_guest(&vm, false);
> snippet_init(&vm, SNIPPET_NAME_START(c, mvpg_snippet),
> - SNIPPET_LEN(c, mvpg_snippet), SNIPPET_OFF_C);
> + SNIPPET_LEN(c, mvpg_snippet), SNIPPET_UNPACK_OFF);
>
> /* Enable MVPG interpretation as we want to test KVM and not ourselves */
> vm.sblk->eca = ECA_MVPGI;
> diff --git a/s390x/pv-diags.c b/s390x/pv-diags.c
> index 9ced68c7..5165937a 100644
> --- a/s390x/pv-diags.c
> +++ b/s390x/pv-diags.c
> @@ -28,7 +28,7 @@ static void test_diag_500(void)
>
> snippet_pv_init(&vm, SNIPPET_NAME_START(asm, snippet_pv_diag_500),
> SNIPPET_HDR_START(asm, snippet_pv_diag_500),
> - size_gbin, size_hdr, SNIPPET_OFF_ASM);
> + size_gbin, size_hdr, SNIPPET_UNPACK_OFF);
>
> sie(&vm);
> report(vm.sblk->icptcode == ICPT_PV_INSTR && vm.sblk->ipa == 0x8302 &&
> @@ -83,7 +83,7 @@ static void test_diag_288(void)
>
> snippet_pv_init(&vm, SNIPPET_NAME_START(asm, snippet_pv_diag_288),
> SNIPPET_HDR_START(asm, snippet_pv_diag_288),
> - size_gbin, size_hdr, SNIPPET_OFF_ASM);
> + size_gbin, size_hdr, SNIPPET_UNPACK_OFF);
>
> sie(&vm);
> report(vm.sblk->icptcode == ICPT_PV_INSTR && vm.sblk->ipa == 0x8302 &&
> @@ -124,7 +124,7 @@ static void test_diag_yield(void)
>
> snippet_pv_init(&vm, SNIPPET_NAME_START(asm, snippet_pv_diag_yield),
> SNIPPET_HDR_START(asm, snippet_pv_diag_yield),
> - size_gbin, size_hdr, SNIPPET_OFF_ASM);
> + size_gbin, size_hdr, SNIPPET_UNPACK_OFF);
>
> /* 0x44 */
> report_prefix_push("0x44");

Steffen Eiden