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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 13/23] XENVER_build_id: Provide ld-embedded build-ids (v10)
On 12/02/16 18:05, Konrad Rzeszutek Wilk wrote:
Building the hypervisor with buildid and making it available via
hypercall really should be split into two different patches, especially
given the complexity in each.
> The mechanism to get this is via the XENVER hypercall and
> we add a new sub-command to retrieve the binary build-id
> called XENVER_build_id. The sub-hypercall parameter
> allows an arbitrary size (the buffer and len is provided
> to the hypervisor). A NULL parameter will probe the hypervisor
> for the length of the build-id.
>
> One can also retrieve the value of the build-id by doing
> 'readelf -n xen-syms'.
>
> For EFI builds we re-use the same build-id that the xen-syms
> was built with.
>
> The version of ld that first implemented --build-id is v2.18.
> Hence we check for that or later version - if older version
> found we do not build the hypervisor with the build-id
> (and the return code is -ENODATA for that case).
>
> For x86 we have two binaries - the xen-syms and the xen - an
> smaller version with lots of sections removed. To make it possible
> for readelf -n xen we also modify mkelf32 and xen.lds.S to include
> the PT_NOTE ELF section.
>
> The EFI binary is more complicated. Having any non-recognizable
> sections (.note, .data.note, etc) causes the boot to hang.
> Moving the .note in the .data section makes it work. It is also
> worth noting that the PE/COFF does not have any "comment"
> sections to the author.
>
> Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Martin Pohlack <mpohlack@xxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
> v1: Rebase it on Martin's initial patch
> v2: Move it to XENVER hypercall
> v3: Fix EFI building (Ross's fix)
> v4: Don't use the third argument for length.
> v5: Use new structure for XENVER_build_id with variable buf.
> v6: Include Ross's fix.
> v7: Include detection of bin-utils for build-id support, add
> probing for size, and return -EPERM for XSM denied calls.
> v8: Build xen_build_id under ARM, required adding ELFSIZE in proper file.
> v9: Rebase on top XSM version class.
> v10: Include the build-id .note in the xen ELF binary.
> s/build_id/build_id_linker/
> For EFI build, moved the --build-id values in .data section
> ---
> Config.mk | 11 +++
> tools/flask/policy/policy/modules/xen/xen.te | 4 +-
> tools/libxc/xc_private.c | 7 ++
> tools/libxc/xc_private.h | 10 ++
> xen/arch/arm/Makefile | 2 +-
> xen/arch/arm/xen.lds.S | 13 +++
> xen/arch/x86/Makefile | 31 +++++-
> xen/arch/x86/boot/mkelf32.c | 137
> +++++++++++++++++++++++----
> xen/arch/x86/xen.lds.S | 23 +++++
> xen/common/kernel.c | 36 +++++++
> xen/common/version.c | 48 ++++++++++
> xen/include/public/version.h | 16 +++-
> xen/include/xen/version.h | 1 +
> xen/xsm/flask/hooks.c | 3 +
> xen/xsm/flask/policy/access_vectors | 2 +
> 15 files changed, 319 insertions(+), 25 deletions(-)
>
> diff --git a/Config.mk b/Config.mk
> index 429e460..61186e2 100644
> --- a/Config.mk
> +++ b/Config.mk
> @@ -126,6 +126,17 @@ endef
> check-$(gcc) = $(call cc-ver-check,CC,0x040100,"Xen requires at least
> gcc-4.1")
> $(eval $(check-y))
>
> +ld-ver-build-id = $(shell $(1) --build-id 2>&1 | \
> + grep -q unrecognized && echo n || echo
> y)
> +
> +# binutils 2.18 implement build-id.
> +ifeq ($(call ld-ver-build-id,$(LD)),n)
> +build_id_linker :=
> +else
> +CFLAGS += -DBUILD_ID
> +build_id_linker := --build-id=sha1
> +endif
> +
> # as-insn: Check whether assembler supports an instruction.
> # Usage: cflags-y += $(call as-insn "insn",option-yes,option-no)
> as-insn = $(if $(shell echo 'void _(void) { asm volatile ( $(2) ); }' \
> diff --git a/tools/flask/policy/policy/modules/xen/xen.te
> b/tools/flask/policy/policy/modules/xen/xen.te
> index 9ad648a..2988954 100644
> --- a/tools/flask/policy/policy/modules/xen/xen.te
> +++ b/tools/flask/policy/policy/modules/xen/xen.te
> @@ -79,7 +79,7 @@ allow dom0_t xen_t:xen2 {
> # Note that dom0 is part of domain_type so this has duplicates.
> allow dom0_t xen_t:version {
> version extraversion compile_info capabilities changeset
> - platform_parameters get_features pagesize guest_handle commandline
> + platform_parameters get_features pagesize guest_handle commandline
> build_id
> };
>
> allow dom0_t xen_t:mmu memorymap;
> @@ -146,7 +146,7 @@ if (guest_writeconsole) {
> # pmu_ctrl is for)
> allow domain_type xen_t:xen2 pmu_use;
>
> -# For normal guests all except XENVER_commandline
> +# For normal guests all except XENVER_commandline|build_id
> allow domain_type xen_t:version {
> version extraversion compile_info capabilities changeset
> platform_parameters get_features pagesize guest_handle
> diff --git a/tools/libxc/xc_private.c b/tools/libxc/xc_private.c
> index c41e433..d57c39a 100644
> --- a/tools/libxc/xc_private.c
> +++ b/tools/libxc/xc_private.c
> @@ -495,6 +495,13 @@ int xc_version(xc_interface *xch, int cmd, void *arg)
> case XENVER_commandline:
> sz = sizeof(xen_commandline_t);
> break;
> + case XENVER_build_id:
> + {
> + xen_build_id_t *build_id = (xen_build_id_t *)arg;
> + sz = sizeof(*build_id) + build_id->len;
> + HYPERCALL_BOUNCE_SET_DIR(arg, XC_HYPERCALL_BUFFER_BOUNCE_BOTH);
> + break;
> + }
> default:
> ERROR("xc_version: unknown command %d\n", cmd);
> return -EINVAL;
> diff --git a/tools/libxc/xc_private.h b/tools/libxc/xc_private.h
> index aa8daf1..6b592d3 100644
> --- a/tools/libxc/xc_private.h
> +++ b/tools/libxc/xc_private.h
> @@ -191,6 +191,16 @@ enum {
> #define DECLARE_HYPERCALL_BOUNCE(_ubuf, _sz, _dir)
> DECLARE_NAMED_HYPERCALL_BOUNCE(_ubuf, _ubuf, _sz, _dir)
>
> /*
> + * Change the direction.
> + *
> + * Can only be used if the bounce_pre/bounce_post commands have
> + * not been used.
> + */
> +#define HYPERCALL_BOUNCE_SET_DIR(_buf, _dir) do { if
> ((HYPERCALL_BUFFER(_buf))->hbuf) \
> + assert(1);
> \
> +
> (HYPERCALL_BUFFER(_buf))->dir = _dir; \
> + } while (0)
> +/*
> * Set the size of data to bounce. Useful when the size is not known
> * when the bounce buffer is declared.
> */
> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
> index 35ba293..8491267 100644
> --- a/xen/arch/arm/Makefile
> +++ b/xen/arch/arm/Makefile
> @@ -93,7 +93,7 @@ $(TARGET)-syms: prelink.o xen.lds
> $(BASEDIR)/common/symbols-dummy.o
> $(NM) -pa --format=sysv $(@D)/.$(@F).1 \
> | $(BASEDIR)/tools/symbols --sysv --sort >$(@D)/.$(@F).1.S
> $(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).1.o
> - $(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
> + $(LD) $(LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
> $(@D)/.$(@F).1.o -o $@
> rm -f $(@D)/.$(@F).[0-9]*
>
> diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
> index f501a2f..5cf180f 100644
> --- a/xen/arch/arm/xen.lds.S
> +++ b/xen/arch/arm/xen.lds.S
> @@ -22,6 +22,9 @@ OUTPUT_ARCH(FORMAT)
> PHDRS
> {
> text PT_LOAD /* XXX should be AT ( XEN_PHYS_START ) */ ;
> +#if defined(BUILD_ID)
> + note PT_NOTE ;
> +#endif
> }
> SECTIONS
> {
> @@ -53,6 +56,16 @@ SECTIONS
> _erodata = .; /* End of read-only data */
> } :text
>
> +#if defined(BUILD_ID)
> + .note : {
> + __note_gnu_build_id_start = .;
> + *(.note.gnu.build-id)
> + __note_gnu_build_id_end = .;
> + *(.note)
> + *(.note.*)
> + } :text
> +#endif
This data really should be contained inside rodata.
> diff --git a/xen/include/public/version.h b/xen/include/public/version.h
> index 44f26b0..adca602 100644
> --- a/xen/include/public/version.h
> +++ b/xen/include/public/version.h
> @@ -30,7 +30,8 @@
>
> #include "xen.h"
>
> -/* NB. All ops return zero on success, except XENVER_{version,pagesize} */
> +/* NB. All ops return zero on success, except
> + * XENVER_{version,pagesize,build_id} */
>
> /* arg == NULL; returns major:minor (16:16). */
> #define XENVER_version 0
> @@ -83,6 +84,19 @@ typedef struct xen_feature_info xen_feature_info_t;
> #define XENVER_commandline 9
> typedef char xen_commandline_t[1024];
>
> +/* Return value is the number of bytes written, or XEN_Exx on error.
> + * Calling with empty parameter returns the size of build_id. */
> +#define XENVER_build_id 10
> +struct xen_build_id {
> + uint32_t len; /* IN: size of buf[]. */
> +#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
> + unsigned char buf[];
> +#elif defined(__GNUC__)
> + unsigned char buf[1]; /* OUT: Variable length buffer with
> build_id. */
> +#endif
> +};
> +typedef struct xen_build_id xen_build_id_t;
I am still against trying to perpetuate this broken interface. Variable
length structures are a pain for everyone to use. How about introducing
a brand new hypercall with a separate length and data parameters?
~Andrew
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