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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] livepatch: set -f{function,data}-sections compiler option
commit 6ff9a7e62b8c43fe3e9d360fbd49d5854787bc39
Author: Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Wed Mar 9 13:28:46 2022 +0100
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Mar 10 18:47:55 2022 +0000
livepatch: set -f{function,data}-sections compiler option
If livepatching support is enabled build the hypervisor with
-f{function,data}-sections compiler options, which is required by the
livepatching tools to detect changes and create livepatches.
This shouldn't result in any functional change on the hypervisor
binary image, but does however require some changes in the linker
script in order to handle that each function and data item will now be
placed into its own section in object files. As a result add catch-all
for .text, .data and .bss in order to merge each individual item
section into the final image.
The main difference will be that .text.startup will end up being part
of .text rather than .init, and thus won't be freed. .text.exit will
also be part of .text rather than dropped. Overall this could make the
image bigger, and package some .text code in a sub-optimal way.
On Arm the .data.read_mostly needs to be moved ahead of the .data
section like it's already done on x86, so the .data.* catch-all
doesn't also include .data.read_mostly. The alignment of
.data.read_mostly also needs to be set to PAGE_SIZE so it doesn't end
up being placed at the tail of a read-only page from the previous
section. While there move the alignment of the .data section ahead of
the section declaration, like it's done for other sections.
The benefit of having CONFIG_LIVEPATCH enable those compiler option
is that the livepatch build tools no longer need to fiddle with the
build system in order to enable them. Note the current livepatch tools
are broken after the recent build changes due to the way they
attempt to set -f{function,data}-sections.
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
xen/Kconfig | 4 ++++
xen/Makefile | 2 ++
xen/arch/arm/xen.lds.S | 41 +++++++++++++++++++++--------------------
xen/arch/x86/xen.lds.S | 11 ++++++-----
xen/common/Kconfig | 1 +
5 files changed, 34 insertions(+), 25 deletions(-)
diff --git a/xen/Kconfig b/xen/Kconfig
index bcbd2758e5..d134397a0b 100644
--- a/xen/Kconfig
+++ b/xen/Kconfig
@@ -27,6 +27,10 @@ config CLANG_VERSION
config CC_HAS_VISIBILITY_ATTRIBUTE
def_bool $(cc-option,-fvisibility=hidden)
+# Use -f{function,data}-sections compiler parameters
+config CC_SPLIT_SECTIONS
+ bool
+
source "arch/$(SRCARCH)/Kconfig"
config DEFCONFIG_LIST
diff --git a/xen/Makefile b/xen/Makefile
index 5c21492d6f..18a4f7e101 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -273,6 +273,8 @@ else
CFLAGS += -fomit-frame-pointer
endif
+CFLAGS-$(CONFIG_CC_SPLIT_SECTIONS) += -ffunction-sections -fdata-sections
+
CFLAGS += -nostdinc -fno-builtin -fno-common
CFLAGS += -Werror -Wredundant-decls -Wno-pointer-arith
$(call cc-option-add,CFLAGS,CC,-Wvla)
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index 743455a5f9..7921d8fa28 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -36,6 +36,9 @@ SECTIONS
*(.text.unlikely .text.*_unlikely .text.unlikely.*)
*(.text)
+#ifdef CONFIG_CC_SPLIT_SECTIONS
+ *(.text.*)
+#endif
*(.fixup)
*(.gnu.warning)
@@ -82,10 +85,24 @@ SECTIONS
#endif
_erodata = .; /* End of read-only data */
+ . = ALIGN(PAGE_SIZE);
+ .data.read_mostly : {
+ /* Exception table */
+ __start___ex_table = .;
+ *(.ex_table)
+ __stop___ex_table = .;
+
+ /* Pre-exception table */
+ __start___pre_ex_table = .;
+ *(.ex_table.pre)
+ __stop___pre_ex_table = .;
+
+ *(.data.read_mostly)
+ } :text
+
+ . = ALIGN(SMP_CACHE_BYTES);
.data : { /* Data */
- . = ALIGN(PAGE_SIZE);
*(.data.page_aligned)
- *(.data)
. = ALIGN(8);
__start_schedulers_array = .;
*(.data.schedulers)
@@ -98,26 +115,10 @@ SECTIONS
__paramhypfs_end = .;
#endif
- *(.data.rel)
- *(.data.rel.*)
+ *(.data .data.*)
CONSTRUCTORS
} :text
- . = ALIGN(SMP_CACHE_BYTES);
- .data.read_mostly : {
- /* Exception table */
- __start___ex_table = .;
- *(.ex_table)
- __stop___ex_table = .;
-
- /* Pre-exception table */
- __start___pre_ex_table = .;
- *(.ex_table.pre)
- __stop___pre_ex_table = .;
-
- *(.data.read_mostly)
- } :text
-
. = ALIGN(8);
.arch.info : {
_splatform = .;
@@ -211,7 +212,7 @@ SECTIONS
*(.bss.percpu.read_mostly)
. = ALIGN(SMP_CACHE_BYTES);
__per_cpu_data_end = .;
- *(.bss)
+ *(.bss .bss.*)
. = ALIGN(POINTER_ALIGN);
__bss_end = .;
} :text
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 960c51eb4c..4103763f63 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -87,9 +87,12 @@ SECTIONS
*(.text.cold)
*(.text.unlikely .text.*_unlikely .text.unlikely.*)
+ *(.text.page_aligned)
*(.text)
+#ifdef CONFIG_CC_SPLIT_SECTIONS
+ *(.text.*)
+#endif
*(.text.__x86_indirect_thunk_*)
- *(.text.page_aligned)
*(.fixup)
*(.gnu.warning)
@@ -292,9 +295,7 @@ SECTIONS
DECL_SECTION(.data) {
*(.data.page_aligned)
- *(.data)
- *(.data.rel)
- *(.data.rel.*)
+ *(.data .data.*)
} PHDR(text)
DECL_SECTION(.bss) {
@@ -309,7 +310,7 @@ SECTIONS
*(.bss.percpu.read_mostly)
. = ALIGN(SMP_CACHE_BYTES);
__per_cpu_data_end = .;
- *(.bss)
+ *(.bss .bss.*)
. = ALIGN(POINTER_ALIGN);
__bss_end = .;
} PHDR(text)
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 6443943889..d921c74d61 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -354,6 +354,7 @@ config LIVEPATCH
bool "Live patching support"
default X86
depends on "$(XEN_HAS_BUILD_ID)" = "y"
+ select CC_SPLIT_SECTIONS
---help---
Allows a running Xen hypervisor to be dynamically patched using
binary patches without rebooting. This is primarily used to binarily
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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