Leverage the new infrastructure in xen/linkage.h to also switch to per- function sections (when configured), deriving the specific name from the "base" section in use at the time FUNC() is invoked.
Signed-off-by: Jan Beulich <[email protected]> --- TBD: Since we use .subsection in UNLIKELY_START(), a perhaps not really wanted side effect of this change is that respective out-of-line code now moves much closer to its original (invoking) code. TBD: Of course something with the same overall effect, but less impactful might do in Config.mk. E.g. $(filter-out -D%,$(3)) instead of $(firstword (3)). TBD: On top of Roger's respective patch (for livepatch), also respect CONFIG_FUNCTION_ALIGNMENT. Note that we'd need to split DATA() in order to separate r/w and r/o contributions. Further splitting might be needed to also support more advanced attributes (e.g. merge), hence why this isn't done right here. Sadly while a new section's name can be derived from the presently in use, its attributes cannot be. Perhaps the only thing we can do is give DATA() a 2nd mandatory parameter. Then again I guess most data definitions could be moved to C anyway. --- v5: Re-base over changes earlier in the series. v4: Re-base. v2: Make detection properly fail on old gas (by adjusting cc-option-add-closure). --- a/Config.mk +++ b/Config.mk @@ -102,7 +102,7 @@ cc-option = $(shell if $(1) $(2:-Wno-%=- # Usage: $(call cc-option-add CFLAGS,CC,-march=winchip-c6) cc-option-add = $(eval $(call cc-option-add-closure,$(1),$(2),$(3))) define cc-option-add-closure - ifneq ($$(call cc-option,$$($(2)),$(3),n),n) + ifneq ($$(call cc-option,$$($(2)),$(firstword $(3)),n),n) $(1) += $(3) endif endef --- a/xen/Makefile +++ b/xen/Makefile @@ -409,6 +409,9 @@ AFLAGS += -D__ASSEMBLY__ $(call cc-option-add,AFLAGS,CC,-Wa$$(comma)--noexecstack) +# Check to see whether the assmbler supports the --sectname-subst option. +$(call cc-option-add,AFLAGS,CC,-Wa$$(comma)--sectname-subst -DHAVE_AS_SECTNAME_SUBST) + LDFLAGS-$(call ld-option,--warn-rwx-segments) += --no-warn-rwx-segments CFLAGS += $(CFLAGS-y) --- a/xen/arch/arm/xen.lds.S +++ b/xen/arch/arm/xen.lds.S @@ -156,6 +156,9 @@ SECTIONS .init.text : { _sinittext = .; *(.init.text) +#ifdef CONFIG_CC_SPLIT_SECTIONS + *(.init.text.*) +#endif _einittext = .; . = ALIGN(PAGE_SIZE); /* Avoid mapping alt insns executable */ *(.altinstr_replacement) --- a/xen/arch/ppc/xen.lds.S +++ b/xen/arch/ppc/xen.lds.S @@ -104,6 +104,9 @@ SECTIONS .init.text : { _sinittext = .; *(.init.text) +#ifdef CONFIG_CC_SPLIT_SECTIONS + *(.init.text.*) +#endif _einittext = .; . = ALIGN(PAGE_SIZE); /* Avoid mapping alt insns executable */ } :text --- a/xen/arch/riscv/xen.lds.S +++ b/xen/arch/riscv/xen.lds.S @@ -104,6 +104,9 @@ SECTIONS .init.text : { _sinittext = .; *(.init.text) +#ifdef CONFIG_CC_SPLIT_SECTIONS + *(.init.text.*) +#endif _einittext = .; . = ALIGN(PAGE_SIZE); /* Avoid mapping alt insns executable */ } :text --- a/xen/arch/x86/xen.lds.S +++ b/xen/arch/x86/xen.lds.S @@ -86,6 +86,9 @@ SECTIONS . = ALIGN(PAGE_SIZE); _stextentry = .; *(.text.entry) +#ifdef CONFIG_CC_SPLIT_SECTIONS + *(.text.entry.*) +#endif . = ALIGN(PAGE_SIZE); _etextentry = .; @@ -214,6 +217,9 @@ SECTIONS #endif _sinittext = .; *(.init.text) +#ifdef CONFIG_CC_SPLIT_SECTIONS + *(.init.text.*) +#endif *(.text.startup) _einittext = .; /* --- a/xen/include/xen/linkage.h +++ b/xen/include/xen/linkage.h @@ -19,6 +19,14 @@ #define SYM_ALIGN(align...) .balign align +#if defined(HAVE_AS_SECTNAME_SUBST) && defined(CONFIG_CC_SPLIT_SECTIONS) +# define SYM_PUSH_SECTION(name, attr) \ + .pushsection %S.name, attr, %progbits; \ + .equ .Lsplit_section, 1 +#else +# define SYM_PUSH_SECTION(name, attr) +#endif + #define SYM_L_GLOBAL(name) .globl name; .hidden name #define SYM_L_WEAK(name) .weak name #define SYM_L_LOCAL(name) /* nothing */ @@ -33,7 +41,14 @@ SYM_ALIGN(align); \ name: -#define END(name) .size name, . - name +#define END(name) \ + .size name, . - name; \ + .ifdef .Lsplit_section; \ + .if .Lsplit_section; \ + .popsection; \ + .equ .Lsplit_section, 0; \ + .endif; \ + .endif /* * CODE_FILL in particular may need to expand to nothing (e.g. for RISC-V), in @@ -47,6 +62,7 @@ #endif #define FUNC(name, align...) \ + SYM_PUSH_SECTION(name, "ax"); \ SYM(name, FUNC, GLOBAL, DO_CODE_ALIGN(align)) #define LABEL(name, align...) \ SYM(name, NONE, GLOBAL, DO_CODE_ALIGN(align)) @@ -54,6 +70,7 @@ SYM(name, DATA, GLOBAL, LASTARG(DATA_ALIGN, ## align), DATA_FILL) #define FUNC_LOCAL(name, align...) \ + SYM_PUSH_SECTION(name, "ax"); \ SYM(name, FUNC, LOCAL, DO_CODE_ALIGN(align)) #define LABEL_LOCAL(name, align...) \ SYM(name, NONE, LOCAL, DO_CODE_ALIGN(align))
