[Xen-devel] [PATCH 3/4] xen/link: Fold .data.read_mostly into .data

[Andrew Cooper <andrew.cooper3@citrix.com>]

.data.read_mostly only needs separating from adjacent data by one cache line
to be effective, and placing it adjacent to .data.page_aligned fulfills this
requirement.

For ARM, .ex_table appears to be a vestigial remnant.  Nothing in the
resulting build ever inspects or acts on the contents of the table.  The arm32
build does however have some assembly routines which fill .ex_table.

Drop all of ARM's .ex_table infrastructure, to reduce the size of the compiled
binary, and avoid giving the illusion of exception handling working.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien.grall@arm.com>

Only compile tested on ARM.
---
 xen/arch/arm/arm32/lib/assembler.h | 19 ++-----------------
 xen/arch/arm/xen.lds.S             | 16 +---------------
 xen/arch/x86/xen.lds.S             |  7 ++-----
 3 files changed, 5 insertions(+), 37 deletions(-)

diff --git a/xen/arch/arm/arm32/lib/assembler.h b/xen/arch/arm/arm32/lib/assembler.h
index 6de2638..42eaabb 100644
--- a/xen/arch/arm/arm32/lib/assembler.h
+++ b/xen/arch/arm/arm32/lib/assembler.h
@@ -160,13 +160,6 @@
 	restore_irqs_notrace \oldcpsr
 	.endm
 
-#define USER(x...)				\
-9999:	x;					\
-	.pushsection __ex_table,"a";		\
-	.align	3;				\
-	.long	9999b,9001f;			\
-	.popsection
-
 #ifdef CONFIG_SMP
 #define ALT_SMP(instr...)					\
 9998:	instr
@@ -247,7 +240,7 @@
 #ifdef CONFIG_THUMB2_KERNEL
 
 	.macro	usraccoff, instr, reg, ptr, inc, off, cond, abort, t=T()
-9999:
+
 	.if	\inc == 1
 	\instr\cond\()b\()\t\().w \reg, [\ptr, #\off]
 	.elseif	\inc == 4
@@ -256,10 +249,6 @@
 	.error	"Unsupported inc macro argument"
 	.endif
 
-	.pushsection __ex_table,"a"
-	.align	3
-	.long	9999b, \abort
-	.popsection
 	.endm
 
 	.macro	usracc, instr, reg, ptr, inc, cond, rept, abort
@@ -288,7 +277,7 @@
 
 	.macro	usracc, instr, reg, ptr, inc, cond, rept, abort, t=T()
 	.rept	\rept
-9999:
+
 	.if	\inc == 1
 	\instr\cond\()b\()\t \reg, [\ptr], #\inc
 	.elseif	\inc == 4
@@ -297,10 +286,6 @@
 	.error	"Unsupported inc macro argument"
 	.endif
 
-	.pushsection __ex_table,"a"
-	.align	3
-	.long	9999b, \abort
-	.popsection
 	.endr
 	.endm
 
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index 2b44e5d..3dc5117 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -94,27 +94,13 @@ SECTIONS
   _erodata = .;                /* End of read-only data */
 
   .data : {                    /* Data */
+       *(.data.read_mostly)
        . = ALIGN(PAGE_SIZE);
        *(.data.page_aligned)
        *(.data)
        *(.data.*)
   } :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 = .;
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 9fa6c99..ef11949 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -264,12 +264,9 @@ SECTIONS
   __2M_init_end = .;
 
   __2M_rwdata_start = .;       /* Start of 2M superpages, mapped RW. */
-  . = ALIGN(SMP_CACHE_BYTES);
-  DECL_SECTION(.data.read_mostly) {
-       *(.data.read_mostly)
-  } :text
-
   DECL_SECTION(.data) {
+       *(.data.read_mostly)
+       . = ALIGN(PAGE_SIZE);
        *(.data.page_aligned)
        *(.data)
        *(.data.*)
-- 
2.1.4


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