On 19/09/2016 16:34, Julien Grall wrote:
Hi Konrad,
On 16/09/2016 18:38, Konrad Rzeszutek Wilk wrote:
Most of the WARN_ON or BUG_ON sections are properly aligned on
x86. However on ARM and on x86 assembler the macros don't include
any aligment information - hence they end up being the default
s/aligment/alignment/
byte granularity.
On ARM32 it is paramount that the aligment is word-size (4)
Ditto
otherwise if one tries to use (uint32_t*) access (such
as livepatch ELF relocations) we get a Data Abort.
Enforcing bug_frames to have the proper aligment across all
Ditto
architectures and in both C and x86 makes them all the same.
Furthermore on x86 the bloat-o-meter detects that with this
change:
add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
function old new delta
On ARM32:
add/remove: 1/0 grow/shrink: 0/1 up/down: 384/-288 (96)
function old new delta
gnttab_unpopulate_status_frames - 384 +384
do_grant_table_op 10808 10520 -288
And ARM64:
add/remove: 1/2 grow/shrink: 0/1 up/down: 4164/-4236 (-72)
function old new delta
gnttab_map_grant_ref - 4164 +4164
do_grant_table_op 9892 9836 -56
grant_map_exists 300 - -300
__gnttab_map_grant_ref 3880 - -3880
Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
I forgot to mention that with those NITs fixed:
Reviewed-by: Julien Grall <julien.gr...@arm.com>
---
Cc: Julien Grall <julien.gr...@arm.com>
Cc: Stefano Stabellini <sstabell...@kernel.org>
Cc: Jan Beulich <jbeul...@suse.com>
Cc: Andrew Cooper <andrew.coop...@citrix.com>
v3: First submission. Replaces the "livepatch/elf: Adjust section
aligment to word"
patch.
v4: Remove the .ALIGN(4) in xen.lds.S for x86 (the only place needing
that change).
Update the commit description with correct x86 results
Remove the . = ALIGN(4); in linker filer on x86 [the only file
needing the change]
---
xen/arch/x86/xen.lds.S | 1 -
xen/include/asm-arm/bug.h | 1 +
xen/include/asm-x86/bug.h | 1 +
3 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index d903c31..7676de9 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -79,7 +79,6 @@ SECTIONS
.rodata : {
_srodata = .;
/* Bug frames table */
- . = ALIGN(4);
__start_bug_frames = .;
*(.bug_frames.0)
__stop_bug_frames_0 = .;
diff --git a/xen/include/asm-arm/bug.h b/xen/include/asm-arm/bug.h
index 68353e1..773d63e 100644
--- a/xen/include/asm-arm/bug.h
+++ b/xen/include/asm-arm/bug.h
@@ -52,6 +52,7 @@ struct bug_frame {
".popsection\n" \
".pushsection .bug_frames." __stringify(type) ", \"a\",
%progbits\n"\
"4:\n" \
+ ".align
4\n" \
".long (1b -
4b)\n" \
".long (2b -
4b)\n" \
".long (3b -
4b)\n" \
diff --git a/xen/include/asm-x86/bug.h b/xen/include/asm-x86/bug.h
index c5d2d4c..9bb4a19 100644
--- a/xen/include/asm-x86/bug.h
+++ b/xen/include/asm-x86/bug.h
@@ -98,6 +98,7 @@ extern const struct bug_frame __start_bug_frames[],
.popsection
.pushsection .bug_frames.\type, "a", @progbits
+ .p2align 2
.L\@bf:
.long (.L\@ud - .L\@bf) + \
((\line >> BUG_LINE_LO_WIDTH) << BUG_DISP_WIDTH)
Regards,
--
Julien Grall
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel