[Xen-changelog] [xen master] bug/x86/arm: Align bug_frames sections.

[patchbot@xxxxxxx]

commit 137c59b9ff3f7a214f03b52d9c00a0a02374af1f
Author:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
AuthorDate: Wed Sep 7 11:57:05 2016 -0400
Commit:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CommitDate: Fri Sep 23 12:39:46 2016 -0400

    bug/x86/arm: Align bug_frames sections.
    
    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 alignment information - hence they end up being the default
    byte granularity.
    
    On ARM32 it is paramount that the alignment is word-size (4)
    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 alignment across all
    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
    
    Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx> [x86 parts]
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 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..4704e2d 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"                                                             \
+         ".p2align 2\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)
--
generated by git-patchbot for /home/xen/git/xen.git#master

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog