[Xen-devel] [PATCH] xen/xsm: Generate the permission in a spec-compliant way

[Julien Grall <julien.grall@xxxxxxxxxx>]

Each class can contains 32 permisions which are encoded on a word (one
bit per permission).

Currently the awk script will generate an hexadecimal value for each
permission. This may result to generate an invalid value on some version
of awk.

For instance debian jessie is using a version of mawk where (1 << 31)
will result to 0x7fffffff.

This is because the awk specification requires to do the arithmetic with
float. So the resulting integer may vary following the implementation.

As the generated headers are only used by C code, generate the
permission define via "1UL << n".

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

---
https://bugs.launchpad.net/ubuntu/+source/mawk/+bug/1159933

This bug impacts every version of Xen built on Debian Jessie when XSM is
enabled.

It would be interesting to backport it.
---
 xen/xsm/flask/policy/mkaccess_vector.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/xsm/flask/policy/mkaccess_vector.sh 
b/xen/xsm/flask/policy/mkaccess_vector.sh
index 8ec87f7..7fa4aaf 100644
--- a/xen/xsm/flask/policy/mkaccess_vector.sh
+++ b/xen/xsm/flask/policy/mkaccess_vector.sh
@@ -42,7 +42,7 @@ $1 == "class" {
                        } 
                        av_defined[tclass] = 1;
 
-                       permission = 1;
+                       permission = 0;
 
                        nextstate = "INHERITS_OR_CLASS-OPENBRACKET";
                        next;
@@ -108,8 +108,8 @@ $1 == "{"   {
 
                        for (i = 0; i < spaces; i++) 
                                printf(" ") > outfile; 
-                       printf("0x%08xUL\n", permission) > outfile; 
-                       permission = permission * 2;
+                       printf("(1UL << %u)\n", permission) > outfile;
+                       permission = permission + 1;
                }
 $1 == "}"      {
                        if (nextstate != "CLASS-CLOSEBRACKET" && 
-- 
2.1.4


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