x86, um: actually mark system call tables readonly

commit b485342bd79af363c77ef1a421c4a0aef2de9812 upstream.

Commit a074335a370e ("x86, um: Mark system call tables readonly") was
supposed to mark the sys_call_table in UML as RO by adding the const,
but it doesn't have the desired effect as it's nevertheless being placed
into the data section since __cacheline_aligned enforces sys_call_table
being placed into .data..cacheline_aligned instead. We need to use
the ____cacheline_aligned version instead to fix this issue.

Before:

$ nm -v arch/x86/um/sys_call_table_64.o | grep -1 "sys_call_table"
                 U sys_writev
0000000000000000 D sys_call_table
0000000000000000 D syscall_table_size

After:

$ nm -v arch/x86/um/sys_call_table_64.o | grep -1 "sys_call_table"
                 U sys_writev
0000000000000000 R sys_call_table
0000000000000000 D syscall_table_size

Fixes: a074335a370e ("x86, um: Mark system call tables readonly")
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/um/sys_call_table_32.c b/arch/x86/um/sys_call_table_32.c
index 531d4269e2e3c5303e8b40e6753dd20ddab3c405..bd16d6c370ec9aaeb3328779e277de8129ef61f3 100644 (file)
--- a/arch/x86/um/sys_call_table_32.c
+++ b/arch/x86/um/sys_call_table_32.c
@@ -34,7 +34,7 @@ typedef asmlinkage void (*sys_call_ptr_t)(void);
 
 extern asmlinkage void sys_ni_syscall(void);
 
-const sys_call_ptr_t sys_call_table[] __cacheline_aligned = {
+const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
        /*
         * Smells like a compiler bug -- it doesn't work
         * when the & below is removed.

diff --git a/arch/x86/um/sys_call_table_64.c b/arch/x86/um/sys_call_table_64.c
index f2f0723070caea848a88fe1f96863943fc3df121..95783087f0d3432170d879355d6cb893c33bed51 100644 (file)
--- a/arch/x86/um/sys_call_table_64.c
+++ b/arch/x86/um/sys_call_table_64.c
@@ -46,7 +46,7 @@ typedef void (*sys_call_ptr_t)(void);
 
 extern void sys_ni_syscall(void);
 
-const sys_call_ptr_t sys_call_table[] __cacheline_aligned = {
+const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
        /*
         * Smells like a compiler bug -- it doesn't work
         * when the & below is removed.