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Subject[PATCH] powerpc/vdso: Fix multiple issues with sys_call_table
The VDSO exports a bitmap of valid syscalls. vdso_setup_syscall_map()
sets this up, but there are both little and big endian bugs. The issue
is with:

if (sys_call_table[i] != sys_ni_syscall)

On little endian, instead of comparing pointers to the two functions,
we compare the first two instructions of each function. If a function
happens to have the same first two instructions as sys_ni_syscall, then
we have a spurious match and mark the instruction as not implemented.
Fix this by removing the inline declarations.

On big endian we have a further issue where sys_ni_syscall is a function
descriptor and sys_call_table[] holds pointers to the instruction text.
Fix this by using dereference_kernel_function_descriptor().

Signed-off-by: Anton Blanchard <>

diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index b9a108411c0d..d186b729026e 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -17,6 +17,7 @@
#include <linux/elf.h>
#include <linux/security.h>
#include <linux/memblock.h>
+#include <linux/syscalls.h>

#include <asm/pgtable.h>
#include <asm/processor.h>
@@ -30,6 +31,7 @@
#include <asm/vdso.h>
#include <asm/vdso_datapage.h>
#include <asm/setup.h>
+#include <asm/syscall.h>

#undef DEBUG

@@ -644,19 +646,16 @@ static __init int vdso_setup(void)
static void __init vdso_setup_syscall_map(void)
unsigned int i;
- extern unsigned long *sys_call_table;
-#ifdef CONFIG_PPC64
- extern unsigned long *compat_sys_call_table;
- extern unsigned long sys_ni_syscall;
+ unsigned long ni_syscall;

+ ni_syscall = (unsigned long)dereference_kernel_function_descriptor(sys_ni_syscall);

for (i = 0; i < NR_syscalls; i++) {
#ifdef CONFIG_PPC64
- if (sys_call_table[i] != sys_ni_syscall)
+ if (sys_call_table[i] != ni_syscall)
vdso_data->syscall_map_64[i >> 5] |=
0x80000000UL >> (i & 0x1f);
- if (compat_sys_call_table[i] != sys_ni_syscall)
+ if (compat_sys_call_table[i] != ni_syscall)
vdso_data->syscall_map_32[i >> 5] |=
0x80000000UL >> (i & 0x1f);
#else /* CONFIG_PPC64 */
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