@@ -64,7 +64,7 @@ static inline void syscall_get_arguments(struct task_struct *task,
unsigned int i, unsigned int n,
unsigned long *args)
{
- unsigned long mask = -1UL;
+ unsigned long val, mask = -1UL;
BUG_ON(i + n > 6);
@@ -72,8 +72,14 @@ static inline void syscall_get_arguments(struct task_struct *task,
if (test_tsk_thread_flag(task, TIF_32BIT))
mask = 0xffffffff;
#endif
- while (n--)
- args[n] = regs->gpr[3 + i + n] & mask;
+ while (n--) {
+ if (n == 0 && i == 0)
+ val = regs->orig_gpr3;
+ else
+ val = regs->gpr[3 + i + n];
+
+ args[n] = val & mask;
+ }
}
static inline void syscall_set_arguments(struct task_struct *task,
@@ -83,6 +89,10 @@ static inline void syscall_set_arguments(struct task_struct *task,
{
BUG_ON(i + n > 6);
memcpy(®s->gpr[3 + i], args, n * sizeof(args[0]));
+
+ /* Also copy the first argument into orig_gpr3 */
+ if (i == 0 && n > 0)
+ regs->orig_gpr3 = args[0];
}
static inline int syscall_get_arch(void)
Currently syscall_get_arguments() is used by syscall tracepoints, and collect_syscall() which is used in some debugging as well as /proc/pid/syscall. The current implementation just copies regs->gpr[3 .. 5] out, which is fine for all the current use cases. When we enable seccomp filter, that will also start using syscall_get_arguments(). However for seccomp filter we want to use r3 as the return value of the syscall, and orig_gpr3 as the first parameter. This will allow seccomp to modify the return value in r3. To support this we need to modify syscall_get_arguments() to return orig_gpr3 instead of r3. This is safe for all uses because orig_gpr3 always contains the r3 value that was passed to the syscall. We store it in the syscall entry path and never modify it. Update syscall_set_arguments() while we're here, even though it's never used. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> --- arch/powerpc/include/asm/syscall.h | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)