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powerpc: Use orig_gpr3 in syscall_get_arguments() 

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>
Reviewed-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Michael Ellerman 2015-07-23 20:21:06 +10:00
parent a765784429
commit 1cb9839b73
1 changed files with 13 additions and 3 deletions
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16
arch/powerpc/include/asm/syscall.h
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@ -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(&regs->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)