From 1cb9839b73e7f2b006a1cc9452c30f15ff8b1748 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Thu, 23 Jul 2015 20:21:06 +1000 Subject: [PATCH] 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 Reviewed-by: Kees Cook --- arch/powerpc/include/asm/syscall.h | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h index 403e2303fe18..8d79a87c0511 100644 --- a/arch/powerpc/include/asm/syscall.h +++ b/arch/powerpc/include/asm/syscall.h @@ -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) -- 2.11.4.GIT