powerpc: Add a proper syscall for switching endianness
We currently have a "special" syscall for switching endianness. This is
syscall number 0x1ebe, which is handled explicitly in the 64-bit syscall
exception entry.
That has a few problems, firstly the syscall number is outside of the
usual range, which confuses various tools. For example strace doesn't
recognise the syscall at all.
Secondly it's handled explicitly as a special case in the syscall
exception entry, which is complicated enough without it.
As a first step toward removing the special syscall, we need to add a
regular syscall that implements the same functionality.
The logic is simple, it simply toggles the MSR_LE bit in the userspace
MSR. This is the same as the special syscall, with the caveat that the
special syscall clobbers fewer registers.
This version clobbers r9-r12, XER, CTR, and CR0-1,5-7.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index d180caf2..afbc200 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -356,6 +356,11 @@
bl sys_swapcontext
b .Lsyscall_exit
+_GLOBAL(ppc_switch_endian)
+ bl save_nvgprs
+ bl sys_switch_endian
+ b .Lsyscall_exit
+
_GLOBAL(ret_from_fork)
bl schedule_tail
REST_NVGPRS(r1)
diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index b2702e8..5fa9270 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -121,3 +121,20 @@
return sys_fadvise64(fd, (u64)offset_high << 32 | offset_low,
(u64)len_high << 32 | len_low, advice);
}
+
+long sys_switch_endian(void)
+{
+ struct thread_info *ti;
+
+ current->thread.regs->msr ^= MSR_LE;
+
+ /*
+ * Set TIF_RESTOREALL so that r3 isn't clobbered on return to
+ * userspace. That also has the effect of restoring the non-volatile
+ * GPRs, so we saved them on the way in here.
+ */
+ ti = current_thread_info();
+ ti->flags |= _TIF_RESTOREALL;
+
+ return 0;
+}
diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.S
index 7ab5d43..4d6b1d3 100644
--- a/arch/powerpc/kernel/systbl.S
+++ b/arch/powerpc/kernel/systbl.S
@@ -22,6 +22,7 @@
#define PPC_SYS(func) .llong DOTSYM(ppc_##func),DOTSYM(ppc_##func)
#define OLDSYS(func) .llong DOTSYM(sys_ni_syscall),DOTSYM(sys_ni_syscall)
#define SYS32ONLY(func) .llong DOTSYM(sys_ni_syscall),DOTSYM(compat_sys_##func)
+#define PPC64ONLY(func) .llong DOTSYM(ppc_##func),DOTSYM(sys_ni_syscall)
#define SYSX(f, f3264, f32) .llong DOTSYM(f),DOTSYM(f3264)
#else
#define SYSCALL(func) .long sys_##func
@@ -29,6 +30,7 @@
#define PPC_SYS(func) .long ppc_##func
#define OLDSYS(func) .long sys_##func
#define SYS32ONLY(func) .long sys_##func
+#define PPC64ONLY(func) .long sys_ni_syscall
#define SYSX(f, f3264, f32) .long f32
#endif
#define SYSCALL_SPU(func) SYSCALL(func)
diff --git a/arch/powerpc/kernel/systbl_chk.c b/arch/powerpc/kernel/systbl_chk.c
index 238aa63..2384129 100644
--- a/arch/powerpc/kernel/systbl_chk.c
+++ b/arch/powerpc/kernel/systbl_chk.c
@@ -21,9 +21,11 @@
#ifdef CONFIG_PPC64
#define OLDSYS(func) -1
#define SYS32ONLY(func) -1
+#define PPC64ONLY(func) __NR_##func
#else
#define OLDSYS(func) __NR_old##func
#define SYS32ONLY(func) __NR_##func
+#define PPC64ONLY(func) -1
#endif
#define SYSX(f, f3264, f32) -1
