[PATCH v4 1/2] powerpc: Add a proper syscall for switching endianness
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2015-03-28 01:19:12
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> --- v3: Don't provide the syscall on 32-bit. v4: No change. arch/powerpc/include/asm/systbl.h | 1 + arch/powerpc/include/asm/unistd.h | 2 +- arch/powerpc/include/uapi/asm/unistd.h | 1 + arch/powerpc/kernel/entry_64.S | 5 +++++ arch/powerpc/kernel/syscalls.c | 17 +++++++++++++++++ arch/powerpc/kernel/systbl.S | 2 ++ arch/powerpc/kernel/systbl_chk.c | 2 ++ arch/powerpc/platforms/cell/spu_callbacks.c | 1 + 8 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/systbl.h b/arch/powerpc/include/asm/systbl.h
index 91062eef582f..f1863a138b4a 100644
--- a/arch/powerpc/include/asm/systbl.h
+++ b/arch/powerpc/include/asm/systbl.h@@ -367,3 +367,4 @@ SYSCALL_SPU(getrandom) SYSCALL_SPU(memfd_create) SYSCALL_SPU(bpf) COMPAT_SYS(execveat) +PPC64ONLY(switch_endian)
diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
index 36b79c31eedd..f4f8b667d75b 100644
--- a/arch/powerpc/include/asm/unistd.h
+++ b/arch/powerpc/include/asm/unistd.h@@ -12,7 +12,7 @@ #include <uapi/asm/unistd.h> -#define __NR_syscalls 363 +#define __NR_syscalls 364 #define __NR__exit __NR_exit #define NR_syscalls __NR_syscalls
diff --git a/arch/powerpc/include/uapi/asm/unistd.h b/arch/powerpc/include/uapi/asm/unistd.h
index ef5b5b1f3123..e4aa173dae62 100644
--- a/arch/powerpc/include/uapi/asm/unistd.h
+++ b/arch/powerpc/include/uapi/asm/unistd.h@@ -385,5 +385,6 @@ #define __NR_memfd_create 360 #define __NR_bpf 361 #define __NR_execveat 362 +#define __NR_switch_endian 363 #endif /* _UAPI_ASM_POWERPC_UNISTD_H_ */
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index d180caf2d6de..afbc20019c2e 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S@@ -356,6 +356,11 @@ _GLOBAL(ppc64_swapcontext) 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 b2702e87db0d..5fa92706444b 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c@@ -121,3 +121,20 @@ long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low, 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 7ab5d434e2ee..4d6b1d3a747f 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 238aa63ced8f..2384129f5893 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
diff --git a/arch/powerpc/platforms/cell/spu_callbacks.c b/arch/powerpc/platforms/cell/spu_callbacks.c
index b0ec78e8ad68..a494028b2cdf 100644
--- a/arch/powerpc/platforms/cell/spu_callbacks.c
+++ b/arch/powerpc/platforms/cell/spu_callbacks.c@@ -39,6 +39,7 @@ static void *spu_syscall_table[] = { #define PPC_SYS(func) sys_ni_syscall, #define OLDSYS(func) sys_ni_syscall, #define SYS32ONLY(func) sys_ni_syscall, +#define PPC64ONLY(func) sys_ni_syscall, #define SYSX(f, f3264, f32) sys_ni_syscall, #define SYSCALL_SPU(func) sys_##func,
--
2.1.0