[RFC PATCH 11/11] prctl: Refactor PR_{SET,GET}_UNALIGN to reduce boilerplate

From: Dave Martin
Date: Mon May 14 2018 - 13:16:00 EST

The PR_SET_UNALIGN and PR_GET_UNALIGN prctl() calls are implemented
by five architectures today, but there is some irregularity and
duplication in the way they are implemented.

This patch moves the common put_user() operation to common code,
since the user pointer type is the same in all cases.

Because this is hardly hot-path code, there is no strong reason to
inline the arch backends for these operations, so this patch also
pushes them down into the arch trees as proper C functions, and
regularises the style of the backends somewhat.

Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
Cc: Rich Felker <dalias@xxxxxxxx>
---
arch/Kconfig | 3 +++
arch/alpha/Kconfig | 1 +
arch/alpha/include/asm/thread_info.h | 23 -----------------------
arch/alpha/kernel/Makefile | 2 +-
arch/alpha/kernel/sys.c | 36 ++++++++++++++++++++++++++++++++++++
arch/ia64/Kconfig | 1 +
arch/ia64/include/asm/processor.h | 12 ------------
arch/ia64/kernel/sys_ia64.c | 15 +++++++++++++++
arch/parisc/Kconfig | 1 +
arch/parisc/include/asm/processor.h | 14 --------------
arch/parisc/kernel/sys_parisc.c | 15 +++++++++++++++
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/processor.h | 6 ------
arch/powerpc/kernel/process.c | 6 +++---
arch/sh/Kconfig | 1 +
arch/sh/include/asm/processor.h | 7 -------
arch/sh/mm/alignment.c | 8 ++++----
include/linux/prctl.h | 8 ++++++++
kernel/sys.c | 20 ++++++++++----------
19 files changed, 100 insertions(+), 80 deletions(-)
create mode 100644 arch/alpha/kernel/sys.c

diff --git a/arch/Kconfig b/arch/Kconfig
index b34b3e8..a9195ffc 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -972,4 +972,7 @@ config REFCOUNT_FULL
config HAVE_PRCTL_ARCH
bool

+config HAVE_ARCH_PR_SET_GET_UNALIGN
+ bool
+
source "kernel/gcov/Kconfig"
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index b202288..afb9aaa 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -23,6 +23,7 @@ config ALPHA
select GENERIC_STRNCPY_FROM_USER
select GENERIC_STRNLEN_USER
select HAVE_ARCH_AUDITSYSCALL
+ select HAVE_ARCH_PR_SET_GET_UNALIGN
select HAVE_MOD_ARCH_SPECIFIC
select MODULES_USE_ELF_RELA
select ODD_RT_SIGACTION
diff --git a/arch/alpha/include/asm/thread_info.h b/arch/alpha/include/asm/thread_info.h
index 403b3c8..7ba2099 100644
--- a/arch/alpha/include/asm/thread_info.h
+++ b/arch/alpha/include/asm/thread_info.h
@@ -85,28 +85,5 @@ register struct thread_info *__current_thread_info __asm__("$8");
#define TS_UAC_NOFIX 0x0002 /* ! flags as they match */
#define TS_UAC_SIGBUS 0x0004 /* ! userspace part of 'osf_sysinfo' */

-#define SET_UNALIGN_CTL(value) ({ \
- __u32 status = current_thread_info()->status & ~UAC_BITMASK; \
- if (value & PR_UNALIGN_NOPRINT) \
- status |= TS_UAC_NOPRINT; \
- if (value & PR_UNALIGN_SIGBUS) \
- status |= TS_UAC_SIGBUS; \
- if (value & 4) /* alpha-specific */ \
- status |= TS_UAC_NOFIX; \
- current_thread_info()->status = status; \
- 0; })
-
-#define GET_UNALIGN_CTL(value) ({ \
- __u32 status = current_thread_info()->status & ~UAC_BITMASK; \
- __u32 res = 0; \
- if (status & TS_UAC_NOPRINT) \
- res |= PR_UNALIGN_NOPRINT; \
- if (status & TS_UAC_SIGBUS) \
- res |= PR_UNALIGN_SIGBUS; \
- if (status & TS_UAC_NOFIX) \
- res |= 4; \
- put_user(res, (int __user *)(value)); \
- })
-
#endif /* __KERNEL__ */
#endif /* _ALPHA_THREAD_INFO_H */
diff --git a/arch/alpha/kernel/Makefile b/arch/alpha/kernel/Makefile
index 5a74581..e4b5294 100644
--- a/arch/alpha/kernel/Makefile
+++ b/arch/alpha/kernel/Makefile
@@ -9,7 +9,7 @@ ccflags-y := -Wno-sign-compare

obj-y := entry.o traps.o process.o osf_sys.o irq.o \
irq_alpha.o signal.o setup.o ptrace.o time.o \
- systbls.o err_common.o io.o bugs.o
+ systbls.o err_common.o io.o bugs.o sys.o

obj-$(CONFIG_VGA_HOSE) += console.o
obj-$(CONFIG_SMP) += smp.o
diff --git a/arch/alpha/kernel/sys.c b/arch/alpha/kernel/sys.c
new file mode 100644
index 0000000..3dc454f
--- /dev/null
+++ b/arch/alpha/kernel/sys.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/prctl.h>
+#include <linux/thread_info.h>
+#include <linux/uaccess.h>
+
+int arch_set_unalign_ctl(unsigned int val)
+{
+ __u32 status = current_thread_info()->status & ~UAC_BITMASK;
+
+ if (val & PR_UNALIGN_NOPRINT)
+ status |= TS_UAC_NOPRINT;
+ if (val & PR_UNALIGN_SIGBUS)
+ status |= TS_UAC_SIGBUS;
+ if (val & 4) /* alpha-specific */
+ status |= TS_UAC_NOFIX;
+
+ current_thread_info()->status = status;
+
+ return 0;
+}
+
+int arch_get_unalign_ctl(void)
+{
+ __u32 status = current_thread_info()->status & ~UAC_BITMASK;
+ int res = 0;
+
+ if (status & TS_UAC_NOPRINT)
+ res |= PR_UNALIGN_NOPRINT;
+ if (status & TS_UAC_SIGBUS)
+ res |= PR_UNALIGN_SIGBUS;
+ if (status & TS_UAC_NOFIX)
+ res |= 4;
+
+ return res;
+}
diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index a673dd7..ab62a57 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -55,6 +55,7 @@ config IA64
select ARCH_USE_CMPXCHG_LOCKREF
select HAVE_ARCH_AUDITSYSCALL
select HAVE_PRCTL_ARCH
+ select HAVE_ARCH_PR_SET_GET_UNALIGN
default y
help
The Itanium Processor Family is Intel's 64-bit successor to
diff --git a/arch/ia64/include/asm/processor.h b/arch/ia64/include/asm/processor.h
index 8d5184f..49f4ef9 100644
--- a/arch/ia64/include/asm/processor.h
+++ b/arch/ia64/include/asm/processor.h
@@ -247,18 +247,6 @@ typedef struct {
unsigned long seg;
} mm_segment_t;

-#define SET_UNALIGN_CTL(value) \
-({ \
- current->thread.flags = ((current->thread.flags & ~IA64_THREAD_UAC_MASK) \
- | (((value) << IA64_THREAD_UAC_SHIFT) & IA64_THREAD_UAC_MASK)); \
- 0; \
-})
-#define GET_UNALIGN_CTL(addr) \
-({ \
- put_user((current->thread.flags & IA64_THREAD_UAC_MASK) >> IA64_THREAD_UAC_SHIFT, \
- (int __user *) (addr)); \
-})
-
struct thread_struct {
__u32 flags; /* various thread flags (see IA64_THREAD_*) */
/* writing on_ustack is performance-critical, so it's worth spending 8 bits on it... */
diff --git a/arch/ia64/kernel/sys_ia64.c b/arch/ia64/kernel/sys_ia64.c
index d996585..2c2fd65 100644
--- a/arch/ia64/kernel/sys_ia64.c
+++ b/arch/ia64/kernel/sys_ia64.c
@@ -206,3 +206,18 @@ int prctl_arch(int option, unsigned long arg2, unsigned long arg3,
return -EINVAL;
}
}
+
+int arch_set_unalign_ctl(unsigned int val)
+{
+ current->thread.flags &= ~IA64_THREAD_UAC_MASK;
+ current->thread.flags |= (val << IA64_THREAD_UAC_SHIFT) &
+ IA64_THREAD_UAC_MASK;
+
+ return 0;
+}
+
+int arch_get_unalign_ctl(void)
+{
+ return (current->thread.flags & IA64_THREAD_UAC_MASK) >>
+ IA64_THREAD_UAC_SHIFT;
+}
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index fc5a574..a2f0f0a 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -44,6 +44,7 @@ config PARISC
select HAVE_DEBUG_STACKOVERFLOW
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_HASH
+ select HAVE_ARCH_PR_SET_GET_UNALIGN
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select GENERIC_SCHED_CLOCK
diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
index b59720f..dbea6e9 100644
--- a/arch/parisc/include/asm/processor.h
+++ b/arch/parisc/include/asm/processor.h
@@ -139,20 +139,6 @@ struct thread_struct {
#define PARISC_UAC_SHIFT 0
#define PARISC_UAC_MASK (PARISC_UAC_NOPRINT|PARISC_UAC_SIGBUS)

-#define SET_UNALIGN_CTL(value) \
- ({ \
- current->thread.flags = ((current->thread.flags & ~PARISC_UAC_MASK) \
- | (((value) << PARISC_UAC_SHIFT) & \
- PARISC_UAC_MASK)); \
- 0; \
- })
-
-#define GET_UNALIGN_CTL(addr) \
- ({ \
- put_user((current->thread.flags & PARISC_UAC_MASK) \
- >> PARISC_UAC_SHIFT, (int __user *) (addr)); \
- })
-
#define INIT_THREAD { \
.regs = { .gr = { 0, }, \
.fr = { 0, }, \
diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
index 43b308c..e3a7f29 100644
--- a/arch/parisc/kernel/sys_parisc.c
+++ b/arch/parisc/kernel/sys_parisc.c
@@ -30,6 +30,7 @@
#include <linux/linkage.h>
#include <linux/mm.h>
#include <linux/mman.h>
+#include <linux/prctl.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/shm.h>
@@ -37,6 +38,7 @@
#include <linux/utsname.h>
#include <linux/personality.h>
#include <linux/random.h>
+#include <asm/processor.h>

/* we construct an artificial offset for the mapping based on the physical
* address of the kernel mapping variable */
@@ -391,3 +393,16 @@ long parisc_personality(unsigned long personality)

return err;
}
+
+int arch_set_unalign_ctl(unsigned int val)
+{
+ current->thread.flags &= ~PARISC_UAC_MASK;
+ current->thread.flags |= (val << PARISC_UAC_SHIFT) & PARISC_UAC_MASK;
+
+ return 0;
+}
+
+int arch_get_unalign_ctl(void)
+{
+ return (current->thread.flags & PARISC_UAC_MASK) >> PARISC_UAC_SHIFT;
+}
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b94323e..68c31fb 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -181,6 +181,7 @@ config PPC
select HAVE_ARCH_KGDB
select HAVE_ARCH_MMAP_RND_BITS
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
+ select HAVE_ARCH_PR_SET_GET_UNALIGN
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select HAVE_CBPF_JIT if !PPC64
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index b8d9306..8bac2f6 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -413,12 +413,6 @@ extern int set_fpexc_mode(unsigned int val);
extern int get_endian(unsigned long adr);
extern int set_endian(unsigned int val);

-#define GET_UNALIGN_CTL(adr) get_unalign_ctl((adr))
-#define SET_UNALIGN_CTL(val) set_unalign_ctl((val))
-
-extern int get_unalign_ctl(unsigned long adr);
-extern int set_unalign_ctl(unsigned int val);
-
extern void load_fp_state(struct thread_fp_state *fp);
extern void store_fp_state(struct thread_fp_state *fp);
extern void load_vr_state(struct thread_vr_state *vr);
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 17708b7..a623373 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -2020,15 +2020,15 @@ int get_endian(unsigned long adr)
return put_user(val, (unsigned int __user *)adr);
}

-int set_unalign_ctl(unsigned int val)
+int arch_set_unalign_ctl(unsigned int val)
{
current->thread.align_ctl = val;
return 0;
}

-int get_unalign_ctl(unsigned long adr)
+int arch_get_unalign_ctl(void)
{
- return put_user(current->thread.align_ctl, (unsigned int __user *)adr);
+ return current->thread.align_ctl;
}

static inline int valid_irq_stack(unsigned long sp, struct task_struct *p,
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 97fe293..f9631bf 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -48,6 +48,7 @@ config SUPERH
select OLD_SIGSUSPEND
select OLD_SIGACTION
select HAVE_ARCH_AUDITSYSCALL
+ select HAVE_ARCH_PR_SET_GET_UNALIGN
select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_NMI
help
diff --git a/arch/sh/include/asm/processor.h b/arch/sh/include/asm/processor.h
index ce3d9f6..ff4d332 100644
--- a/arch/sh/include/asm/processor.h
+++ b/arch/sh/include/asm/processor.h
@@ -116,13 +116,6 @@ extern unsigned int xstate_size;
extern void free_thread_xstate(struct task_struct *);
extern struct kmem_cache *task_xstate_cachep;

-/* arch/sh/mm/alignment.c */
-extern int get_unalign_ctl(unsigned long addr);
-extern int set_unalign_ctl(unsigned int val);
-
-#define GET_UNALIGN_CTL(addr) get_unalign_ctl((addr))
-#define SET_UNALIGN_CTL(val) set_unalign_ctl((val))
-
/* arch/sh/mm/init.c */
extern unsigned int mem_init_done;

diff --git a/arch/sh/mm/alignment.c b/arch/sh/mm/alignment.c
index bad2a31..63fc963 100644
--- a/arch/sh/mm/alignment.c
+++ b/arch/sh/mm/alignment.c
@@ -11,6 +11,7 @@
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/seq_file.h>
+#include <linux/prctl.h>
#include <linux/proc_fs.h>
#include <linux/uaccess.h>
#include <linux/ratelimit.h>
@@ -80,13 +81,12 @@ unsigned int unaligned_user_action(void)
return action;
}

-int get_unalign_ctl(unsigned long addr)
+int arch_get_unalign_ctl(void)
{
- return put_user(current->thread.flags & SH_THREAD_UAC_MASK,
- (unsigned int __user *)addr);
+ return current->thread.flags & SH_THREAD_UAC_MASK;
}

-int set_unalign_ctl(unsigned int val)
+int arch_set_unalign_ctl(unsigned int val)
{
current->thread.flags = (current->thread.flags & ~SH_THREAD_UAC_MASK) |
(val & SH_THREAD_UAC_MASK);
diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index 5ce3713..abc803e 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -16,4 +16,12 @@ static inline int prctl_arch(int option, unsigned long arg2,
}
#endif

+#ifdef CONFIG_HAVE_ARCH_PR_SET_GET_UNALIGN
+extern int arch_set_unalign_ctl(unsigned int val);
+extern int arch_get_unalign_ctl(void);
+#else
+static inline int arch_set_unalign_ctl(unsigned int val) { return -EINVAL; }
+static inline int arch_get_unalign_ctl(void) { return -EINVAL; }
+#endif
+
#endif /* ! _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 47cf999..562ffbe 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -71,13 +71,6 @@

#include "uid16.h"

-#ifndef SET_UNALIGN_CTL
-# define SET_UNALIGN_CTL(a) (-EINVAL)
-#endif
-#ifndef GET_UNALIGN_CTL
-# define GET_UNALIGN_CTL(a) (-EINVAL)
-#endif
-
/*
* this is where the system-wide overflow UID and GID are defined, for
* architectures that now have 32-bit UID/GID but didn't in the past
@@ -2235,10 +2228,17 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
break;

case PR_SET_UNALIGN:
- error = SET_UNALIGN_CTL(arg2);
+ error = arch_set_unalign_ctl(arg2);
break;
- case PR_GET_UNALIGN:
- error = GET_UNALIGN_CTL(arg2);
+ case PR_GET_UNALIGN: {
+ int res;
+
+ res = arch_get_unalign_ctl();
+ if (res >= 0)
+ error = put_user(res, (int __user *)arg2);
+ else
+ error = res;
+ }
break;
case PR_GET_TIMING:
error = PR_TIMING_STATISTICAL;
--
2.1.4