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kernel: add kcompat_sys_{f,}statfs64() 

Using this helper allows us to avoid the in-kernel calls to the
compat_sys_{f,}statfs64() sycalls, as are necessary for parameter
mangling in arm64's compat handling.

Following the example of ksys_* functions, kcompat_sys_* functions are
intended to be a drop-in replacement for their compat_sys_*
counterparts, with the same calling convention.

This is necessary to enable conversion of arm64's syscall handling to
use pt_regs wrappers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mark Rutland 2018-07-11 14:56:51 +01:00 committed by Will Deacon
parent bf1c77b464
commit 9b54bf9d6a
2 changed files with 23 additions and 2 deletions
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14
fs/statfs.c
View File

@ -335,7 +335,7 @@ static int put_compat_statfs64(struct compat_statfs64 __user *ubuf, struct kstat
return 0;
}
COMPAT_SYSCALL_DEFINE3(statfs64, const char __user *, pathname, compat_size_t, sz, struct compat_statfs64 __user *, buf)
int kcompat_sys_statfs64(const char __user * pathname, compat_size_t sz, struct compat_statfs64 __user * buf)
{
struct kstatfs tmp;
int error;
@ -349,7 +349,12 @@ COMPAT_SYSCALL_DEFINE3(statfs64, const char __user *, pathname, compat_size_t, s
return error;
}
COMPAT_SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, compat_size_t, sz, struct compat_statfs64 __user *, buf)
COMPAT_SYSCALL_DEFINE3(statfs64, const char __user *, pathname, compat_size_t, sz, struct compat_statfs64 __user *, buf)
{
return kcompat_sys_statfs64(pathname, sz, buf);
}
int kcompat_sys_fstatfs64(unsigned int fd, compat_size_t sz, struct compat_statfs64 __user * buf)
{
struct kstatfs tmp;
int error;
@ -363,6 +368,11 @@ COMPAT_SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, compat_size_t, sz, struct co
return error;
}
COMPAT_SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, compat_size_t, sz, struct compat_statfs64 __user *, buf)
{
return kcompat_sys_fstatfs64(fd, sz, buf);
}
/*
* This is a copy of sys_ustat, just dealing with a structure layout.
* Given how simple this syscall is that apporach is more maintainable

11
include/linux/compat.h
View File

@ -1028,6 +1028,17 @@ static inline struct compat_timeval ns_to_compat_timeval(s64 nsec)
return ctv;
}
/*
* Kernel code should not call compat syscalls (i.e., compat_sys_xyzyyz())
* directly. Instead, use one of the functions which work equivalently, such
* as the kcompat_sys_xyzyyz() functions prototyped below.
*/
int kcompat_sys_statfs64(const char __user * pathname, compat_size_t sz,
struct compat_statfs64 __user * buf);
int kcompat_sys_fstatfs64(unsigned int fd, compat_size_t sz,
struct compat_statfs64 __user * buf);
#else /* !CONFIG_COMPAT */
#define is_compat_task() (0)