fs: add do_faccessat() helper and ksys_access() wrapper; remove in-kernel calls to syscall
Using the fs-internal do_faccessat() helper allows us to get rid of fs-internal calls to the sys_faccessat() syscall. Introducing the ksys_access() wrapper allows us to avoid the in-kernel calls to the sys_access() syscall. The ksys_ prefix denotes that this function is meant as a drop-in replacement for the syscall. In particular, it uses the same calling convention as sys_access(). This patch is part of a series which removes in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. For details, see http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
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@ -119,6 +119,7 @@ extern struct file *do_filp_open(int dfd, struct filename *pathname,
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extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
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const char *, const struct open_flags *);
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long do_faccessat(int dfd, const char __user *filename, int mode);
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int do_fchmodat(int dfd, const char __user *filename, umode_t mode);
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extern int open_check_o_direct(struct file *f);
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@ -350,7 +350,7 @@ SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
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* We do this by temporarily clearing all FS-related capabilities and
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* switching the fsuid/fsgid around to the real ones.
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*/
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SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
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long do_faccessat(int dfd, const char __user *filename, int mode)
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{
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const struct cred *old_cred;
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struct cred *override_cred;
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@ -426,9 +426,14 @@ out:
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return res;
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}
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SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
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{
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return do_faccessat(dfd, filename, mode);
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}
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SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
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{
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return sys_faccessat(AT_FDCWD, filename, mode);
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return do_faccessat(AT_FDCWD, filename, mode);
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}
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int ksys_chdir(const char __user *filename)
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@ -1014,4 +1014,11 @@ static inline int ksys_chmod(const char __user *filename, umode_t mode)
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return do_fchmodat(AT_FDCWD, filename, mode);
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}
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extern long do_faccessat(int dfd, const char __user *filename, int mode);
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static inline long ksys_access(const char __user *filename, int mode)
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{
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return do_faccessat(AT_FDCWD, filename, mode);
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}
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#endif
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@ -1087,7 +1087,8 @@ static noinline void __init kernel_init_freeable(void)
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if (!ramdisk_execute_command)
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ramdisk_execute_command = "/init";
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if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
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if (ksys_access((const char __user *)
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ramdisk_execute_command, 0) != 0) {
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ramdisk_execute_command = NULL;
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prepare_namespace();
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}
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