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missing_syscall: when adding syscall replacements, use different names (#8229)

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In meson.build we check that functions are available using:
    meson.get_compiler('c').has_function('foo')
which checks the following:
- if __stub_foo or __stub___foo are defined, return false
- if foo is declared (a pointer to the function can be taken), return true
- otherwise check for __builtin_memfd_create

_stub is documented by glibc as
   It defines a symbol '__stub_FUNCTION' for each function
   in the C library which is a stub, meaning it will fail
   every time called, usually setting errno to ENOSYS.

So if __stub is defined, we know we don't want to use the glibc version, but
this doesn't tell us if the name itself is defined or not. If it _is_ defined,
and we define our replacement as an inline static function, we get an error:

In file included from ../src/basic/missing.h:1358:0,
                 from ../src/basic/util.h:47,
                 from ../src/basic/calendarspec.h:29,
                 from ../src/basic/calendarspec.c:34:
../src/basic/missing_syscall.h:65:19: error: static declaration of 'memfd_create' follows non-static declaration
 static inline int memfd_create(const char *name, unsigned int flags) {
                   ^~~~~~~~~~~~
.../usr/include/bits/mman-shared.h:46:5: note: previous declaration of 'memfd_create' was here
 int memfd_create (const char *__name, unsigned int __flags) __THROW;
     ^~~~~~~~~~~~

To avoid this problem, call our inline functions different than glibc,
and use a #define to map the official name to our replacement.

Fixes #8099.

v2:
- use "missing_" as the prefix instead of "_"

v3:
- rebase and update for statx()

  Unfortunately "statx" is also present in "struct statx", so the define
  causes issues. Work around this by using a typedef.

I checked that systemd compiles with current glibc
(glibc-devel-2.26-24.fc27.x86_64) if HAVE_MEMFD_CREATE, HAVE_GETTID,
HAVE_PIVOT_ROOT, HAVE_SETNS, HAVE_RENAMEAT2, HAVE_KCMP, HAVE_KEYCTL,
HAVE_COPY_FILE_RANGE, HAVE_BPF, HAVE_STATX are forced to 0.

Setting HAVE_NAME_TO_HANDLE_AT to 0 causes an issue, but it's not because of
the define, but because of struct file_handle.

(cherry picked from commit 5187dd2c40)
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2018-02-21 14:04:50 +01:00
parent fded60e0fc
commit f265658d0f
1 changed files with 33 additions and 11 deletions
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44
src/basic/missing.h
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@ -135,9 +135,11 @@
#endif
#if !HAVE_DECL_PIVOT_ROOT
static inline int pivot_root(const char *new_root, const char *put_old) {
static inline int missing_pivot_root(const char *new_root, const char *put_old) {
return syscall(SYS_pivot_root, new_root, put_old);
}
# define pivot_root missing_pivot_root
#endif
#ifndef __NR_memfd_create
@ -168,9 +170,11 @@ static inline int pivot_root(const char *new_root, const char *put_old) {
#endif
#ifndef HAVE_MEMFD_CREATE
static inline int memfd_create(const char *name, unsigned int flags) {
static inline int missing_memfd_create(const char *name, unsigned int flags) {
return syscall(__NR_memfd_create, name, flags);
}
# define memfd_create missing_memfd_create
#endif
#ifndef __NR_getrandom
@ -207,9 +211,11 @@ static inline int memfd_create(const char *name, unsigned int flags) {
#endif
#if !HAVE_DECL_GETRANDOM
static inline int getrandom(void *buffer, size_t count, unsigned flags) {
static inline int missing_getrandom(void *buffer, size_t count, unsigned flags) {
return syscall(__NR_getrandom, buffer, count, flags);
}
# define getrandom missing_getrandom
#endif
#ifndef GRND_NONBLOCK
@ -527,9 +533,11 @@ struct btrfs_ioctl_quota_ctl_args {
#endif
#if !HAVE_DECL_GETTID
static inline pid_t gettid(void) {
static inline pid_t missing_gettid(void) {
return (pid_t) syscall(SYS_gettid);
}
# define gettid missing_gettid
#endif
#ifndef SCM_SECURITY
@ -581,9 +589,11 @@ struct file_handle {
unsigned char f_handle[0];
};
static inline int name_to_handle_at(int fd, const char *name, struct file_handle *handle, int *mnt_id, int flags) {
static inline int missing_name_to_handle_at(int fd, const char *name, struct file_handle *handle, int *mnt_id, int flags) {
return syscall(__NR_name_to_handle_at, fd, name, handle, mnt_id, flags);
}
# define name_to_handle_at missing_name_to_handle_at
#endif
#ifndef HAVE_SECURE_GETENV
@ -645,9 +655,11 @@ static inline int name_to_handle_at(int fd, const char *name, struct file_handle
#endif
#if !HAVE_DECL_SETNS
static inline int setns(int fd, int nstype) {
static inline int missing_setns(int fd, int nstype) {
return syscall(__NR_setns, fd, nstype);
}
# define setns missing_setns
#endif
#if !HAVE_DECL_LO_FLAGS_PARTSCAN
@ -1060,9 +1072,11 @@ static inline pid_t raw_getpid(void) {
# endif
#endif
static inline int renameat2(int oldfd, const char *oldname, int newfd, const char *newname, unsigned flags) {
static inline int missing_renameat2(int oldfd, const char *oldname, int newfd, const char *newname, unsigned flags) {
return syscall(__NR_renameat2, oldfd, oldname, newfd, newname, flags);
}
# define renameat2 missing_renameat2
#endif
#ifndef RENAME_NOREPLACE
@ -1070,7 +1084,7 @@ static inline int renameat2(int oldfd, const char *oldname, int newfd, const cha
#endif
#if !HAVE_DECL_KCMP
static inline int kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, unsigned long idx2) {
static inline int missing_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, unsigned long idx2) {
#if defined(__NR_kcmp)
return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2);
#else
@ -1078,6 +1092,8 @@ static inline int kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, uns
return -1;
#endif
}
# define kcmp missing_kcmp
#endif
#ifndef KCMP_FILE
@ -1097,7 +1113,7 @@ typedef int32_t key_serial_t;
#endif
#if !HAVE_DECL_KEYCTL
static inline long keyctl(int cmd, unsigned long arg2, unsigned long arg3, unsigned long arg4,unsigned long arg5) {
static inline long missing_keyctl(int cmd, unsigned long arg2, unsigned long arg3, unsigned long arg4,unsigned long arg5) {
#if defined(__NR_keyctl)
return syscall(__NR_keyctl, cmd, arg2, arg3, arg4, arg5);
#else
@ -1106,7 +1122,9 @@ static inline long keyctl(int cmd, unsigned long arg2, unsigned long arg3, unsig
#endif
}
static inline key_serial_t add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid) {
# define keyctl missing_keyctl
static inline key_serial_t missing_add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid) {
#if defined (__NR_add_key)
return syscall(__NR_add_key, type, description, payload, plen, ringid);
#else
@ -1115,7 +1133,9 @@ static inline key_serial_t add_key(const char *type, const char *description, co
#endif
}
static inline key_serial_t request_key(const char *type, const char *description, const char * callout_info, key_serial_t destringid) {
# define add_key missing_add_key
static inline key_serial_t missing_request_key(const char *type, const char *description, const char * callout_info, key_serial_t destringid) {
#if defined (__NR_request_key)
return syscall(__NR_request_key, type, description, callout_info, destringid);
#else
@ -1123,6 +1143,8 @@ static inline key_serial_t request_key(const char *type, const char *description
return -1;
#endif
}
# define request_key missing_request_key
#endif
#ifndef KEYCTL_READ