From: Zbigniew Jędrzejewski-Szmek Date: Wed, 21 Feb 2018 13:04:50 +0000 (+0100) Subject: missing_syscall: when adding syscall replacements, use different names (#8229) X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=6770df07ec3583ec56b39523312ecbdda8534011;p=elogind.git missing_syscall: when adding syscall replacements, use different names (#8229) 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 5187dd2c403caf92d09f3491e41f1ceb3f10491f) --- diff --git a/src/basic/missing_syscall.h b/src/basic/missing_syscall.h index 9e3e27633..1c8c84ea3 100644 --- a/src/basic/missing_syscall.h +++ b/src/basic/missing_syscall.h @@ -27,9 +27,11 @@ #include #if !HAVE_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 #endif // 0 @@ -64,7 +66,7 @@ static inline int pivot_root(const char *new_root, const char *put_old) { # endif # endif -static inline int memfd_create(const char *name, unsigned int flags) { +static inline int missing_memfd_create(const char *name, unsigned int flags) { # ifdef __NR_memfd_create return syscall(__NR_memfd_create, name, flags); # else @@ -72,6 +74,8 @@ static inline int memfd_create(const char *name, unsigned int flags) { return -1; # endif } + +# define memfd_create missing_memfd_create #endif /* ======================================================================= */ @@ -111,7 +115,7 @@ static inline int memfd_create(const char *name, unsigned int flags) { # endif # endif -static inline int getrandom(void *buffer, size_t count, unsigned flags) { +static inline int missing_getrandom(void *buffer, size_t count, unsigned flags) { # ifdef __NR_getrandom return syscall(__NR_getrandom, buffer, count, flags); # else @@ -119,14 +123,18 @@ static inline int getrandom(void *buffer, size_t count, unsigned flags) { return -1; # endif } + +# define getrandom missing_getrandom #endif /* ======================================================================= */ #if !HAVE_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 /* ======================================================================= */ @@ -154,7 +162,7 @@ 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) { # ifdef __NR_name_to_handle_at return syscall(__NR_name_to_handle_at, fd, name, handle, mnt_id, flags); # else @@ -162,6 +170,8 @@ static inline int name_to_handle_at(int fd, const char *name, struct file_handle return -1; # endif } + +# define name_to_handle_at missing_name_to_handle_at #endif /* ======================================================================= */ @@ -179,7 +189,7 @@ static inline int name_to_handle_at(int fd, const char *name, struct file_handle # endif # endif -static inline int setns(int fd, int nstype) { +static inline int missing_setns(int fd, int nstype) { # ifdef __NR_setns return syscall(__NR_setns, fd, nstype); # else @@ -187,6 +197,8 @@ static inline int setns(int fd, int nstype) { return -1; # endif } + +# define setns missing_setns #endif /* ======================================================================= */ @@ -232,7 +244,7 @@ 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) { # ifdef __NR_renameat2 return syscall(__NR_renameat2, oldfd, oldname, newfd, newname, flags); # else @@ -240,12 +252,14 @@ static inline int renameat2(int oldfd, const char *oldname, int newfd, const cha return -1; # endif } + +# define renameat2 missing_renameat2 #endif /* ======================================================================= */ #if !HAVE_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) { # ifdef __NR_kcmp return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2); # else @@ -253,36 +267,45 @@ static inline int kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, uns return -1; # endif } + +# define kcmp missing_kcmp #endif + /* ======================================================================= */ #if !HAVE_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) { # ifdef __NR_keyctl return syscall(__NR_keyctl, cmd, arg2, arg3, arg4, arg5); # else errno = ENOSYS; return -1; # endif + +# define keyctl missing_keyctl } -static inline key_serial_t add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid) { +static inline key_serial_t missing_add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid) { # ifdef __NR_add_key return syscall(__NR_add_key, type, description, payload, plen, ringid); # else errno = ENOSYS; return -1; # endif + +# define add_key missing_add_key } -static inline key_serial_t request_key(const char *type, const char *description, const char * callout_info, key_serial_t destringid) { +static inline key_serial_t missing_request_key(const char *type, const char *description, const char * callout_info, key_serial_t destringid) { # ifdef __NR_request_key return syscall(__NR_request_key, type, description, callout_info, destringid); # else errno = ENOSYS; return -1; # endif + +# define request_key missing_request_key } #endif @@ -309,10 +332,10 @@ static inline key_serial_t request_key(const char *type, const char *description # endif # endif -static inline ssize_t copy_file_range(int fd_in, loff_t *off_in, - int fd_out, loff_t *off_out, - size_t len, - unsigned int flags) { +static inline ssize_t missing_copy_file_range(int fd_in, loff_t *off_in, + int fd_out, loff_t *off_out, + size_t len, + unsigned int flags) { # ifdef __NR_copy_file_range return syscall(__NR_copy_file_range, fd_in, off_in, fd_out, off_out, len, flags); # else @@ -320,6 +343,8 @@ static inline ssize_t copy_file_range(int fd_in, loff_t *off_in, return -1; # endif } + +# define copy_file_range missing_copy_file_range #endif /* ======================================================================= */ @@ -347,7 +372,7 @@ static inline ssize_t copy_file_range(int fd_in, loff_t *off_in, union bpf_attr; -static inline int bpf(int cmd, union bpf_attr *attr, size_t size) { +static inline int missing_bpf(int cmd, union bpf_attr *attr, size_t size) { #ifdef __NR_bpf return (int) syscall(__NR_bpf, cmd, attr, size); #else @@ -356,6 +381,7 @@ static inline int bpf(int cmd, union bpf_attr *attr, size_t size) { #endif } +# define bpf missing_bpf #endif /* ======================================================================= */