From: "Amit K. Arora" This is the patch suggested by Martin Schwidefsky to support sys_fallocate() on s390(x) platform. He also suggested a wrapper in glibc to handle this system call on s390. Posting it here so that we get feedback for this too. .globl __fallocate ENTRY(__fallocate) stm %r6,%r7,28(%r15) /* save %r6/%r7 on stack */ cfi_offset (%r7, -68) cfi_offset (%r6, -72) lm %r6,%r7,96(%r15) /* load loff_t len from stack */ svc SYS_ify(fallocate) lm %r6,%r7,28(%r15) /* restore %r6/%r7 from stack */ br %r14 PSEUDO_END(__fallocate) Here are the comments and the patch to linux kernel from him. This patch implements support of fallocate system call on s390(x) platform. A wrapper is added to address the issue which s390 ABI has with the arguments of this system call. Signed-off-by: Martin Schwidefsky Cc: Martin Schwidefsky Cc: Heiko Carstens Signed-off-by: Andrew Morton --- arch/s390/kernel/compat_wrapper.S | 10 +++++++++ arch/s390/kernel/sys_s390.c | 29 ++++++++++++++++++++++++++++ arch/s390/kernel/syscalls.S | 1 include/asm-s390/unistd.h | 3 +- 4 files changed, 42 insertions(+), 1 deletion(-) diff -puN arch/s390/kernel/compat_wrapper.S~fallocate-on-s390 arch/s390/kernel/compat_wrapper.S --- a/arch/s390/kernel/compat_wrapper.S~fallocate-on-s390 +++ a/arch/s390/kernel/compat_wrapper.S @@ -1710,3 +1710,13 @@ compat_sys_timerfd_wrapper: sys_eventfd_wrapper: llgfr %r2,%r2 # unsigned int jg sys_eventfd + + .globl sys_fallocate_wrapper +sys_fallocate_wrapper: + lgfr %r2,%r2 # int + lgfr %r3,%r3 # int + sllg %r4,%r4,32 # get high word of 64bit loff_t + lr %r4,%r5 # get low word of 64bit loff_t + sllg %r5,%r6,32 # get high word of 64bit loff_t + l %r5,164(%r15) # get low word of 64bit loff_t + jg sys_fallocate diff -puN arch/s390/kernel/sys_s390.c~fallocate-on-s390 arch/s390/kernel/sys_s390.c --- a/arch/s390/kernel/sys_s390.c~fallocate-on-s390 +++ a/arch/s390/kernel/sys_s390.c @@ -265,3 +265,32 @@ s390_fadvise64_64(struct fadvise64_64_ar return -EFAULT; return sys_fadvise64_64(a.fd, a.offset, a.len, a.advice); } + +#ifndef CONFIG_64BIT +/* + * This is a wrapper to call sys_fallocate(). For 31 bit s390 the last + * 64 bit argument "len" is split into the upper and lower 32 bits. The + * system call wrapper in the user space loads the value to %r6/%r7. + * The code in entry.S keeps the values in %r2 - %r6 where they are and + * stores %r7 to 96(%r15). But the standard C linkage requires that + * the whole 64 bit value for len is stored on the stack and doesn't + * use %r6 at all. So s390_fallocate has to convert the arguments from + * %r2: fd, %r3: mode, %r4/%r5: offset, %r6/96(%r15)-99(%r15): len + * to + * %r2: fd, %r3: mode, %r4/%r5: offset, 96(%r15)-103(%r15): len + */ +asmlinkage long s390_fallocate(int fd, int mode, loff_t offset, + u32 len_high, u32 len_low) +{ + union { + u64 len; + struct { + u32 high; + u32 low; + }; + } cv; + cv.high = len_high; + cv.low = len_low; + return sys_fallocate(fd, mode, offset, cv.len); +} +#endif diff -puN arch/s390/kernel/syscalls.S~fallocate-on-s390 arch/s390/kernel/syscalls.S --- a/arch/s390/kernel/syscalls.S~fallocate-on-s390 +++ a/arch/s390/kernel/syscalls.S @@ -327,3 +327,4 @@ SYSCALL(sys_utimensat,sys_utimensat,comp SYSCALL(sys_signalfd,sys_signalfd,compat_sys_signalfd_wrapper) SYSCALL(sys_timerfd,sys_timerfd,compat_sys_timerfd_wrapper) SYSCALL(sys_eventfd,sys_eventfd,sys_eventfd_wrapper) +SYSCALL(s390_fallocate,sys_fallocate,sys_fallocate_wrapper) diff -puN include/asm-s390/unistd.h~fallocate-on-s390 include/asm-s390/unistd.h --- a/include/asm-s390/unistd.h~fallocate-on-s390 +++ a/include/asm-s390/unistd.h @@ -256,7 +256,8 @@ #define __NR_signalfd 316 #define __NR_timerfd 317 #define __NR_eventfd 318 -#define NR_syscalls 319 +#define __NR_fallocate 319 +#define NR_syscalls 320 /* * There are some system calls that are not present on 64 bit, some _