| Message ID | 20220704174858.329326-6-ammar.faizi@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | aarch64 support | expand |
On Tue, Jul 5, 2022 at 12:54 AM Ammar Faizi wrote: > From: Ammar Faizi <ammarfaizi2@gnuweeb.org> > > A prep patch to add aarch64 nolibc support. > > aarch64 supports three values of page size: 4K, 16K, and 64K which are > selected at kernel compilation time. Therefore, we can't hard code the > page size for this arch. Utilize open(), read() and close() syscall to > find the page size from /proc/self/auxv. For more details about the > auxv data structure, check the link below [1]. > > v3: > - Split open/read/close in get_page_size() into a new function. > - Cache the fallback value when we fail on the syscalls. > - No need to init the static var to zero. > > v2: > - Fallback to 4K if the syscall fails. > - Cache the page size after read as suggested by Jens. > > Link: https://github.com/torvalds/linux/blob/v5.19-rc4/fs/binfmt_elf.c#L260 [1] > Link: https://lore.kernel.org/io-uring/3895dbe1-8d5f-cf53-e94b-5d1545466de1@kernel.dk > Link: https://lore.kernel.org/io-uring/8bfba71c-55d7-fb49-6593-4d0f9d9c3611@kernel.dk > Link: https://lore.kernel.org/io-uring/49ed1c4c-46ca-15c4-f288-f6808401b0ff@kernel.dk > Suggested-by: Jens Axboe <axboe@kernel.dk> > Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org> [...] > +static inline long __get_page_size(void) > +{ > + static const long fallback_ret = 4096; > + Elf64_Off buf[2]; > + long ret; > + int fd; > + > + fd = __sys_open("/proc/self/auxv", O_RDONLY, 0); > + if (fd < 0) > + return fallback_ret; > + > + while (1) { > + ssize_t x; > + > + x = __sys_read(fd, buf, sizeof(buf)); > + if (x < sizeof(buf)) { > + ret = fallback_ret; > + break; > + } > + > + if (buf[0] == AT_PAGESZ) { > + ret = buf[1]; > + break; > + } > + } > + > + __sys_close(fd); > + return ret; > +} fallback_ret var is not needed, just do this, simpler: static inline long __get_page_size(void) { Elf64_Off buf[2]; long ret = 4096; int fd; fd = __sys_open("/proc/self/auxv", O_RDONLY, 0); if (fd < 0) return ret; while (1) { ssize_t x; x = __sys_read(fd, buf, sizeof(buf)); if (x < sizeof(buf)) break; if (buf[0] == AT_PAGESZ) { ret = buf[1]; break; } } __sys_close(fd); return ret; } with that simplification: Reviewed-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org> tq -- Viro
On 7/5/22 1:18 AM, Alviro Iskandar Setiawan wrote: > fallback_ret var is not needed, just do this, simpler: > > static inline long __get_page_size(void) > { > Elf64_Off buf[2]; > long ret = 4096; > int fd; > > fd = __sys_open("/proc/self/auxv", O_RDONLY, 0); > if (fd < 0) > return ret; > > while (1) { > ssize_t x; > > x = __sys_read(fd, buf, sizeof(buf)); > if (x < sizeof(buf)) > break; > > if (buf[0] == AT_PAGESZ) { > ret = buf[1]; > break; > } > } > > __sys_close(fd); > return ret; > } Agree with that, will fold this in for v4. > with that simplification: > > Reviewed-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org> Thanks!
diff --git a/src/arch/aarch64/lib.h b/src/arch/aarch64/lib.h new file mode 100644 index 0000000..eb7e4cb --- /dev/null +++ b/src/arch/aarch64/lib.h @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: MIT */ + +#ifndef LIBURING_ARCH_AARCH64_LIB_H +#define LIBURING_ARCH_AARCH64_LIB_H + +#include <elf.h> +#include <sys/auxv.h> +#include "../../syscall.h" + +static inline long __get_page_size(void) +{ + static const long fallback_ret = 4096; + Elf64_Off buf[2]; + long ret; + int fd; + + fd = __sys_open("/proc/self/auxv", O_RDONLY, 0); + if (fd < 0) + return fallback_ret; + + while (1) { + ssize_t x; + + x = __sys_read(fd, buf, sizeof(buf)); + if (x < sizeof(buf)) { + ret = fallback_ret; + break; + } + + if (buf[0] == AT_PAGESZ) { + ret = buf[1]; + break; + } + } + + __sys_close(fd); + return ret; +} + +static inline long get_page_size(void) +{ + static long cache_val; + + if (cache_val) + return cache_val; + + cache_val = __get_page_size(); + return cache_val; +} + +#endif /* #ifndef LIBURING_ARCH_AARCH64_LIB_H */