| Message ID | 1364235486-17738-4-git-send-email-will.deacon@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Mar 25, 2013 at 06:18:06PM +0000, Will Deacon wrote: > The cacheflush system call flushes a contiguous range, specified by a > pair of addresses. This means that user applications wishing to flush > discrete ranges must issue multiple system calls, since attempting to > flush past a vma results in range truncation. > > This patch introduces a new private system call for ARM, cacheflush_iov, > which processes a range of addresses described in an iovec structure. > > Signed-off-by: Will Deacon <will.deacon@arm.com> > --- > arch/arm/include/uapi/asm/unistd.h | 1 + > arch/arm/kernel/traps.c | 36 ++++++++++++++++++++++++++++++++++++ > 2 files changed, 37 insertions(+) > > diff --git a/arch/arm/include/uapi/asm/unistd.h b/arch/arm/include/uapi/asm/unistd.h > index af33b44..bcad38c 100644 > --- a/arch/arm/include/uapi/asm/unistd.h > +++ b/arch/arm/include/uapi/asm/unistd.h > @@ -421,6 +421,7 @@ > #define __ARM_NR_usr26 (__ARM_NR_BASE+3) > #define __ARM_NR_usr32 (__ARM_NR_BASE+4) > #define __ARM_NR_set_tls (__ARM_NR_BASE+5) > +#define __ARM_NR_cacheflush_iov (__ARM_NR_BASE+6) > > /* > * *NOTE*: This is a ghost syscall private to the kernel. Only the > diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c > index da5e268..f83eed6 100644 > --- a/arch/arm/kernel/traps.c > +++ b/arch/arm/kernel/traps.c > @@ -25,6 +25,7 @@ > #include <linux/delay.h> > #include <linux/init.h> > #include <linux/sched.h> > +#include <linux/slab.h> > > #include <linux/atomic.h> > #include <asm/cacheflush.h> > @@ -515,6 +516,37 @@ do_cache_op(unsigned long start, unsigned long end, int flags) > return flush_cache_user_range(start, end); > } > > +static inline int > +do_cache_op_iov(const struct iovec __user *uiov, unsigned long cnt, int flags) > +{ > + int i, ret = 0; > + unsigned long len = cnt * sizeof(struct iovec); > + struct iovec *iov = kmalloc(len, GFP_KERNEL); > + > + if (iov == NULL) { > + ret = -ENOMEM; > + goto out; > + } > + > + if (copy_from_user(iov, uiov, len)) { > + ret = -EFAULT; > + goto out_free; > + } > + > + for (i = 0; i < cnt; ++i) { > + unsigned long start = (unsigned long __force)iov[i].iov_base; > + unsigned long end = start + iov[i].iov_len; > + ret = do_cache_op(start, end, flags); > + if (ret) > + break; > + } Could you use get_user() on struct iovec fields directly to avoid kmalloc? It would be slightly faster.
On Wed, Mar 27, 2013 at 11:12:11AM +0000, Catalin Marinas wrote: > On Mon, Mar 25, 2013 at 06:18:06PM +0000, Will Deacon wrote: > > +static inline int > > +do_cache_op_iov(const struct iovec __user *uiov, unsigned long cnt, int flags) > > +{ > > + int i, ret = 0; > > + unsigned long len = cnt * sizeof(struct iovec); > > + struct iovec *iov = kmalloc(len, GFP_KERNEL); > > + > > + if (iov == NULL) { > > + ret = -ENOMEM; > > + goto out; > > + } > > + > > + if (copy_from_user(iov, uiov, len)) { > > + ret = -EFAULT; > > + goto out_free; > > + } > > + > > + for (i = 0; i < cnt; ++i) { > > + unsigned long start = (unsigned long __force)iov[i].iov_base; > > + unsigned long end = start + iov[i].iov_len; > > + ret = do_cache_op(start, end, flags); > > + if (ret) > > + break; > > + } > > Could you use get_user() on struct iovec fields directly to avoid > kmalloc? It would be slightly faster. I just had a look at this, but the problem is that we want to know the entire (combined) region size so that we may just decide to flush the entire cache, rather than iterate over each region line-by-line. This requires copying the whole iovec into kernel space up front, so that we can iterate over the regions with iov_length. Will
diff --git a/arch/arm/include/uapi/asm/unistd.h b/arch/arm/include/uapi/asm/unistd.h index af33b44..bcad38c 100644 --- a/arch/arm/include/uapi/asm/unistd.h +++ b/arch/arm/include/uapi/asm/unistd.h @@ -421,6 +421,7 @@ #define __ARM_NR_usr26 (__ARM_NR_BASE+3) #define __ARM_NR_usr32 (__ARM_NR_BASE+4) #define __ARM_NR_set_tls (__ARM_NR_BASE+5) +#define __ARM_NR_cacheflush_iov (__ARM_NR_BASE+6) /* * *NOTE*: This is a ghost syscall private to the kernel. Only the diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index da5e268..f83eed6 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -25,6 +25,7 @@ #include <linux/delay.h> #include <linux/init.h> #include <linux/sched.h> +#include <linux/slab.h> #include <linux/atomic.h> #include <asm/cacheflush.h> @@ -515,6 +516,37 @@ do_cache_op(unsigned long start, unsigned long end, int flags) return flush_cache_user_range(start, end); } +static inline int +do_cache_op_iov(const struct iovec __user *uiov, unsigned long cnt, int flags) +{ + int i, ret = 0; + unsigned long len = cnt * sizeof(struct iovec); + struct iovec *iov = kmalloc(len, GFP_KERNEL); + + if (iov == NULL) { + ret = -ENOMEM; + goto out; + } + + if (copy_from_user(iov, uiov, len)) { + ret = -EFAULT; + goto out_free; + } + + for (i = 0; i < cnt; ++i) { + unsigned long start = (unsigned long __force)iov[i].iov_base; + unsigned long end = start + iov[i].iov_len; + ret = do_cache_op(start, end, flags); + if (ret) + break; + } + +out_free: + kfree(iov); +out: + return ret; +} + /* * Handle all unrecognised system calls. * 0x9f0000 - 0x9fffff are some more esoteric system calls @@ -560,6 +592,10 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs) case NR(cacheflush): return do_cache_op(regs->ARM_r0, regs->ARM_r1, regs->ARM_r2); + case NR(cacheflush_iov): + return do_cache_op_iov((const struct iovec __user *)regs->ARM_r0, + regs->ARM_r1, regs->ARM_r2); + case NR(usr26): if (!(elf_hwcap & HWCAP_26BIT)) break;
The cacheflush system call flushes a contiguous range, specified by a pair of addresses. This means that user applications wishing to flush discrete ranges must issue multiple system calls, since attempting to flush past a vma results in range truncation. This patch introduces a new private system call for ARM, cacheflush_iov, which processes a range of addresses described in an iovec structure. Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm/include/uapi/asm/unistd.h | 1 + arch/arm/kernel/traps.c | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+)