On Thu, Mar 25, 2010 at 2:17 AM, Matt Helsley <matthltc@xxxxxxxxxx> wrote: > On Wed, Mar 24, 2010 at 06:11:32PM -0700, Matt Helsley wrote: >> On Wed, Mar 24, 2010 at 08:36:39PM +0100, Christoffer Dall wrote: > <snip> >> > Re-using the assembly code or factoring it out so that it can be used >> > from multiple places doesn't seem very pleasing to me, as the assembly >> > code is in the critical path and written specifically for the context >> > of a process entering the kernel. Please correct me if I'm wrong. >> > >> > I imagine simply a function in C, more or less re-implementing the >> > logic that's already in entry-common.S, might do the trick. I wouldn't >> > worry much about the performance in this case as it will not be used >> > often. The following _untested_ snippet illustrates my idea: >> > >> > --- >> > arch/arm/include/asm/syscall.h | 93 +++++++++++++++++++++++++++++++++++++++- >> > 1 files changed, 92 insertions(+), 1 deletions(-) >> > >> > diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h >> > index 3b3248f..a7f2615 100644 >> > --- a/arch/arm/include/asm/syscall.h >> > +++ b/arch/arm/include/asm/syscall.h >> > @@ -10,10 +10,101 @@ >> > #ifndef _ASM_ARM_SYSCALLS_H >> > #define _ASM_ARM_SYSCALLS_H >> > >> > +static inline int get_swi_instruction(struct task_struct *task, >> > + struct pt_regs *regs, >> > + unsigned long *instr) >> > +{ >> > + struct page *page = NULL; >> > + unsigned long instr_addr; >> > + unsigned long *ptr; >> > + int ret; >> > + >> > + instr_addr = regs->ARM_pc - 4; >> > + >> > + down_read(&task->mm->mmap_sem); >> > + ret = get_user_pages(task, task->mm, instr_addr, >> > + 1, 0, 0, &page, NULL); >> > + up_read(&task->mm->mmap_sem); >> > + >> > + if (ret < 0) >> > + return ret; >> > + >> > + ptr = (unsigned long *)kmap_atomic(page, KM_USER1); >> > + memcpy(instr, >> > + ptr + (instr_addr >> PAGE_SHIFT), >> ^shouldn't this be: >> instr_addr & PAGE_MASK > > Oops, made my own mistake. I think the address of the kmap'd instruction > would be: > > ptr + (instr_addr & ~PAGE_MASK) > Yes. Thanks for pointing it out. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers