Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH 20/30] microblaze_mmu_v1: uaccess MMU update | Date | Wed, 29 Apr 2009 17:35:28 +0200 |
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On Wednesday 29 April 2009, Michal Simek wrote: > > The above is just the nommu variant. For mmu, you need to > > have exception handling in __clear_user to take care of the > > case where the address is part of the user mapping (access_ok) > > but not currently mapped. > > Is it possible to do it for noMMU kernel too? I mean current MMU > implementation of __clear_user in asm is faster than call memset > for noMMU. I think I can use MMU implementation for noMMU too. > Add two words to __ex_table just extend size of one section but > not too much and won't be used for noMMU.
Well, you can probably do something like this:
#ifdef CONFIG_MMU #define __FIXUP_SECTION ".section .fixup,\"ax\"\n" #define __EX_TABLE_SECTION ".section __ex_table,\"a\"\n" #else #define __FIXUP_SECTION ".section .discard,\"ax\"\n" #define __EX_TABLE_SECTION ".section .discard,\"a\"\n" #endif
+#define __get_user_asm(insn, __gu_ptr, __gu_val, __gu_err) \ +({ \ + __asm__ __volatile__ ( \ + "1:" insn " %1, %2, r0; \n" \ + " addk %0, r0, r0; \n" \ + "2: \n" \ + __FIXUP_SECTION \ + "3: brid 2b \n" \ + " addik %0, r0, %3 \n" \ + ".previous \n" \ + __EX_TABLE_SECTION \ + ".word 1b,3b \n" \ + ".previous \n" \ + : "=r"(__gu_err), "=r"(__gu_val) \ + : "r"(__gu_ptr), "i"(-EFAULT) \ + ); \ +})
This should simply throw away all the fixups if you list the .discard section in vmlinux.lds.S under '/DISCARD/:', so you have no overhead at all.
Arnd <><
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