Messages in this thread Patch in this message | | | From | Christophe Leroy <> | Subject | [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault() | Date | Wed, 19 Apr 2017 14:56:26 +0200 (CEST) |
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Only the get_user() in store_updates_sp() has to be done outside the mm semaphore. All the comparison can be done within the semaphore, so only when really needed.
As we got a DSI exception, the address pointed by regs->nip is obviously valid, otherwise we would have had a instruction exception. So __get_user() can be used instead of get_user()
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> --- arch/powerpc/mm/fault.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 67fefb59d40e..9d21e5fd383d 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -73,12 +73,8 @@ static inline int notify_page_fault(struct pt_regs *regs) * Check whether the instruction at regs->nip is a store using * an update addressing form which will update r1. */ -static int store_updates_sp(struct pt_regs *regs) +static int store_updates_sp(unsigned int inst) { - unsigned int inst; - - if (get_user(inst, (unsigned int __user *)regs->nip)) - return 0; /* check for 1 in the rA field */ if (((inst >> 16) & 0x1f) != 1) return 0; @@ -207,7 +203,8 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, int trap = TRAP(regs); int is_exec = trap == 0x400; int fault; - int rc = 0, store_update_sp = 0; + int rc = 0; + unsigned int inst = 0; #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) /* @@ -288,7 +285,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, * mmap_sem held */ if (is_write && user_mode(regs)) - store_update_sp = store_updates_sp(regs); + __get_user(inst, (unsigned int __user *)regs->nip); if (user_mode(regs)) flags |= FAULT_FLAG_USER; @@ -358,7 +355,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, * between the last mapped region and the stack will * expand the stack rather than segfaulting. */ - if (address + 2048 < uregs->gpr[1] && !store_update_sp) + if (address + 2048 < uregs->gpr[1] && !store_updates_sp(inst)) goto bad_area; } if (expand_stack(vma, address)) -- 2.12.0
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