From 429124d992648b924408a912dc939cdb42d870b2 Mon Sep 17 00:00:00 2001 From: Thomas Bogendoerfer Date: Tue, 22 Feb 2022 16:53:44 +0100 Subject: [PATCH] MIPS: Handle address errors for accesses above CPU max virtual user address Address errors have always been treated as unaliged accesses and handled as such. But address errors are also issued for illegal accesses like user to kernel space or accesses outside of implemented spaces. This change implements Linux exception handling for accesses to the illegal space above the CPU implemented maximum virtual user address and the MIPS 64bit architecture maximum. With this we can now use a fixed value for the maximum task size on every MIPS CPU and get a more optimized access_ok(). Signed-off-by: Thomas Bogendoerfer Signed-off-by: Arnd Bergmann --- arch/mips/kernel/unaligned.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c index df4b708..7b5aba5 100644 --- a/arch/mips/kernel/unaligned.c +++ b/arch/mips/kernel/unaligned.c @@ -1480,6 +1480,23 @@ asmlinkage void do_ade(struct pt_regs *regs) prev_state = exception_enter(); perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, regs->cp0_badvaddr); + +#ifdef CONFIG_64BIT + /* + * check, if we are hitting space between CPU implemented maximum + * virtual user address and 64bit maximum virtual user address + * and do exception handling to get EFAULTs for get_user/put_user + */ + if ((regs->cp0_badvaddr >= (1UL << cpu_vmbits)) && + (regs->cp0_badvaddr < XKSSEG)) { + if (fixup_exception(regs)) { + current->thread.cp0_baduaddr = regs->cp0_badvaddr; + return; + } + goto sigbus; + } +#endif + /* * Did we catch a fault trying to load an instruction? */ -- 2.7.4