Messages in this thread |  | | Date | Sat, 16 Apr 2022 15:41:09 +0800 | Subject | Re: [RFC PATCH -next V3 4/6] arm64: add copy_{to, from}_user to machine check safe | From | Tong Tiangen <> |
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在 2022/4/13 1:17, Robin Murphy 写道: > On 12/04/2022 6:08 pm, Robin Murphy wrote: > [...] >>> @@ -62,7 +63,11 @@ SYM_FUNC_START(__arch_copy_from_user) >>> ret >>> // Exception fixups >>> -9997: cmp dst, dstin >>> +9997: mrs esr, esr_el1 // Check exception first >>> + and esr, esr, #ESR_ELx_FSC >>> + cmp esr, #ESR_ELx_FSC_EXTABT >> >> Should we be checking EC to make sure it's a data abort - and thus FSC >> is valid - in the first place? I'm a little fuzzy on all the possible >> paths into fixup_exception(), and it's not entirely obvious whether >> this is actually safe or not. > > In fact, thinking some more about that, I don't think there should be > any need for this sort of logic in these handlers at all. The > fixup_exception() machinery should already know enough about the > exception that's happened and the extable entry to figure this out and > not bother calling the handler at all. > > Thanks, > Robin. > .
Hi Robin: As you said, it seems that it's not good to judge esr here, how about using the following method, i need your suggestion :)
+#define FIXUP_TYPE_NORMAL 0 +#define FIXUP_TYPE_MC 1
arch/arm64/mm/extable.c static bool ex_handler_fixup(const struct exception_table_entry *ex, - struct pt_regs *regs) + struct pt_regs *regs, int fixuptype) { + regs->regs[16] = fixuptype; [...] }
bool fixup_exception(struct pt_regs *regs) { [...] switch(ex->type) { case EX_TYPE_UACCESS_MC: - return ex_handler_fixup(ex, regs) + return ex_handler_fixup(ex, regs, FIXUP_TYPE_NORMAL) break; } [...] }
bool fixup_exception_mc(struct pt_regs *regs) { [...] switch(ex->type) { case EX_TYPE_UACCESS_MC: - return ex_handler_fixup(ex, regs) + return ex_handler_fixup(ex, regs, FIXUP_TYPE_MC) break; } [...] }
arch/arm64/lib/copy_from_user.S arch/arm64/lib/copy_to_user.S
+fixup_type .req x16
// Exception fixups //x16: fixup type written by ex_handler_fixup -9997: cmp dst, dstin +9997: cmp fixup_type, #FIXUP_TYPE_MC + b.eq 9998f + cmp dst, dstin b.ne 9998f
Thanks, Tong.
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