Re: [RFC v6 27/62] powerpc: helper to validate key-access permissions of a pte
From: Thiago Jung Bauermann <hidden>
Date: 2017-07-28 21:00:23
Also in:
linux-arch, linux-mm, lkml
Ram Pai [off-list ref] writes:
quoted hunk ↗ jump to hunk
--- a/arch/powerpc/mm/pkeys.c +++ b/arch/powerpc/mm/pkeys.c@@ -201,3 +201,36 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, */ return vma_pkey(vma); } + +static bool pkey_access_permitted(int pkey, bool write, bool execute) +{ + int pkey_shift; + u64 amr; + + if (!pkey) + return true; + + pkey_shift = pkeyshift(pkey); + if (!(read_uamor() & (0x3UL << pkey_shift))) + return true; + + if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift))) + return true; + + if (!write) { + amr = read_amr(); + if (!(amr & (AMR_RD_BIT << pkey_shift))) + return true; + } + + amr = read_amr(); /* delay reading amr uptil absolutely needed */
Actually, this is causing amr to be read twice in case control enters the "if (!write)" block above but doesn't enter the other if block nested in it. read_amr should be called only once, right before "if (!write)". -- Thiago Jung Bauermann IBM Linux Technology Center