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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=itPDN3uOMullCrqvdWp4VHOtEiVy99lUJjyxqObTixM=; b=abEvTQdytRwZVrhooiECmDUFnTimGV3ovlVW+NN/kWmDa8QR8d52zbgDrkEIyPlmkn 6y7B7ZoQJZbmIhQjVX9guCjYEXGkup70ydRmIjwnkh3vJKMIVq6RqINZUkzluKZKG/QY HNdyXwcjSOzlZeBBji2TGUaIGypHiUYXAZDNW3BYEqJvSajD+bvpBmUlfzQJXgdFm5Cw ZHkwgqxVQUOwXwg7SPsOaF/fTBK7Ehk9rPtj6PtkONUbH1AlskajmtPzEfN+F7EH0amG XfhRnWo/jhc3hWrktGuJ58cKPJpRw9pkCW6RxMMc14TvMF/WcYBDGdostpoSO62g2GgN o3Sg== X-Gm-Message-State: APjAAAXmn+QSs3xNj1sd0P4F5xHUC18vhY2hvlEEwoLzrvnw3cojEPJ9 82YREAsL+OCvENxxPKU6Waxu0OhUk6pQZLh37b1Ctg== X-Google-Smtp-Source: APXvYqxjABHlLirt3mzHAGsgLEpxUZMPZex/FsD7C0vJFW62s876ojGzoWlX6A4J5FwacSy764TFAtK8KXx4Wiz+QQw= X-Received: by 2002:a17:902:9b83:: with SMTP id y3mr10710877plp.179.1571417011191; Fri, 18 Oct 2019 09:43:31 -0700 (PDT) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191018161033.261971-2-samitolvanen@google.com> In-Reply-To: <20191018161033.261971-2-samitolvanen@google.com> From: Nick Desaulniers Date: Fri, 18 Oct 2019 09:43:20 -0700 Message-ID: Subject: Re: [PATCH 01/18] arm64: mm: don't use x18 in idmap_kpti_install_ng_mappings To: Sami Tolvanen X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191018_094341_783133_9854FDC0 X-CRM114-Status: GOOD ( 15.87 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Kees Cook , Ard Biesheuvel , Catalin Marinas , kernel-hardening@lists.openwall.com, LKML , Steven Rostedt , clang-built-linux , Laura Abbott , Will Deacon , Dave Martin , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Oct 18, 2019 at 9:10 AM Sami Tolvanen wrote: > > idmap_kpti_install_ng_mappings uses x18 as a temporary register, which > will result in a conflict when x18 is reserved. Use x16 and x17 instead > where needed. > > Signed-off-by: Sami Tolvanen TIL about .req/.unreq. Seems like a nice way of marking "variable" lifetime. Technically, only `pte` needed to be moved to reuse {w|x}16, but moving most the unreqs together is nicer than splitting them apart. The usage all looks correct to me. Reviewed-by: Nick Desaulniers > --- > arch/arm64/mm/proc.S | 63 ++++++++++++++++++++++---------------------- > 1 file changed, 32 insertions(+), 31 deletions(-) > > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S > index a1e0592d1fbc..fdabf40a83c8 100644 > --- a/arch/arm64/mm/proc.S > +++ b/arch/arm64/mm/proc.S > @@ -250,15 +250,15 @@ ENTRY(idmap_kpti_install_ng_mappings) > /* We're the boot CPU. Wait for the others to catch up */ > sevl > 1: wfe > - ldaxr w18, [flag_ptr] > - eor w18, w18, num_cpus > - cbnz w18, 1b > + ldaxr w17, [flag_ptr] > + eor w17, w17, num_cpus > + cbnz w17, 1b > > /* We need to walk swapper, so turn off the MMU. */ > pre_disable_mmu_workaround > - mrs x18, sctlr_el1 > - bic x18, x18, #SCTLR_ELx_M > - msr sctlr_el1, x18 > + mrs x17, sctlr_el1 > + bic x17, x17, #SCTLR_ELx_M > + msr sctlr_el1, x17 > isb > > /* Everybody is enjoying the idmap, so we can rewrite swapper. */ > @@ -281,9 +281,9 @@ skip_pgd: > isb > > /* We're done: fire up the MMU again */ > - mrs x18, sctlr_el1 > - orr x18, x18, #SCTLR_ELx_M > - msr sctlr_el1, x18 > + mrs x17, sctlr_el1 > + orr x17, x17, #SCTLR_ELx_M > + msr sctlr_el1, x17 > isb > > /* > @@ -353,46 +353,47 @@ skip_pte: > b.ne do_pte > b next_pmd > > + .unreq cpu > + .unreq num_cpus > + .unreq swapper_pa > + .unreq cur_pgdp > + .unreq end_pgdp > + .unreq pgd > + .unreq cur_pudp > + .unreq end_pudp > + .unreq pud > + .unreq cur_pmdp > + .unreq end_pmdp > + .unreq pmd > + .unreq cur_ptep > + .unreq end_ptep > + .unreq pte > + > /* Secondary CPUs end up here */ > __idmap_kpti_secondary: > /* Uninstall swapper before surgery begins */ > - __idmap_cpu_set_reserved_ttbr1 x18, x17 > + __idmap_cpu_set_reserved_ttbr1 x16, x17 > > /* Increment the flag to let the boot CPU we're ready */ > -1: ldxr w18, [flag_ptr] > - add w18, w18, #1 > - stxr w17, w18, [flag_ptr] > +1: ldxr w16, [flag_ptr] > + add w16, w16, #1 > + stxr w17, w16, [flag_ptr] > cbnz w17, 1b > > /* Wait for the boot CPU to finish messing around with swapper */ > sevl > 1: wfe > - ldxr w18, [flag_ptr] > - cbnz w18, 1b > + ldxr w16, [flag_ptr] > + cbnz w16, 1b > > /* All done, act like nothing happened */ > - offset_ttbr1 swapper_ttb, x18 > + offset_ttbr1 swapper_ttb, x16 > msr ttbr1_el1, swapper_ttb > isb > ret > > - .unreq cpu > - .unreq num_cpus > - .unreq swapper_pa > .unreq swapper_ttb > .unreq flag_ptr > - .unreq cur_pgdp > - .unreq end_pgdp > - .unreq pgd > - .unreq cur_pudp > - .unreq end_pudp > - .unreq pud > - .unreq cur_pmdp > - .unreq end_pmdp > - .unreq pmd > - .unreq cur_ptep > - .unreq end_ptep > - .unreq pte > ENDPROC(idmap_kpti_install_ng_mappings) > .popsection > #endif > -- > 2.23.0.866.gb869b98d4c-goog > -- Thanks, ~Nick Desaulniers _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel