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Thu, 10 Feb 2022 14:44:45 -0800 (PST) Date: Thu, 10 Feb 2022 14:41:44 -0800 In-Reply-To: <20220210224220.4076151-1-kaleshsingh@google.com> Message-Id: <20220210224220.4076151-4-kaleshsingh@google.com> Mime-Version: 1.0 References: <20220210224220.4076151-1-kaleshsingh@google.com> X-Mailer: git-send-email 2.35.1.265.g69c8d7142f-goog Subject: [PATCH 3/7] arm64: asm: Introduce test_sp_overflow macro From: Kalesh Singh Cc: will@kernel.org, maz@kernel.org, qperret@google.com, tabba@google.com, surenb@google.com, kernel-team@android.com, Kalesh Singh , Catalin Marinas , James Morse , Alexandru Elisei , Suzuki K Poulose , Ard Biesheuvel , Mark Rutland , Pasha Tatashin , Joey Gouly , Peter Collingbourne , Andrew Walbran , Andrew Scull , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu X-Spam-Status: No, score=-8.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MISSING_HEADERS, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE, USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-ZohoMail-DKIM: pass (identity @google.com) X-ZM-MESSAGEID: 1644533093536100001 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Quentin Perret The asm entry code in the kernel uses a trick to check if VMAP'd stacks have overflowed by aligning them at THREAD_SHIFT * 2 granularity and checking the SP's THREAD_SHIFT bit. Protected KVM will soon make use of a similar trick to detect stack overflows, so factor out the asm code in a re-usable macro. Signed-off-by: Quentin Perret [Kalesh - Resolve minor conflicts] Signed-off-by: Kalesh Singh --- arch/arm64/include/asm/assembler.h | 11 +++++++++++ arch/arm64/kernel/entry.S | 9 ++------- 2 files changed, 13 insertions(+), 7 deletions(-) diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/as= sembler.h index e8bd0af0141c..ad40eb0eee83 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -850,4 +850,15 @@ alternative_endif =20 #endif /* GNU_PROPERTY_AARCH64_FEATURE_1_DEFAULT */ =20 +/* + * Test whether the SP has overflowed, without corrupting a GPR. + */ +.macro test_sp_overflow shift, label + add sp, sp, x0 // sp' =3D sp + x0 + sub x0, sp, x0 // x0' =3D sp' - x0 =3D (sp + x0) - x0 =3D sp + tbnz x0, #\shift, \label + sub x0, sp, x0 // x0'' =3D sp' - x0' =3D (sp + x0) - sp =3D x0 + sub sp, sp, x0 // sp'' =3D sp' - x0 =3D (sp + x0) - x0 =3D sp +.endm + #endif /* __ASM_ASSEMBLER_H */ diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 772ec2ecf488..2632bc47b348 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -53,16 +53,11 @@ alternative_else_nop_endif sub sp, sp, #PT_REGS_SIZE #ifdef CONFIG_VMAP_STACK /* - * Test whether the SP has overflowed, without corrupting a GPR. * Task and IRQ stacks are aligned so that SP & (1 << THREAD_SHIFT) * should always be zero. */ - add sp, sp, x0 // sp' =3D sp + x0 - sub x0, sp, x0 // x0' =3D sp' - x0 =3D (sp + x0) - x0 =3D sp - tbnz x0, #THREAD_SHIFT, 0f - sub x0, sp, x0 // x0'' =3D sp' - x0' =3D (sp + x0) - sp =3D x0 - sub sp, sp, x0 // sp'' =3D sp' - x0 =3D (sp + x0) - x0 =3D sp - b el\el\ht\()_\regsize\()_\label + test_sp_overflow THREAD_SHIFT, 0f + b el\el\ht\()_\regsize\()_\label =20 0: /* --=20 2.35.1.265.g69c8d7142f-goog