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Peter Anvin" , x86@kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: [PATCH v8 10/11] x86/paravirt: Adapt assembly for PIE support Date: Mon, 8 Jul 2019 10:49:03 -0700 Message-Id: <20190708174913.123308-11-thgarnie@chromium.org> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog In-Reply-To: <20190708174913.123308-1-thgarnie@chromium.org> References: <20190708174913.123308-1-thgarnie@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org if PIE is enabled, switch the paravirt assembly constraints to be compatible. The %c/i constrains generate smaller code so is kept by default. Position Independent Executable (PIE) support will allow to extend the KASLR randomization range below 0xffffffff80000000. Signed-off-by: Thomas Garnier Acked-by: Juergen Gross --- arch/x86/include/asm/paravirt_types.h | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index 946f8f1f1efc..5ec59abc5cb5 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -343,9 +343,25 @@ extern struct paravirt_patch_template pv_ops; #define PARAVIRT_PATCH(x) \ (offsetof(struct paravirt_patch_template, x) / sizeof(void *)) +#ifdef CONFIG_X86_PIE +#define paravirt_opptr_call "a" +#define paravirt_opptr_type "p" + +/* + * Alternative patching requires a maximum of 7 bytes but the relative call is + * only 6 bytes. If PIE is enabled, add an additional nop to the call + * instruction to ensure patching is possible. + * */ +#define PARAVIRT_CALL_POST "nop;" +#else +#define paravirt_opptr_call "c" +#define paravirt_opptr_type "i" +#define PARAVIRT_CALL_POST "" +#endif + #define paravirt_type(op) \ [paravirt_typenum] "i" (PARAVIRT_PATCH(op)), \ - [paravirt_opptr] "i" (&(pv_ops.op)) + [paravirt_opptr] paravirt_opptr_type (&(pv_ops.op)) #define paravirt_clobber(clobber) \ [paravirt_clobber] "i" (clobber) @@ -384,9 +400,10 @@ int paravirt_disable_iospace(void); * offset into the paravirt_patch_template structure, and can therefore be * freely converted back into a structure offset. */ -#define PARAVIRT_CALL \ - ANNOTATE_RETPOLINE_SAFE \ - "call *%c[paravirt_opptr];" +#define PARAVIRT_CALL \ + ANNOTATE_RETPOLINE_SAFE \ + "call *%" paravirt_opptr_call "[paravirt_opptr];" \ + PARAVIRT_CALL_POST /* * These macros are intended to wrap calls through one of the paravirt -- 2.22.0.410.gd8fdbe21b5-goog