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Tue, 16 Jun 2020 00:55:58 -0700 (PDT) From: Andrei Vagin To: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon Subject: [PATCH 3/6] arm64/vdso: Add time namespace page Date: Tue, 16 Jun 2020 00:55:42 -0700 Message-Id: <20200616075545.312684-4-avagin@gmail.com> X-Mailer: git-send-email 2.17.2 In-Reply-To: <20200616075545.312684-1-avagin@gmail.com> References: <20200616075545.312684-1-avagin@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200616_005559_551289_278CD334 X-CRM114-Status: GOOD ( 20.83 ) X-Spam-Score: -0.2 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (-0.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:1044 listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider [avagin[at]gmail.com] -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 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 , Dmitry Safonov , linux-kernel@vger.kernel.org, Andrei Vagin , Thomas Gleixner , Vincenzo Frascino MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Allocate the time namespace page among VVAR pages. Provide __arch_get_timens_vdso_data() helper for VDSO code to get the code-relative position of VVARs on that special page. If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. That page has vdso_data->seq set to 1 to enforce the slow path and vdso_data->clock_mode set to VCLOCK_TIMENS to enforce the time namespace handling path. The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again. If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page. Cc: Mark Rutland Reviewed-by: Vincenzo Frascino Reviewed-by: Dmitry Safonov Signed-off-by: Andrei Vagin --- arch/arm64/include/asm/vdso.h | 2 ++ .../include/asm/vdso/compat_gettimeofday.h | 12 ++++++++++++ arch/arm64/include/asm/vdso/gettimeofday.h | 8 ++++++++ arch/arm64/kernel/vdso.c | 19 ++++++++++++++++--- arch/arm64/kernel/vdso/vdso.lds.S | 5 ++++- arch/arm64/kernel/vdso32/vdso.lds.S | 5 ++++- include/vdso/datapage.h | 1 + 7 files changed, 47 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/vdso.h b/arch/arm64/include/asm/vdso.h index 07468428fd29..f99dcb94b438 100644 --- a/arch/arm64/include/asm/vdso.h +++ b/arch/arm64/include/asm/vdso.h @@ -12,6 +12,8 @@ */ #define VDSO_LBASE 0x0 +#define __VVAR_PAGES 2 + #ifndef __ASSEMBLY__ #include diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h b/arch/arm64/include/asm/vdso/compat_gettimeofday.h index b6907ae78e53..b7c549d46d18 100644 --- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h +++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h @@ -152,6 +152,18 @@ static __always_inline const struct vdso_data *__arch_get_vdso_data(void) return ret; } +#ifdef CONFIG_TIME_NS +static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void) +{ + const struct vdso_data *ret; + + /* See __arch_get_vdso_data(). */ + asm volatile("mov %0, %1" : "=r"(ret) : "r"(_timens_data)); + + return ret; +} +#endif + #endif /* !__ASSEMBLY__ */ #endif /* __ASM_VDSO_GETTIMEOFDAY_H */ diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h index afba6ba332f8..cf39eae5eaaf 100644 --- a/arch/arm64/include/asm/vdso/gettimeofday.h +++ b/arch/arm64/include/asm/vdso/gettimeofday.h @@ -96,6 +96,14 @@ const struct vdso_data *__arch_get_vdso_data(void) return _vdso_data; } +#ifdef CONFIG_TIME_NS +static __always_inline +const struct vdso_data *__arch_get_timens_vdso_data(void) +{ + return _timens_data; +} +#endif + #endif /* !__ASSEMBLY__ */ #endif /* __ASM_VDSO_GETTIMEOFDAY_H */ diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c index df4bb736d28a..14d5b7642b62 100644 --- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -40,6 +40,12 @@ enum vdso_abi { #endif /* CONFIG_COMPAT_VDSO */ }; +enum vvar_pages { + VVAR_DATA_PAGE_OFFSET, + VVAR_TIMENS_PAGE_OFFSET, + VVAR_NR_PAGES, +}; + struct vdso_abi_info { const char *name; const char *vdso_code_start; @@ -126,6 +132,11 @@ static int __vdso_init(enum vdso_abi abi) } #ifdef CONFIG_TIME_NS +struct vdso_data *arch_get_vdso_data(void *vvar_page) +{ + return (struct vdso_data *)(vvar_page); +} + /* * The vvar page layout depends on whether a task belongs to the root or * non-root time namespace. Whenever a task changes its namespace, the VVAR @@ -175,9 +186,11 @@ static int __setup_additional_pages(enum vdso_abi abi, unsigned long gp_flags = 0; void *ret; + BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); + vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT; /* Be sure to map the data page */ - vdso_mapping_len = vdso_text_len + PAGE_SIZE; + vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE; vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); if (IS_ERR_VALUE(vdso_base)) { @@ -185,7 +198,7 @@ static int __setup_additional_pages(enum vdso_abi abi, goto up_fail; } - ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE, + ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE, VM_READ|VM_MAYREAD|VM_PFNMAP, vdso_info[abi].dm); if (IS_ERR(ret)) @@ -194,7 +207,7 @@ static int __setup_additional_pages(enum vdso_abi abi, if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti()) gp_flags = VM_ARM64_BTI; - vdso_base += PAGE_SIZE; + vdso_base += VVAR_NR_PAGES * PAGE_SIZE; mm->context.vdso = (void *)vdso_base; ret = _install_special_mapping(mm, vdso_base, vdso_text_len, VM_READ|VM_EXEC|gp_flags| diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S index 7ad2d3a0cd48..d808ad31e01f 100644 --- a/arch/arm64/kernel/vdso/vdso.lds.S +++ b/arch/arm64/kernel/vdso/vdso.lds.S @@ -17,7 +17,10 @@ OUTPUT_ARCH(aarch64) SECTIONS { - PROVIDE(_vdso_data = . - PAGE_SIZE); + PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE); +#ifdef CONFIG_TIME_NS + PROVIDE(_timens_data = _vdso_data + PAGE_SIZE); +#endif . = VDSO_LBASE + SIZEOF_HEADERS; .hash : { *(.hash) } :text diff --git a/arch/arm64/kernel/vdso32/vdso.lds.S b/arch/arm64/kernel/vdso32/vdso.lds.S index a3944927eaeb..06cc60a9630f 100644 --- a/arch/arm64/kernel/vdso32/vdso.lds.S +++ b/arch/arm64/kernel/vdso32/vdso.lds.S @@ -17,7 +17,10 @@ OUTPUT_ARCH(arm) SECTIONS { - PROVIDE_HIDDEN(_vdso_data = . - PAGE_SIZE); + PROVIDE_HIDDEN(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE); +#ifdef CONFIG_TIME_NS + PROVIDE_HIDDEN(_timens_data = _vdso_data + PAGE_SIZE); +#endif . = VDSO_LBASE + SIZEOF_HEADERS; .hash : { *(.hash) } :text diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h index 7955c56d6b3c..ee810cae4e1e 100644 --- a/include/vdso/datapage.h +++ b/include/vdso/datapage.h @@ -109,6 +109,7 @@ struct vdso_data { * relocation, and this is what we need. */ extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden"))); +extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden"))); /* * The generic vDSO implementation requires that gettimeofday.h