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Tue, 24 Oct 2023 09:17:51 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.9.0-alpha0-1048-g9229b632c5-fm-20231019.001-g9229b632 MIME-Version: 1.0 Message-Id: In-Reply-To: References: <20231023110308.1202042-1-arnd@kernel.org> Date: Tue, 24 Oct 2023 15:17:30 +0200 From: "Arnd Bergmann" To: "Baoquan He" Subject: Re: [PATCH 1/2] kexec: fix KEXEC_FILE dependencies Content-Type: text/plain X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-s390@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, eric_devolder@yahoo.com, Andrew Morton , linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, Vivek Goyal Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Oct 24, 2023, at 14:44, Baoquan He wrote: > Just add people and mailing list to CC since I didn't find this mail in > my box, just drag it via 'b4 am'. > > On 10/23/23 at 01:01pm, Arnd Bergmann wrote: > ...... >> diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec >> index 7aff28ded2f48..bfc636d64ff2b 100644 >> --- a/kernel/Kconfig.kexec >> +++ b/kernel/Kconfig.kexec >> @@ -36,6 +36,7 @@ config KEXEC >> config KEXEC_FILE >> bool "Enable kexec file based system call" >> depends on ARCH_SUPPORTS_KEXEC_FILE >> + depends on CRYPTO_SHA256=y || !ARCH_SUPPORTS_KEXEC_PURGATORY > > I am not sure if the logic is correct. In theory, kexec_file code > utilizes purgatory to verify the checksum digested during kernel loading > when try to jump to the kernel. That means kexec_file depends on > purgatory, but not contrary? The expression I wrote is a bit confusing, but I think this just keeps the existing behavior: - on architectures that select ARCH_SUPPORTS_KEXEC_PURGATORY (powerpc, riscv, s390 and x86), we also require CRYPTO_SHA256 to be built-in. - on architectures that do not have ARCH_SUPPORTS_KEXEC_PURGATORY (arm64 and parisc), CRYPTO_SHA256 is not used and can be disabled or =m. Since ARCH_SUPPORTS_KEXEC_PURGATORY is a 'bool' symbol, it could be written as depends on (ARCH_SUPPORTS_KEXEC_PURGATORY && CRYPTO_SHA256=y) \ || !ARCH_SUPPORTS_KEXEC_PURGATORY if you find that clearer. I see that the second patch actually gets this wrong, it should actually do select CRYPTO if ARCH_SUPPORTS_KEXEC_PURGATORY select CRYPTO_SHA256 if ARCH_SUPPORTS_KEXEC_PURGATORY > With these changes, we can achieve the goal to avoid building issue, > whereas the code logic becomes confusing. E.g people could disable > CONFIG_KEXEC_FILE, but still get purgatory code built in which is > totally useless. > > Not sure if I think too much over this. I see your point here, and I would suggest changing the CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY symbol to just indicate the availability of the purgatory code for the arch, rather than actually controlling the code itself. I already mentioned this for s390, but riscv would need the same thing on top. I think the change below should address your concern. Arnd diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c index e60fbd8660c4..3ac341d296db 100644 --- a/arch/riscv/kernel/elf_kexec.c +++ b/arch/riscv/kernel/elf_kexec.c @@ -266,7 +266,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf, cmdline = modified_cmdline; } -#ifdef CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY +#ifdef CONFIG_KEXEC_FILE /* Add purgatory to the image */ kbuf.top_down = true; kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; @@ -280,7 +280,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf, sizeof(kernel_start), 0); if (ret) pr_err("Error update purgatory ret=%d\n", ret); -#endif /* CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY */ +#endif /* CONFIG_KEXEC_FILE */ /* Add the initrd to the image */ if (initrd != NULL) { diff --git a/arch/riscv/Kbuild b/arch/riscv/Kbuild index d25ad1c19f88..ab181d187c23 100644 --- a/arch/riscv/Kbuild +++ b/arch/riscv/Kbuild @@ -5,7 +5,7 @@ obj-$(CONFIG_BUILTIN_DTB) += boot/dts/ obj-y += errata/ obj-$(CONFIG_KVM) += kvm/ -obj-$(CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY) += purgatory/ +obj-$(CONFIG_KEXEC_FILE) += purgatory/ # for cleaning subdir- += boot diff --git a/arch/s390/Kbuild b/arch/s390/Kbuild index a5d3503b353c..361aa01dbd49 100644 --- a/arch/s390/Kbuild +++ b/arch/s390/Kbuild @@ -7,7 +7,7 @@ obj-$(CONFIG_S390_HYPFS) += hypfs/ obj-$(CONFIG_APPLDATA_BASE) += appldata/ obj-y += net/ obj-$(CONFIG_PCI) += pci/ -obj-$(CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY) += purgatory/ +obj-$(CONFIG_KEXEC_FILE) += purgatory/ # for cleaning subdir- += boot tools