[PATCH v9 03/11] arm64: kexec_file: invoke the kernel without purgatory
From: james.morse@arm.com (James Morse)
Date: 2018-05-01 17:49:10
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kexec, lkml
Hi Akashi, On 25/04/18 07:26, AKASHI Takahiro wrote:
On arm64, purugatory would do almosty nothing. So just invoke secondary kernel directy by jumping into its entry code.
(Nits: purgatory, almost, directly)
While, in this case, cpu_soft_restart() must be called with dtb address in the fifth argument, the behavior still stays compatible with kexec_load case as long as the argument is null.
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S index 8021b46c9743..391df91328ac 100644 --- a/arch/arm64/kernel/cpu-reset.S +++ b/arch/arm64/kernel/cpu-reset.S@@ -24,9 +24,9 @@ * * @el2_switch: Flag to indicate a swich to EL2 is needed.
(Nit: switch)
* @entry: Location to jump to for soft reset. - * arg0: First argument passed to @entry. - * arg1: Second argument passed to @entry. - * arg2: Third argument passed to @entry. + * arg0: First argument passed to @entry. (relocation list) + * arg1: Second argument passed to @entry.(physcal kernel entry)
(Nit: physical)
quoted hunk ↗ jump to hunk
+ * arg2: Third argument passed to @entry. (physical dtb address) * * Put the CPU into the same state as it would be if it had been reset, and * branch to what would be the reset vector. It must be executed with thediff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c index f76ea92dff91..f7dbba00be10 100644 --- a/arch/arm64/kernel/machine_kexec.c +++ b/arch/arm64/kernel/machine_kexec.c@@ -205,10 +205,17 @@ void machine_kexec(struct kimage *kimage) * uses physical addressing to relocate the new image to its final * position and transfers control to the image entry point when the * relocation is complete. + * In case of kexec_file_load syscall, we directly start the kernel, + * skipping purgatory.
We're not really skipping purgatory, purgatory doesn't exist! For regular kexec the image/payload we run is up to kexec-tools. For kexec_file_load its a kernel-image. Purgatory is a kexec-tools-ism.
cpu_soft_restart(kimage != kexec_crash_image, - reboot_code_buffer_phys, kimage->head, kimage->start, 0); + reboot_code_buffer_phys, kimage->head, kimage->start, +#ifdef CONFIG_KEXEC_FILE + kimage->purgatory_info.purgatory_buf ? + 0 : kimage->arch.dtb_mem); +#else + 0); +#endif
Where does kimage->arch.dtb_mem come from? This patch won't build until patch 8 adds the config option, which is going to make bisecting any kexec side-effects tricky. purgatory_buf seems to only be set in kexec_purgatory_setup_kbuf(), called from kexec_load_purgatory(), which we don't use. How does this get a value? Would it be better to always use kimage->arch.dtb_mem, and ensure that is 0 for regular kexec (as we can't know where the dtb is)? (image_arg may then be a better name). Thanks, James