Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] kexec: arch_crash_get_elfcorehdr_size() exports undersized buffer when MEMORY_HOTPLUG is disabled --
commit fd293f9cfd1a12554d9352f4ad58fc9f85721fa3 Author: Jinjie Ruan <[email protected]> arm64: crash: Add crash hotplug support This commit introduces kernel mechanisms to update only the elfcorehdr on memory hotplug events for arm64. It adds ARCH_SUPPORTS_CRASH_HOTPLUG and implements arch-specific functions to handle memory hotplug, avoiding full kdump image reloads from userspace. Link: https://lore.kernel.org/all/[email protected]/ > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index b5a51b0ef9440..96de2660b1cbb 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1720,6 +1720,9 @@ config ARCH_DEFAULT_CRASH_DUMP > config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION > def_bool CRASH_RESERVE > > +config ARCH_SUPPORTS_CRASH_HOTPLUG > + def_bool y > + [Severity: High] Does unconditionally enabling ARCH_SUPPORTS_CRASH_HOTPLUG here expose an undersized buffer to userspace when CONFIG_MEMORY_HOTPLUG is disabled? Since CONFIG_HOTPLUG_CPU natively selects CONFIG_CRASH_HOTPLUG on architectures that support it, having this default to 'y' allows CRASH_HOTPLUG to be active even without MEMORY_HOTPLUG. This leads to the size calculation issue below. [ ... ] > diff --git a/arch/arm64/kernel/crash.c b/arch/arm64/kernel/crash.c > new file mode 100644 > index 0000000000000..08dc9b952498e > --- /dev/null > +++ b/arch/arm64/kernel/crash.c [ ... ] > +unsigned int arch_crash_get_elfcorehdr_size(void) > +{ > + unsigned long phdr_cnt; > + > + /* A program header for possible CPUs, vmcoreinfo and kernel_map */ > + phdr_cnt = 2 + num_possible_cpus(); > + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) > + phdr_cnt += CONFIG_CRASH_MAX_MEMORY_RANGES; > + [Severity: High] Is this calculation missing the static memory ranges when CONFIG_MEMORY_HOTPLUG is disabled? If compiled with CONFIG_HOTPLUG_CPU=y (which natively selects CONFIG_CRASH_HOTPLUG) and CONFIG_MEMORY_HOTPLUG=n, phdr_cnt is computed as exactly 2 + num_possible_cpus(). This does not account for the mandatory memblock ranges from arch_get_system_nr_ranges(). Unlike x86 or powerpc which might survive this due to heavily padded CONFIG_NR_CPUS_DEFAULT values, arm64's precise num_possible_cpus() leaves zero headroom. As a result, the exported maximum elfcorehdr size is strictly smaller than the required size to hold static memory ranges, and any attempt to arm kdump (kexec -p) will fail because kexec-tools cannot load the crash kernel into the undersized segment. -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=17
