From 8757dc970f550dc399f899be0e7a2c00b7e82e8f Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Fri, 20 Dec 2019 08:22:49 -0800 Subject: x86/crash: Define arch_crash_save_vmcoreinfo() if CONFIG_CRASH_CORE=y On x86 kernels configured with CONFIG_PROC_KCORE=y and CONFIG_KEXEC_CORE=n, the vmcoreinfo note in /proc/kcore is incomplete. Specifically, it is missing arch-specific information like the KASLR offset and whether 5-level page tables are enabled. This breaks applications like drgn [1] and crash [2], which need this information for live debugging via /proc/kcore. This happens because: 1. CONFIG_PROC_KCORE selects CONFIG_CRASH_CORE. 2. kernel/crash_core.c (compiled if CONFIG_CRASH_CORE=y) calls arch_crash_save_vmcoreinfo() to get the arch-specific parts of vmcoreinfo. If it is not defined, then it uses a no-op fallback. 3. x86 defines arch_crash_save_vmcoreinfo() in arch/x86/kernel/machine_kexec_*.c, which is only compiled if CONFIG_KEXEC_CORE=y. Therefore, an x86 kernel with CONFIG_CRASH_CORE=y and CONFIG_KEXEC_CORE=n uses the no-op fallback and gets incomplete vmcoreinfo data. This isn't relevant to kdump, which requires CONFIG_KEXEC_CORE. It only affects applications which read vmcoreinfo at runtime, like the ones mentioned above. Fix it by moving arch_crash_save_vmcoreinfo() into two new arch/x86/kernel/crash_core_*.c files, which are gated behind CONFIG_CRASH_CORE. 1: https://github.com/osandov/drgn/blob/73dd7def1217e24cc83d8ca95c995decbd9ba24c/libdrgn/program.c#L385 2: https://github.com/crash-utility/crash/commit/60a42d709280cdf38ab06327a5b4fa9d9208ef86 Signed-off-by: Omar Sandoval Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Greg Kroah-Hartman Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Kairui Song Cc: Lianbo Jiang Cc: Masahiro Yamada Cc: "Peter Zijlstra (Intel)" Cc: Thomas Gleixner Cc: x86-ml Link: https://lkml.kernel.org/r/0589961254102cca23e3618b96541b89f2b249e2.1576858905.git.osandov@fb.com --- arch/x86/kernel/machine_kexec_32.c | 12 ------------ 1 file changed, 12 deletions(-) (limited to 'arch/x86/kernel/machine_kexec_32.c') diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c index 7b45e8daad22..02bddfc122a4 100644 --- a/arch/x86/kernel/machine_kexec_32.c +++ b/arch/x86/kernel/machine_kexec_32.c @@ -250,15 +250,3 @@ void machine_kexec(struct kimage *image) __ftrace_enabled_restore(save_ftrace_enabled); } - -void arch_crash_save_vmcoreinfo(void) -{ -#ifdef CONFIG_NUMA - VMCOREINFO_SYMBOL(node_data); - VMCOREINFO_LENGTH(node_data, MAX_NUMNODES); -#endif -#ifdef CONFIG_X86_PAE - VMCOREINFO_CONFIG(X86_PAE); -#endif -} - -- cgit v1.2.3-59-g8ed1b