From: Lianbo Jiang <lijiang@xxxxxxxxxx> [ Upstream commit 6f599d84231fd27e42f4ca2a786a6641e8cddf00 ] On x86, purgatory() copies the first 640K of memory to a backup region because the kernel needs those first 640K for the real mode trampoline during boot, among others. However, when SME is enabled, the kernel cannot properly copy the old memory to the backup area but reads only its encrypted contents. The result is that the crash tool gets invalid pointers when parsing vmcore: crash> kmem -s|grep -i invalid kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 crash> So reserve the remaining low 1M memory when the crashkernel option is specified (after reserving real mode memory) so that allocated memory does not fall into the low 1M area and thus the copying of the contents of the first 640k to a backup region in purgatory() can be avoided altogether. This way, it does not need to be included in crash dumps or used for anything except the trampolines that must live in the low 1M. [ bp: Heavily rewrite commit message, flip check logic in crash_reserve_low_1M().] Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: bhe@xxxxxxxxxx Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: d.hatayama@xxxxxxxxxxx Cc: dhowells@xxxxxxxxxx Cc: ebiederm@xxxxxxxxxxxx Cc: horms@xxxxxxxxxxxx Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Jürgen Gross <jgross@xxxxxxxx> Cc: kexec@xxxxxxxxxxxxxxxxxxx Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx> Cc: vgoyal@xxxxxxxxxx Cc: x86-ml <x86@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20191108090027.11082-2-lijiang@xxxxxxxxxx Link: https://bugzilla.kernel.org/show_bug.cgi?id=204793 Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- arch/x86/include/asm/crash.h | 6 ++++++ arch/x86/kernel/crash.c | 15 +++++++++++++++ arch/x86/realmode/init.c | 2 ++ 3 files changed, 23 insertions(+) diff --git a/arch/x86/include/asm/crash.h b/arch/x86/include/asm/crash.h index ef5638f641f2b..88eadd08ad708 100644 --- a/arch/x86/include/asm/crash.h +++ b/arch/x86/include/asm/crash.h @@ -10,4 +10,10 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params); void crash_smp_send_stop(void); +#ifdef CONFIG_KEXEC_CORE +void __init crash_reserve_low_1M(void); +#else +static inline void __init crash_reserve_low_1M(void) { } +#endif + #endif /* _ASM_X86_CRASH_H */ diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index eb651fbde92ac..ff25a2ea271cf 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -24,6 +24,7 @@ #include <linux/export.h> #include <linux/slab.h> #include <linux/vmalloc.h> +#include <linux/memblock.h> #include <asm/processor.h> #include <asm/hardirq.h> @@ -39,6 +40,7 @@ #include <asm/virtext.h> #include <asm/intel_pt.h> #include <asm/crash.h> +#include <asm/cmdline.h> /* Used while preparing memory map entries for second kernel */ struct crash_memmap_data { @@ -68,6 +70,19 @@ static inline void cpu_crash_vmclear_loaded_vmcss(void) rcu_read_unlock(); } +/* + * When the crashkernel option is specified, only use the low + * 1M for the real mode trampoline. + */ +void __init crash_reserve_low_1M(void) +{ + if (cmdline_find_option(boot_command_line, "crashkernel", NULL, 0) < 0) + return; + + memblock_reserve(0, 1<<20); + pr_info("Reserving the low 1M of memory for crashkernel\n"); +} + #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC) static void kdump_nmi_callback(int cpu, struct pt_regs *regs) diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c index 7dce39c8c034a..262f83cad3551 100644 --- a/arch/x86/realmode/init.c +++ b/arch/x86/realmode/init.c @@ -8,6 +8,7 @@ #include <asm/pgtable.h> #include <asm/realmode.h> #include <asm/tlbflush.h> +#include <asm/crash.h> struct real_mode_header *real_mode_header; u32 *trampoline_cr4_features; @@ -34,6 +35,7 @@ void __init reserve_real_mode(void) memblock_reserve(mem, size); set_real_mode_mem(mem); + crash_reserve_low_1M(); } static void __init setup_real_mode(void) -- 2.25.1
