Re: [PATCHv2] x86/boot/KASLR: skip the specified crashkernel reserved region

[Pingfan Liu]

On Thu, Mar 21, 2019 at 2:38 PM Chao Fan <fanc.fnst@xxxxxxxxxxxxxx> wrote:
>
> On Wed, Mar 13, 2019 at 12:19:31PM +0800, Pingfan Liu wrote:
>
> I tested it in Qemu test with 12G memory, and set crashkernel=6G@6G.
> Without this PATCH, it successed to reserve memory just 4 times(total
> 10 times).
> With this PATCH, it successed to reserve memory 15 times(total 15
> times).
>
> So I think if you post new version, you can add:
>
> Tested-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
>
Appreciate for your testing. I had done some test on a real machine
with a private patch to narrow down the KASLR range. I think your test
method is more simple and I will add the tested-by you.

Regards,
Pingfan

> Thanks,
> Chao Fan
>
> >crashkernel=x@y option may fail to reserve the required memory region if
> >KASLR puts kernel into the region. To avoid this uncertainty, making KASLR
> >skip the required region.
> >
> >Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
> >Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> >Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> >Cc: Borislav Petkov <bp@xxxxxxxxx>
> >Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> >Cc: Baoquan He <bhe@xxxxxxxxxx>
> >Cc: Will Deacon <will.deacon@xxxxxxx>
> >Cc: Nicolas Pitre <nico@xxxxxxxxxx>
> >Cc: Pingfan Liu <kernelfans@xxxxxxxxx>
> >Cc: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
> >Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> >Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> >Cc: linux-kernel@xxxxxxxxxxxxxxx
> >---
> >v1 -> v2: fix some trival format
> >
> > arch/x86/boot/compressed/kaslr.c | 26 ++++++++++++++++++++++++--
> > 1 file changed, 24 insertions(+), 2 deletions(-)
> >
> >diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> >index 9ed9709..e185318 100644
> >--- a/arch/x86/boot/compressed/kaslr.c
> >+++ b/arch/x86/boot/compressed/kaslr.c
> >@@ -109,6 +109,7 @@ enum mem_avoid_index {
> >       MEM_AVOID_BOOTPARAMS,
> >       MEM_AVOID_MEMMAP_BEGIN,
> >       MEM_AVOID_MEMMAP_END = MEM_AVOID_MEMMAP_BEGIN + MAX_MEMMAP_REGIONS - 1,
> >+      MEM_AVOID_CRASHKERNEL,
> >       MEM_AVOID_MAX,
> > };
> >
> >@@ -240,6 +241,25 @@ static void parse_gb_huge_pages(char *param, char *val)
> >       }
> > }
> >
> >+/* parse crashkernel=x@y option */
> >+static void mem_avoid_crashkernel_simple(char *option)
> >+{
> >+      unsigned long long crash_size, crash_base;
> >+      char *cur = option;
> >+
> >+      crash_size = memparse(option, &cur);
> >+      if (option == cur)
> >+              return;
> >+
> >+      if (*cur == '@') {
> >+              option = cur + 1;
> >+              crash_base = memparse(option, &cur);
> >+              if (option == cur)
> >+                      return;
> >+              mem_avoid[MEM_AVOID_CRASHKERNEL].start = crash_base;
> >+              mem_avoid[MEM_AVOID_CRASHKERNEL].size = crash_size;
> >+      }
> >+}
> >
> > static void handle_mem_options(void)
> > {
> >@@ -250,7 +270,7 @@ static void handle_mem_options(void)
> >       u64 mem_size;
> >
> >       if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
> >-              !strstr(args, "hugepages"))
> >+              !strstr(args, "hugepages") && !strstr(args, "crashkernel="))
> >               return;
> >
> >       tmp_cmdline = malloc(len + 1);
> >@@ -286,6 +306,8 @@ static void handle_mem_options(void)
> >                               goto out;
> >
> >                       mem_limit = mem_size;
> >+              } else if (strstr(param, "crashkernel")) {
> >+                      mem_avoid_crashkernel_simple(val);
> >               }
> >       }
> >
> >@@ -414,7 +436,7 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
> >
> >       /* We don't need to set a mapping for setup_data. */
> >
> >-      /* Mark the memmap regions we need to avoid */
> >+      /* Mark the regions we need to avoid */
> >       handle_mem_options();
> >
> > #ifdef CONFIG_X86_VERBOSE_BOOTUP
> >--
> >2.7.4
> >
> >
> >
>
>