On Mon, Feb 21, 2022 at 10:09 AM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx> wrote:
-----Original Message-----
> Previously for x86_64, when memory is randomized, the region addresses
> such as vmalloc_start_addr/vmemmap_vaddr/modules_vaddr are firstly set
> to a default value before POST_RELOC phase, then get refreshed with the
> actual value in POST_GDB phase.
>
> However for crash mininal mode, POST_GDB phase is not called, which
> leaving the region addresses unrefreshed and incorrect. As a consequence,
> the x86_64_IS_VMALLOC_ADDR check will give a faulty result when
> value_search tries to search a symbol by address.
>
Good findings, Tao.
> For example, in crash minimal mode we can observe the following issue:
>
> crash> dis -f panic
> dis: cannot resolve address: ffffffffb20e0d30
>
> crash> sym panic
> ffffffffb20e0d30 (T) panic /usr/src/debug/kernel-4.18.0-290/linux-4.18.0-290/kernel/panic.c: 168
> crash> sym ffffffffb20e0d30
> symbol not found: ffffffffb20e0d30
>
> In this patch, we will move the code which update the region addresses into
> POST_RELOC phase, so in mininal mode the regions can get the correct
> addresses.
>
> Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
The patch looks good to me, but with fixing the comment for the if block
in POST_RELOC like this:
/*
- * Check for CONFIG_RANDOMIZE_MEMORY, and set page_offset here.
- * The remainder of the virtual address range setups will get
- * done below in POST_GDB.
+ * Check for CONFIG_RANDOMIZE_MEMORY, and set page_offset and
+ * the virtual address ranges.
*/
if (kernel_symbol_exists("page_offset_base") &&
Acked-by: Kazuhito Hagio <k-hagio-ab@xxxxxxx>
This looks good to me. Applied(with the above fix).
Thanks,
Kazu
> ---
> x86_64.c | 52 ++++++++++++++++++++++++++--------------------------
> 1 file changed, 26 insertions(+), 26 deletions(-)
>
> diff --git a/x86_64.c b/x86_64.c
> index 552d619..2fb1277 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -384,6 +384,31 @@ x86_64_init(int when)
> "page_offset_base", QUIET|FAULT_ON_ERROR);
> machdep->kvbase = machdep->machspec->page_offset;
> machdep->identity_map_base = machdep->machspec->page_offset;
> +
> + readmem(symbol_value("vmalloc_base"), KVADDR,
> + &machdep->machspec->vmalloc_start_addr,
> + sizeof(ulong), "vmalloc_base", FAULT_ON_ERROR);
> + if (machdep->flags & VM_5LEVEL)
> + machdep->machspec->vmalloc_end =
> + machdep->machspec->vmalloc_start_addr + TERABYTES(1280) - 1;
> + else
> + machdep->machspec->vmalloc_end =
> + machdep->machspec->vmalloc_start_addr + TERABYTES(32) - 1;
> + if (kernel_symbol_exists("vmemmap_base")) {
> + readmem(symbol_value("vmemmap_base"), KVADDR,
> + &machdep->machspec->vmemmap_vaddr, sizeof(ulong),
> + "vmemmap_base", FAULT_ON_ERROR);
> + machdep->machspec->vmemmap_end =
> + machdep->machspec->vmemmap_vaddr +
> + TERABYTES(1) - 1;
> + } else {
> + machdep->machspec->vmemmap_vaddr = VMEMMAP_VADDR_2_6_31;
> + machdep->machspec->vmemmap_end = VMEMMAP_END_2_6_31;
> + }
> + machdep->machspec->modules_vaddr = __START_KERNEL_map +
> + (machdep->machspec->kernel_image_size ?
> + machdep->machspec->kernel_image_size : GIGABYTES(1));
> + machdep->machspec->modules_end = MODULES_END_2_6_31;
> }
> break;
>
> @@ -414,32 +439,7 @@ x86_64_init(int when)
> machdep->machspec->modules_end = MODULES_END_2_6_27;
> }
> if (THIS_KERNEL_VERSION >= LINUX(2,6,31)) {
> - if (machdep->flags & RANDOMIZED) {
> - readmem(symbol_value("vmalloc_base"), KVADDR,
> - &machdep->machspec->vmalloc_start_addr,
> - sizeof(ulong), "vmalloc_base", FAULT_ON_ERROR);
> - if (machdep->flags & VM_5LEVEL)
> - machdep->machspec->vmalloc_end =
> - machdep->machspec->vmalloc_start_addr + TERABYTES(1280) - 1;
> - else
> - machdep->machspec->vmalloc_end =
> - machdep->machspec->vmalloc_start_addr + TERABYTES(32) - 1;
> - if (kernel_symbol_exists("vmemmap_base")) {
> - readmem(symbol_value("vmemmap_base"), KVADDR,
> - &machdep->machspec->vmemmap_vaddr, sizeof(ulong),
> - "vmemmap_base", FAULT_ON_ERROR);
> - machdep->machspec->vmemmap_end =
> - machdep->machspec->vmemmap_vaddr +
> - TERABYTES(1) - 1;
> - } else {
> - machdep->machspec->vmemmap_vaddr = VMEMMAP_VADDR_2_6_31;
> - machdep->machspec->vmemmap_end = VMEMMAP_END_2_6_31;
> - }
> - machdep->machspec->modules_vaddr = __START_KERNEL_map +
> - (machdep->machspec->kernel_image_size ?
> - machdep->machspec->kernel_image_size : GIGABYTES(1));
> - machdep->machspec->modules_end = MODULES_END_2_6_31;
> - } else {
> + if (!(machdep->flags & RANDOMIZED)) {
> machdep->machspec->vmalloc_start_addr = VMALLOC_START_ADDR_2_6_31;
> machdep->machspec->vmalloc_end = VMALLOC_END_2_6_31;
> machdep->machspec->vmemmap_vaddr = VMEMMAP_VADDR_2_6_31;
> --
> 2.33.1
>
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