[Crash-utility] [External Mail][ANNOUNCE] crash gcore command, version 1.6.0 is released

[d.hatayama at fujitsu.com]

> Hi,hatayama

Hi Zhao. Thanks for your prompt response.

> 
> I've noticed a issue that has not been fixed in this version,gcore unable to parse register correctly in arm64,i found crash-utility is fixed,gcore-command can refer to below change:

I see. I'll include fix for this issue into v1.6.1.
But I'm waiting for bug reports from other archs a few more weeks.

By the way,

> 
> commit c975008e61121ef8785622c3bc26964da8fe0deb
> Author: Dave Anderson <anderson at redhat.com>
> Date:   Fri Sep 22 14:59:10 2017 -0400
> 
>     Fix for the ARM64 "bt" command's display of the user mode exception
>     frame at the top of the stack in Linux 4.7 and later kernels.
>     Without the patch, the contents of the user mode exception frame are
>     invalid due to the miscalculation of the starting address of the
>     pt_regs structure on the kernel stack.
>     (anderson at redhat.com)
> 
> gcore patch:
> commit 837182cc6589095c0d08f71f57953c50ad61cc19
> Author: zhaoqianli <zhaoqianli at xiaomi.com>
> Date:   Thu Nov 12 19:41:01 2020 +0800
> 
>     Fix register parsing error caused by miscalculation of the
>     starting address of the pt_regs structure on the kernel stack
> 
>     Signed-off-by: zhaoqianli <zhaoqianli at xiaomi.com>
> 
> diff --git a/libgcore/gcore_arm64.c b/libgcore/gcore_arm64.c
> index 3257389..c828fee 100644
> --- a/libgcore/gcore_arm64.c
> +++ b/libgcore/gcore_arm64.c
> @@ -28,7 +28,7 @@ static int gpr_get(struct task_context *target,
> 
>         BZERO(regs, sizeof(*regs));
> 
> -       readmem(machdep->get_stacktop(target->task) - 16 - SIZE(pt_regs), KVADDR,
> +       readmem(machdep->get_stacktop(target->task) - machdep->machspec->user_eframe_offset, KVADDR,

it looks that the commit c975008e61121ef8785622c3bc26964da8fe0deb of crash utility
has the condition MEMBER_EXISTS("pt_regs", "stackframe").

@@ -1376,6 +1377,11 @@ arm64_stackframe_init(void)
        MEMBER_OFFSET_INIT(elf_prstatus_pr_pid, "elf_prstatus", "pr_pid");
        MEMBER_OFFSET_INIT(elf_prstatus_pr_reg, "elf_prstatus", "pr_reg");

+       if (MEMBER_EXISTS("pt_regs", "stackframe"))
+               machdep->machspec->user_eframe_offset = SIZE(pt_regs);
+       else
+               machdep->machspec->user_eframe_offset = SIZE(pt_regs) + 16;
+
        machdep->machspec->__exception_text_start =
                symbol_value("__exception_text_start");
        machdep->machspec->__exception_text_end =
@

I guess with this patch set, gcore would result in similar issue for
kernels before 4.7.

Could you improve the patch so that gcore works well for kernls both before and later v4.7 kernel?

Thanks.
HATAYAMA, Daisuke