On 09/17/2018 06:46 PM, Daniel Thompson wrote:
> On Tue, Sep 11, 2018 at 01:29:42PM -0400, Prarit Bhargava wrote:
>> As a test I hacked the buffer size to 16 and entered kdb:
>>
>> [16]kdb>
>> 117661 symbols are found. But only first 30 symbols will be printed.
>> You can change the environment variable DTABCOUNT.
>> irq_stack_union __per_cpu_start cpu_debug_store cpu_tss_rw gdt_page
>> exception_stack... entry_stack_sto... espfix_waddr espfix_stack cpu_llc_id
>> cpu_llc_shared_... cpu_core_map cpu_sibling_map cpu_info cpu_number
>> this_cpu_off x86_cpu_to_acpi... x86_cpu_to_apic... x86_bios_cpu_ap...
>> sched_core_prio... cpu_loops_per_j... pmc_prev_left cpu_hw_events bts_ctx
>> insn_buffer pt_ctx xen_vcpu_info xen_vcpu_id xen_vcpu mc_buffer ...
>
> I don't quite understand what is being tested here (I thought the code
> you changed was only reached after tab is pressed twice) and you haven't
> shared what conclusion you have drawn from this test.
>
Hi Daniel, my apologies. Here's a more detailed explanation.
I didn't feel comfortable submitting the code without testing and the problem is
that I couldn't think of a kernel symbol that was 128 bytes in size that would
be truncated so that ellipses would be printed out. What I decided to do is
apply my patch *and* change the buffer size to 16, then rebuilt the kernel,
booted the kernel, and selected the ttyS0 as the buffer console. I entered kdb
using "echo g > /proc/sysrq-trigger" and hit tab twice to test the code.
The above output confirms that the code is working as expected. Any symbol
larger than 15 is truncated and appended with ellipses, for example
"cpu_llc_shared_...". Symbols smaller than 15 are fully output, for example,
cpu_llc_id.
IOW, it looks like the code works as expected.
P.
>
> Daniel.
>
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