Hi Yeping,
On Mon, Jul 29, 2024 at 2:20 PM yp z <wonderzyp@xxxxxxxxx> wrote:
>
> Hi Lianbo and Tao,
> Thank you for your suggestions, and I have rewrote a patch in two cases:
>
> [1] with vmcoreinfo:
> + if (kernel_symbol_exists("kasan_enable_current")) {
> + min_thread_shift += 1;
> + thread_shift = (min_thread_shift < machdep->pageshift) ? machdep->pageshift : min_thread_shift;
> + }
>
This looks fine to me.
>> BTW: can you help point out the current issue is with or without the vmcoreinfo? Yeping
>
> My issue is with vmcoreinfo of "SYMBOL("kasan_enable_current")", and works well with this patch.
>
> [2] without vmcoreinfo:
>>
>> What about somehow the disassembly gives us hex values like:
>> #0xe? It won't work by then. Any ideas for this?
>
> In order to use stol() as expected, I have changed the first non-numeric char to '\0':
> + if ((pos1 = strstr(buf1, "tbnz"))) {
> + if ((pos2 = strchr(pos1, '#'))) {
> + pos2 += 1;
> + pos1 = pos2;
> + while (*pos2 != '\0') {
> + if (!((*pos2 >= '0' && *pos2 <= '9')
> + || (*pos2 >= 'A' && *pos2 <= 'F')
> + || (*pos2 >= 'a' && *pos2 <= 'f'))) {
There are 'x' 'X' not covered, it will not work for the "#0xe" case.
Can we make it simpler, since the value we are looking for is the 2nd
oprand of tbnz, there must be a ',' after the value.
tbnz w2, #0x1f, 0xffff80008001bed0
Can we make it like the following? I haven't tested the following code...
if ((pos2 = strchr(pos1, '#'))) {
pos2 += 1;
for (pos1 = pos2; *pos2 != '\0' && *pos2 != ','; pos2++);
*pos2 = '\0';
thread_shift = stol(pos1, RETURN_ON_ERROR|QUIET, &errflag);
if (errflag) {
thread_shift = 0;
}
break;
}
Thanks,
Tao Liu
> + *pos2 = '\0';
> + break;
> + }
> + ++pos2;
> + }
> + thread_shift = stol(pos1, RETURN_ON_ERROR|QUIET, &errflag);
>
> Thanks.
> Yeping.ZHENG
>
> lijiang <lijiang@xxxxxxxxxx> 于2024年7月26日周五 17:23写道：
>>
>> On Fri, Jul 19, 2024 at 6:40 AM Tao Liu <ltao@xxxxxxxxxx> wrote:
>>>
>>> Hi Lianbo,
>>>
>>> On Thu, Jul 18, 2024 at 10:50 PM Lianbo Jiang <lijiang@xxxxxxxxxx> wrote:
>>> >
>>> > On 7/16/24 4:22 PM, Tao Liu wrote:
>>> >
>>> > > Hi Yeping,
>>> > >
>>> > > Thanks for the fix.
>>> > >
>>> > > On Thu, Jul 11, 2024 at 1:38 PM <wonderzyp@xxxxxxxxx> wrote:
>>> > >> When using the crash tool to parse the ARM64 dump file with KASAN enabled, I found that using the bt -a command will cause this tool to crash, the following is the backtrace infomation.
>>> > >>
>>> > >> (gdb) bt
>>> > >> #0 0x00005635ac2b166b in arm64_unwind_frame (frame=0x7ffdaf35cb70, bt=0x7ffdaf35d430)
>>> > >> at arm64.c:2821
>>> > >> #1 arm64_back_trace_cmd (bt=0x7ffdaf35d430) at arm64.c:3306
>>> > >> #2 0x00005635ac27b108 in back_trace (bt=bt@entry=0x7ffdaf35d430) at kernel.c:3239
>>> > >> #3 0x00005635ac2880ae in cmd_bt () at kernel.c:2863
>>> > >> #4 0x00005635ac1f16dc in exec_command () at main.c:893
>>> > >> #5 0x00005635ac1f192a in main_loop () at main.c:840
>>> > >> #6 0x00005635ac50df81 in captured_main (data=<optimized out>) at main.c:1284
>>> > >> #7 gdb_main (args=<optimized out>) at main.c:1313
>>> > >> #8 0x00005635ac50e000 in gdb_main_entry (argc=<optimized out>, argv=<optimized out>)
>>> > >> at main.c:1338
>>> > >> #9 0x00005635ac1ea2a5 in main (argc=5, argv=0x7ffdaf35dde8) at main.c:721
>>> > >> Eventually, I found that it was may caused by not setting irq_stack_size properly, and provide this patch to solve it.
>>> > >>
>>> > > Could you please re-draft your commit message? The original one looks
>>> > > informal. E.g:
>>> > >
>>> > > A segfault issue was observed on KASAN enabled arm64 kernel due to the
>>> > > incorrect irq_stack_size, see the following stack trace:
>>> > > ...
>>> > > The issue was caused by ...., and this patch will fix the issue by ....
>>> > >
>>> > >> From 34b28aa8c11e77d20adec4f7705a14d239c8a55f Mon Sep 17 00:00:00 2001
>>> > >> From: wonderzyp <wonderzyp@xxxxxx>
>>> > >> Date: Mon, 8 Jul 2024 20:11:38 +0800
>>> > >> Subject: [PATCH 1131/1131] set_arm64_irq_stack_size
>>> > >>
>>> > >> Signed-off-by: Yeping Zheng <wonderzyp@xxxxxxxxx>
>>> > >> ---
>>> > >> arm64.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
>>> > >> 1 file changed, 47 insertions(+), 2 deletions(-)
>>> > >>
>>> > >> diff --git a/arm64.c b/arm64.c
>>> > >> index b3040d7..39d891b 100644
>>> > >> --- a/arm64.c
>>> > >> +++ b/arm64.c
>>> > >> @@ -93,6 +93,7 @@ static void arm64_calc_VA_BITS(void);
>>> > >> static int arm64_is_uvaddr(ulong, struct task_context *);
>>> > >> static void arm64_calc_KERNELPACMASK(void);
>>> > >> static int arm64_get_vmcoreinfo(unsigned long *vaddr, const char *label, int base);
>>> > >> +static ulong arm64_set_irq_stack_size(struct machine_specific *ms);
>>> > >>
>>> > >> struct kernel_range {
>>> > >> unsigned long modules_vaddr, modules_end;
>>> > >> @@ -2223,8 +2224,14 @@ arm64_irq_stack_init(void)
>>> > >> if (MEMBER_EXISTS("thread_union", "stack")) {
>>> > >> if ((sz = MEMBER_SIZE("thread_union", "stack")) > 0)
>>> > >> ms->irq_stack_size = sz;
>>> > >> - } else
>>> > >> - ms->irq_stack_size = ARM64_IRQ_STACK_SIZE;
>>> > >> + } else {
>>> > >> + ulong res = arm64_set_irq_stack_size(ms);
>>> > >> + if (res > 0){
>>> > >> + ms->irq_stack_size = res;
>>> > >> + } else {
>>> > >> + ms->irq_stack_size = ARM64_IRQ_STACK_SIZE;
>>> > >> + }
>>> > >> + }
>>> > >>
>>> > >> machdep->flags |= IRQ_STACKS;
>>> > >>
>>> > >> @@ -4921,6 +4928,44 @@ static void arm64_calc_KERNELPACMASK(void)
>>> > >> }
>>> > >> }
>>> > >>
>>> > >> +static ulong arm64_set_irq_stack_size(struct machine_specific *ms)
>>> > >> +{
>>> > >> + char *string;
>>> > >> + int ret;
>>> > >> + int KASAN_THREAD_SHIFT = 0;
>>> > >> + int MIN_THREAD_SHIFT;
>>> > >> + ulong ARM64_PAGE_SHIFT;
>>> > >> + ulong THREAD_SHIFT = 0;
>>> > >> + ulong THREAD_SIZE;
>>> > > I guess the upper case of variable names is not encouraged, though it
>>> > > is the variable that comes from kernel config file.
>>> > >
>>> > >> + if (kt->ikconfig_flags & IKCONFIG_AVAIL) {
>>> > >> + if ((ret = get_kernel_config("CONFIG_KASAN_GENERIC", NULL) == IKCONFIG_Y) ||
>>> > >> + (ret = get_kernel_config("CONFIG_KASAN_SW_TAGS", NULL) == IKCONFIG_Y)) {
>>> > >> + KASAN_THREAD_SHIFT = 1;
>>> > >> + }
>>> > >> + }
>>> > >> + MIN_THREAD_SHIFT = 14 + KASAN_THREAD_SHIFT;
>>> > >> +
>>> > >> + if (kt->ikconfig_flags & IKCONFIG_AVAIL) {
>>> > > Could the if condition be merged with the prior one?
>>> > >
>>> > >> + if ((ret = get_kernel_config("CONFIG_VMAP_STACK", NULL)) == IKCONFIG_Y){
>>> > >> + if ((ret = get_kernel_config("CONFIG_ARM64_PAGE_SHIFT", &string)) ==
>>> >
>>> > The "CONFIG_ARM64_PAGE_SHIFT " has been removed since kernel v6.9-rc1,
>>> > so this can not work on the latest kernel. See:
>>> >
>>> > d3e5bab923d3 ("arch: simplify architecture specific page size
>>> > configuration")
>>> >
>>> >
>>> > In addition, the IKCONFIG is not available in most distributions, it
>>> > can not cover this case. There is a similar discussion there:
>>> >
>>> > https://www.mail-archive.com/devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx/msg00880.html
>>> >
>>> > Can you try to handle the current issue with a similar solution?
>>> >
>>> >
>>> > >> IKCONFIG_STR){
>>> > >> + ARM64_PAGE_SHIFT = atol(string);
>>> > >> + }
>>> > >> + if (MIN_THREAD_SHIFT < ARM64_PAGE_SHIFT){
>>> > >> + THREAD_SHIFT = ARM64_PAGE_SHIFT;
>>> > >> + } else {
>>> > >> + THREAD_SHIFT = MIN_THREAD_SHIFT;
>>> > >> + }
>>> > >> + }
>>> > >> + }
>>> > >> +
>>> > >> + if (THREAD_SHIFT == 0) {
>>> > >> + return -1;
>>> > >> + }
>>> > >> +
>>> > >> + THREAD_SIZE = ((1UL) << THREAD_SHIFT);
>>> > >> + return THREAD_SIZE;
>>> > >> +}
>>> > > I'm OK with the approach above, since it directly came from the kernel
>>> > > source. However I'm not a fan of checking kernel configs, there might
>>> > > be kernels which are compiled without CONFIG_IKCONFIG.
>>> > >
>>> > > Could we add an approach here, to get the value from disassembly when
>>> > > CONFIG_IKCONFIG is negative?
>>> > >
>>> > > kernel source: arch/arm64/kernel/entry.S:
>>> > >
>>> > > .macro kernel_ventry, el:req, ht:req, regsize:req, label:req
>>> > > ....
>>> > > add sp, sp, x0 // sp' = sp + x0
>>> > > sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp
>>> > > tbnz x0, #THREAD_SHIFT, 0f <<<<<<<<
>>> > >
>>> > > $ objdump -d vmlinux
>>> > > ...
>>> > > ffff800080010800 <vectors>:
>>> > > ffff800080010800: d10543ff sub sp, sp, #0x150
>>> > > ffff800080010804: 8b2063ff add sp, sp, x0
>>> > > ffff800080010808: cb2063e0 sub x0, sp, x0
>>> > > ffff80008001080c: 37800080 tbnz w0, #16,
>>> > > ffff80008001081c <vectors+0x1c> <<<<<<<<<<
>>> > >
>>> > > It is easy to get the THREAD_SHIFT value by disassembling the tbnz
>>> > > instruction. What do you think @Lianbo Jiang
>>> >
>>> > This is a good idea, but it still relies on compiler.
>>> >
>>> > As we discussed, usually I would recommend finding its values via some
>>> > kernel symbols.
>>>
>>> Yeah, but I didn't find a suitable symbol so far... In addition, the
>>
>>
>> It's true. For the KASAN, it is easy to find a suitable symbol, but it's not easy for the PAGESIZE or PAGESHIFT.
>>
>> Given that I would suggest covering two cases:
>> [1] with vmcoreinfo(see mm/kasan/common.c)
>> ...
>> int min_thread_shift = 14;
>> if (kernel_symbol_exists("kasan_enable_current"))
>> min_thread_shift += 1;
>>
>> thread_shift = (min_thread_shift < machdep->pageshift) ? machdep->pageshift : min_thread_shift;
>> ...
>>
>> [2] without vmcoreinfo
>> Use Tao's solution(disassemble kernel code)
>>
>> The first one is better than the second one in case of having vmcoreinfo, If I understand correctly.
>> But we still need to cover the above two cases in the crash tools.
>>
>> BTW: can you help point out the current issue is with or without the vmcoreinfo? Yeping
>>
>> Thanks
>> Lianbo
>>
>>> above case is a little different here, the tbnz instruction is not
>>> generated from C code, it is written in assembly in
>>> arch/arm64/kernel/entry.S file. So I guess there would be a lower
>>> possibility if tbnz instruction gets replaced or eliminated by the
>>> compilers. Anyway, it's OK to me if you don't want to accept the
>>> approach.
>>>
>>> Thanks,
>>> Tao Liu
>>>
>>>
>>> >
>>> >
>>> > Thanks
>>> >
>>> > Lianbo
>>> >
>>> > >
>>> > > Thanks,
>>> > > Tao Liu
>>> > >
>>> > >> +
>>> > >> #endif /* ARM64 */
>>> > >>
>>> > >>
>>> > >> --
>>> > >> 2.25.1
>>> > >>
>>> >
>>>
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