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="" 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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