On Fri, May 31, 2024 at 5:30 PM <devel-requ...@lists.crash-utility.osci.io>
wrote:
> Date: Fri, 31 May 2024 17:19:30 +0800
> From: Tao Liu <l...@redhat.com>
> Subject: [Crash-utility] [PATCH v4 07/16] Stop stack unwinding at
> non-kernel address
> To: devel@lists.crash-utility.osci.io
> Cc: Mahesh J Salgaonkar <mah...@linux.ibm.com>, "Naveen N . Rao"
> <naveen.n....@linux.vnet.ibm.com>, Lianbo Jiang <
> liji...@redhat.com>,
> Alexey Makhalov <alexey.makha...@broadcom.com>
> Message-ID: <20240531091939.97828-8-l...@redhat.com>
> Content-Type: text/plain; charset=UTF-8
>
> The stack unwinding is for kernel addresses only. If non-kernel address
> encountered, it is usually a user space address, or non-address value
> like a function call parameter. So stopping stack unwinding at non-kernel
> address will decrease the invalid unwind results.
>
> Before:
> crash> gdb bt
> #0 0xffffffff816a8f65 in context_switch ...
> #1 __schedule () ...
> #2 0xffffffff816a94e9 in schedule ...
> #3 0xffffffff816a86fd in schedule_hrtimeout_range_clock ...
> #4 0xffffffff816a8733 in schedule_hrtimeout_range ...
> #5 0xffffffff8124bb7e in ep_poll ...
> #6 0xffffffff8124d00d in SYSC_epoll_wait ...
> #7 SyS_epoll_wait ...
> #8 <signal handler called>
> #9 0x00007f0449407923 in ?? ()
> #10 0xffff880100000001 in ?? ()
> #11 0xffff880169b3c010 in ?? ()
> #12 0x0000000000000040 in irq_stack_union ()
> #13 0xffff880169b3c058 in ?? ()
> #14 0xffff880169b3c048 in ?? ()
> #15 0xffff880169b3c050 in ?? ()
> #16 0x0000000000000000 in ?? ()
>
> After:
> crash> gdb bt
> #0 0xffffffff816a8f65 in context_switch ...
> #1 __schedule () ...
> #2 0xffffffff816a94e9 in schedule () ...
> #3 0xffffffff816a86fd in schedule_hrtimeout_range_clock ...
> #4 0xffffffff816a8733 in schedule_hrtimeout_range ...
> #5 0xffffffff8124bb7e in ep_poll ...
> #6 0xffffffff8124d00d in SYSC_epoll_wait ...
> #7 SyS_epoll_wait ...
> #8 <signal handler called>
> #9 0x00007f0449407923 in ?? ()
>
>
It seems that there are still some non-kernel addresses that do not get
filtered. Can you help double check?
For example:
crash> gdb bt
#0 crash_setup_regs (newregs=0xffffb5bb4f197938, oldregs=0x0) at
./arch/x86/include/asm/kexec.h:114
#1 0xffffffff8e61e32e in __crash_kexec (regs=regs@entry=0x0) at
kernel/crash_core.c:122
#2 0xffffffff8e51a64d in panic (fmt=fmt@entry=0xffffffff8fa51609 "sysrq
triggered crash\n") at kernel/panic.c:366
#3 0xffffffff8ec21f86 in sysrq_handle_crash (key=<optimized out>) at
drivers/tty/sysrq.c:154
#4 0xffffffff8ec22550 in __handle_sysrq (key=<optimized out>,
check_mask=check_mask@entry=false) at drivers/tty/sysrq.c:612
#5 0xffffffff8ec22bf5 in write_sysrq_trigger (file=<optimized out>,
buf=<optimized out>, count=2, ppos=<optimized out>) at
drivers/tty/sysrq.c:1183
#6 0xffffffff8e935ae5 in pde_write (ppos=<optimized out>, count=<optimized
out>, buf=<optimized out>, file=0xffffb5bb4f197938, pde=0xffff98338b78e0c0)
at fs/proc/inode.c:334
#7 proc_reg_write (file=0xffffb5bb4f197938, buf=0x0, count=1, ppos=0x0) at
fs/proc/inode.c:346
#8 0xffffffff8e88d382 in vfs_write (file=file@entry=0xffff98338b789200,
buf=buf@entry=0x5614d58a22c0 <error: Cannot access memory at address
0x5614d58a22c0>, count=count@entry=2, pos=pos@entry=0xffffb5bb4f197b78) at
fs/read_write.c:588
#9 0xffffffff8e88d9ff in ksys_write (fd=<optimized out>,
buf=0x5614d58a22c0 <error: Cannot access memory at address 0x5614d58a22c0>,
count=2) at fs/read_write.c:643
#10 0xffffffff8f124429 in do_syscall_x64 (nr=1, regs=0xffffb5bb4f197f58) at
arch/x86/entry/common.c:52
#11 do_syscall_64 (regs=0xffffb5bb4f197f58, nr=1) at
arch/x86/entry/common.c:83
#12 0xffffffff8f20012b in entry_SYSCALL_64 () at
arch/x86/entry/entry_64.S:121
#13 0x00007f9a147f69e0 in ?? ()
The frame #13 looks like a non-kernel address.
Thanks
Lianbo
> Cc: Sourabh Jain <sourabhj...@linux.ibm.com>
> Cc: Hari Bathini <hbath...@linux.ibm.com>
> Cc: Mahesh J Salgaonkar <mah...@linux.ibm.com>
> Cc: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> Cc: Lianbo Jiang <liji...@redhat.com>
> Cc: HAGIO KAZUHITO(萩尾 一仁) <k-hagio...@nec.com>
> Cc: Tao Liu <l...@redhat.com>
> Cc: Alexey Makhalov <alexey.makha...@broadcom.com>
> Signed-off-by: Tao Liu <l...@redhat.com>
> ---
> defs.h | 1 +
> gdb-10.2.patch | 26 ++++++++++++++++++++++++++
> gdb_interface.c | 6 ++++++
> 3 files changed, 33 insertions(+)
>
> diff --git a/defs.h b/defs.h
> index 012ffdc..c0e6a29 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -7902,6 +7902,7 @@ extern unsigned char *gdb_prettyprint_arrays;
> extern unsigned int *gdb_repeat_count_threshold;
> extern unsigned char *gdb_stop_print_at_null;
> extern unsigned int *gdb_output_radix;
> +int is_kvaddr(ulong);
>
> /*
> * gdb/top.c
> diff --git a/gdb-10.2.patch b/gdb-10.2.patch
> index 0bed96a..3ed40c0 100644
> --- a/gdb-10.2.patch
> +++ b/gdb-10.2.patch
> @@ -16171,3 +16171,29 @@ exit 0
> }
>
> /*
> +--- gdb-10.2/gdb/frame.c.orig
> ++++ gdb-10.2/gdb/frame.c
> +@@ -2331,6 +2331,10 @@ inside_entry_func (frame_info *this_frame)
> + This function should not contain target-dependent tests, such as
> + checking whether the program-counter is zero. */
> +
> ++#ifdef CRASH_MERGE
> ++extern "C" int is_kvaddr(ulong);
> ++#endif
> ++
> + struct frame_info *
> + get_prev_frame (struct frame_info *this_frame)
> + {
> +@@ -2353,7 +2357,11 @@ get_prev_frame (struct frame_info *this_frame)
> + get_frame_id (this_frame);
> +
> + frame_pc_p = get_frame_pc_if_available (this_frame, &frame_pc);
> +-
> ++#ifdef CRASH_MERGE
> ++ if (!is_kvaddr(frame_pc)) {
> ++ return NULL;
> ++ }
> ++#endif
> + /* tausq/2004-12-07: Dummy frames are skipped because it doesn't make
> much
> + sense to stop unwinding at a dummy frame. One place where a dummy
> + frame may have an address "inside_main_func" is on HPUX. On HPUX,
> the
> diff --git a/gdb_interface.c b/gdb_interface.c
> index b13d5fd..e76ecc6 100644
> --- a/gdb_interface.c
> +++ b/gdb_interface.c
> @@ -947,6 +947,12 @@ gdb_lookup_module_symbol(ulong addr, ulong *offset)
> }
> }
>
> +int
> +is_kvaddr(ulong addr)
> +{
> + return IS_KVADDR(addr);
> +}
> +
> /*
> * Used by gdb_interface() to catch gdb-related errors, if desired.
> */
> --
> 2.40.1
>
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