Currently, almost all archs (x86, arm64, mips...) support fast call
of crash_kexec() when "regs && kexec_should_crash()" is true. But
RISC-V not, it can only enter crash system via panic(). However panic()
doesn't pass the regs of the real accident scene to crash_kexec(),
it caused we can't get accurate backtrace via gdb,
$ riscv64-linux-gnu-gdb vmlinux vmcore
Reading symbols from vmlinux...
[New LWP 95]
#0 console_unlock () at kernel/printk/printk.c:2557
2557 if (do_cond_resched)
(gdb) bt
#0 console_unlock () at kernel/printk/printk.c:2557
#1 0x0000000000000000 in ?? ()
With the patch we can get the accurate backtrace,
$ riscv64-linux-gnu-gdb vmlinux vmcore
Reading symbols from vmlinux...
[New LWP 95]
#0 0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/test_crash.c:81
81 *(int *)p = 0xdead;
(gdb)
(gdb) bt
#0 0xffffffe00064d5c0 in test_thread (data=<optimized out>) at drivers/test_crash.c:81
#1 0x0000000000000000 in ?? ()
Test code to produce NULL address dereference in test_crash.c,
void *p = NULL;
*(int *)p = 0xdead;
Reviewed-by: Guo Ren <[email protected]>
Tested-by: Xianting Tian <[email protected]>
Signed-off-by: Xianting Tian <[email protected]>
---
Changes from v1:
- simplify the commit message
---
arch/riscv/kernel/traps.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index fe92e119e6a3..e666ebfa2a64 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -16,6 +16,7 @@
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/irq.h>
+#include <linux/kexec.h>
#include <asm/asm-prototypes.h>
#include <asm/bug.h>
@@ -44,6 +45,9 @@ void die(struct pt_regs *regs, const char *str)
ret = notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
+ if (regs && kexec_should_crash(current))
+ crash_kexec(regs);
+
bust_spinlocks(0);
add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
spin_unlock_irq(&die_lock);
--
2.17.1
On Mon, 06 Jun 2022 01:23:08 PDT (-0700), [email protected] wrote:
> Currently, almost all archs (x86, arm64, mips...) support fast call
> of crash_kexec() when "regs && kexec_should_crash()" is true. But
> RISC-V not, it can only enter crash system via panic(). However panic()
> doesn't pass the regs of the real accident scene to crash_kexec(),
> it caused we can't get accurate backtrace via gdb,
> $ riscv64-linux-gnu-gdb vmlinux vmcore
> Reading symbols from vmlinux...
> [New LWP 95]
> #0 console_unlock () at kernel/printk/printk.c:2557
> 2557 if (do_cond_resched)
> (gdb) bt
> #0 console_unlock () at kernel/printk/printk.c:2557
> #1 0x0000000000000000 in ?? ()
>
> With the patch we can get the accurate backtrace,
> $ riscv64-linux-gnu-gdb vmlinux vmcore
> Reading symbols from vmlinux...
> [New LWP 95]
> #0 0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/test_crash.c:81
> 81 *(int *)p = 0xdead;
> (gdb)
> (gdb) bt
> #0 0xffffffe00064d5c0 in test_thread (data=<optimized out>) at drivers/test_crash.c:81
> #1 0x0000000000000000 in ?? ()
>
> Test code to produce NULL address dereference in test_crash.c,
> void *p = NULL;
> *(int *)p = 0xdead;
>
> Reviewed-by: Guo Ren <[email protected]>
> Tested-by: Xianting Tian <[email protected]>
> Signed-off-by: Xianting Tian <[email protected]>
> ---
> Changes from v1:
> - simplify the commit message
> ---
> arch/riscv/kernel/traps.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index fe92e119e6a3..e666ebfa2a64 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -16,6 +16,7 @@
> #include <linux/mm.h>
> #include <linux/module.h>
> #include <linux/irq.h>
> +#include <linux/kexec.h>
>
> #include <asm/asm-prototypes.h>
> #include <asm/bug.h>
> @@ -44,6 +45,9 @@ void die(struct pt_regs *regs, const char *str)
>
> ret = notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
>
> + if (regs && kexec_should_crash(current))
> + crash_kexec(regs);
> +
> bust_spinlocks(0);
> add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
> spin_unlock_irq(&die_lock);
Thanks, this is on for-next.
在 2022/7/22 上午8:11, Palmer Dabbelt 写道:
> On Mon, 06 Jun 2022 01:23:08 PDT (-0700),
> [email protected] wrote:
>> Currently, almost all archs (x86, arm64, mips...) support fast call
>> of crash_kexec() when "regs && kexec_should_crash()" is true. But
>> RISC-V not, it can only enter crash system via panic(). However panic()
>> doesn't pass the regs of the real accident scene to crash_kexec(),
>> it caused we can't get accurate backtrace via gdb,
>> $ riscv64-linux-gnu-gdb vmlinux vmcore
>> Reading symbols from vmlinux...
>> [New LWP 95]
>> #0 console_unlock () at kernel/printk/printk.c:2557
>> 2557 if (do_cond_resched)
>> (gdb) bt
>> #0 console_unlock () at kernel/printk/printk.c:2557
>> #1 0x0000000000000000 in ?? ()
>>
>> With the patch we can get the accurate backtrace,
>> $ riscv64-linux-gnu-gdb vmlinux vmcore
>> Reading symbols from vmlinux...
>> [New LWP 95]
>> #0 0xffffffe00063a4e0 in test_thread (data=<optimized out>) at
>> drivers/test_crash.c:81
>> 81 *(int *)p = 0xdead;
>> (gdb)
>> (gdb) bt
>> #0 0xffffffe00064d5c0 in test_thread (data=<optimized out>) at
>> drivers/test_crash.c:81
>> #1 0x0000000000000000 in ?? ()
>>
>> Test code to produce NULL address dereference in test_crash.c,
>> void *p = NULL;
>> *(int *)p = 0xdead;
>>
>> Reviewed-by: Guo Ren <[email protected]>
>> Tested-by: Xianting Tian <[email protected]>
>> Signed-off-by: Xianting Tian <[email protected]>
>> ---
>> Changes from v1:
>> - simplify the commit message
>> ---
>> arch/riscv/kernel/traps.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
>> index fe92e119e6a3..e666ebfa2a64 100644
>> --- a/arch/riscv/kernel/traps.c
>> +++ b/arch/riscv/kernel/traps.c
>> @@ -16,6 +16,7 @@
>> #include <linux/mm.h>
>> #include <linux/module.h>
>> #include <linux/irq.h>
>> +#include <linux/kexec.h>
>>
>> #include <asm/asm-prototypes.h>
>> #include <asm/bug.h>
>> @@ -44,6 +45,9 @@ void die(struct pt_regs *regs, const char *str)
>>
>> ret = notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
>>
>> + if (regs && kexec_should_crash(current))
>> + crash_kexec(regs);
>> +
>> bust_spinlocks(0);
>> add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
>> spin_unlock_irq(&die_lock);
>
> Thanks, this is on for-next.
Palmer, thanks for the reply,
Last week, I commit a series of
patches(https://lkml.org/lkml/2022/7/17/64
<https://lkml.org/lkml/2022/7/17/64>), which contains this one.
This series of patches worked with crash-utility for RISCV64, Could you
please review it?
We expect 5.19 could support crash-utility, it is a good functionality.
crash-utility patches for RISCV64:
https://lore.kernel.org/all/[email protected]/
<https://lore.kernel.org/all/[email protected]/>