kdb: use correct pointer when 'btc' calls 'btt'

Message ID ff05bd36b338f4f914780176e9eba8138e1b254b.1536927765.git.christophe.leroy@c-s.fr
State New
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  • kdb: use correct pointer when 'btc' calls 'btt'
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Commit Message

Christophe LEROY Sept. 14, 2018, 12:35 p.m.
On a powerpc 8xx, 'btc' fails as follows:

Entering kdb (current=0x(ptrval), pid 282) due to Keyboard Entry
kdb> btc
btc: cpu status: Currently on cpu 0
Available cpus: 0
kdb_getarea: Bad address 0x0

when booting the kernel with 'debug_boot_weak_hash', it fails as well

Entering kdb (current=0xba99ad80, pid 284) due to Keyboard Entry
kdb> btc
btc: cpu status: Currently on cpu 0
Available cpus: 0
kdb_getarea: Bad address 0xba99ad80

On other platforms, Oopses have been observed too, see
https://github.com/linuxppc/linux/issues/139

This is due to btc calling 'btt' with %p pointer as an argument.

This patch replaces %p by %px to get the real pointer value as
expected by 'btt'

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: <stable@vger.kernel.org> # 4.15+
---
 kernel/debug/kdb/kdb_bt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Daniel Thompson Sept. 16, 2018, 7:06 p.m. | #1
On Fri, Sep 14, 2018 at 12:35:44PM +0000, Christophe Leroy wrote:
> On a powerpc 8xx, 'btc' fails as follows:
> 
> Entering kdb (current=0x(ptrval), pid 282) due to Keyboard Entry
> kdb> btc
> btc: cpu status: Currently on cpu 0
> Available cpus: 0
> kdb_getarea: Bad address 0x0
> 
> when booting the kernel with 'debug_boot_weak_hash', it fails as well
> 
> Entering kdb (current=0xba99ad80, pid 284) due to Keyboard Entry
> kdb> btc
> btc: cpu status: Currently on cpu 0
> Available cpus: 0
> kdb_getarea: Bad address 0xba99ad80
> 
> On other platforms, Oopses have been observed too, see
> https://github.com/linuxppc/linux/issues/139
> 
> This is due to btc calling 'btt' with %p pointer as an argument.
> 
> This patch replaces %p by %px to get the real pointer value as
> expected by 'btt'
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> Cc: <stable@vger.kernel.org> # 4.15+

Would a Fixes: be better here?
Fixes: ad67b74d2469d9b82 ("printk: hash addresses printed with %p")

No blame attached to Tobin, but the fixes makes it super clear what
changed and why this breaks kdb (which was not explicitly called out
the patch description).


Daniel.

> ---
>  kernel/debug/kdb/kdb_bt.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
> index 6ad4a9fcbd6f..7921ae4fca8d 100644
> --- a/kernel/debug/kdb/kdb_bt.c
> +++ b/kernel/debug/kdb/kdb_bt.c
> @@ -179,14 +179,14 @@ kdb_bt(int argc, const char **argv)
>  				kdb_printf("no process for cpu %ld\n", cpu);
>  				return 0;
>  			}
> -			sprintf(buf, "btt 0x%p\n", KDB_TSK(cpu));
> +			sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu));
>  			kdb_parse(buf);
>  			return 0;
>  		}
>  		kdb_printf("btc: cpu status: ");
>  		kdb_parse("cpu\n");
>  		for_each_online_cpu(cpu) {
> -			sprintf(buf, "btt 0x%p\n", KDB_TSK(cpu));
> +			sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu));
>  			kdb_parse(buf);
>  			touch_nmi_watchdog();
>  		}
> -- 
> 2.13.3
>
Tobin C. Harding Sept. 16, 2018, 10:18 p.m. | #2
On Sun, Sep 16, 2018 at 12:06:10PM -0700, Daniel Thompson wrote:
> On Fri, Sep 14, 2018 at 12:35:44PM +0000, Christophe Leroy wrote:
> > On a powerpc 8xx, 'btc' fails as follows:
> > 
> > Entering kdb (current=0x(ptrval), pid 282) due to Keyboard Entry
> > kdb> btc
> > btc: cpu status: Currently on cpu 0
> > Available cpus: 0
> > kdb_getarea: Bad address 0x0
> > 
> > when booting the kernel with 'debug_boot_weak_hash', it fails as well
> > 
> > Entering kdb (current=0xba99ad80, pid 284) due to Keyboard Entry
> > kdb> btc
> > btc: cpu status: Currently on cpu 0
> > Available cpus: 0
> > kdb_getarea: Bad address 0xba99ad80
> > 
> > On other platforms, Oopses have been observed too, see
> > https://github.com/linuxppc/linux/issues/139
> > 
> > This is due to btc calling 'btt' with %p pointer as an argument.
> > 
> > This patch replaces %p by %px to get the real pointer value as
> > expected by 'btt'
> > 
> > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> > Cc: <stable@vger.kernel.org> # 4.15+
> 
> Would a Fixes: be better here?
> Fixes: ad67b74d2469d9b82 ("printk: hash addresses printed with %p")
> 
> No blame attached to Tobin, but the fixes makes it super clear what

:)

> changed and why this breaks kdb (which was not explicitly called out
> the patch description).
> 
> 
> Daniel.

Patch

diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
index 6ad4a9fcbd6f..7921ae4fca8d 100644
--- a/kernel/debug/kdb/kdb_bt.c
+++ b/kernel/debug/kdb/kdb_bt.c
@@ -179,14 +179,14 @@  kdb_bt(int argc, const char **argv)
 				kdb_printf("no process for cpu %ld\n", cpu);
 				return 0;
 			}
-			sprintf(buf, "btt 0x%p\n", KDB_TSK(cpu));
+			sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu));
 			kdb_parse(buf);
 			return 0;
 		}
 		kdb_printf("btc: cpu status: ");
 		kdb_parse("cpu\n");
 		for_each_online_cpu(cpu) {
-			sprintf(buf, "btt 0x%p\n", KDB_TSK(cpu));
+			sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu));
 			kdb_parse(buf);
 			touch_nmi_watchdog();
 		}