Generic implementation fails to remove breakpoints after init
when CONFIG_STRICT_KERNEL_RWX is selected:
[ 13.251285] KGDB: BP remove failed: c001c338
[ 13.259587] kgdbts: ERROR PUT: end of test buffer on 'do_fork_test' line 8 expected OK got $E14#aa
[ 13.268969] KGDB: re-enter exception: ALL breakpoints killed
[ 13.275099] CPU: 0 PID: 1 Comm: init Not tainted 4.18.0-g82bbb913ffd8 #860
[ 13.282836] Call Trace:
[ 13.285313] [c60e1ba0] [c0080ef0] kgdb_handle_exception+0x6f4/0x720 (unreliable)
[ 13.292618] [c60e1c30] [c000e97c] kgdb_handle_breakpoint+0x3c/0x98
[ 13.298709] [c60e1c40] [c000af54] program_check_exception+0x104/0x700
[ 13.305083] [c60e1c60] [c000e45c] ret_from_except_full+0x0/0x4
[ 13.310845] [c60e1d20] [c02a22ac] run_simple_test+0x2b4/0x2d4
[ 13.316532] [c60e1d30] [c0081698] put_packet+0xb8/0x158
[ 13.321694] [c60e1d60] [c00820b4] gdb_serial_stub+0x230/0xc4c
[ 13.327374] [c60e1dc0] [c0080af8] kgdb_handle_exception+0x2fc/0x720
[ 13.333573] [c60e1e50] [c000e928] kgdb_singlestep+0xb4/0xcc
[ 13.339068] [c60e1e70] [c000ae1c] single_step_exception+0x90/0xac
[ 13.345100] [c60e1e80] [c000e45c] ret_from_except_full+0x0/0x4
[ 13.350865] [c60e1f40] [c000e11c] ret_from_syscall+0x0/0x38
[ 13.356346] Kernel panic - not syncing: Recursive entry to debugger
This patch creates powerpc specific version of
kgdb_arch_set_breakpoint() and kgdb_arch_remove_breakpoint()
using patch_instruction()
Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs")
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/include/asm/kgdb.h | 5 ++++-
arch/powerpc/kernel/kgdb.c | 43 +++++++++++++++++++++++++++++++++--------
2 files changed, 39 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/include/asm/kgdb.h b/arch/powerpc/include/asm/kgdb.h
index 9db24e77b9f4..a9e098a3b881 100644
--- a/arch/powerpc/include/asm/kgdb.h
+++ b/arch/powerpc/include/asm/kgdb.h
@@ -26,9 +26,12 @@
#define BREAK_INSTR_SIZE 4
#define BUFMAX ((NUMREGBYTES * 2) + 512)
#define OUTBUFMAX ((NUMREGBYTES * 2) + 512)
+
+#define BREAK_INSTR 0x7d821008 /* twge r2, r2 */
+
static inline void arch_kgdb_breakpoint(void)
{
- asm(".long 0x7d821008"); /* twge r2, r2 */
+ asm(stringify_in_c(.long BREAK_INSTR));
}
#define CACHE_FLUSH_IS_SAFE 1
#define DBG_MAX_REG_NUM 70
diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index 35e240a0a408..59c578f865aa 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -24,6 +24,7 @@
#include <asm/processor.h>
#include <asm/machdep.h>
#include <asm/debug.h>
+#include <asm/code-patching.h>
#include <linux/slab.h>
/*
@@ -144,7 +145,7 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
if (kgdb_handle_exception(1, SIGTRAP, 0, regs) != 0)
return 0;
- if (*(u32 *) (regs->nip) == *(u32 *) (&arch_kgdb_ops.gdb_bpt_instr))
+ if (*(u32 *)regs->nip == BREAK_INSTR)
regs->nip += BREAK_INSTR_SIZE;
return 1;
@@ -441,16 +442,42 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
return -1;
}
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
+{
+ int err;
+ unsigned int instr;
+ unsigned int *addr = (unsigned int *)bpt->bpt_addr;
+
+ err = probe_kernel_address(addr, instr);
+ if (err)
+ return err;
+
+ err = patch_instruction(addr, BREAK_INSTR);
+ if (err)
+ return -EFAULT;
+
+ *(unsigned int *)bpt->saved_instr = instr;
+
+ return 0;
+}
+
+int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
+{
+ int err;
+ unsigned int instr = *(unsigned int *)bpt->saved_instr;
+ unsigned int *addr = (unsigned int *)bpt->bpt_addr;
+
+ err = patch_instruction(addr, instr);
+ if (err)
+ return -EFAULT;
+
+ return 0;
+}
+
/*
* Global data
*/
-struct kgdb_arch arch_kgdb_ops = {
-#ifdef __LITTLE_ENDIAN__
- .gdb_bpt_instr = {0x08, 0x10, 0x82, 0x7d},
-#else
- .gdb_bpt_instr = {0x7d, 0x82, 0x10, 0x08},
-#endif
-};
+struct kgdb_arch arch_kgdb_ops;
static int kgdb_not_implemented(struct pt_regs *regs)
{
--
2.13.3
On the below patch, checkpatch reports
WARNING: struct kgdb_arch should normally be const
#127: FILE: arch/powerpc/kernel/kgdb.c:480:
+struct kgdb_arch arch_kgdb_ops;
But when I add 'const', I get compilation failure
CC arch/powerpc/kernel/kgdb.o
arch/powerpc/kernel/kgdb.c:480:24: error: conflicting type qualifiers
for ‘arch_kgdb_ops’
const struct kgdb_arch arch_kgdb_ops;
^
In file included from arch/powerpc/kernel/kgdb.c:18:0:
./include/linux/kgdb.h:284:26: note: previous declaration of
‘arch_kgdb_ops’ was here
extern struct kgdb_arch arch_kgdb_ops;
^
make[1]: *** [arch/powerpc/kernel/kgdb.o] Error 1
Christophe
On 09/18/2018 09:26 AM, Christophe Leroy wrote:
> Generic implementation fails to remove breakpoints after init
> when CONFIG_STRICT_KERNEL_RWX is selected:
>
> [ 13.251285] KGDB: BP remove failed: c001c338
> [ 13.259587] kgdbts: ERROR PUT: end of test buffer on 'do_fork_test' line 8 expected OK got $E14#aa
> [ 13.268969] KGDB: re-enter exception: ALL breakpoints killed
> [ 13.275099] CPU: 0 PID: 1 Comm: init Not tainted 4.18.0-g82bbb913ffd8 #860
> [ 13.282836] Call Trace:
> [ 13.285313] [c60e1ba0] [c0080ef0] kgdb_handle_exception+0x6f4/0x720 (unreliable)
> [ 13.292618] [c60e1c30] [c000e97c] kgdb_handle_breakpoint+0x3c/0x98
> [ 13.298709] [c60e1c40] [c000af54] program_check_exception+0x104/0x700
> [ 13.305083] [c60e1c60] [c000e45c] ret_from_except_full+0x0/0x4
> [ 13.310845] [c60e1d20] [c02a22ac] run_simple_test+0x2b4/0x2d4
> [ 13.316532] [c60e1d30] [c0081698] put_packet+0xb8/0x158
> [ 13.321694] [c60e1d60] [c00820b4] gdb_serial_stub+0x230/0xc4c
> [ 13.327374] [c60e1dc0] [c0080af8] kgdb_handle_exception+0x2fc/0x720
> [ 13.333573] [c60e1e50] [c000e928] kgdb_singlestep+0xb4/0xcc
> [ 13.339068] [c60e1e70] [c000ae1c] single_step_exception+0x90/0xac
> [ 13.345100] [c60e1e80] [c000e45c] ret_from_except_full+0x0/0x4
> [ 13.350865] [c60e1f40] [c000e11c] ret_from_syscall+0x0/0x38
> [ 13.356346] Kernel panic - not syncing: Recursive entry to debugger
>
> This patch creates powerpc specific version of
> kgdb_arch_set_breakpoint() and kgdb_arch_remove_breakpoint()
> using patch_instruction()
>
> Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs")
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
> arch/powerpc/include/asm/kgdb.h | 5 ++++-
> arch/powerpc/kernel/kgdb.c | 43 +++++++++++++++++++++++++++++++++--------
> 2 files changed, 39 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kgdb.h b/arch/powerpc/include/asm/kgdb.h
> index 9db24e77b9f4..a9e098a3b881 100644
> --- a/arch/powerpc/include/asm/kgdb.h
> +++ b/arch/powerpc/include/asm/kgdb.h
> @@ -26,9 +26,12 @@
> #define BREAK_INSTR_SIZE 4
> #define BUFMAX ((NUMREGBYTES * 2) + 512)
> #define OUTBUFMAX ((NUMREGBYTES * 2) + 512)
> +
> +#define BREAK_INSTR 0x7d821008 /* twge r2, r2 */
> +
> static inline void arch_kgdb_breakpoint(void)
> {
> - asm(".long 0x7d821008"); /* twge r2, r2 */
> + asm(stringify_in_c(.long BREAK_INSTR));
> }
> #define CACHE_FLUSH_IS_SAFE 1
> #define DBG_MAX_REG_NUM 70
> diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
> index 35e240a0a408..59c578f865aa 100644
> --- a/arch/powerpc/kernel/kgdb.c
> +++ b/arch/powerpc/kernel/kgdb.c
> @@ -24,6 +24,7 @@
> #include <asm/processor.h>
> #include <asm/machdep.h>
> #include <asm/debug.h>
> +#include <asm/code-patching.h>
> #include <linux/slab.h>
>
> /*
> @@ -144,7 +145,7 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
> if (kgdb_handle_exception(1, SIGTRAP, 0, regs) != 0)
> return 0;
>
> - if (*(u32 *) (regs->nip) == *(u32 *) (&arch_kgdb_ops.gdb_bpt_instr))
> + if (*(u32 *)regs->nip == BREAK_INSTR)
> regs->nip += BREAK_INSTR_SIZE;
>
> return 1;
> @@ -441,16 +442,42 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
> return -1;
> }
>
> +int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
> +{
> + int err;
> + unsigned int instr;
> + unsigned int *addr = (unsigned int *)bpt->bpt_addr;
> +
> + err = probe_kernel_address(addr, instr);
> + if (err)
> + return err;
> +
> + err = patch_instruction(addr, BREAK_INSTR);
> + if (err)
> + return -EFAULT;
> +
> + *(unsigned int *)bpt->saved_instr = instr;
> +
> + return 0;
> +}
> +
> +int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
> +{
> + int err;
> + unsigned int instr = *(unsigned int *)bpt->saved_instr;
> + unsigned int *addr = (unsigned int *)bpt->bpt_addr;
> +
> + err = patch_instruction(addr, instr);
> + if (err)
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> /*
> * Global data
> */
> -struct kgdb_arch arch_kgdb_ops = {
> -#ifdef __LITTLE_ENDIAN__
> - .gdb_bpt_instr = {0x08, 0x10, 0x82, 0x7d},
> -#else
> - .gdb_bpt_instr = {0x7d, 0x82, 0x10, 0x08},
> -#endif
> -};
> +struct kgdb_arch arch_kgdb_ops;
>
> static int kgdb_not_implemented(struct pt_regs *regs)
> {
>
On Tue, 2018-09-18 at 09:33 +0000, Christophe Leroy wrote:
> On the below patch, checkpatch reports
>
> WARNING: struct kgdb_arch should normally be const
> #127: FILE: arch/powerpc/kernel/kgdb.c:480:
> +struct kgdb_arch arch_kgdb_ops;
>
> But when I add 'const', I get compilation failure
So don't add const.
checkpatch is stupid. You are not.
_Always_ take checkpatch bleats with very
large grains of salt.
Perhaps send a patch to remove kgbd_arch
from scripts/const_structs.checkpatch as
it seems not ever to be const.
Joe Perches <[email protected]> writes:
> On Tue, 2018-09-18 at 09:33 +0000, Christophe Leroy wrote:
>> On the below patch, checkpatch reports
>>
>> WARNING: struct kgdb_arch should normally be const
>> #127: FILE: arch/powerpc/kernel/kgdb.c:480:
>> +struct kgdb_arch arch_kgdb_ops;
>>
>> But when I add 'const', I get compilation failure
>
> So don't add const.
>
> checkpatch is stupid. You are not.
>
> _Always_ take checkpatch bleats with very
> large grains of salt.
>
> Perhaps send a patch to remove kgbd_arch
> from scripts/const_structs.checkpatch as
> it seems not ever to be const.
I think it could/should be const though, it just requires updating all
arches.
cheers
Le 20/09/2018 à 15:13, Michael Ellerman a écrit :
> Joe Perches <[email protected]> writes:
>
>> On Tue, 2018-09-18 at 09:33 +0000, Christophe Leroy wrote:
>>> On the below patch, checkpatch reports
>>>
>>> WARNING: struct kgdb_arch should normally be const
>>> #127: FILE: arch/powerpc/kernel/kgdb.c:480:
>>> +struct kgdb_arch arch_kgdb_ops;
>>>
>>> But when I add 'const', I get compilation failure
>>
>> So don't add const.
>>
>> checkpatch is stupid. You are not.
>>
>> _Always_ take checkpatch bleats with very
>> large grains of salt.
>>
>> Perhaps send a patch to remove kgbd_arch
>> from scripts/const_structs.checkpatch as
>> it seems not ever to be const.
>
> I think it could/should be const though, it just requires updating all
> arches.
>
Yes I was thinking about doing it, but first thing is to change the way
MIPS initialises it:
struct kgdb_arch arch_kgdb_ops;
int kgdb_arch_init(void)
{
union mips_instruction insn = {
.r_format = {
.opcode = spec_op,
.func = break_op,
}
};
memcpy(arch_kgdb_ops.gdb_bpt_instr, insn.byte, BREAK_INSTR_SIZE);
Can this be done staticaly ?
Christophe
Adding MIPS arch in the loop
On 09/20/2018 01:19 PM, Christophe LEROY wrote:
>
>
> Le 20/09/2018 à 15:13, Michael Ellerman a écrit :
>> Joe Perches <[email protected]> writes:
>>
>>> On Tue, 2018-09-18 at 09:33 +0000, Christophe Leroy wrote:
>>>> On the below patch, checkpatch reports
>>>>
>>>> WARNING: struct kgdb_arch should normally be const
>>>> #127: FILE: arch/powerpc/kernel/kgdb.c:480:
>>>> +struct kgdb_arch arch_kgdb_ops;
>>>>
>>>> But when I add 'const', I get compilation failure
>>>
>>> So don't add const.
>>>
>>> checkpatch is stupid. You are not.
>>>
>>> _Always_ take checkpatch bleats with very
>>> large grains of salt.
>>>
>>> Perhaps send a patch to remove kgbd_arch
>>> from scripts/const_structs.checkpatch as
>>> it seems not ever to be const.
>>
>> I think it could/should be const though, it just requires updating all
>> arches.
>>
>
> Yes I was thinking about doing it, but first thing is to change the way
> MIPS initialises it:
>
>
> struct kgdb_arch arch_kgdb_ops;
>
> int kgdb_arch_init(void)
> {
> union mips_instruction insn = {
> .r_format = {
> .opcode = spec_op,
> .func = break_op,
> }
> };
> memcpy(arch_kgdb_ops.gdb_bpt_instr, insn.byte, BREAK_INSTR_SIZE);
>
>
> Can this be done staticaly ?
>
> Christophe
Adding MIPS arch in the loop
On 09/20/2018 01:19 PM, Christophe LEROY wrote:
>
>
> Le 20/09/2018 à 15:13, Michael Ellerman a écrit :
>> Joe Perches <[email protected]> writes:
>>
>>> On Tue, 2018-09-18 at 09:33 +0000, Christophe Leroy wrote:
>>>> On the below patch, checkpatch reports
>>>>
>>>> WARNING: struct kgdb_arch should normally be const
>>>> #127: FILE: arch/powerpc/kernel/kgdb.c:480:
>>>> +struct kgdb_arch arch_kgdb_ops;
>>>>
>>>> But when I add 'const', I get compilation failure
>>>
>>> So don't add const.
>>>
>>> checkpatch is stupid. You are not.
>>>
>>> _Always_ take checkpatch bleats with very
>>> large grains of salt.
>>>
>>> Perhaps send a patch to remove kgbd_arch
>>> from scripts/const_structs.checkpatch as
>>> it seems not ever to be const.
>>
>> I think it could/should be const though, it just requires updating all
>> arches.
>>
>
> Yes I was thinking about doing it, but first thing is to change the way
> MIPS initialises it:
>
>
> struct kgdb_arch arch_kgdb_ops;
>
> int kgdb_arch_init(void)
> {
> union mips_instruction insn = {
> .r_format = {
> .opcode = spec_op,
> .func = break_op,
> }
> };
> memcpy(arch_kgdb_ops.gdb_bpt_instr, insn.byte, BREAK_INSTR_SIZE);
>
>
> Can this be done staticaly ?
>
> Christophe
Hi Christophe,
On Thu, Sep 20, 2018 at 01:23:55AM +0000, Christophe Leroy wrote:
> On 09/20/2018 01:19 PM, Christophe LEROY wrote:
> > Le 20/09/2018 ? 15:13, Michael Ellerman a ?crit?:
> > > Joe Perches <[email protected]> writes:
> > > > On Tue, 2018-09-18 at 09:33 +0000, Christophe Leroy wrote:
> > > > > On the below patch, checkpatch reports
> > > > >
> > > > > WARNING: struct kgdb_arch should normally be const
> > > > > #127: FILE: arch/powerpc/kernel/kgdb.c:480:
> > > > > +struct kgdb_arch arch_kgdb_ops;
> > > > >
> > > > > But when I add 'const', I get compilation failure
> > > >
> > > > So don't add const.
> > > >
> > > > checkpatch is stupid.? You are not.
> > > >
> > > > _Always_ take checkpatch bleats with very
> > > > large grains of salt.
> > > >
> > > > Perhaps send a patch to remove kgbd_arch
> > > > from scripts/const_structs.checkpatch as
> > > > it seems not ever to be const.
> > >
> > > I think it could/should be const though, it just requires updating all
> > > arches.
> > >
> >
> > Yes I was thinking about doing it, but first thing is to change the way
> > MIPS initialises it:
> >
> > struct kgdb_arch arch_kgdb_ops;
> >
> > int kgdb_arch_init(void)
> > {
> > ????union mips_instruction insn = {
> > ??????? .r_format = {
> > ??????????? .opcode = spec_op,
> > ??????????? .func??? = break_op,
> > ??????? }
> > ????};
> > ????memcpy(arch_kgdb_ops.gdb_bpt_instr, insn.byte, BREAK_INSTR_SIZE);
> >
> >
> > Can this be done staticaly ?
Something like this ought to do the trick:
diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c
index eb6c0d582626..31eff1bec577 100644
--- a/arch/mips/kernel/kgdb.c
+++ b/arch/mips/kernel/kgdb.c
@@ -394,18 +394,16 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
return -1;
}
-struct kgdb_arch arch_kgdb_ops;
+struct kgdb_arch arch_kgdb_ops = {
+#ifdef CONFIG_CPU_BIG_ENDIAN
+ .gdb_bpt_instr = { spec_op << 2, 0x00, 0x00, break_op },
+#else
+ .gdb_bpt_instr = { break_op, 0x00, 0x00, spec_op << 2 },
+#endif
+};
int kgdb_arch_init(void)
{
- union mips_instruction insn = {
- .r_format = {
- .opcode = spec_op,
- .func = break_op,
- }
- };
- memcpy(arch_kgdb_ops.gdb_bpt_instr, insn.byte, BREAK_INSTR_SIZE);
-
register_die_notifier(&kgdb_notifier);
return 0;
Thanks,
Paul
On Tue, 2018-09-18 at 09:26:03 UTC, Christophe Leroy wrote:
> Generic implementation fails to remove breakpoints after init
> when CONFIG_STRICT_KERNEL_RWX is selected:
>
> [ 13.251285] KGDB: BP remove failed: c001c338
> [ 13.259587] kgdbts: ERROR PUT: end of test buffer on 'do_fork_test' line 8 expected OK got $E14#aa
> [ 13.268969] KGDB: re-enter exception: ALL breakpoints killed
> [ 13.275099] CPU: 0 PID: 1 Comm: init Not tainted 4.18.0-g82bbb913ffd8 #860
> [ 13.282836] Call Trace:
> [ 13.285313] [c60e1ba0] [c0080ef0] kgdb_handle_exception+0x6f4/0x720 (unreliable)
> [ 13.292618] [c60e1c30] [c000e97c] kgdb_handle_breakpoint+0x3c/0x98
> [ 13.298709] [c60e1c40] [c000af54] program_check_exception+0x104/0x700
> [ 13.305083] [c60e1c60] [c000e45c] ret_from_except_full+0x0/0x4
> [ 13.310845] [c60e1d20] [c02a22ac] run_simple_test+0x2b4/0x2d4
> [ 13.316532] [c60e1d30] [c0081698] put_packet+0xb8/0x158
> [ 13.321694] [c60e1d60] [c00820b4] gdb_serial_stub+0x230/0xc4c
> [ 13.327374] [c60e1dc0] [c0080af8] kgdb_handle_exception+0x2fc/0x720
> [ 13.333573] [c60e1e50] [c000e928] kgdb_singlestep+0xb4/0xcc
> [ 13.339068] [c60e1e70] [c000ae1c] single_step_exception+0x90/0xac
> [ 13.345100] [c60e1e80] [c000e45c] ret_from_except_full+0x0/0x4
> [ 13.350865] [c60e1f40] [c000e11c] ret_from_syscall+0x0/0x38
> [ 13.356346] Kernel panic - not syncing: Recursive entry to debugger
>
> This patch creates powerpc specific version of
> kgdb_arch_set_breakpoint() and kgdb_arch_remove_breakpoint()
> using patch_instruction()
>
> Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs")
> Signed-off-by: Christophe Leroy <[email protected]>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/fb978ca207743badfe7efd9eebe68b
cheers