[PATCH 0/3] s390/probes: Various fixes

[PATCH 0/3] s390/probes: Various fixes

[Heiko Carstens]

Fix various bugs in uprobes/kprobes instruction fixup handling:

- For cgrb a wrong (non existing) opcode is used for comparison
- Handling for bctgr and bic instructions is missing
- Wrong comment for clgib

Thanks,
Heiko

Heiko Carstens (3):
  s390/probes: Fix wrong opcode for cgrb fixup
  s390/probes: Add missing fixup for bctgr and bic
  s390/probes: Fix wrong mnemonic comment for clgib

 arch/s390/lib/probes.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

-- 
2.53.0

[PATCH 1/3] s390/probes: Fix wrong opcode for cgrb fixup

[Heiko Carstens]

The last byte of the cgrb instruction is 0xe4, however the probes code
compares against 0xe6. Fix it.

Fixes: 6b169ac9b434 ("s390/kprobes: add support for compare and branch instructions")
Cc: stable@vger.kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/lib/probes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/lib/probes.c b/arch/s390/lib/probes.c
index 1e184a03442d..049300b68ddd 100644
--- a/arch/s390/lib/probes.c
+++ b/arch/s390/lib/probes.c
@@ -99,8 +99,8 @@ int probe_get_fixup_type(u16 *insn)
 		break;
 	case 0xec:
 		switch (insn[2] & 0xff) {
+		case 0xe4: /* cgrb  */
 		case 0xe5: /* clgrb */
-		case 0xe6: /* cgrb  */
 		case 0xf6: /* crb   */
 		case 0xf7: /* clrb  */
 		case 0xfc: /* cgib  */
-- 
2.53.0

[PATCH 2/3] s390/probes: Add missing fixup for bctgr and bic

[Heiko Carstens]

For the bctgr and bic instructions the probes fixup is missing.
For both instructions the instruction address must only be fixed up
if the branch is not taken. If the branch is taken the instruction
address is already correct.

Return FIXUP_BRANCH_NOT_TAKEN instead of the default FIXUP_PSW_NORMAL
to reflect that.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/lib/probes.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/s390/lib/probes.c b/arch/s390/lib/probes.c
index 049300b68ddd..3e7654223b05 100644
--- a/arch/s390/lib/probes.c
+++ b/arch/s390/lib/probes.c
@@ -77,6 +77,10 @@ int probe_get_fixup_type(u16 *insn)
 		if ((insn[0] & 0xff) == 0xb2)
 			fixup = FIXUP_NOT_REQUIRED;
 		break;
+	case 0xb9:	/* bctgr */
+		if ((insn[0] & 0xff) == 0x46)
+			fixup = FIXUP_BRANCH_NOT_TAKEN;
+		break;
 	case 0xa7:	/* bras	*/
 		if ((insn[0] & 0x0f) == 0x05)
 			fixup |= FIXUP_RETURN_REGISTER;
@@ -85,6 +89,14 @@ int probe_get_fixup_type(u16 *insn)
 		if ((insn[0] & 0x0f) == 0x05)	/* brasl */
 			fixup |= FIXUP_RETURN_REGISTER;
 		break;
+	case 0xe3:
+		switch (insn[2] & 0xff) {
+		case 0x46: /* bctg */
+		case 0x47: /* bic  */
+			fixup = FIXUP_BRANCH_NOT_TAKEN;
+			break;
+		}
+		break;
 	case 0xeb:
 		switch (insn[2] & 0xff) {
 		case 0x44: /* bxhg  */
@@ -93,10 +105,6 @@ int probe_get_fixup_type(u16 *insn)
 			break;
 		}
 		break;
-	case 0xe3:	/* bctg	*/
-		if ((insn[2] & 0xff) == 0x46)
-			fixup = FIXUP_BRANCH_NOT_TAKEN;
-		break;
 	case 0xec:
 		switch (insn[2] & 0xff) {
 		case 0xe4: /* cgrb  */
-- 
2.53.0

[PATCH 3/3] s390/probes: Fix wrong mnemonic comment for clgib

[Heiko Carstens]

There is no cglib instruction; the correct mnemonic is clgib.
Fix the comment.

Fixes: 6b169ac9b434 ("s390/kprobes: add support for compare and branch instructions")
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/lib/probes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/lib/probes.c b/arch/s390/lib/probes.c
index 3e7654223b05..66221ec16822 100644
--- a/arch/s390/lib/probes.c
+++ b/arch/s390/lib/probes.c
@@ -112,7 +112,7 @@ int probe_get_fixup_type(u16 *insn)
 		case 0xf6: /* crb   */
 		case 0xf7: /* clrb  */
 		case 0xfc: /* cgib  */
-		case 0xfd: /* cglib */
+		case 0xfd: /* clgib */
 		case 0xfe: /* cib   */
 		case 0xff: /* clib  */
 			fixup = FIXUP_BRANCH_NOT_TAKEN;
-- 
2.53.0

Re: [PATCH 3/3] s390/probes: Fix wrong mnemonic comment for clgib

[sashiko-bot]

> There is no cglib instruction; the correct mnemonic is clgib.
> Fix the comment.
> 
> Fixes: 6b169ac9b434 ("s390/kprobes: add support for compare and branch instructions")
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261012083629.2109206-1-hca@linux.ibm.com?part=3

Re: [PATCH 1/3] s390/probes: Fix wrong opcode for cgrb fixup

[sashiko-bot]

> The last byte of the cgrb instruction is 0xe4, however the probes code
> compares against 0xe6. Fix it.
> 
> Fixes: 6b169ac9b434 ("s390/kprobes: add support for compare and branch instructions")
> Cc: stable@vger.kernel.org
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261012083629.2109206-1-hca@linux.ibm.com?part=1

Re: [PATCH 2/3] s390/probes: Add missing fixup for bctgr and bic

[sashiko-bot]

> For the bctgr and bic instructions the probes fixup is missing.
> For both instructions the instruction address must only be fixed up
> if the branch is not taken. If the branch is taken the instruction
> address is already correct.
> 
> Return FIXUP_BRANCH_NOT_TAKEN instead of the default FIXUP_PSW_NORMAL
> to reflect that.
> 
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261012083629.2109206-1-hca@linux.ibm.com?part=2