Commit 940d4113f330 ("sh: New gcc support") added new shift helpers
that use r4 as a scratch register while dispatching to the selected shift
sequence. But, the helpers return without restoring r4. With GCC 17, the
register allocator can keep a live value in r4 across the helper call.
Clobbering it results in runtime data corruption. Restore r4 before
jumping to the selected shift sequence.
Fixes: 940d4113f330 ("sh: New gcc support")
Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
---
Without the patch, the early boot on e.g J2 gets a kernel BUG at
mm/percpu.c:2604 / "can't handle more than one group."
PCPU_SETUP_BUG_ON(pcpu_verify_alloc_info(ai) < 0);
As the static condition in mm/percpu-km.c wasn't true:
ai->nr_groups != 1
nr_groups contained 60 - the clobbered value from the shift helper.
This change was tested on the J2 core on the Mimas v2 board. It can
theoretically also target other SH2 devices, but I don't have any other
than J2 sadly.
The flow of operations matches now the state in the libgcc, see also
in gcc: libgcc/config/sh/lib1funcs.S
---
arch/sh/lib/ashlsi3.S | 3 ++-
arch/sh/lib/ashrsi3.S | 3 ++-
arch/sh/lib/lshrsi3.S | 3 ++-
3 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/sh/lib/ashlsi3.S b/arch/sh/lib/ashlsi3.S
index 4df4401cdf31..73a9d709b169 100644
--- a/arch/sh/lib/ashlsi3.S
+++ b/arch/sh/lib/ashlsi3.S
@@ -63,8 +63,9 @@ __ashlsi3_r0:
mova ashlsi3_table,r0
mov.b @(r0,r4),r4
add r4,r0
+ mov.l @r15+,r4
jmp @r0
- mov.l @r15+,r0
+ mov r4,r0
.align 2
ashlsi3_table:
diff --git a/arch/sh/lib/ashrsi3.S b/arch/sh/lib/ashrsi3.S
index bf3c4e03e6ff..9962d7c587df 100644
--- a/arch/sh/lib/ashrsi3.S
+++ b/arch/sh/lib/ashrsi3.S
@@ -62,8 +62,9 @@ __ashrsi3_r0:
mova ashrsi3_table,r0
mov.b @(r0,r4),r4
add r4,r0
+ mov.l @r15+,r4
jmp @r0
- mov.l @r15+,r0
+ mov r4,r0
.align 2
ashrsi3_table:
diff --git a/arch/sh/lib/lshrsi3.S b/arch/sh/lib/lshrsi3.S
index b79b8170061f..9218f0bad1cc 100644
--- a/arch/sh/lib/lshrsi3.S
+++ b/arch/sh/lib/lshrsi3.S
@@ -62,8 +62,9 @@ __lshrsi3_r0:
mova lshrsi3_table,r0
mov.b @(r0,r4),r4
add r4,r0
+ mov.l @r15+,r4
jmp @r0
- mov.l @r15+,r0
+ mov r4,r0
.align 2
lshrsi3_table:
--
2.43.0