[PATCH 6.8 051/336] s390/vdso: Add CFI for RA register to asm macro vdso_func

Greg Kroah-Hartman
2024-05-14T10:26:18Z

From: Jens Remus <jremus@linux.ibm.com>

[ Upstream commit b961ec10b9f9719987470236feb50c967db5a652 ]

The return-address (RA) register r14 is specified as volatile in the
s390x ELF ABI [1]. Nevertheless proper CFI directives must be provided
for an unwinder to restore the return address, if the RA register
value is changed from its value at function entry, as it is the case.

[1]: s390x ELF ABI, https://github.com/IBM/s390x-abi/releases

Fixes: 4bff8cb54502 ("s390: convert to GENERIC_VDSO")
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/include/asm/dwarf.h | 1 +
arch/s390/kernel/vdso64/vdso_user_wrapper.S | 2 ++
2 files changed, 3 insertions(+)

diff --git a/arch/s390/include/asm/dwarf.h b/arch/s390/include/asm/dwarf.h
index 4f21ae561e4dd..390906b8e386e 100644
--- a/arch/s390/include/asm/dwarf.h
+++ b/arch/s390/include/asm/dwarf.h
@@ -9,6 +9,7 @@
#define CFI_DEF_CFA_OFFSET .cfi_def_cfa_offset
#define CFI_ADJUST_CFA_OFFSET .cfi_adjust_cfa_offset
#define CFI_RESTORE .cfi_restore
+#define CFI_REL_OFFSET .cfi_rel_offset

#ifdef CONFIG_AS_CFI_VAL_OFFSET
#define CFI_VAL_OFFSET .cfi_val_offset
diff --git a/arch/s390/kernel/vdso64/vdso_user_wrapper.S b/arch/s390/kernel/vdso64/vdso_user_wrapper.S
index 57f62596e53b9..85247ef5a41b8 100644
--- a/arch/s390/kernel/vdso64/vdso_user_wrapper.S
+++ b/arch/s390/kernel/vdso64/vdso_user_wrapper.S
@@ -24,8 +24,10 @@ __kernel_\func:
CFI_DEF_CFA_OFFSET (STACK_FRAME_OVERHEAD + WRAPPER_FRAME_SIZE)
CFI_VAL_OFFSET 15, -STACK_FRAME_OVERHEAD
stg %r14,STACK_FRAME_OVERHEAD(%r15)
+ CFI_REL_OFFSET 14, STACK_FRAME_OVERHEAD
brasl %r14,__s390_vdso_\func
lg %r14,STACK_FRAME_OVERHEAD(%r15)
+ CFI_RESTORE 14
aghi %r15,WRAPPER_FRAME_SIZE
CFI_DEF_CFA_OFFSET STACK_FRAME_OVERHEAD
CFI_RESTORE 15
--
2.43.0