While r15 is clobbered always with PPC_FTRACE_OUT_OF_LINE, it is not restored in livepatch sequence leading to not so obvious fails like below:
BUG: Unable to handle kernel data access on write at 0xc0000000000f9078 Faulting instruction address: 0xc0000000018ff958 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP: c0000000018ff958 LR: c0000000018ff930 CTR: c0000000009c0790 REGS: c00000005f2e7790 TRAP: 0300 Tainted: G K (6.14.0+) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 2822880b XER: 20040000 CFAR: c0000000008addc0 DAR: c0000000000f9078 DSISR: 0a000000 IRQMASK: 1 GPR00: c0000000018f2584 c00000005f2e7a30 c00000000280a900 c000000017ffa488 GPR04: 0000000000000008 0000000000000000 c0000000018f24fc 000000000000000d GPR08: fffffffffffe0000 000000000000000d 0000000000000000 0000000000008000 GPR12: c0000000009c0790 c000000017ffa480 c00000005f2e7c78 c0000000000f9070 GPR16: c00000005f2e7c90 0000000000000000 0000000000000000 0000000000000000 GPR20: 0000000000000000 c00000005f3efa80 c00000005f2e7c60 c00000005f2e7c88 GPR24: c00000005f2e7c60 0000000000000001 c0000000000f9078 0000000000000000 GPR28: 00007fff97960000 c000000017ffa480 0000000000000000 c0000000000f9078 ... Call Trace: check_heap_object+0x34/0x390 (unreliable) __mutex_unlock_slowpath.isra.0+0xe4/0x230 seq_read_iter+0x430/0xa90 proc_reg_read_iter+0xa4/0x200 vfs_read+0x41c/0x510 ksys_read+0xa4/0x190 system_call_exception+0x1d0/0x440 system_call_vectored_common+0x15c/0x2ec
Fix it by restoring r15 always.
Fixes: eec37961a56a ("powerpc64/ftrace: Move ftrace sequence out of line") Reported-by: Viktor Malik vmalik@redhat.com Closes: https://lore.kernel.org/lkml/1aec4a9a-a30b-43fd-b303-7a351caeccb7@redhat.com Cc: stable@vger.kernel.org # v6.13+ Signed-off-by: Hari Bathini hbathini@linux.ibm.com --- arch/powerpc/kernel/trace/ftrace_entry.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S index 2c1b24100eca..3565c67fc638 100644 --- a/arch/powerpc/kernel/trace/ftrace_entry.S +++ b/arch/powerpc/kernel/trace/ftrace_entry.S @@ -212,10 +212,10 @@ bne- 1f
mr r3, r15 +1: mtlr r3 .if \allregs == 0 REST_GPR(15, r1) .endif -1: mtlr r3 #endif
/* Restore gprs */
On 4/16/25 21:12, Hari Bathini wrote:
While r15 is clobbered always with PPC_FTRACE_OUT_OF_LINE, it is not restored in livepatch sequence leading to not so obvious fails like below:
BUG: Unable to handle kernel data access on write at 0xc0000000000f9078 Faulting instruction address: 0xc0000000018ff958 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP: c0000000018ff958 LR: c0000000018ff930 CTR: c0000000009c0790 REGS: c00000005f2e7790 TRAP: 0300 Tainted: G K (6.14.0+) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 2822880b XER: 20040000 CFAR: c0000000008addc0 DAR: c0000000000f9078 DSISR: 0a000000 IRQMASK: 1 GPR00: c0000000018f2584 c00000005f2e7a30 c00000000280a900 c000000017ffa488 GPR04: 0000000000000008 0000000000000000 c0000000018f24fc 000000000000000d GPR08: fffffffffffe0000 000000000000000d 0000000000000000 0000000000008000 GPR12: c0000000009c0790 c000000017ffa480 c00000005f2e7c78 c0000000000f9070 GPR16: c00000005f2e7c90 0000000000000000 0000000000000000 0000000000000000 GPR20: 0000000000000000 c00000005f3efa80 c00000005f2e7c60 c00000005f2e7c88 GPR24: c00000005f2e7c60 0000000000000001 c0000000000f9078 0000000000000000 GPR28: 00007fff97960000 c000000017ffa480 0000000000000000 c0000000000f9078 ... Call Trace: check_heap_object+0x34/0x390 (unreliable) __mutex_unlock_slowpath.isra.0+0xe4/0x230 seq_read_iter+0x430/0xa90 proc_reg_read_iter+0xa4/0x200 vfs_read+0x41c/0x510 ksys_read+0xa4/0x190 system_call_exception+0x1d0/0x440 system_call_vectored_common+0x15c/0x2ec
Fix it by restoring r15 always.
Fixes: eec37961a56a ("powerpc64/ftrace: Move ftrace sequence out of line") Reported-by: Viktor Malik vmalik@redhat.com Closes: https://lore.kernel.org/lkml/1aec4a9a-a30b-43fd-b303-7a351caeccb7@redhat.com Cc: stable@vger.kernel.org # v6.13+ Signed-off-by: Hari Bathini hbathini@linux.ibm.com
After applying the patch, the panic doesn't happen anymore and livepatch works as expected.
Thanks!
Tested-by: Viktor Malik vmalik@redhat.com
arch/powerpc/kernel/trace/ftrace_entry.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S index 2c1b24100eca..3565c67fc638 100644 --- a/arch/powerpc/kernel/trace/ftrace_entry.S +++ b/arch/powerpc/kernel/trace/ftrace_entry.S @@ -212,10 +212,10 @@ bne- 1f mr r3, r15 +1: mtlr r3 .if \allregs == 0 REST_GPR(15, r1) .endif -1: mtlr r3 #endif /* Restore gprs */
On Thu, Apr 17, 2025 at 12:42:27AM +0530, Hari Bathini wrote:
While r15 is clobbered always with PPC_FTRACE_OUT_OF_LINE, it is not restored in livepatch sequence leading to not so obvious fails like below:
BUG: Unable to handle kernel data access on write at 0xc0000000000f9078 Faulting instruction address: 0xc0000000018ff958 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP: c0000000018ff958 LR: c0000000018ff930 CTR: c0000000009c0790 REGS: c00000005f2e7790 TRAP: 0300 Tainted: G K (6.14.0+) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 2822880b XER: 20040000 CFAR: c0000000008addc0 DAR: c0000000000f9078 DSISR: 0a000000 IRQMASK: 1 GPR00: c0000000018f2584 c00000005f2e7a30 c00000000280a900 c000000017ffa488 GPR04: 0000000000000008 0000000000000000 c0000000018f24fc 000000000000000d GPR08: fffffffffffe0000 000000000000000d 0000000000000000 0000000000008000 GPR12: c0000000009c0790 c000000017ffa480 c00000005f2e7c78 c0000000000f9070 GPR16: c00000005f2e7c90 0000000000000000 0000000000000000 0000000000000000 GPR20: 0000000000000000 c00000005f3efa80 c00000005f2e7c60 c00000005f2e7c88 GPR24: c00000005f2e7c60 0000000000000001 c0000000000f9078 0000000000000000 GPR28: 00007fff97960000 c000000017ffa480 0000000000000000 c0000000000f9078 ... Call Trace: check_heap_object+0x34/0x390 (unreliable) __mutex_unlock_slowpath.isra.0+0xe4/0x230 seq_read_iter+0x430/0xa90 proc_reg_read_iter+0xa4/0x200 vfs_read+0x41c/0x510 ksys_read+0xa4/0x190 system_call_exception+0x1d0/0x440 system_call_vectored_common+0x15c/0x2ec
Fix it by restoring r15 always.
Fixes: eec37961a56a ("powerpc64/ftrace: Move ftrace sequence out of line") Reported-by: Viktor Malik vmalik@redhat.com Closes: https://lore.kernel.org/lkml/1aec4a9a-a30b-43fd-b303-7a351caeccb7@redhat.com Cc: stable@vger.kernel.org # v6.13+ Signed-off-by: Hari Bathini hbathini@linux.ibm.com
arch/powerpc/kernel/trace/ftrace_entry.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S index 2c1b24100eca..3565c67fc638 100644 --- a/arch/powerpc/kernel/trace/ftrace_entry.S +++ b/arch/powerpc/kernel/trace/ftrace_entry.S @@ -212,10 +212,10 @@ bne- 1f mr r3, r15 +1: mtlr r3 .if \allregs == 0 REST_GPR(15, r1) .endif -1: mtlr r3 #endif
LGTM. Acked-by: Naveen N Rao (AMD) naveen@kernel.org
- Naveen
linux-stable-mirror@lists.linaro.org
-
Hari Bathini -
Naveen N Rao -
Viktor Malik