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Message-ID: <20250710163522.3195293-14-jremus@linux.ibm.com>
Date: Thu, 10 Jul 2025 18:35:19 +0200
From: Jens Remus <jremus@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
bpf@...r.kernel.org, x86@...nel.org,
Steven Rostedt <rostedt@...nel.org>
Cc: Jens Remus <jremus@...ux.ibm.com>, Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Ilya Leoshkevich <iii@...ux.ibm.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Andrii Nakryiko <andrii@...nel.org>,
Indu Bhagat <indu.bhagat@...cle.com>,
"Jose E. Marchesi" <jemarch@....org>,
Beau Belgrave <beaub@...ux.microsoft.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Jens Axboe <axboe@...nel.dk>, Florian Weimer <fweimer@...hat.com>,
Sam James <sam@...too.org>
Subject: [RFC PATCH v1 13/16] s390/unwind_user/backchain: Enable HAVE_UNWIND_USER_BACKCHAIN
Enable unwinding of user space using back chain on s390. Based on
arch_stack_walk_user_common() in arch/s390/kernel/stacktrace.c.
Signed-off-by: Jens Remus <jremus@...ux.ibm.com>
---
arch/s390/Kconfig | 1 +
arch/s390/include/asm/unwind_user_backchain.h | 127 ++++++++++++++++++
2 files changed, 128 insertions(+)
create mode 100644 arch/s390/include/asm/unwind_user_backchain.h
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 8b29a8f0f9c3..49f231123040 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -239,6 +239,7 @@ config S390
select HAVE_SETUP_PER_CPU_AREA
select HAVE_SOFTIRQ_ON_OWN_STACK
select HAVE_SYSCALL_TRACEPOINTS
+ select HAVE_UNWIND_USER_BACKCHAIN
select HAVE_UNWIND_USER_LOC_REG
select HAVE_UNWIND_USER_SFRAME
select HAVE_USER_RA_REG
diff --git a/arch/s390/include/asm/unwind_user_backchain.h b/arch/s390/include/asm/unwind_user_backchain.h
new file mode 100644
index 000000000000..ceb56b9d8411
--- /dev/null
+++ b/arch/s390/include/asm/unwind_user_backchain.h
@@ -0,0 +1,127 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_S390_UNWIND_USER_BACKCHAIN_H
+#define _ASM_S390_UNWIND_USER_BACKCHAIN_H
+
+#include <linux/security.h>
+#ifndef ASM_OFFSETS_C
+#include <asm/asm-offsets.h>
+#endif
+
+struct stack_frame_user {
+ unsigned long backchain;
+ unsigned long unused;
+ /* Argument register save area. */
+ unsigned long r2;
+ unsigned long r3;
+ unsigned long r4;
+ unsigned long r5;
+ unsigned long r6;
+ /* Other register save area. */
+ unsigned long r7;
+ unsigned long r8;
+ unsigned long r9;
+ unsigned long r10;
+ unsigned long r11;
+ unsigned long r12;
+ unsigned long r13;
+ unsigned long r14;
+ unsigned long r15;
+ /* FP argument register save area. */
+ unsigned long f0;
+ unsigned long f2;
+ unsigned long f4;
+ unsigned long f6;
+};
+
+struct stack_frame_vdso_wrapper {
+ struct stack_frame_user sf;
+ unsigned long return_address;
+};
+
+/**
+ * ip_invalid - Perform some basic checks whether an instruction pointer (IP)
+ * taken from an unreliable source is invalid
+ * @ip: The instruction pointer to be validated
+ *
+ * returns whether the instruction pointer is invalid
+ */
+static inline bool ip_invalid(unsigned long ip)
+{
+ if (ip & 1)
+ return true;
+ if (ip < mmap_min_addr)
+ return true;
+ if (ip >= current->mm->context.asce_limit)
+ return true;
+ return false;
+}
+
+/**
+ * ip_within_vdso - Check whether an instruction pointer (IP) is within vDSO
+ * @ip: The instruction pointer
+ *
+ * returns whether the instruction pointer is within vDSO
+ */
+static inline bool ip_within_vdso(unsigned long ip)
+{
+ return in_range(ip, current->mm->context.vdso_base, vdso_text_size());
+}
+
+/**
+ * arch_unwind_user_backchain_next - Unwind one frame using backchain
+ * @state: The unwind user state
+ *
+ * returns zero when successful, otherwise -EINVAL.
+ */
+static inline int arch_unwind_user_backchain_next(struct unwind_user_state *state)
+{
+ struct stack_frame_user __user *sf;
+ unsigned long sp, ra;
+
+ sf = (void __user *)state->sp;
+ if (__get_user(sp, (unsigned long __user *)&sf->backchain))
+ return -EINVAL;
+
+ /*
+ * vDSO entry code on s390 has a non-standard stack frame layout.
+ * See vDSO user wrapper code for details.
+ */
+ if (!sp && ip_within_vdso(state->ip)) {
+ struct stack_frame_vdso_wrapper *sf_vdso = (void __user *)sf;
+
+ if (__get_user(ra, (unsigned long __user *)&sf_vdso->return_address))
+ return -EINVAL;
+ sf = (void __user *)((unsigned long)sf + STACK_FRAME_VDSO_OVERHEAD);
+ if (__get_user(sp, (unsigned long __user *)&sf->backchain))
+ return -EINVAL;
+ } else {
+ sf = (void __user *)sp;
+ if (__get_user(ra, (unsigned long __user *)&sf->r14))
+ return -EINVAL;
+ }
+
+ /* ABI requires SP to be 8-byte aligned. */
+ if (sp & 0x7)
+ return -EINVAL;
+
+ /*
+ * If the IP is invalid and this is the topmost frame,
+ * assume the RA register has not been saved yet.
+ */
+ if (ip_invalid(ra)) {
+ if (!state->topmost || !IS_ENABLED(CONFIG_HAVE_USER_RA_REG))
+ return -EINVAL;
+
+ ra = user_return_address(task_pt_regs(current));
+ if (ip_invalid(ra))
+ return -EINVAL;
+ }
+
+ state->sp = sp;
+ state->ip = ra;
+ state->fp = 0;
+
+ return 0;
+}
+
+#endif /* _ASM_S390_UNWIND_USER_BACKCHAIN_H */
--
2.48.1
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