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Message-ID: <f89a9137e983902f22611e5379606062a64b2382.1730150953.git.jpoimboe@kernel.org>
Date: Mon, 28 Oct 2024 14:47:34 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...nel.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
linux-kernel@...r.kernel.org,
Indu Bhagat <indu.bhagat@...cle.com>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
linux-perf-users@...r.kernel.org,
Mark Brown <broonie@...nel.org>,
linux-toolchains@...r.kernel.org,
Jordan Rome <jordalgo@...a.com>,
Sam James <sam@...too.org>,
linux-trace-kernel@...r.kerne.org,
Andrii Nakryiko <andrii.nakryiko@...il.com>,
Jens Remus <jremus@...ux.ibm.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Florian Weimer <fweimer@...hat.com>,
Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v3 07/19] unwind: Add user space unwinding API
Introduce a user space unwinder API which provides a generic way to
unwind user stacks.
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
arch/Kconfig | 7 +++
include/linux/unwind_user.h | 41 +++++++++++++++
kernel/Makefile | 1 +
kernel/unwind/Makefile | 1 +
kernel/unwind/user.c | 99 +++++++++++++++++++++++++++++++++++++
5 files changed, 149 insertions(+)
create mode 100644 include/linux/unwind_user.h
create mode 100644 kernel/unwind/Makefile
create mode 100644 kernel/unwind/user.c
diff --git a/arch/Kconfig b/arch/Kconfig
index 7a95c1052cd5..ee8ec97ea0ef 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -435,6 +435,13 @@ config HAVE_HARDLOCKUP_DETECTOR_ARCH
It uses the same command line parameters, and sysctl interface,
as the generic hardlockup detectors.
+config UNWIND_USER
+ bool
+
+config HAVE_UNWIND_USER_FP
+ bool
+ select UNWIND_USER
+
config HAVE_PERF_REGS
bool
help
diff --git a/include/linux/unwind_user.h b/include/linux/unwind_user.h
new file mode 100644
index 000000000000..9d28db06f33f
--- /dev/null
+++ b/include/linux/unwind_user.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_UNWIND_USER_H
+#define _LINUX_UNWIND_USER_H
+
+#include <linux/types.h>
+
+enum unwind_user_type {
+ UNWIND_USER_TYPE_FP,
+};
+
+struct unwind_stacktrace {
+ unsigned int nr;
+ unsigned long *entries;
+};
+
+struct unwind_user_frame {
+ s32 cfa_off;
+ s32 ra_off;
+ s32 fp_off;
+ bool use_fp;
+};
+
+struct unwind_user_state {
+ unsigned long ip;
+ unsigned long sp;
+ unsigned long fp;
+ enum unwind_user_type type;
+ bool done;
+};
+
+/* Synchronous interfaces: */
+
+int unwind_user_start(struct unwind_user_state *state);
+int unwind_user_next(struct unwind_user_state *state);
+
+int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries);
+
+#define for_each_user_frame(state) \
+ for (unwind_user_start((state)); !(state)->done; unwind_user_next((state)))
+
+#endif /* _LINUX_UNWIND_USER_H */
diff --git a/kernel/Makefile b/kernel/Makefile
index 87866b037fbe..6cb4b0e02a34 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -50,6 +50,7 @@ obj-y += rcu/
obj-y += livepatch/
obj-y += dma/
obj-y += entry/
+obj-y += unwind/
obj-$(CONFIG_MODULES) += module/
obj-$(CONFIG_KCMP) += kcmp.o
diff --git a/kernel/unwind/Makefile b/kernel/unwind/Makefile
new file mode 100644
index 000000000000..349ce3677526
--- /dev/null
+++ b/kernel/unwind/Makefile
@@ -0,0 +1 @@
+ obj-$(CONFIG_UNWIND_USER) += user.o
diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
new file mode 100644
index 000000000000..54b989810a0e
--- /dev/null
+++ b/kernel/unwind/user.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+* Generic interfaces for unwinding user space
+*
+* Copyright (C) 2024 Josh Poimboeuf <jpoimboe@...nel.org>
+*/
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/unwind_user.h>
+#include <linux/uaccess.h>
+#include <asm/unwind_user.h>
+
+static struct unwind_user_frame fp_frame = {
+ ARCH_INIT_USER_FP_FRAME
+};
+
+int unwind_user_next(struct unwind_user_state *state)
+{
+ struct unwind_user_frame _frame;
+ struct unwind_user_frame *frame = &_frame;
+ unsigned long prev_ip, cfa, fp, ra = 0;
+
+ if (state->done)
+ return -EINVAL;
+
+ prev_ip = state->ip;
+
+ switch (state->type) {
+ case UNWIND_USER_TYPE_FP:
+ frame = &fp_frame;
+ break;
+ default:
+ BUG();
+ }
+
+ cfa = (frame->use_fp ? state->fp : state->sp) + frame->cfa_off;
+
+ if (frame->ra_off && get_user(ra, (unsigned long __user *)(cfa + frame->ra_off)))
+ goto the_end;
+
+ if (ra == prev_ip)
+ goto the_end;
+
+ if (frame->fp_off && get_user(fp, (unsigned long __user *)(cfa + frame->fp_off)))
+ goto the_end;
+
+ state->sp = cfa;
+ state->ip = ra;
+ if (frame->fp_off)
+ state->fp = fp;
+
+ return 0;
+
+the_end:
+ state->done = true;
+ return -EINVAL;
+}
+
+int unwind_user_start(struct unwind_user_state *state)
+{
+ struct pt_regs *regs = task_pt_regs(current);
+
+ memset(state, 0, sizeof(*state));
+
+ if (!current->mm) {
+ state->done = true;
+ return -EINVAL;
+ }
+
+ state->type = UNWIND_USER_TYPE_FP;
+
+ state->sp = user_stack_pointer(regs);
+ state->ip = instruction_pointer(regs);
+ state->fp = frame_pointer(regs);
+
+ return 0;
+}
+
+int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries)
+{
+ struct unwind_user_state state;
+
+ trace->nr = 0;
+
+ if (!max_entries)
+ return -EINVAL;
+
+ if (!current->mm)
+ return 0;
+
+ for_each_user_frame(&state) {
+ trace->entries[trace->nr++] = state.ip;
+ if (trace->nr >= max_entries)
+ break;
+ }
+
+ return 0;
+}
--
2.47.0
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