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Message-ID: <f27e8463783febfa0dabb0432a3dd6be8ad98412.1737511963.git.jpoimboe@kernel.org>
Date: Tue, 21 Jan 2025 18:31:09 -0800
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.kernel.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>,
Masami Hiramatsu <mhiramat@...nel.org>,
Weinan Liu <wnliu@...gle.com>
Subject: [PATCH v4 17/39] unwind_user/sframe: Add support for reading .sframe headers
In preparation for unwinding user space stacks with sframe, add basic
sframe compile infrastructure and support for reading the .sframe
section header.
sframe_add_section() reads the header and unconditionally returns an
error, so it's not very useful yet. A subsequent patch will improve
that.
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
arch/Kconfig | 3 +
include/linux/sframe.h | 36 +++++++++++
kernel/unwind/Makefile | 3 +-
kernel/unwind/sframe.c | 136 +++++++++++++++++++++++++++++++++++++++++
kernel/unwind/sframe.h | 71 +++++++++++++++++++++
5 files changed, 248 insertions(+), 1 deletion(-)
create mode 100644 include/linux/sframe.h
create mode 100644 kernel/unwind/sframe.c
create mode 100644 kernel/unwind/sframe.h
diff --git a/arch/Kconfig b/arch/Kconfig
index f1f7a3857c97..23edd0e4e16a 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -446,6 +446,9 @@ config HAVE_UNWIND_USER_COMPAT_FP
bool
depends on HAVE_UNWIND_USER_FP
+config HAVE_UNWIND_USER_SFRAME
+ bool
+
config AS_SFRAME
def_bool $(as-instr,.cfi_sections .sframe\n.cfi_startproc\n.cfi_endproc)
diff --git a/include/linux/sframe.h b/include/linux/sframe.h
new file mode 100644
index 000000000000..3bfaf21869c2
--- /dev/null
+++ b/include/linux/sframe.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_SFRAME_H
+#define _LINUX_SFRAME_H
+
+#include <linux/mm_types.h>
+#include <linux/unwind_user_types.h>
+
+#ifdef CONFIG_HAVE_UNWIND_USER_SFRAME
+
+struct sframe_section {
+ unsigned long sframe_start;
+ unsigned long sframe_end;
+ unsigned long text_start;
+ unsigned long text_end;
+
+ unsigned long fdes_start;
+ unsigned long fres_start;
+ unsigned long fres_end;
+ unsigned int num_fdes;
+
+ signed char ra_off;
+ signed char fp_off;
+};
+
+extern int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end,
+ unsigned long text_start, unsigned long text_end);
+extern int sframe_remove_section(unsigned long sframe_addr);
+
+#else /* !CONFIG_HAVE_UNWIND_USER_SFRAME */
+
+static inline int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end, unsigned long text_start, unsigned long text_end) { return -ENOSYS; }
+static inline int sframe_remove_section(unsigned long sframe_addr) { return -ENOSYS; }
+
+#endif /* CONFIG_HAVE_UNWIND_USER_SFRAME */
+
+#endif /* _LINUX_SFRAME_H */
diff --git a/kernel/unwind/Makefile b/kernel/unwind/Makefile
index 349ce3677526..f70380d7a6a6 100644
--- a/kernel/unwind/Makefile
+++ b/kernel/unwind/Makefile
@@ -1 +1,2 @@
- obj-$(CONFIG_UNWIND_USER) += user.o
+ obj-$(CONFIG_UNWIND_USER) += user.o
+ obj-$(CONFIG_HAVE_UNWIND_USER_SFRAME) += sframe.o
diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
new file mode 100644
index 000000000000..20287f795b36
--- /dev/null
+++ b/kernel/unwind/sframe.c
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Userspace sframe access functions
+ */
+
+#define pr_fmt(fmt) "sframe: " fmt
+
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/srcu.h>
+#include <linux/uaccess.h>
+#include <linux/mm.h>
+#include <linux/string_helpers.h>
+#include <linux/sframe.h>
+#include <linux/unwind_user_types.h>
+
+#include "sframe.h"
+
+#define dbg(fmt, ...) \
+ pr_debug("%s (%d): " fmt, current->comm, current->pid, ##__VA_ARGS__)
+
+static void free_section(struct sframe_section *sec)
+{
+ kfree(sec);
+}
+
+static int sframe_read_header(struct sframe_section *sec)
+{
+ unsigned long header_end, fdes_start, fdes_end, fres_start, fres_end;
+ struct sframe_header shdr;
+ unsigned int num_fdes;
+
+ if (copy_from_user(&shdr, (void __user *)sec->sframe_start, sizeof(shdr))) {
+ dbg("header usercopy failed\n");
+ return -EFAULT;
+ }
+
+ if (shdr.preamble.magic != SFRAME_MAGIC ||
+ shdr.preamble.version != SFRAME_VERSION_2 ||
+ !(shdr.preamble.flags & SFRAME_F_FDE_SORTED) ||
+ shdr.auxhdr_len) {
+ dbg("bad/unsupported sframe header\n");
+ return -EINVAL;
+ }
+
+ if (!shdr.num_fdes || !shdr.num_fres) {
+ dbg("no fde/fre entries\n");
+ return -EINVAL;
+ }
+
+ header_end = sec->sframe_start + SFRAME_HEADER_SIZE(shdr);
+ if (header_end >= sec->sframe_end) {
+ dbg("header doesn't fit in section\n");
+ return -EINVAL;
+ }
+
+ num_fdes = shdr.num_fdes;
+ fdes_start = header_end + shdr.fdes_off;
+ fdes_end = fdes_start + (num_fdes * sizeof(struct sframe_fde));
+
+ fres_start = header_end + shdr.fres_off;
+ fres_end = fres_start + shdr.fre_len;
+
+ if (fres_start < fdes_end || fres_end > sec->sframe_end) {
+ dbg("inconsistent fde/fre offsets\n");
+ return -EINVAL;
+ }
+
+ sec->num_fdes = num_fdes;
+ sec->fdes_start = fdes_start;
+ sec->fres_start = fres_start;
+ sec->fres_end = fres_end;
+
+ sec->ra_off = shdr.cfa_fixed_ra_offset;
+ sec->fp_off = shdr.cfa_fixed_fp_offset;
+
+ return 0;
+}
+
+int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end,
+ unsigned long text_start, unsigned long text_end)
+{
+ struct maple_tree *sframe_mt = ¤t->mm->sframe_mt;
+ struct vm_area_struct *sframe_vma, *text_vma;
+ struct mm_struct *mm = current->mm;
+ struct sframe_section *sec;
+ int ret;
+
+ if (!sframe_start || !sframe_end || !text_start || !text_end) {
+ dbg("zero-length sframe/text address\n");
+ return -EINVAL;
+ }
+
+ scoped_guard(mmap_read_lock, mm) {
+ sframe_vma = vma_lookup(mm, sframe_start);
+ if (!sframe_vma || sframe_end > sframe_vma->vm_end) {
+ dbg("bad sframe address (0x%lx - 0x%lx)\n",
+ sframe_start, sframe_end);
+ return -EINVAL;
+ }
+
+ text_vma = vma_lookup(mm, text_start);
+ if (!text_vma ||
+ !(text_vma->vm_flags & VM_EXEC) ||
+ text_end > text_vma->vm_end) {
+ dbg("bad text address (0x%lx - 0x%lx)\n",
+ text_start, text_end);
+ return -EINVAL;
+ }
+ }
+
+ sec = kzalloc(sizeof(*sec), GFP_KERNEL);
+ if (!sec)
+ return -ENOMEM;
+
+ sec->sframe_start = sframe_start;
+ sec->sframe_end = sframe_end;
+ sec->text_start = text_start;
+ sec->text_end = text_end;
+
+ ret = sframe_read_header(sec);
+ if (ret)
+ goto err_free;
+
+ /* TODO nowhere to store it yet - just free it and return an error */
+ ret = -ENOSYS;
+
+err_free:
+ free_section(sec);
+ return ret;
+}
+
+int sframe_remove_section(unsigned long sframe_start)
+{
+ return -ENOSYS;
+}
diff --git a/kernel/unwind/sframe.h b/kernel/unwind/sframe.h
new file mode 100644
index 000000000000..e9bfccfaf5b4
--- /dev/null
+++ b/kernel/unwind/sframe.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * From https://www.sourceware.org/binutils/docs/sframe-spec.html
+ */
+#ifndef _SFRAME_H
+#define _SFRAME_H
+
+#include <linux/types.h>
+
+#define SFRAME_VERSION_1 1
+#define SFRAME_VERSION_2 2
+#define SFRAME_MAGIC 0xdee2
+
+#define SFRAME_F_FDE_SORTED 0x1
+#define SFRAME_F_FRAME_POINTER 0x2
+
+#define SFRAME_ABI_AARCH64_ENDIAN_BIG 1
+#define SFRAME_ABI_AARCH64_ENDIAN_LITTLE 2
+#define SFRAME_ABI_AMD64_ENDIAN_LITTLE 3
+
+#define SFRAME_FDE_TYPE_PCINC 0
+#define SFRAME_FDE_TYPE_PCMASK 1
+
+struct sframe_preamble {
+ u16 magic;
+ u8 version;
+ u8 flags;
+} __packed;
+
+struct sframe_header {
+ struct sframe_preamble preamble;
+ u8 abi_arch;
+ s8 cfa_fixed_fp_offset;
+ s8 cfa_fixed_ra_offset;
+ u8 auxhdr_len;
+ u32 num_fdes;
+ u32 num_fres;
+ u32 fre_len;
+ u32 fdes_off;
+ u32 fres_off;
+} __packed;
+
+#define SFRAME_HEADER_SIZE(header) \
+ ((sizeof(struct sframe_header) + header.auxhdr_len))
+
+#define SFRAME_AARCH64_PAUTH_KEY_A 0
+#define SFRAME_AARCH64_PAUTH_KEY_B 1
+
+struct sframe_fde {
+ s32 start_addr;
+ u32 func_size;
+ u32 fres_off;
+ u32 fres_num;
+ u8 info;
+ u8 rep_size;
+ u16 padding;
+} __packed;
+
+#define SFRAME_FUNC_FRE_TYPE(data) (data & 0xf)
+#define SFRAME_FUNC_FDE_TYPE(data) ((data >> 4) & 0x1)
+#define SFRAME_FUNC_PAUTH_KEY(data) ((data >> 5) & 0x1)
+
+#define SFRAME_BASE_REG_FP 0
+#define SFRAME_BASE_REG_SP 1
+
+#define SFRAME_FRE_CFA_BASE_REG_ID(data) (data & 0x1)
+#define SFRAME_FRE_OFFSET_COUNT(data) ((data >> 1) & 0xf)
+#define SFRAME_FRE_OFFSET_SIZE(data) ((data >> 5) & 0x3)
+#define SFRAME_FRE_MANGLED_RA_P(data) ((data >> 7) & 0x1)
+
+#endif /* _SFRAME_H */
--
2.48.1
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