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pgo.patch
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pgo.patch
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Add Clang's Profile Guided Optimization infrastructure
Enable the use of clang's Profile-Guided Optimization[1]. To generate a
profile, the kernel is instrumented with PGO counters, a representative
workload is run, and the raw profile data is collected from
/proc/pgo/vmlinux.profraw.
The raw profile data must be processed by clang's "llvm-profdata" tool
before it can be used during recompilation:
$ cp /proc/pgo/vmlinux.profraw vmlinux.profraw
$ llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw
Multiple raw profiles may be merged during this step.
The data can now be used by the compiler:
$ make LLVM=1 KCFLAGS=-fprofile-use=vmlinux.profdata
This initial submission is restricted to x86, as that's the platform we
know works. This restriction can be lifted once other platforms have
been verified to work with PGO.
Note that this method of profiling the kernel is clang-native, unlike
the clang support in kernel/gcov.
[1] https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization
---
Documentation/dev-tools/pgo.rst | 127 ++++++++
Makefile | 3 +
arch/Kconfig | 1 +
arch/x86/Kconfig | 1 +
arch/x86/boot/Makefile | 1 +
arch/x86/boot/compressed/Makefile | 1 +
arch/x86/crypto/Makefile | 3 +
arch/x86/entry/vdso/Makefile | 1 +
arch/x86/kernel/Makefile | 3 +
arch/x86/kernel/vmlinux.lds.S | 2 +
arch/x86/platform/efi/Makefile | 1 +
arch/x86/purgatory/Makefile | 1 +
arch/x86/realmode/rm/Makefile | 1 +
arch/x86/um/vdso/Makefile | 1 +
drivers/firmware/efi/libstub/Makefile | 1 +
include/asm-generic/vmlinux.lds.h | 32 ++
kernel/Makefile | 1 +
kernel/pgo/Kconfig | 37 +++
kernel/pgo/Makefile | 5 +
kernel/pgo/fs.c | 420 ++++++++++++++++++++++++++
kernel/pgo/instrument.c | 188 ++++++++++++
kernel/pgo/pgo.h | 221 ++++++++++++++
scripts/Makefile.lib | 10 +
23 files changed, 1062 insertions(+)
create mode 100644 Documentation/dev-tools/pgo.rst
create mode 100644 kernel/pgo/Kconfig
create mode 100644 kernel/pgo/Makefile
create mode 100644 kernel/pgo/fs.c
create mode 100644 kernel/pgo/instrument.c
create mode 100644 kernel/pgo/pgo.h
diff --git a/Documentation/dev-tools/pgo.rst b/Documentation/dev-tools/pgo.rst
new file mode 100644
index 000000000000..76175c523f4f
--- /dev/null
+++ b/Documentation/dev-tools/pgo.rst
@@ -0,0 +1,127 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================
+Using PGO with the Linux kernel
+===============================
+
+Clang's profiling kernel support (PGO_) enables profiling of the Linux kernel
+when building with Clang. The profiling data is exported via the ``pgo``
+procfs directory.
+
+.. _PGO: https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization
+
+
+Preparation
+===========
+
+Configure the kernel with:
+
+.. code-block:: make
+
+ CONFIG_PROC_FS=y
+ CONFIG_PGO_CLANG=y
+
+Note that kernels compiled with profiling flags will be significantly larger
+and run slower.
+
+Profiling data will only become accessible once procfs has been mounted:
+
+.. code-block:: sh
+
+ mount -t proc proc /proc
+
+
+Customization
+=============
+
+You can enable or disable profiling for individual file and directories by
+adding a line similar to the following to the respective kernel Makefile:
+
+- For a single file (e.g. main.o)
+
+ .. code-block:: make
+
+ PGO_PROFILE_main.o := y
+
+- For all files in one directory
+
+ .. code-block:: make
+
+ PGO_PROFILE := y
+
+To exclude files from being profiled use
+
+ .. code-block:: make
+
+ PGO_PROFILE_main.o := n
+
+and
+
+ .. code-block:: make
+
+ PGO_PROFILE := n
+
+Only files which are linked to the main kernel image or are compiled as kernel
+modules are supported by this mechanism.
+
+
+Files
+=====
+
+The PGO kernel support creates the following files in procfs:
+
+``/proc/pgo``
+ Parent directory for all PGO-related files.
+
+``/proc/pgo/reset``
+ Global reset file: resets all coverage data to zero when written to.
+
+``/proc/pgo/vmlinux.profraw``
+ The raw PGO data that must be processed with ``llvm_profdata``.
+
+
+Workflow
+========
+
+The PGO kernel can be run on the host or test machines. The data though should
+be analyzed with Clang's tools from the same Clang version as the kernel was
+compiled. Clang's tolerant of version skew, but it's easier to use the same
+Clang version.
+
+The profiling data is useful for optimizing the kernel, analyzing coverage,
+etc. Clang offers tools to perform these tasks.
+
+Here is an example workflow for profiling an instrumented kernel with PGO and
+using the result to optimize the kernel:
+
+1) Install the kernel on the TEST machine.
+
+2) Reset the data counters right before running the load tests
+
+ .. code-block:: sh
+
+ $ echo 1 > /proc/pgo/reset
+
+3) Run the load tests.
+
+4) Collect the raw profile data
+
+ .. code-block:: sh
+
+ $ cp -a /proc/pgo/vmlinux.profraw /tmp/vmlinux.profraw
+
+5) (Optional) Download the raw profile data to the HOST machine.
+
+6) Process the raw profile data
+
+ .. code-block:: sh
+
+ $ llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw
+
+ Note that multiple raw profile data files can be merged during this step.
+
+7) Rebuild the kernel using the processed profile data (PGO disabled)
+
+ .. code-block:: sh
+
+ $ make LLVM=1 KCFLAGS=-fprofile-use=vmlinux.profdata ...
diff --git a/Makefile b/Makefile
index 62a7398c8d06..65d7ea816bf9 100644
--- a/Makefile
+++ b/Makefile
@@ -690,6 +690,9 @@ endif # KBUILD_EXTMOD
# Defaults to vmlinux, but the arch makefile usually adds further targets
all: vmlinux
+CFLAGS_PGO_CLANG := -fprofile-generate
+export CFLAGS_PGO_CLANG
+
CFLAGS_GCOV := -fprofile-arcs -ftest-coverage
ifdef CONFIG_CC_IS_GCC
CFLAGS_GCOV += -fno-tree-loop-im
diff --git a/arch/Kconfig b/arch/Kconfig
index 8b311e400ec1..565158f8db8e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1419,6 +1419,7 @@ config HAVE_ARCH_NODE_DEV_GROUP
bool
source "kernel/gcov/Kconfig"
+source "kernel/pgo/Kconfig"
source "scripts/gcc-plugins/Kconfig"
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 159c025ebb03..d9d9ef044acb 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -109,6 +109,7 @@ config X86
select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
select ARCH_SUPPORTS_LTO_CLANG
select ARCH_SUPPORTS_LTO_CLANG_THIN
+ select ARCH_SUPPORTS_PGO_CLANG if X86_64
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_MEMTEST
select ARCH_USE_QUEUED_RWLOCKS
diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index ffec8bb01ba8..3619832a83de 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -71,6 +71,7 @@ KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
GCOV_PROFILE := n
+PGO_PROFILE := n
UBSAN_SANITIZE := n
$(obj)/bzImage: asflags-y := $(SVGA_MODE)
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 35ce1a64068b..cdff85f3a394 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -59,6 +59,7 @@ CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/
KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
GCOV_PROFILE := n
+PGO_PROFILE := n
UBSAN_SANITIZE :=n
KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)
diff --git a/arch/x86/crypto/Makefile b/arch/x86/crypto/Makefile
index 04d07ab744b2..0299ef71085d 100644
--- a/arch/x86/crypto/Makefile
+++ b/arch/x86/crypto/Makefile
@@ -89,6 +89,9 @@ nhpoly1305-sse2-y := nh-sse2-x86_64.o nhpoly1305-sse2-glue.o
obj-$(CONFIG_CRYPTO_NHPOLY1305_AVX2) += nhpoly1305-avx2.o
nhpoly1305-avx2-y := nh-avx2-x86_64.o nhpoly1305-avx2-glue.o
+# Disable PGO for curve25519-x86_64. With PGO enabled, clang runs out of
+# registers for some of the functions.
+PGO_PROFILE_curve25519-x86_64.o := n
obj-$(CONFIG_CRYPTO_CURVE25519_X86) += curve25519-x86_64.o
obj-$(CONFIG_CRYPTO_SM3_AVX_X86_64) += sm3-avx-x86_64.o
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 12f6c4d714cd..dcb08018ab57 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -182,6 +182,7 @@ quiet_cmd_vdso = VDSO $@
VDSO_LDFLAGS = -shared --hash-style=both --build-id=sha1 \
$(call ld-option, --eh-frame-hdr) -Bsymbolic -z noexecstack
GCOV_PROFILE := n
+PGO_PROFILE := n
quiet_cmd_vdso_and_check = VDSO $@
cmd_vdso_and_check = $(cmd_vdso); $(cmd_vdso_check)
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index a20a5ebfacd7..e1ac66b5717d 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -30,6 +30,9 @@ KASAN_SANITIZE_stacktrace.o := n
KASAN_SANITIZE_paravirt.o := n
KASAN_SANITIZE_sev.o := n
+# Cannot write to profiling regions before the page tables are set up.
+PGO_PROFILE_head$(BITS).o := n
+
# With some compiler versions the generated code results in boot hangs, caused
# by several compilation units. To be safe, disable all instrumentation.
KCSAN_SANITIZE := n
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 15f29053cec4..2c193031d219 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -183,6 +183,8 @@ SECTIONS
BUG_TABLE
+ PGO_CLANG_DATA
+
ORC_UNWIND_TABLE
. = ALIGN(PAGE_SIZE);
diff --git a/arch/x86/platform/efi/Makefile b/arch/x86/platform/efi/Makefile
index a50245157685..9fa343deea6d 100644
--- a/arch/x86/platform/efi/Makefile
+++ b/arch/x86/platform/efi/Makefile
@@ -1,6 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
KASAN_SANITIZE := n
GCOV_PROFILE := n
+PGO_PROFILE := n
obj-$(CONFIG_EFI) += quirks.o efi.o efi_$(BITS).o efi_stub_$(BITS).o
obj-$(CONFIG_EFI_MIXED) += efi_thunk_$(BITS).o
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 31c634a22818..ffbb7498c13b 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -23,6 +23,7 @@ targets += purgatory.ro purgatory.chk
# Sanitizer, etc. runtimes are unavailable and cannot be linked here.
GCOV_PROFILE := n
+PGO_PROFILE := n
KASAN_SANITIZE := n
UBSAN_SANITIZE := n
KCSAN_SANITIZE := n
diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
index 83f1b6a56449..21797192f958 100644
--- a/arch/x86/realmode/rm/Makefile
+++ b/arch/x86/realmode/rm/Makefile
@@ -76,4 +76,5 @@ KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \
KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
GCOV_PROFILE := n
+PGO_PROFILE := n
UBSAN_SANITIZE := n
diff --git a/arch/x86/um/vdso/Makefile b/arch/x86/um/vdso/Makefile
index 6fbe97c52c99..8667f7249441 100644
--- a/arch/x86/um/vdso/Makefile
+++ b/arch/x86/um/vdso/Makefile
@@ -67,6 +67,7 @@ quiet_cmd_vdso = VDSO $@
VDSO_LDFLAGS = -fPIC -shared -Wl,--hash-style=sysv -z noexecstack
GCOV_PROFILE := n
+PGO_PROFILE := n
#
# Install the unstripped copy of vdso*.so listed in $(vdso-install-y).
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 2c67f71f2375..3d0699c8b6d4 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -50,6 +50,7 @@ KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
GCOV_PROFILE := n
+PGO_PROFILE := n
# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
KCSAN_SANITIZE := n
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 7c90b1ab3e00..ca8c67cf36eb 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -321,6 +321,37 @@
#define THERMAL_TABLE(name)
#endif
+#ifdef CONFIG_PGO_CLANG
+#define PGO_CLANG_DATA \
+ __llvm_prf_data : AT(ADDR(__llvm_prf_data) - LOAD_OFFSET) { \
+ __llvm_prf_data_start = .; \
+ *(__llvm_prf_data) \
+ __llvm_prf_data_end = .; \
+ } \
+ __llvm_prf_cnts : AT(ADDR(__llvm_prf_cnts) - LOAD_OFFSET) { \
+ __llvm_prf_cnts_start = .; \
+ *(__llvm_prf_cnts) \
+ __llvm_prf_cnts_end = .; \
+ } \
+ __llvm_prf_names : AT(ADDR(__llvm_prf_names) - LOAD_OFFSET) { \
+ __llvm_prf_names_start = .; \
+ *(__llvm_prf_names) \
+ __llvm_prf_names_end = .; \
+ } \
+ __llvm_prf_vals : AT(ADDR(__llvm_prf_vals) - LOAD_OFFSET) { \
+ __llvm_prf_vals_start = .; \
+ *(__llvm_prf_vals) \
+ __llvm_prf_vals_end = .; \
+ } \
+ __llvm_prf_vnds : AT(ADDR(__llvm_prf_vnds) - LOAD_OFFSET) { \
+ __llvm_prf_vnds_start = .; \
+ *(__llvm_prf_vnds) \
+ __llvm_prf_vnds_end = .; \
+ }
+#else
+#define PGO_CLANG_DATA
+#endif
+
#define KERNEL_DTB() \
STRUCT_ALIGN(); \
__dtb_start = .; \
@@ -1140,6 +1171,7 @@
CONSTRUCTORS \
} \
BUG_TABLE \
+ PGO_CLANG_DATA
#define INIT_TEXT_SECTION(inittext_align) \
. = ALIGN(inittext_align); \
diff --git a/kernel/Makefile b/kernel/Makefile
index 318789c728d3..26c6035133ef 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -114,6 +114,7 @@ obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o
obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call_inline.o
obj-$(CONFIG_CFI_CLANG) += cfi.o
+obj-$(CONFIG_PGO_CLANG) += pgo/
obj-$(CONFIG_PERF_EVENTS) += events/
diff --git a/kernel/pgo/Kconfig b/kernel/pgo/Kconfig
new file mode 100644
index 000000000000..18d301a6d1a1
--- /dev/null
+++ b/kernel/pgo/Kconfig
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menu "Profile Guided Optimization (PGO) (EXPERIMENTAL)"
+
+config ARCH_SUPPORTS_PGO_CLANG
+ bool
+
+config PGO_CLANG
+ bool "Enable clang's PGO-based kernel profiling"
+ depends on PROC_FS
+ depends on ARCH_SUPPORTS_PGO_CLANG
+ depends on CC_IS_CLANG
+ depends on !ARCH_WANTS_NO_INSTR || CC_HAS_NO_PROFILE_FN_ATTR
+ help
+ This option enables clang's PGO (Profile Guided Optimization) based
+ code profiling to better optimize the kernel.
+
+ If unsure, say N.
+
+ Run a representative workload for your application on a kernel
+ compiled with this option and download the raw profile file from
+ /proc/pgo/vmlinux.profraw. This file needs to be
+ processed with llvm-profdata. It may be merged with other collected
+ raw profiles.
+
+ Copy the processed profile file into vmlinux.profdata, and enable
+ KCFLAGS=-fprofile-use=vmlinux.profdata to produce an optimized
+ kernel.
+
+ Note that a kernel compiled with profiling flags will be
+ significantly larger and run slower. Also be sure to exclude files
+ from profiling which are not linked to the kernel image to prevent
+ linker errors.
+
+ Note that the procfs filesystem has to be mounted to access
+ profiling data.
+
+endmenu
diff --git a/kernel/pgo/Makefile b/kernel/pgo/Makefile
new file mode 100644
index 000000000000..41e27cefd9a4
--- /dev/null
+++ b/kernel/pgo/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+GCOV_PROFILE := n
+PGO_PROFILE := n
+
+obj-y += fs.o instrument.o
diff --git a/kernel/pgo/fs.c b/kernel/pgo/fs.c
new file mode 100644
index 000000000000..cd9187b138a9
--- /dev/null
+++ b/kernel/pgo/fs.c
@@ -0,0 +1,420 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Google, Inc.
+ *
+ * Author:
+ * Sami Tolvanen <samitolvanen@google.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#define pr_fmt(fmt) "pgo: " fmt
+
+#include <linux/kernel.h>
+#include <linux/proc_fs.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include "pgo.h"
+
+static struct proc_dir_entry *directory;
+
+struct prf_private_data {
+ void *buffer;
+ size_t size;
+};
+
+/*
+ * Raw profile data format:
+ *
+ * - llvm_prf_header
+ * - __llvm_prf_data
+ * - __llvm_prf_cnts
+ * - __llvm_prf_names
+ * - zero padding to 8 bytes
+ * - for each llvm_prf_data in __llvm_prf_data:
+ * - llvm_prf_value_data
+ * - llvm_prf_value_record + site count array
+ * - llvm_prf_value_node_data
+ * ...
+ * ...
+ * ...
+ */
+
+static void prf_fill_header(void **buffer)
+{
+ struct llvm_prf_header *header = *(struct llvm_prf_header **)buffer;
+
+#ifdef CONFIG_64BIT
+ header->magic = LLVM_INSTR_PROF_RAW_MAGIC_64;
+#else
+ header->magic = LLVM_INSTR_PROF_RAW_MAGIC_32;
+#endif
+ header->version = LLVM_VARIANT_MASK_IR_PROF | LLVM_INSTR_PROF_RAW_VERSION;
+#if __clang_major__ >= 13
+ header->binary_ids_size = 0;
+#endif
+ header->data_size = prf_data_count();
+ header->padding_bytes_before_counters = 0;
+ header->counters_size = prf_cnts_count();
+ header->padding_bytes_after_counters = 0;
+ header->names_size = prf_names_count();
+#if __clang_major__ >= 14
+ header->counters_delta = (u64)__llvm_prf_cnts_start - (u64)__llvm_prf_data_start;
+#else
+ header->counters_delta = (u64)__llvm_prf_cnts_start;
+#endif
+ header->names_delta = (u64)__llvm_prf_names_start;
+ header->value_kind_last = LLVM_INSTR_PROF_IPVK_LAST;
+
+ *buffer += sizeof(*header);
+}
+
+/*
+ * Copy the source into the buffer, incrementing the pointer into buffer in the
+ * process.
+ */
+static void prf_copy_to_buffer(void **buffer, void *src, unsigned long size)
+{
+ memcpy(*buffer, src, size);
+ *buffer += size;
+}
+
+static u32 __prf_get_value_size(struct llvm_prf_data *p, u32 *value_kinds)
+{
+ struct llvm_prf_value_node **nodes =
+ (struct llvm_prf_value_node **)p->values;
+ u32 kinds = 0;
+ u32 size = 0;
+ unsigned int kind;
+ unsigned int n;
+ unsigned int s = 0;
+
+ for (kind = 0; kind < ARRAY_SIZE(p->num_value_sites); kind++) {
+ unsigned int sites = p->num_value_sites[kind];
+
+ if (!sites)
+ continue;
+
+ /* Record + site count array */
+ size += prf_get_value_record_size(sites);
+ kinds++;
+
+ if (!nodes)
+ continue;
+
+ for (n = 0; n < sites; n++) {
+ u32 count = 0;
+ struct llvm_prf_value_node *site = nodes[s + n];
+
+ while (site && ++count <= U8_MAX)
+ site = site->next;
+
+ size += count *
+ sizeof(struct llvm_prf_value_node_data);
+ }
+
+ s += sites;
+ }
+
+ if (size)
+ size += sizeof(struct llvm_prf_value_data);
+
+ if (value_kinds)
+ *value_kinds = kinds;
+
+ return size;
+}
+
+static u32 prf_get_value_size(void)
+{
+ u32 size = 0;
+ struct llvm_prf_data *p;
+
+ for (p = __llvm_prf_data_start; p < __llvm_prf_data_end; p++)
+ size += __prf_get_value_size(p, NULL);
+
+ return size;
+}
+
+/* Serialize the profiling's value. */
+static void prf_serialize_value(struct llvm_prf_data *p, void **buffer)
+{
+ struct llvm_prf_value_data header;
+ struct llvm_prf_value_node **nodes =
+ (struct llvm_prf_value_node **)p->values;
+ unsigned int kind;
+ unsigned int n;
+ unsigned int s = 0;
+
+ header.total_size = __prf_get_value_size(p, &header.num_value_kinds);
+
+ if (!header.num_value_kinds)
+ /* Nothing to write. */
+ return;
+
+ prf_copy_to_buffer(buffer, &header, sizeof(header));
+
+ for (kind = 0; kind < ARRAY_SIZE(p->num_value_sites); kind++) {
+ struct llvm_prf_value_record *record;
+ u8 *counts;
+ unsigned int sites = p->num_value_sites[kind];
+
+ if (!sites)
+ continue;
+
+ /* Profiling value record. */
+ record = *(struct llvm_prf_value_record **)buffer;
+ *buffer += prf_get_value_record_header_size();
+
+ record->kind = kind;
+ record->num_value_sites = sites;
+
+ /* Site count array. */
+ counts = *(u8 **)buffer;
+ *buffer += prf_get_value_record_site_count_size(sites);
+
+ /*
+ * If we don't have nodes, we can skip updating the site count
+ * array, because the buffer is zero filled.
+ */
+ if (!nodes)
+ continue;
+
+ for (n = 0; n < sites; n++) {
+ u32 count = 0;
+ struct llvm_prf_value_node *site = nodes[s + n];
+
+ while (site && ++count <= U8_MAX) {
+ prf_copy_to_buffer(buffer, site,
+ sizeof(struct llvm_prf_value_node_data));
+ site = site->next;
+ }
+
+ counts[n] = (u8)count;
+ }
+
+ s += sites;
+ }
+}
+
+static void prf_serialize_values(void **buffer)
+{
+ struct llvm_prf_data *p;
+
+ for (p = __llvm_prf_data_start; p < __llvm_prf_data_end; p++)
+ prf_serialize_value(p, buffer);
+}
+
+static inline unsigned long prf_get_padding(unsigned long size)
+{
+ return 7 & (sizeof(u64) - size % sizeof(u64));
+}
+
+/* Note: caller *must* hold pgo_lock */
+static unsigned long prf_buffer_size(void)
+{
+ return sizeof(struct llvm_prf_header) +
+ prf_data_size() +
+ prf_cnts_size() +
+ prf_names_size() +
+ prf_get_padding(prf_names_size()) +
+ prf_get_value_size();
+}
+
+/*
+ * Serialize the profiling data into a format LLVM's tools can understand.
+ * Returns actual buffer size in p->size.
+ * Note: p->buffer must point into vzalloc()'d
+ * area of at least prf_buffer_size() in size.
+ * Note: caller *must* hold pgo_lock.
+ */
+static int prf_serialize(struct prf_private_data *p, size_t buf_size)
+{
+ void *buffer;
+
+ /* get buffer size, again. */
+ p->size = prf_buffer_size();
+
+ /* check for unlikely overflow. */
+ if (p->size > buf_size)
+ return -EAGAIN;
+
+ buffer = p->buffer;
+
+ prf_fill_header(&buffer);
+ prf_copy_to_buffer(&buffer, __llvm_prf_data_start, prf_data_size());
+ prf_copy_to_buffer(&buffer, __llvm_prf_cnts_start, prf_cnts_size());
+ prf_copy_to_buffer(&buffer, __llvm_prf_names_start, prf_names_size());
+ buffer += prf_get_padding(prf_names_size());
+
+ prf_serialize_values(&buffer);
+
+ return 0;
+}
+
+/* open() implementation for PGO. Creates a copy of the profiling data set. */
+static int prf_open(struct inode *inode, struct file *file)
+{
+ struct prf_private_data *data;
+ unsigned long flags;
+ size_t buf_size;
+ int err = -EINVAL;
+
+ data = kzalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ /* Get initial buffer size. */
+ flags = prf_lock();
+ data->size = prf_buffer_size();
+ prf_unlock(flags);
+
+ do {
+ vfree(data->buffer);
+
+ /* Allocate, round up to page size. */
+ buf_size = PAGE_ALIGN(data->size);
+ data->buffer = vzalloc(buf_size);
+
+ if (!data->buffer) {
+ err = -ENOMEM;
+ break;
+ }
+
+ /*
+ * Try serialize and get actual
+ * data length in data->size.
+ */
+ flags = prf_lock();
+ err = prf_serialize(data, buf_size);
+ prf_unlock(flags);
+ /* In unlikely case, try again. */
+ } while (err == -EAGAIN);
+
+ if (err < 0) {
+ if (data)
+ vfree(data->buffer);
+ kfree(data);
+ } else {
+ file->private_data = data;
+ }
+
+ return err;
+}
+
+/* read() implementation for PGO. */
+static ssize_t prf_read(struct file *file, char __user *buf, size_t count,
+ loff_t *ppos)
+{
+ struct prf_private_data *data = file->private_data;
+
+ if (WARN_ON_ONCE(!data))
+ return -ENOMEM;
+
+ return simple_read_from_buffer(buf, count, ppos, data->buffer,
+ data->size);
+}
+
+/* release() implementation for PGO. Release resources allocated by open(). */
+static int prf_release(struct inode *inode, struct file *file)
+{
+ struct prf_private_data *data = file->private_data;
+
+ if (data) {
+ vfree(data->buffer);
+ kfree(data);
+ }
+
+ return 0;
+}
+
+static const struct proc_ops prf_pops = {
+ .proc_open = prf_open,
+ .proc_read = prf_read,
+ .proc_lseek = default_llseek,
+ .proc_release = prf_release
+};
+
+
+/* write() implementation for resetting PGO's profile data. */
+static ssize_t reset_write(struct file *file, const char __user *addr,
+ size_t len, loff_t *pos)
+{
+ struct llvm_prf_data *data;
+
+ memset(__llvm_prf_cnts_start, 0, prf_cnts_size());
+
+ for (data = __llvm_prf_data_start; data < __llvm_prf_data_end; data++) {
+ struct llvm_prf_value_node **vnodes;
+ u64 current_vsite_count;
+ u32 i;
+
+ if (!data->values)
+ continue;
+
+ current_vsite_count = 0;
+ vnodes = (struct llvm_prf_value_node **)data->values;
+
+ for (i = LLVM_INSTR_PROF_IPVK_FIRST; i <= LLVM_INSTR_PROF_IPVK_LAST; i++)
+ current_vsite_count += data->num_value_sites[i];
+
+ for (i = 0; i < current_vsite_count; i++) {
+ struct llvm_prf_value_node *current_vnode = vnodes[i];
+
+ while (current_vnode) {
+ current_vnode->count = 0;
+ current_vnode = current_vnode->next;
+ }
+ }
+ }
+
+ return len;
+}
+
+static const struct proc_ops prf_reset_pops = {
+ .proc_write = reset_write,
+ .proc_lseek = noop_llseek,
+};
+
+
+/* Create procfs entries. */
+static int __init pgo_init(void)
+{
+ directory = proc_mkdir("pgo", NULL);
+ if (!directory)
+ goto err_remove;
+
+ if (!proc_create("vmlinux.profraw", 0600, directory,
+ &prf_pops))
+ goto err_remove;
+
+ if (!proc_create("reset", 0200, directory,
+ &prf_reset_pops))
+ goto err_remove;
+
+ return 0;
+
+err_remove:
+ pr_err("initialization failed\n");
+ return -EIO;
+}
+
+/* Remove procfs entries. */
+static void __exit pgo_exit(void)
+{
+ proc_remove(directory);
+}
+
+module_init(pgo_init);
+module_exit(pgo_exit);
diff --git a/kernel/pgo/instrument.c b/kernel/pgo/instrument.c
new file mode 100644
index 000000000000..8b54fb6be336
--- /dev/null
+++ b/kernel/pgo/instrument.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Google, Inc.
+ *
+ * Author:
+ * Sami Tolvanen <samitolvanen@google.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#define pr_fmt(fmt) "pgo: " fmt
+
+#include <asm/sections.h>
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include "pgo.h"
+
+/*
+ * This lock guards both profile count updating and serialization of the
+ * profiling data. Keeping both of these activities separate via locking
+ * ensures that we don't try to serialize data that's only partially updated.
+ */
+static DEFINE_SPINLOCK(pgo_lock);
+static int current_node;
+
+unsigned long prf_lock(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&pgo_lock, flags);
+
+ return flags;
+}
+
+void prf_unlock(unsigned long flags)
+{
+ spin_unlock_irqrestore(&pgo_lock, flags);
+}
+
+/*
+ * Return a newly allocated profiling value node which contains the tracked
+ * value by the value profiler.
+ * Note: caller *must* hold pgo_lock.
+ */
+static struct llvm_prf_value_node *allocate_node(struct llvm_prf_data *p,
+ u32 index, u64 value)
+{
+ const int max_vnds = prf_vnds_count();
+
+ /*
+ * Check that p is within vmlinux __llvm_prf_data section.
+ * If not, don't allocate since we can't handle modules yet.
+ */
+ if (!memory_contains(__llvm_prf_data_start,
+ __llvm_prf_data_end, p, sizeof(*p)))
+ return NULL;
+
+ if (WARN_ON_ONCE(current_node >= max_vnds))
+ return NULL; /* Out of nodes */
+
+ /* reserve vnode for vmlinux */
+ return &__llvm_prf_vnds_start[current_node++];
+}
+
+/*
+ * Counts the number of times a target value is seen.
+ *
+ * Records the target value for the index if not seen before. Otherwise,
+ * increments the counter associated w/ the target value.
+ */
+void __llvm_profile_instrument_target(u64 target_value, void *data, u32 index)
+{
+ struct llvm_prf_data *p = (struct llvm_prf_data *)data;
+ struct llvm_prf_value_node **counters;
+ struct llvm_prf_value_node *curr;
+ struct llvm_prf_value_node *min = NULL;