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Message-ID: <172656198744.2471820.14081573146419941141.tglx@xen13>
Date: Tue, 17 Sep 2024 10:54:10 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] x86/fpu for v6.12-rc1
Linus,
please pull the latest x86/fpu branch from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-fpu-2024-09-17
up to: ba386777a30b: x86/elf: Add a new FPU buffer layout info to x86 core files
Provide FPU buffer layout in core dumps:
Debuggers have guess the FPU buffer layout in core dumps, which is error
prone. This is because AMD and Intel layouts differ.
To avoid buggy heuristics add a ELF section which describes the buffer
layout which can be retrieved by tools.
Thanks,
tglx
------------------>
Vignesh Balasubramanian (1):
x86/elf: Add a new FPU buffer layout info to x86 core files
arch/x86/Kconfig | 1 +
arch/x86/include/uapi/asm/elf.h | 16 ++++++++
arch/x86/kernel/fpu/xstate.c | 89 +++++++++++++++++++++++++++++++++++++++++
fs/binfmt_elf.c | 4 +-
include/uapi/linux/elf.h | 1 +
5 files changed, 109 insertions(+), 2 deletions(-)
create mode 100644 arch/x86/include/uapi/asm/elf.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 007bab9f2a0e..c15b4b3fb328 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -107,6 +107,7 @@ config X86
select ARCH_HAS_DEBUG_WX
select ARCH_HAS_ZONE_DMA_SET if EXPERT
select ARCH_HAVE_NMI_SAFE_CMPXCHG
+ select ARCH_HAVE_EXTRA_ELF_NOTES
select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
select ARCH_MIGHT_HAVE_PC_PARPORT
diff --git a/arch/x86/include/uapi/asm/elf.h b/arch/x86/include/uapi/asm/elf.h
new file mode 100644
index 000000000000..468e135fa285
--- /dev/null
+++ b/arch/x86/include/uapi/asm/elf.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_ASM_X86_ELF_H
+#define _UAPI_ASM_X86_ELF_H
+
+#include <linux/types.h>
+
+struct x86_xfeat_component {
+ __u32 type;
+ __u32 size;
+ __u32 offset;
+ __u32 flags;
+} __packed;
+
+_Static_assert(sizeof(struct x86_xfeat_component) % 4 == 0, "x86_xfeat_component is not aligned");
+
+#endif /* _UAPI_ASM_X86_ELF_H */
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index c5a026fee5e0..f3a2e59a28e7 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -13,6 +13,7 @@
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/vmalloc.h>
+#include <linux/coredump.h>
#include <asm/fpu/api.h>
#include <asm/fpu/regset.h>
@@ -23,6 +24,8 @@
#include <asm/prctl.h>
#include <asm/elf.h>
+#include <uapi/asm/elf.h>
+
#include "context.h"
#include "internal.h"
#include "legacy.h"
@@ -1838,3 +1841,89 @@ int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
return 0;
}
#endif /* CONFIG_PROC_PID_ARCH_STATUS */
+
+#ifdef CONFIG_COREDUMP
+static const char owner_name[] = "LINUX";
+
+/*
+ * Dump type, size, offset and flag values for every xfeature that is present.
+ */
+static int dump_xsave_layout_desc(struct coredump_params *cprm)
+{
+ int num_records = 0;
+ int i;
+
+ for_each_extended_xfeature(i, fpu_user_cfg.max_features) {
+ struct x86_xfeat_component xc = {
+ .type = i,
+ .size = xstate_sizes[i],
+ .offset = xstate_offsets[i],
+ /* reserved for future use */
+ .flags = 0,
+ };
+
+ if (!dump_emit(cprm, &xc, sizeof(xc)))
+ return 0;
+
+ num_records++;
+ }
+ return num_records;
+}
+
+static u32 get_xsave_desc_size(void)
+{
+ u32 cnt = 0;
+ u32 i;
+
+ for_each_extended_xfeature(i, fpu_user_cfg.max_features)
+ cnt++;
+
+ return cnt * (sizeof(struct x86_xfeat_component));
+}
+
+int elf_coredump_extra_notes_write(struct coredump_params *cprm)
+{
+ int num_records = 0;
+ struct elf_note en;
+
+ if (!fpu_user_cfg.max_features)
+ return 0;
+
+ en.n_namesz = sizeof(owner_name);
+ en.n_descsz = get_xsave_desc_size();
+ en.n_type = NT_X86_XSAVE_LAYOUT;
+
+ if (!dump_emit(cprm, &en, sizeof(en)))
+ return 1;
+ if (!dump_emit(cprm, owner_name, en.n_namesz))
+ return 1;
+ if (!dump_align(cprm, 4))
+ return 1;
+
+ num_records = dump_xsave_layout_desc(cprm);
+ if (!num_records)
+ return 1;
+
+ /* Total size should be equal to the number of records */
+ if ((sizeof(struct x86_xfeat_component) * num_records) != en.n_descsz)
+ return 1;
+
+ return 0;
+}
+
+int elf_coredump_extra_notes_size(void)
+{
+ int size;
+
+ if (!fpu_user_cfg.max_features)
+ return 0;
+
+ /* .note header */
+ size = sizeof(struct elf_note);
+ /* Name plus alignment to 4 bytes */
+ size += roundup(sizeof(owner_name), 4);
+ size += get_xsave_desc_size();
+
+ return size;
+}
+#endif /* CONFIG_COREDUMP */
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 19fa49cd9907..01bcbe7fdebd 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2039,7 +2039,7 @@ static int elf_core_dump(struct coredump_params *cprm)
{
size_t sz = info.size;
- /* For cell spufs */
+ /* For cell spufs and x86 xstate */
sz += elf_coredump_extra_notes_size();
phdr4note = kmalloc(sizeof(*phdr4note), GFP_KERNEL);
@@ -2103,7 +2103,7 @@ static int elf_core_dump(struct coredump_params *cprm)
if (!write_note_info(&info, cprm))
goto end_coredump;
- /* For cell spufs */
+ /* For cell spufs and x86 xstate */
if (elf_coredump_extra_notes_write(cprm))
goto end_coredump;
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index b54b313bcf07..e30a9b47dc87 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -411,6 +411,7 @@ typedef struct elf64_shdr {
#define NT_X86_XSTATE 0x202 /* x86 extended state using xsave */
/* Old binutils treats 0x203 as a CET state */
#define NT_X86_SHSTK 0x204 /* x86 SHSTK state */
+#define NT_X86_XSAVE_LAYOUT 0x205 /* XSAVE layout description */
#define NT_S390_HIGH_GPRS 0x300 /* s390 upper register halves */
#define NT_S390_TIMER 0x301 /* s390 timer register */
#define NT_S390_TODCMP 0x302 /* s390 TOD clock comparator register */
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