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Subject[PATCH] [RFC] making uapi/linux/elfcore.h useful again
Date
After finding a bug in glibc the question came up how linux/elfcore.h
is supposed to be used from user space. As far as I can tell, it's
not possible, as it references data types that are simply unavailable
there.

The #ifndef __KERNEL__ section in that header dates back to when the
file was introduced in linux-1.3.5, and presumably was meant to
provide the structures for the libc sys/procfs.h implementation.
However, this was never portable to architectures other than x86-32,
and has been broken on that architecture at a later point.

These are the steps that I needed to make it possible to include the
header file, e.g. for libc self-testing in order to make sure the
structures are compatible with its own:

- drop the #ifndef __KERNEL__ section that are obviously useless
and get in the way

- change the pid_t references to __kernel_pid_t

- Move required data from the private x86 asm/elf.h file into
a new uapi/asm/elf.h. Some other architectures already do that,
but most of them do not. Before applying the patch, we have
to do this for all architectures

- Change ELF_NGREG to an integer literal constant instead of
a sizeof operation based on a private type.

Cc: Joseph Myers <joseph@codesourcery.com>
Cc: David Howells <dhowells@redhat.com>
Cc: libc-alpha@sourceware.org
Link: https://patchwork.ozlabs.org/patch/969540/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/x86/include/asm/elf.h | 24 +-----------------------
arch/x86/include/uapi/asm/elf.h | 30 ++++++++++++++++++++++++++++++
arch/x86/include/uapi/asm/signal.h | 2 +-
include/uapi/linux/elf.h | 1 +
include/uapi/linux/elfcore.h | 26 +++++---------------------
5 files changed, 38 insertions(+), 45 deletions(-)
create mode 100644 arch/x86/include/uapi/asm/elf.h

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 0d157d2a1e2a..973bd7b5b164 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -10,18 +10,10 @@
#include <asm/ptrace.h>
#include <asm/user.h>
#include <asm/auxvec.h>
-
-typedef unsigned long elf_greg_t;
-
-#define ELF_NGREG (sizeof(struct user_regs_struct) / sizeof(elf_greg_t))
-typedef elf_greg_t elf_gregset_t[ELF_NGREG];
-
-typedef struct user_i387_struct elf_fpregset_t;
+#include <uapi/asm/elf.h>

#ifdef __i386__

-typedef struct user_fxsr_struct elf_fpxregset_t;
-
#define R_386_NONE 0
#define R_386_32 1
#define R_386_PC32 2
@@ -35,13 +27,6 @@ typedef struct user_fxsr_struct elf_fpxregset_t;
#define R_386_GOTPC 10
#define R_386_NUM 11

-/*
- * These are used to set parameters in the core dumps.
- */
-#define ELF_CLASS ELFCLASS32
-#define ELF_DATA ELFDATA2LSB
-#define ELF_ARCH EM_386
-
#else

/* x86-64 relocation types */
@@ -65,13 +50,6 @@ typedef struct user_fxsr_struct elf_fpxregset_t;

#define R_X86_64_NUM 16

-/*
- * These are used to set parameters in the core dumps.
- */
-#define ELF_CLASS ELFCLASS64
-#define ELF_DATA ELFDATA2LSB
-#define ELF_ARCH EM_X86_64
-
#endif

#include <asm/vdso.h>
diff --git a/arch/x86/include/uapi/asm/elf.h b/arch/x86/include/uapi/asm/elf.h
new file mode 100644
index 000000000000..a640e1224939
--- /dev/null
+++ b/arch/x86/include/uapi/asm/elf.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_ASM_X86_ELF_H
+#define _UAPI_ASM_X86_ELF_H
+
+#ifdef __i386__
+
+/*
+ * These are used to set parameters in the core dumps.
+ */
+#define ELF_CLASS ELFCLASS32
+#define ELF_DATA ELFDATA2LSB
+#define ELF_ARCH EM_386
+#define ELF_NGREG 17
+
+#else
+
+/*
+ * These are used to set parameters in the core dumps.
+ */
+#define ELF_CLASS ELFCLASS64
+#define ELF_DATA ELFDATA2LSB
+#define ELF_ARCH EM_X86_64
+#define ELF_NGREG 27
+
+#endif /* __i386__ */
+
+typedef unsigned long elf_greg_t;
+typedef elf_greg_t elf_gregset_t[ELF_NGREG];
+
+#endif
diff --git a/arch/x86/include/uapi/asm/signal.h b/arch/x86/include/uapi/asm/signal.h
index e5745d593dc7..00f273eaddf7 100644
--- a/arch/x86/include/uapi/asm/signal.h
+++ b/arch/x86/include/uapi/asm/signal.h
@@ -128,7 +128,7 @@ struct sigaction {
typedef struct sigaltstack {
void __user *ss_sp;
int ss_flags;
- size_t ss_size;
+ __kernel_size_t ss_size;
} stack_t;

#endif /* __ASSEMBLY__ */
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index c5358e0ae7c5..e1e4561ed9c2 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -4,6 +4,7 @@

#include <linux/types.h>
#include <linux/elf-em.h>
+#include <asm/elf.h>

/* 32-bit ELF base types. */
typedef __u32 Elf32_Addr;
diff --git a/include/uapi/linux/elfcore.h b/include/uapi/linux/elfcore.h
index baf03562306d..9c0078004275 100644
--- a/include/uapi/linux/elfcore.h
+++ b/include/uapi/linux/elfcore.h
@@ -16,15 +16,6 @@ struct elf_siginfo
int si_errno; /* errno */
};

-
-#ifndef __KERNEL__
-typedef elf_greg_t greg_t;
-typedef elf_gregset_t gregset_t;
-typedef elf_fpregset_t fpregset_t;
-typedef elf_fpxregset_t fpxregset_t;
-#define NGREG ELF_NGREG
-#endif
-
/*
* Definitions to generate Intel SVR4-like core files.
* These mostly have the same names as the SVR4 types with "elf_"
@@ -49,10 +40,10 @@ struct elf_prstatus
struct sigaltstack pr_altstack; /* Alternate stack info */
struct sigaction pr_action; /* Signal action for current sig */
#endif
- pid_t pr_pid;
- pid_t pr_ppid;
- pid_t pr_pgrp;
- pid_t pr_sid;
+ __kernel_pid_t pr_pid;
+ __kernel_pid_t pr_ppid;
+ __kernel_pid_t pr_pgrp;
+ __kernel_pid_t pr_sid;
struct __kernel_old_timeval pr_utime; /* User time */
struct __kernel_old_timeval pr_stime; /* System time */
struct __kernel_old_timeval pr_cutime; /* Cumulative user time */
@@ -85,17 +76,10 @@ struct elf_prpsinfo
unsigned long pr_flag; /* flags */
__kernel_uid_t pr_uid;
__kernel_gid_t pr_gid;
- pid_t pr_pid, pr_ppid, pr_pgrp, pr_sid;
+ __kernel_pid_t pr_pid, pr_ppid, pr_pgrp, pr_sid;
/* Lots missing */
char pr_fname[16]; /* filename of executable */
char pr_psargs[ELF_PRARGSZ]; /* initial part of arg list */
};

-#ifndef __KERNEL__
-typedef struct elf_prstatus prstatus_t;
-typedef struct elf_prpsinfo prpsinfo_t;
-#define PRARGSZ ELF_PRARGSZ
-#endif
-
-
#endif /* _UAPI_LINUX_ELFCORE_H */
--
2.18.0
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