[PATCH 03/10] [elfcore-compat][amd64] clean PRSTATUS_SIZE/SET_PR_FPVALID up properly

Al Viro
2020-12-03T21:47:43Z

From: Al Viro <viro@zeniv.linux.org.uk>

To get rid of hardcoded size/offset in those macros we need to have
a definition of i386 variant of struct elf_prstatus. However, we can't
do that in asm/compat.h - the types needed for that are not there and
adding an include of asm/user32.h into asm/compat.h would cause a lot
of mess.

That could be conveniently done in elfcore-compat.h, but currently there
is nowhere to put arch-dependent parts of it - no asm/elfcore-compat.h.
So we introduce a new file (asm/elfcore-compat.h, present on architectures
that have CONFIG_ARCH_HAS_ELFCORE_COMPAT set, currently only on x86),
have it pulled by linux/elfcore-compat.h and move the definitions there.

As a side benefit, we don't need to worry about accidental inclusion of
that file into binfmt_elf.c itself, so we don't need the dance with
COMPAT_PRSTATUS_SIZE, etc. - only fs/compat_binfmt_elf.c will see
that header.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/Kconfig | 3 +++
arch/x86/Kconfig | 1 +
arch/x86/include/asm/compat.h | 14 --------------
arch/x86/include/asm/elfcore-compat.h | 31 +++++++++++++++++++++++++++++++
fs/compat_binfmt_elf.c | 8 --------
include/linux/elfcore-compat.h | 18 +++++++++++-------
6 files changed, 46 insertions(+), 29 deletions(-)
create mode 100644 arch/x86/include/asm/elfcore-compat.h

diff --git a/arch/Kconfig b/arch/Kconfig
index 56b6ccc0e32d..b4d7eb7ef833 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1028,6 +1028,9 @@ config HAVE_STATIC_CALL_INLINE
bool
depends on HAVE_STATIC_CALL

+config ARCH_HAS_ELFCORE_COMPAT
+ bool
+
source "kernel/gcov/Kconfig"

source "scripts/gcc-plugins/Kconfig"
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f6946b81f74a..8eea77cf53a7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -30,6 +30,7 @@ config X86_64
select MODULES_USE_ELF_RELA
select NEED_DMA_MAP_STATE
select SWIOTLB
+ select ARCH_HAS_ELFCORE_COMPAT

config FORCE_DYNAMIC_FTRACE
def_bool y
diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index 1897e1dcbdd2..423bafe8b797 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -159,20 +159,6 @@ struct compat_shmid64_ds {
compat_ulong_t __unused5;
};

-/*
- * The type of struct elf_prstatus.pr_reg in compatible core dumps.
- */
-typedef struct user_regs_struct compat_elf_gregset_t;
-
-/* Full regset -- prstatus on x32, otherwise on ia32 */
-#define COMPAT_PRSTATUS_SIZE (test_thread_flag(TIF_X32) \
- ? sizeof(struct compat_elf_prstatus) \
- : 144)
-#define COMPAT_SET_PR_FPVALID(S) \
- (*(test_thread_flag(TIF_X32) \
- ? &(S)->pr_fpvalid \
- : (int *)((void *)(S) + 140)) = 1)
-
#ifdef CONFIG_X86_X32_ABI
#define COMPAT_USE_64BIT_TIME \
(!!(task_pt_regs(current)->orig_ax & __X32_SYSCALL_BIT))
diff --git a/arch/x86/include/asm/elfcore-compat.h b/arch/x86/include/asm/elfcore-compat.h
new file mode 100644
index 000000000000..614308ba3b95
--- /dev/null
+++ b/arch/x86/include/asm/elfcore-compat.h
@@ -0,0 +1,31 @@
+#ifndef _ASM_X86_ELFCORE_COMPAT_H
+#define _ASM_X86_ELFCORE_COMPAT_H
+
+#include <asm/user32.h>
+
+/*
+ * On amd64 we have two 32bit ABIs - i386 and x32. The latter
+ * has bigger registers, so we use it for compat_elf_regset_t.
+ * The former uses i386_elf_prstatus and PRSTATUS_SIZE/SET_PR_FPVALID
+ * are used to choose the size and location of ->pr_fpvalid of
+ * the layout actually used.
+ */
+typedef struct user_regs_struct compat_elf_gregset_t;
+
+struct i386_elf_prstatus
+{
+ struct compat_elf_prstatus_common common;
+ struct user_regs_struct32 pr_reg;
+ compat_int_t pr_fpvalid;
+};
+
+#define PRSTATUS_SIZE \
+ (test_thread_flag(TIF_X32) \
+ ? sizeof(struct compat_elf_prstatus) \
+ : sizeof(struct i386_elf_prstatus))
+#define SET_PR_FPVALID(S) \
+ (*(test_thread_flag(TIF_X32) \
+ ? &(S)->pr_fpvalid \
+ : &((struct i386_elf_prstatus *)(S))->pr_fpvalid) = 1)
+
+#endif
diff --git a/fs/compat_binfmt_elf.c b/fs/compat_binfmt_elf.c
index a40df32acff5..41b51b99f492 100644
--- a/fs/compat_binfmt_elf.c
+++ b/fs/compat_binfmt_elf.c
@@ -96,14 +96,6 @@
#define ELF_EXEC_PAGESIZE COMPAT_ELF_EXEC_PAGESIZE
#endif

-#ifdef COMPAT_PRSTATUS_SIZE
-#define PRSTATUS_SIZE COMPAT_PRSTATUS_SIZE
-#endif
-
-#ifdef COMPAT_SET_PR_FPVALID
-#define SET_PR_FPVALID(S) COMPAT_SET_PR_FPVALID(S)
-#endif
-
#ifdef COMPAT_ELF_PLAT_INIT
#undef ELF_PLAT_INIT
#define ELF_PLAT_INIT COMPAT_ELF_PLAT_INIT
diff --git a/include/linux/elfcore-compat.h b/include/linux/elfcore-compat.h
index 4aeda5f1f038..e272c3d452ce 100644
--- a/include/linux/elfcore-compat.h
+++ b/include/linux/elfcore-compat.h
@@ -33,13 +33,6 @@ struct compat_elf_prstatus_common
struct old_timeval32 pr_cstime;
};

-struct compat_elf_prstatus
-{
- struct compat_elf_prstatus_common common;
- compat_elf_gregset_t pr_reg;
- compat_int_t pr_fpvalid;
-};
-
struct compat_elf_prpsinfo
{
char pr_state;
@@ -54,4 +47,15 @@ struct compat_elf_prpsinfo
char pr_psargs[ELF_PRARGSZ];
};

+#ifdef CONFIG_ARCH_HAS_ELFCORE_COMPAT
+#include <asm/elfcore-compat.h>
+#endif
+
+struct compat_elf_prstatus
+{
+ struct compat_elf_prstatus_common common;
+ compat_elf_gregset_t pr_reg;
+ compat_int_t pr_fpvalid;
+};
+
#endif /* _LINUX_ELFCORE_COMPAT_H */
--
2.11.0