[RFC][PATCH 1/3] elf: Make AT_FLAGS arch configurable

From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Shuah Khan <shuah@kernel.org>,
	Chintan Pandya <cpandya@codeaurora.org>,
	Jacob Bramley <Jacob.Bramley@arm.com>,
	Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Lee Smith <Lee.Smith@arm.com>, Kostya Serebryany <kcc@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Evgeniy Stepanov <eugenis@google.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>
Subject: [RFC][PATCH 1/3] elf: Make AT_FLAGS arch configurable
Date: Mon, 10 Dec 2018 14:30:42 +0000	[thread overview]
Message-ID: <20181210143044.12714-2-vincenzo.frascino@arm.com> (raw)
In-Reply-To: <20181210143044.12714-1-vincenzo.frascino@arm.com>

Currently, the AT_FLAGS in the elf auxiliary vector are set to 0
by default by the kernel.
Some architectures might need to expose to the userspace a non-zero
value to advertise some platform specific ABI functionalities.

This patch makes AT_FLAGS configurable by the architectures that
require it.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
CC: Andrey Konovalov <andreyknvl@google.com>
CC: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 fs/binfmt_elf.c        | 6 +++++-
 fs/binfmt_elf_fdpic.c  | 6 +++++-
 fs/compat_binfmt_elf.c | 5 +++++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 54207327f98f..9fa20cc4a437 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -86,6 +86,10 @@ static int elf_core_dump(struct coredump_params *cprm);
 #define ELF_CORE_EFLAGS	0
 #endif
 
+#ifndef ELF_AT_FLAGS
+#define ELF_AT_FLAGS	0
+#endif
+
 #define ELF_PAGESTART(_v) ((_v) & ~(unsigned long)(ELF_MIN_ALIGN-1))
 #define ELF_PAGEOFFSET(_v) ((_v) & (ELF_MIN_ALIGN-1))
 #define ELF_PAGEALIGN(_v) (((_v) + ELF_MIN_ALIGN - 1) & ~(ELF_MIN_ALIGN - 1))
@@ -251,7 +255,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
 	NEW_AUX_ENT(AT_PHENT, sizeof(struct elf_phdr));
 	NEW_AUX_ENT(AT_PHNUM, exec->e_phnum);
 	NEW_AUX_ENT(AT_BASE, interp_load_addr);
-	NEW_AUX_ENT(AT_FLAGS, 0);
+	NEW_AUX_ENT(AT_FLAGS, ELF_AT_FLAGS);
 	NEW_AUX_ENT(AT_ENTRY, exec->e_entry);
 	NEW_AUX_ENT(AT_UID, from_kuid_munged(cred->user_ns, cred->uid));
 	NEW_AUX_ENT(AT_EUID, from_kuid_munged(cred->user_ns, cred->euid));
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index b53bb3729ac1..cf1e680a6b88 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -82,6 +82,10 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *,
 static int elf_fdpic_core_dump(struct coredump_params *cprm);
 #endif
 
+#ifndef ELF_AT_FLAGS
+#define ELF_AT_FLAGS	0
+#endif
+
 static struct linux_binfmt elf_fdpic_format = {
 	.module		= THIS_MODULE,
 	.load_binary	= load_elf_fdpic_binary,
@@ -651,7 +655,7 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
 	NEW_AUX_ENT(AT_PHENT,	sizeof(struct elf_phdr));
 	NEW_AUX_ENT(AT_PHNUM,	exec_params->hdr.e_phnum);
 	NEW_AUX_ENT(AT_BASE,	interp_params->elfhdr_addr);
-	NEW_AUX_ENT(AT_FLAGS,	0);
+	NEW_AUX_ENT(AT_FLAGS,	ELF_AT_FLAGS);
 	NEW_AUX_ENT(AT_ENTRY,	exec_params->entry_addr);
 	NEW_AUX_ENT(AT_UID,	(elf_addr_t) from_kuid_munged(cred->user_ns, cred->uid));
 	NEW_AUX_ENT(AT_EUID,	(elf_addr_t) from_kuid_munged(cred->user_ns, cred->euid));
diff --git a/fs/compat_binfmt_elf.c b/fs/compat_binfmt_elf.c
index 15f6e96b3bd9..a21cf99701ae 100644
--- a/fs/compat_binfmt_elf.c
+++ b/fs/compat_binfmt_elf.c
@@ -79,6 +79,11 @@
 #define	ELF_HWCAP2		COMPAT_ELF_HWCAP2
 #endif
 
+#ifdef	COMPAT_ELF_AT_FLAGS
+#undef	ELF_AT_FLAGS
+#define	ELF_AT_FLAGS		COMPAT_ELF_AT_FLAGS
+#endif
+
 #ifdef	COMPAT_ARCH_DLINFO
 #undef	ARCH_DLINFO
 #define	ARCH_DLINFO		COMPAT_ARCH_DLINFO
-- 
2.19.2

