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