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.mari...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
CC: Andrey Konovalov <andreyk...@google.com>
CC: Alexander Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Vincenzo Frascino <vincenzo.frasc...@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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