An arch may want to tweak the mmap prot flags for an ELF
executable's initial mappings. For example, arm64 is going to need
to add PROT_BTI_GUARDED for executable pages in an ELF process
whose executable is marked as using Branch Target Identification
(an ARMv8.5-A control flow integrity feature).
So that this can be done in a generic way, add a hook
arch_elf_adjust_prot() to modify the prot flags as desired: arches
can select CONFIG_HAVE_ELF_PROT and implement their own backend
where necessary.
By default, leave the prot flags unchanged.
Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
---
fs/Kconfig.binfmt | 3 +++
fs/binfmt_elf.c | 18 ++++++++++++------
include/linux/elf.h | 13 +++++++++++++
3 files changed, 28 insertions(+), 6 deletions(-)
diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index 175a1f5..cd3d315 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -35,6 +35,9 @@ config COMPAT_BINFMT_ELF
config ARCH_BINFMT_ELF_STATE
bool
+config ARCH_HAVE_ELF_PROT
+ bool
+
config ARCH_USE_GNU_PROPERTY
bool
depends on 64BIT
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 32c9c13..3d88dcc 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -524,7 +524,8 @@ static inline int arch_check_elf(struct elfhdr *ehdr, bool has_interp,
#endif /* !CONFIG_ARCH_BINFMT_ELF_STATE */
-static inline int make_prot(u32 p_flags)
+static inline int make_prot(u32 p_flags, struct arch_elf_state *arch_state,
+ bool has_interp, bool is_interp)
{
int prot = 0;
@@ -534,7 +535,8 @@ static inline int make_prot(u32 p_flags)
prot |= PROT_WRITE;
if (p_flags & PF_X)
prot |= PROT_EXEC;
- return prot;
+
+ return arch_elf_adjust_prot(prot, arch_state, has_interp, is_interp);
}
/* This is much more generalized than the library routine read function,
@@ -544,7 +546,8 @@ static inline int make_prot(u32 p_flags)
static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
struct file *interpreter, unsigned long *interp_map_addr,
- unsigned long no_base, struct elf_phdr *interp_elf_phdata)
+ unsigned long no_base, struct elf_phdr *interp_elf_phdata,
+ struct arch_elf_state *arch_state)
{
struct elf_phdr *eppnt;
unsigned long load_addr = 0;
@@ -576,7 +579,8 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
for (i = 0; i < interp_elf_ex->e_phnum; i++, eppnt++) {
if (eppnt->p_type == PT_LOAD) {
int elf_type = MAP_PRIVATE | MAP_DENYWRITE;
- int elf_prot = make_prot(eppnt->p_flags);
+ int elf_prot = make_prot(eppnt->p_flags, arch_state,
+ true, true);
unsigned long vaddr = 0;
unsigned long k, map_addr;
@@ -952,7 +956,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
elf_fixed = MAP_FIXED;
}
- elf_prot = make_prot(elf_ppnt->p_flags);
+ elf_prot = make_prot(elf_ppnt->p_flags, &arch_state,
+ !!interpreter, false);
elf_flags = MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE;
@@ -1098,7 +1103,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
elf_entry = load_elf_interp(&loc->interp_elf_ex,
interpreter,
&interp_map_addr,
- load_bias, interp_elf_phdata);
+ load_bias, interp_elf_phdata,
+ &arch_state);
if (!IS_ERR((void *)elf_entry)) {
/*
* load_elf_interp() returns relocation
diff --git a/include/linux/elf.h b/include/linux/elf.h
index cfcf154..2057187 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -75,4 +75,17 @@ static inline int arch_parse_property(void *ehdr, void *phdr, struct file *f,
static inline int get_gnu_property(void *ehdr_p, void *phdr_p, struct file *f,
u32 pr_type, u32 *feature) { return 0; }
#endif
+
+#ifdef CONFIG_ARCH_HAVE_ELF_PROT
+int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
+ bool has_interp, bool is_interp);
+#else
+static inline int arch_elf_adjust_prot(int prot,
+ const struct arch_elf_state *state,
+ bool has_interp, bool is_interp)
+{
+ return prot;
+}
+#endif
+
#endif /* _LINUX_ELF_H */
--
2.1.4
