@@ -117,6 +117,20 @@ bool_t arch_livepatch_symbol_ok(const struct livepatch_elf *elf,
return true;
}
+int arch_livepatch_symbol_check(const struct livepatch_elf *elf,
+ const struct livepatch_elf_sym *sym)
+{
+#ifdef CONFIG_ARM_32
+ /*
+ * Xen does not use Thumb instructions - and we should not see any of
+ * them. If we do, abort.
+ */
+ if ( sym->name && *sym->name == '$' && sym->name[1] == 't' )
+ return -EINVAL;
+#endif
+ return 0;
+}
+
int arch_livepatch_perform_rel(struct livepatch_elf *elf,
const struct livepatch_elf_sec *base,
const struct livepatch_elf_sec *rela)
@@ -125,6 +125,13 @@ bool_t arch_livepatch_symbol_ok(const struct livepatch_elf *elf,
return true;
}
+int arch_livepatch_symbol_check(const struct livepatch_elf *elf,
+ const struct livepatch_elf_sym *sym)
+{
+ /* No special checks on x86. */
+ return 0;
+}
+
int arch_livepatch_perform_rel(struct livepatch_elf *elf,
const struct livepatch_elf_sec *base,
const struct livepatch_elf_sec *rela)
@@ -243,6 +243,7 @@ static int elf_get_sym(struct livepatch_elf *elf, const void *data)
for ( i = 1; i < nsym; i++ )
{
const Elf_Sym *s = symtab_sec->data + symtab_sec->sec->sh_entsize * i;
+ int rc;
delta = s->st_name;
/* Boundary check within the .strtab. */
@@ -255,6 +256,14 @@ static int elf_get_sym(struct livepatch_elf *elf, const void *data)
sym[i].sym = s;
sym[i].name = strtab_sec->data + delta;
+ /* On ARM we should NEVER see $t* symbols. */
+ rc = arch_livepatch_symbol_check(elf, &sym[i]);
+ if ( rc )
+ {
+ dprintk(XENLOG_ERR, LIVEPATCH "%s: Symbol '%s' should not be in payload!\n",
+ elf->name, sym[i].name);
+ return rc;
+ }
}
elf->nsym = nsym;
@@ -48,6 +48,8 @@ bool_t is_patch(const void *addr);
int arch_livepatch_verify_elf(const struct livepatch_elf *elf);
bool_t arch_livepatch_symbol_ok(const struct livepatch_elf *elf,
const struct livepatch_elf_sym *sym);
+int arch_livepatch_symbol_check(const struct livepatch_elf *elf,
+ const struct livepatch_elf_sym *sym);
int arch_livepatch_perform_rel(struct livepatch_elf *elf,
const struct livepatch_elf_sec *base,
const struct livepatch_elf_sec *rela);
Certain platforms, such as ARM [32|64] add extra mapping symbols such as $x (for ARM64 instructions), or more interesting to this patch: $t (for Thumb instructions). These symbols are suppose to help the final linker to make any adjustments (such as add an veneer). But more importantly - we do not compile Xen with any Thumb instructions (which are variable length) - and if we find these mapping symbols we should disallow such payload. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> --- Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Ross Lagerwall <ross.lagerwall@citrix.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Julien Grall <julien.grall@arm.com Cc: Jan Beulich <jbeulich@suse.com> Cc: Andrew Cooper <andrew.cooper3@citrix.com> v3: New submission. Use &sym[i] instead of sym (as that will always be NULL). --- xen/arch/arm/livepatch.c | 14 ++++++++++++++ xen/arch/x86/livepatch.c | 7 +++++++ xen/common/livepatch_elf.c | 9 +++++++++ xen/include/xen/livepatch.h | 2 ++ 4 files changed, 32 insertions(+)