[PATCH 3/5] powerpc64: Add .opd based function descriptor dereference

Sergey Senozhatsky
2017-09-16T03:53:45Z

We are moving towards separate kernel and module function descriptor
dereference callbacks. This patch enables it for powerpc64.

For pointers that belong to the kernel
- Added __start_opd and __end_opd pointers, to track the kernel
.opd section address range;

- Added dereference_kernel_function_descriptor(). Now we
will dereference only function pointers that are within
[__start_opd, __end_opd];

For pointers that belong to a module
- Added dereference_module_function_descriptor() to handle module
function descriptor dereference. Now we will dereference only
pointers that are within [module->opd.start, module->opd.end].

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
arch/powerpc/include/asm/module.h | 3 +++
arch/powerpc/include/asm/sections.h | 13 +++++++++++++
arch/powerpc/kernel/module_64.c | 16 ++++++++++++++++
arch/powerpc/kernel/vmlinux.lds.S | 2 ++
4 files changed, 34 insertions(+)

diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index 6c0132c7212f..7e28442827f1 100644
--- a/arch/powerpc/include/asm/module.h
+++ b/arch/powerpc/include/asm/module.h
@@ -45,6 +45,9 @@ struct mod_arch_specific {
unsigned long tramp;
#endif

+ /* For module function descriptor dereference */
+ unsigned long start_opd;
+ unsigned long end_opd;
#else /* powerpc64 */
/* Indices of PLT sections within module. */
unsigned int core_plt_section;
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 7902d6358854..7cc4db86952b 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -16,6 +16,9 @@ extern char __end_interrupts[];
extern char __prom_init_toc_start[];
extern char __prom_init_toc_end[];

+extern char __start_opd[];
+extern char __end_opd[];
+
static inline int in_kernel_text(unsigned long addr)
{
if (addr >= (unsigned long)_stext && addr < (unsigned long)__init_end)
@@ -66,6 +69,8 @@ static inline int overlaps_kvm_tmp(unsigned long start, unsigned long end)

#ifdef PPC64_ELF_ABI_v1
#undef dereference_function_descriptor
+#undef dereference_kernel_function_descriptor
+
static inline void *dereference_function_descriptor(void *ptr)
{
struct ppc64_opd_entry *desc = ptr;
@@ -75,6 +80,14 @@ static inline void *dereference_function_descriptor(void *ptr)
ptr = p;
return ptr;
}
+
+static inline void *dereference_kernel_function_descriptor(void *ptr)
+{
+ if (ptr < (void *)__start_opd || (void *)__end_opd < ptr)
+ return ptr;
+
+ return dereference_function_descriptor(ptr);
+}
#endif /* PPC64_ELF_ABI_v1 */

#endif
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 0b0f89685b67..52aa5d668364 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -344,6 +344,11 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
else if (strcmp(secstrings+sechdrs[i].sh_name,"__versions")=0)
dedotify_versions((void *)hdr + sechdrs[i].sh_offset,
sechdrs[i].sh_size);
+ else if (strcmp(secstrings + sechdrs[i].sh_name, ".opd")=0) {
+ me->arch.start_opd = sechdrs[i].sh_offset;
+ me->arch.end_opd = me->arch.start_opd +
+ sechdrs[i].sh_size;
+ }

/* We don't handle .init for the moment: rename to _init */
while ((p = strstr(secstrings + sechdrs[i].sh_name, ".init")))
@@ -712,6 +717,17 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
return 0;
}

+#ifdef PPC64_ELF_ABI_v1
+unsigned long dereference_module_function_descriptor(struct module *mod,
+ unsigned long addr)
+{
+ if (addr < mod->arch.start_opd || mod->arch.end_opd < addr)
+ return addr;
+
+ return dereference_function_descriptor(addr);
+}
+#endif /* PPC64_ELF_ABI_v1 */
+
#ifdef CONFIG_DYNAMIC_FTRACE

#ifdef CC_USING_MPROFILE_KERNEL
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 882628fa6987..70e10251e083 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -277,7 +277,9 @@ SECTIONS
}

.opd : AT(ADDR(.opd) - LOAD_OFFSET) {
+ __start_opd = .;
*(.opd)
+ __end_opd = .;
}

. = ALIGN(256);
--
2.14.1