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

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Message-Id: <20170916035347.19705-4-sergey.senozhatsky@gmail.com>
Date:   Sat, 16 Sep 2017 12:53:45 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        "James E . J . Bottomley" <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jessica Yu <jeyu@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        linux-ia64@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [PATCH 3/5] powerpc64: Add .opd based function descriptor dereference

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@...il.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