From: Josh Poimboeuf <jpoimboe@redhat.com>
To: live-patching@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Jessica Yu <jeyu@kernel.org>,
Joe Lawrence <joe.lawrence@redhat.com>,
Miroslav Benes <mbenes@suse.cz>,
x86@kernel.org
Subject: [PATCH v4 07/11] x86/module: Use text_poke() for late relocations
Date: Wed, 29 Apr 2020 10:24:49 -0500 [thread overview]
Message-ID: <33247df7035761d5824f27463ab796f8be013005.1588173720.git.jpoimboe@redhat.com> (raw)
In-Reply-To: <cover.1588173720.git.jpoimboe@redhat.com>
From: Peter Zijlstra <peterz@infradead.org>
Because of late module patching, a livepatch module needs to be able to
apply some of its relocations well after it has been loaded. Instead of
playing games with module_{dis,en}able_ro(), use existing text poking
mechanisms to apply relocations after module loading.
So far only x86, s390 and Power have HAVE_LIVEPATCH but only the first
two also have STRICT_MODULE_RWX.
This will allow removal of the last module_disable_ro() usage in
livepatch. The ultimate goal is to completely disallow making
executable mappings writable.
[ jpoimboe: Split up patches. Use mod state to determine whether
memcpy() can be used. Implement text_poke() for UML. ]
Cc: x86@kernel.org
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
---
arch/um/kernel/um_arch.c | 16 ++++++++++++++++
arch/x86/kernel/module.c | 38 +++++++++++++++++++++++++++++++-------
2 files changed, 47 insertions(+), 7 deletions(-)
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 0f40eccbd759..375ab720e4aa 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -362,3 +362,19 @@ void __init check_bugs(void)
void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
{
}
+
+void *text_poke(void *addr, const void *opcode, size_t len)
+{
+ /*
+ * In UML, the only reference to this function is in
+ * apply_relocate_add(), which shouldn't ever actually call this
+ * because UML doesn't have live patching.
+ */
+ WARN_ON(1);
+
+ return memcpy(addr, opcode, len);
+}
+
+void text_poke_sync(void)
+{
+}
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index d5c72cb877b3..7614f478fd7a 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -126,11 +126,12 @@ int apply_relocate(Elf32_Shdr *sechdrs,
return 0;
}
#else /*X86_64*/
-int apply_relocate_add(Elf64_Shdr *sechdrs,
+static int __apply_relocate_add(Elf64_Shdr *sechdrs,
const char *strtab,
unsigned int symindex,
unsigned int relsec,
- struct module *me)
+ struct module *me,
+ void *(*write)(void *dest, const void *src, size_t len))
{
unsigned int i;
Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
@@ -162,19 +163,19 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
case R_X86_64_64:
if (*(u64 *)loc != 0)
goto invalid_relocation;
- *(u64 *)loc = val;
+ write(loc, &val, 8);
break;
case R_X86_64_32:
if (*(u32 *)loc != 0)
goto invalid_relocation;
- *(u32 *)loc = val;
+ write(loc, &val, 4);
if (val != *(u32 *)loc)
goto overflow;
break;
case R_X86_64_32S:
if (*(s32 *)loc != 0)
goto invalid_relocation;
- *(s32 *)loc = val;
+ write(loc, &val, 4);
if ((s64)val != *(s32 *)loc)
goto overflow;
break;
@@ -183,7 +184,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
if (*(u32 *)loc != 0)
goto invalid_relocation;
val -= (u64)loc;
- *(u32 *)loc = val;
+ write(loc, &val, 4);
#if 0
if ((s64)val != *(s32 *)loc)
goto overflow;
@@ -193,7 +194,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
if (*(u64 *)loc != 0)
goto invalid_relocation;
val -= (u64)loc;
- *(u64 *)loc = val;
+ write(loc, &val, 8);
break;
default:
pr_err("%s: Unknown rela relocation: %llu\n",
@@ -215,6 +216,29 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
me->name);
return -ENOEXEC;
}
+
+int apply_relocate_add(Elf64_Shdr *sechdrs,
+ const char *strtab,
+ unsigned int symindex,
+ unsigned int relsec,
+ struct module *me)
+{
+ int ret;
+ bool early = me->state == MODULE_STATE_UNFORMED;
+ void *(*write)(void *, const void *, size_t) = memcpy;
+
+ if (!early)
+ write = text_poke;
+
+ ret = __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
+ write);
+
+ if (!early)
+ text_poke_sync();
+
+ return ret;
+}
+
#endif
int module_finalize(const Elf_Ehdr *hdr,
--
2.21.1
next prev parent reply other threads:[~2020-04-29 15:25 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 15:24 [PATCH v4 00/11] livepatch,module: Remove .klp.arch and module_disable_ro() Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 01/11] livepatch: Disallow vmlinux.ko Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 02/11] livepatch: Apply vmlinux-specific KLP relocations early Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 03/11] livepatch: Remove .klp.arch Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 04/11] livepatch: Prevent module-specific KLP rela sections from referencing vmlinux symbols Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 05/11] s390: Change s390_kernel_write() return type to match memcpy() Josh Poimboeuf
2020-05-07 13:36 ` Jiri Kosina
2020-05-07 16:01 ` Gerald Schaefer
2020-04-29 15:24 ` [PATCH v4 06/11] s390/module: Use s390_kernel_write() for late relocations Josh Poimboeuf
2020-05-07 10:00 ` Jiri Kosina
2020-05-07 12:27 ` Gerald Schaefer
2020-04-29 15:24 ` Josh Poimboeuf [this message]
2020-04-29 15:24 ` [PATCH v4 08/11] livepatch: Remove module_disable_ro() usage Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 09/11] module: Remove module_disable_ro() Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 10/11] x86/module: Use text_mutex in apply_relocate_add() Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 11/11] module: Make module_enable_ro() static again Josh Poimboeuf
2020-04-30 11:10 ` Jessica Yu
2020-04-30 11:35 ` Miroslav Benes
2020-04-30 11:40 ` Jessica Yu
2020-04-30 12:23 ` Jessica Yu
2020-06-05 13:24 ` Guenter Roeck
2020-06-05 14:20 ` Jessica Yu
2020-06-05 14:39 ` Josh Poimboeuf
2020-04-30 11:33 ` [PATCH v4 00/11] livepatch,module: Remove .klp.arch and module_disable_ro() Jessica Yu
2020-05-04 22:20 ` Jiri Kosina
2020-05-07 22:17 ` Jiri Kosina
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