From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Josh Poimboeuf <jpoimboe@redhat.com>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
Petr Mladek <pmladek@suse.com>,
Joe Lawrence <joe.lawrence@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
"Naveen N . Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: "live-patching@vger.kernel.org" <live-patching@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH v2 03/13] powerpc/module_32: Fix livepatching for RO modules
Date: Mon, 20 Dec 2021 16:38:09 +0000 [thread overview]
Message-ID: <d5697157cb7dba3927e19aa17c915a83bc550bb2.1640017960.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1640017960.git.christophe.leroy@csgroup.eu>
Livepatching a loaded module involves applying relocations through
apply_relocate_add(), which attempts to write to read-only memory when
CONFIG_STRICT_MODULE_RWX=y.
R_PPC_ADDR16_LO, R_PPC_ADDR16_HI, R_PPC_ADDR16_HA and R_PPC_REL24 are
the types generated by the kpatch-build userspace tool or klp-convert
kernel tree observed applying a relocation to a post-init module.
Use patch_instruction() to patch those relocations.
Commit 8734b41b3efe ("powerpc/module_64: Fix livepatching for
RO modules") did similar change in module_64.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Russell Currey <ruscur@russell.cc>
---
arch/powerpc/kernel/module_32.c | 44 ++++++++++++++++++++++-----------
1 file changed, 30 insertions(+), 14 deletions(-)
diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c
index a491ad481d85..a0432ef46967 100644
--- a/arch/powerpc/kernel/module_32.c
+++ b/arch/powerpc/kernel/module_32.c
@@ -18,6 +18,7 @@
#include <linux/bug.h>
#include <linux/sort.h>
#include <asm/setup.h>
+#include <asm/code-patching.h>
/* Count how many different relocations (different symbol, different
addend) */
@@ -174,15 +175,25 @@ static uint32_t do_plt_call(void *location,
entry++;
}
- entry->jump[0] = PPC_RAW_LIS(_R12, PPC_HA(val));
- entry->jump[1] = PPC_RAW_ADDI(_R12, _R12, PPC_LO(val));
- entry->jump[2] = PPC_RAW_MTCTR(_R12);
- entry->jump[3] = PPC_RAW_BCTR();
+ if (patch_instruction(&entry->jump[0], ppc_inst(PPC_RAW_LIS(_R12, PPC_HA(val)))))
+ return 0;
+ if (patch_instruction(&entry->jump[1], ppc_inst(PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)))))
+ return 0;
+ if (patch_instruction(&entry->jump[2], ppc_inst(PPC_RAW_MTCTR(_R12))))
+ return 0;
+ if (patch_instruction(&entry->jump[3], ppc_inst(PPC_RAW_BCTR())))
+ return 0;
pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
return (uint32_t)entry;
}
+static int patch_location_16(uint32_t *loc, u16 value)
+{
+ loc = PTR_ALIGN_DOWN(loc, sizeof(u32));
+ return patch_instruction(loc, ppc_inst((*loc & 0xffff0000) | value));
+}
+
int apply_relocate_add(Elf32_Shdr *sechdrs,
const char *strtab,
unsigned int symindex,
@@ -216,37 +227,42 @@ int apply_relocate_add(Elf32_Shdr *sechdrs,
case R_PPC_ADDR16_LO:
/* Low half of the symbol */
- *(uint16_t *)location = value;
+ if (patch_location_16(location, PPC_LO(value)))
+ return -EFAULT;
break;
case R_PPC_ADDR16_HI:
/* Higher half of the symbol */
- *(uint16_t *)location = (value >> 16);
+ if (patch_location_16(location, PPC_HI(value)))
+ return -EFAULT;
break;
case R_PPC_ADDR16_HA:
- /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
- (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
- This is the same, only sane.
- */
- *(uint16_t *)location = (value + 0x8000) >> 16;
+ if (patch_location_16(location, PPC_HA(value)))
+ return -EFAULT;
break;
case R_PPC_REL24:
if ((int)(value - (uint32_t)location) < -0x02000000
- || (int)(value - (uint32_t)location) >= 0x02000000)
+ || (int)(value - (uint32_t)location) >= 0x02000000) {
value = do_plt_call(location, value,
sechdrs, module);
+ if (!value)
+ return -EFAULT;
+ }
/* Only replace bits 2 through 26 */
pr_debug("REL24 value = %08X. location = %08X\n",
value, (uint32_t)location);
pr_debug("Location before: %08X.\n",
*(uint32_t *)location);
- *(uint32_t *)location
- = (*(uint32_t *)location & ~0x03fffffc)
+ value = (*(uint32_t *)location & ~0x03fffffc)
| ((value - (uint32_t)location)
& 0x03fffffc);
+
+ if (patch_instruction(location, ppc_inst(value)))
+ return -EFAULT;
+
pr_debug("Location after: %08X.\n",
*(uint32_t *)location);
pr_debug("ie. jump to %08X+%08X = %08X\n",
--
2.33.1
next prev parent reply other threads:[~2021-12-20 16:40 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-20 16:37 [PATCH v2 00/13] Implement livepatch on PPC32 and more Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 01/13] livepatch: Fix build failure on 32 bits processors Christophe Leroy
2021-12-22 13:47 ` Miroslav Benes
2022-01-04 19:35 ` Joe Lawrence
2021-12-20 16:38 ` [PATCH v2 02/13] tracing: Fix selftest config check for function graph start up test Christophe Leroy
2022-02-24 13:43 ` Christophe Leroy
2022-02-24 14:53 ` Steven Rostedt
2022-02-24 15:13 ` Christophe Leroy
2022-02-24 15:17 ` Steven Rostedt
2022-02-25 2:42 ` Michael Ellerman
2021-12-20 16:38 ` Christophe Leroy [this message]
2022-01-04 19:44 ` [PATCH v2 03/13] powerpc/module_32: Fix livepatching for RO modules Joe Lawrence
2021-12-20 16:38 ` [PATCH v2 04/13] powerpc/ftrace: Add support for livepatch to PPC32 Christophe Leroy
2021-12-22 14:00 ` Miroslav Benes
2021-12-20 16:38 ` [PATCH v2 05/13] powerpc/ftrace: Don't save again LR in ftrace_regs_caller() on PPC32 Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 06/13] powerpc/ftrace: Simplify PPC32's return_to_handler() Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 07/13] powerpc/ftrace: Prepare PPC32's ftrace_caller() for CONFIG_DYNAMIC_FTRACE_WITH_ARGS Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 08/13] powerpc/ftrace: Prepare PPC64's " Christophe Leroy
2022-02-14 15:19 ` Naveen N. Rao
2021-12-20 16:38 ` [PATCH v2 09/13] powerpc/ftrace: Implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS Christophe Leroy
2021-12-22 14:19 ` Miroslav Benes
2022-02-14 15:25 ` Naveen N. Rao
2022-02-15 8:00 ` Christophe Leroy
2022-02-15 11:05 ` Michael Ellerman
2022-02-15 13:36 ` Naveen N. Rao
2022-02-15 14:28 ` Christophe Leroy
2022-02-15 14:51 ` Christophe Leroy
2022-02-15 16:25 ` Naveen N. Rao
2022-02-16 13:04 ` Heiko Carstens
2022-02-16 13:27 ` Sven Schnelle
2022-02-15 14:38 ` Steven Rostedt
2022-02-15 16:26 ` Naveen N. Rao
2021-12-20 16:38 ` [PATCH v2 10/13] powerpc/ftrace: Refactor ftrace_{en/dis}able_ftrace_graph_caller Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 11/13] powerpc/ftrace: directly call of function graph tracer by ftrace caller Christophe Leroy
2022-02-14 17:24 ` Naveen N. Rao
2022-02-14 19:03 ` Steven Rostedt
2021-12-20 16:38 ` [PATCH v2 12/13] powerpc/ftrace: Prepare ftrace_64_mprofile.S for reuse by PPC32 Christophe Leroy
2022-02-14 17:51 ` Naveen N. Rao
2022-02-15 8:33 ` Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 13/13] powerpc/ftrace: Remove ftrace_32.S Christophe Leroy
2022-02-11 7:41 ` [PATCH] Fixup for next-test 3a1a8f078670 ("powerpc/ftrace: Remove ftrace_32.S") Christophe Leroy
2022-02-16 12:26 ` [PATCH v2 00/13] Implement livepatch on PPC32 and more Michael Ellerman
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