summaryrefslogtreecommitdiff
path: root/arch
diff options
context:
space:
mode:
authorJosh Poimboeuf <jpoimboe@redhat.com>2017-11-16 11:45:37 -0600
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-22 09:17:57 +0100
commitf6edf95e54cb18ef12e82298e44eebad2fb9aa7d (patch)
tree764e55d9b3876819dac502a80b523ca470d0bf25 /arch
parent049cff8555d41211c3dfbdcfc46cbb818d32eeae (diff)
powerpc/modules: Don't try to restore r2 after a sibling call
[ Upstream commit b9eab08d012fa093947b230f9a87257c27fb829b ] When attempting to load a livepatch module, I got the following error: module_64: patch_module: Expect noop after relocate, got 3c820000 The error was triggered by the following code in unregister_netdevice_queue(): 14c: 00 00 00 48 b 14c <unregister_netdevice_queue+0x14c> 14c: R_PPC64_REL24 net_set_todo 150: 00 00 82 3c addis r4,r2,0 GCC didn't insert a nop after the branch to net_set_todo() because it's a sibling call, so it never returns. The nop isn't needed after the branch in that case. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Reviewed-and-tested-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/include/asm/code-patching.h1
-rw-r--r--arch/powerpc/kernel/module_64.c12
-rw-r--r--arch/powerpc/lib/code-patching.c5
3 files changed, 17 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 2015b072422c..b4ab1f497335 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -30,6 +30,7 @@ int patch_branch(unsigned int *addr, unsigned long target, int flags);
int patch_instruction(unsigned int *addr, unsigned int instr);
int instr_is_relative_branch(unsigned int instr);
+int instr_is_relative_link_branch(unsigned int instr);
int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr);
unsigned long branch_target(const unsigned int *instr);
unsigned int translate_branch(const unsigned int *dest,
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 183368e008cf..99407cf12ad5 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -494,7 +494,17 @@ static bool is_early_mcount_callsite(u32 *instruction)
restore r2. */
static int restore_r2(u32 *instruction, struct module *me)
{
- if (is_early_mcount_callsite(instruction - 1))
+ u32 *prev_insn = instruction - 1;
+
+ if (is_early_mcount_callsite(prev_insn))
+ return 1;
+
+ /*
+ * Make sure the branch isn't a sibling call. Sibling calls aren't
+ * "link" branches and they don't return, so they don't need the r2
+ * restore afterwards.
+ */
+ if (!instr_is_relative_link_branch(*prev_insn))
return 1;
if (*instruction != PPC_INST_NOP) {
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index d5edbeb8eb82..753d591f1b52 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -95,6 +95,11 @@ int instr_is_relative_branch(unsigned int instr)
return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
}
+int instr_is_relative_link_branch(unsigned int instr)
+{
+ return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK);
+}
+
static unsigned long branch_iform_target(const unsigned int *instr)
{
signed long imm;