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authorJosh Poimboeuf <jpoimboe@redhat.com>2017-11-16 20:45:37 +0300
committerMichael Ellerman <mpe@ellerman.id.au>2017-12-11 05:03:29 +0300
commitb9eab08d012fa093947b230f9a87257c27fb829b (patch)
treefa5f33c519c97d9cbbf59b4598a8fdf8e8f4d273
parenta443bf6e8a7674b86221f4922cae82d67dc9e8ad (diff)
downloadlinux-b9eab08d012fa093947b230f9a87257c27fb829b.tar.xz
powerpc/modules: Don't try to restore r2 after a sibling call
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>
-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 abef812de7f8..2c895e8d07f7 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -33,6 +33,7 @@ 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 1685b40f3935..5b44668c0e45 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -487,7 +487,17 @@ 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 d469224c4ada..096d4e4d31e6 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -302,6 +302,11 @@ 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;