is_early_mcount_callsite() needs to detect either the two instruction or
the three instruction versions of the _mcount() sequence.
But if we're running a kernel with the two instruction sequence, we need
to be careful not to read instruction - 2, otherwise we might fall off
the front of a page and cause an oops.
While we're here convert to bool to make the return semantics clear.
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
---
arch/powerpc/kernel/module_64.c | 30 ++++++++++++++----------------
1 file changed, 14 insertions(+), 16 deletions(-)
Squash.
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 32c10e0d2aa5..495df4340623 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -449,27 +449,25 @@ static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
}
#ifdef CC_USING_MPROFILE_KERNEL
-static int is_early_mcount_callsite(u32 *instruction)
+static bool is_early_mcount_callsite(u32 *instruction)
{
- /* -mprofile-kernel sequence starting with
- * mflr r0 and maybe std r0, LRSAVE(r1).
+ /*
+ * Check if this is one of the -mprofile-kernel sequences.
*/
- if ((instruction[-3] == PPC_INST_MFLR &&
- instruction[-2] == PPC_INST_STD_LR) ||
- instruction[-2] == PPC_INST_MFLR) {
- /* Nothing to be done here, it's an _mcount
- * call location and r2 will have to be
- * restored in the _mcount function.
- */
- return 1;
- }
- return 0;
+ if (instruction[-1] == PPC_INST_STD_LR &&
+ instruction[-2] == PPC_INST_MFLR)
+ return true;
+
+ if (instruction[-1] == PPC_INST_MFLR)
+ return true;
+
+ return false;
}
#else
/* without -mprofile-kernel, mcount calls are never early */
-static int is_early_mcount_callsite(u32 *instruction)
+static bool is_early_mcount_callsite(u32 *instruction)
{
- return 0;
+ return false;
}
#endif
@@ -478,7 +476,7 @@ static int is_early_mcount_callsite(u32 *instruction)
static int restore_r2(u32 *instruction, struct module *me)
{
if (*instruction != PPC_INST_NOP) {
- if (is_early_mcount_callsite(instruction))
+ if (is_early_mcount_callsite(instruction - 1))
return 1;
pr_err("%s: Expect noop after relocate, got %08x\n",
me->name, *instruction);
--
2.5.0
--
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