3.16.68-rc1 review patch. If anyone has any objections, please let me know.
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From: Heiko Carstens heiko.carstens@de.ibm.com
commit d5caa4dbf9bd2ad8cd7f6be0ca76722be947182b upstream.
Use a brcl 0,2 instruction for jump label nops during compile time, so we don't mix up the different nops during mcount/hotpatch call site detection. The initial jump label code instruction replacement will exchange these instructions with either a branch or a brcl 0,0 instruction.
Signed-off-by: Heiko Carstens heiko.carstens@de.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/s390/include/asm/jump_label.h | 7 ++++++- arch/s390/kernel/jump_label.c | 19 +++++++++++++------ 2 files changed, 19 insertions(+), 7 deletions(-)
--- a/arch/s390/include/asm/jump_label.h +++ b/arch/s390/include/asm/jump_label.h @@ -4,6 +4,7 @@ #include <linux/types.h>
#define JUMP_LABEL_NOP_SIZE 6 +#define JUMP_LABEL_NOP_OFFSET 2
#ifdef CONFIG_64BIT #define ASM_PTR ".quad" @@ -13,9 +14,13 @@ #define ASM_ALIGN ".balign 4" #endif
+/* + * We use a brcl 0,2 instruction for jump labels at compile time so it + * can be easily distinguished from a hotpatch generated instruction. + */ static __always_inline bool arch_static_branch(struct static_key *key) { - asm_volatile_goto("0: brcl 0,0\n" + asm_volatile_goto("0: brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n" ".pushsection __jump_table, "aw"\n" ASM_ALIGN "\n" ASM_PTR " 0b, %l[label], %0\n" --- a/arch/s390/kernel/jump_label.c +++ b/arch/s390/kernel/jump_label.c @@ -49,6 +49,11 @@ static void jump_label_bug(struct jump_e panic("Corrupted kernel text"); }
+static struct insn orignop = { + .opcode = 0xc004, + .offset = JUMP_LABEL_NOP_OFFSET >> 1, +}; + static void __jump_label_transform(struct jump_entry *entry, enum jump_label_type type, int init) @@ -59,14 +64,16 @@ static void __jump_label_transform(struc jump_label_make_nop(entry, &old); jump_label_make_branch(entry, &new); } else { - if (init) - jump_label_make_nop(entry, &old); - else - jump_label_make_branch(entry, &old); + jump_label_make_branch(entry, &old); jump_label_make_nop(entry, &new); } - if (memcmp((void *)entry->code, &old, sizeof(old))) - jump_label_bug(entry, &old); + if (init) { + if (memcmp((void *)entry->code, &orignop, sizeof(orignop))) + jump_label_bug(entry, &old); + } else { + if (memcmp((void *)entry->code, &old, sizeof(old))) + jump_label_bug(entry, &old); + } probe_kernel_write((void *)entry->code, &new, sizeof(new)); }