Currently the optprobe trampoline template code ganerate an
almost complete pt_regs on-stack, everything except regs->ss.
The 'regs->ss' points to the top of stack, which is not a
valid segment decriptor.
As same as the rethook does, complete the job by also pushing ss.
Suggested-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
arch/x86/kernel/kprobes/opt.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index b4a54a52aa59..e6b8c5362b94 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -106,7 +106,8 @@ asm (
".global optprobe_template_entry\n"
"optprobe_template_entry:\n"
#ifdef CONFIG_X86_64
- /* We don't bother saving the ss register */
+ " pushq $" __stringify(__KERNEL_DS) "\n"
+ /* Save the 'sp - 8', this will be fixed later. */
" pushq %rsp\n"
" pushfq\n"
".global optprobe_template_clac\n"
@@ -121,14 +122,17 @@ asm (
".global optprobe_template_call\n"
"optprobe_template_call:\n"
ASM_NOP5
- /* Move flags to rsp */
+ /* Copy 'regs->flags' into 'regs->ss'. */
" movq 18*8(%rsp), %rdx\n"
- " movq %rdx, 19*8(%rsp)\n"
+ " movq %rdx, 20*8(%rsp)\n"
RESTORE_REGS_STRING
- /* Skip flags entry */
- " addq $8, %rsp\n"
+ /* Skip 'regs->flags' and 'regs->sp'. */
+ " addq $16, %rsp\n"
+ /* And pop flags register from 'regs->ss'. */
" popfq\n"
#else /* CONFIG_X86_32 */
+ " pushl %ss\n"
+ /* Save the 'sp - 4', this will be fixed later. */
" pushl %esp\n"
" pushfl\n"
".global optprobe_template_clac\n"
@@ -142,12 +146,13 @@ asm (
".global optprobe_template_call\n"
"optprobe_template_call:\n"
ASM_NOP5
- /* Move flags into esp */
+ /* Copy 'regs->flags' into 'regs->ss'. */
" movl 14*4(%esp), %edx\n"
- " movl %edx, 15*4(%esp)\n"
+ " movl %edx, 16*4(%esp)\n"
RESTORE_REGS_STRING
- /* Skip flags entry */
- " addl $4, %esp\n"
+ /* Skip 'regs->flags' and 'regs->sp'. */
+ " addl $8, %esp\n"
+ /* And pop flags register from 'regs->ss'. */
" popfl\n"
#endif
".global optprobe_template_end\n"
@@ -179,6 +184,8 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
kprobes_inc_nmissed_count(&op->kp);
} else {
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+ /* Adjust stack pointer */
+ regs->sp += sizeof(long);
/* Save skipped registers */
regs->cs = __KERNEL_CS;
#ifdef CONFIG_X86_32
