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x86,kprobes: Fix optprobe trampoline to generate complete pt_regs

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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@infradead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164826166027.2455864.14759128090648961900.stgit@devnote2
This commit is contained in:
Masami Hiramatsu 2022-03-26 11:27:40 +09:00 committed by Alexei Starovoitov
parent 0ef6f5c093
commit 45c23bf4d1
1 changed files with 16 additions and 9 deletions
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25
arch/x86/kernel/kprobes/opt.c
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@ -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