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Initial support for kernels with IBT #29

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Initial support for kernels with IBT #29

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3d2e032
Initial support for kernels with IBT
mlq Jun 28, 2022
5f3bf10
Handle IBT for invalidate_tlb_kernel
mlq Jun 29, 2022
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61 changes: 58 additions & 3 deletions module/pteditor.c
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,33 @@
#include <linux/proc_fs.h>
#include <linux/kprobes.h>

#ifdef CONFIG_X86_KERNEL_IBT
__noendbr u64 ibt_save(void)
{
u64 msr = 0;

if (cpu_feature_enabled(X86_FEATURE_IBT)) {
rdmsrl(MSR_IA32_S_CET, msr);
wrmsrl(MSR_IA32_S_CET, msr & ~CET_ENDBR_EN);
}

return msr;
}

__noendbr void ibt_restore(u64 save)
{
u64 msr;

if (cpu_feature_enabled(X86_FEATURE_IBT)) {
rdmsrl(MSR_IA32_S_CET, msr);
msr &= ~CET_ENDBR_EN;
msr |= (save & CET_ENDBR_EN);
wrmsrl(MSR_IA32_S_CET, msr);
}
}

#endif

#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0)
#include <linux/mmap_lock.h>
#endif
Expand Down Expand Up @@ -105,7 +132,23 @@ static inline int pmd_large(pmd_t pmd) {
#define KPROBE_KALLSYMS_LOOKUP 1
typedef unsigned long (*kallsyms_lookup_name_t)(const char *name);
kallsyms_lookup_name_t kallsyms_lookup_name_func;

#ifdef CONFIG_X86_KERNEL_IBT
unsigned long kallsyms_lookup_name_func_ibt(const char* name) {
u64 ibt;
unsigned long r;

ibt = ibt_save();
r = kallsyms_lookup_name_func(name);
ibt_restore(ibt);

return r;
}

#define kallsyms_lookup_name kallsyms_lookup_name_func_ibt
#else
#define kallsyms_lookup_name kallsyms_lookup_name_func
#endif

static struct kprobe kp = {
.symbol_name = "kallsyms_lookup_name"
Expand Down Expand Up @@ -214,7 +257,14 @@ void _flush_tlb_page_smp(void* info) {
static void
invalidate_tlb_kernel(unsigned long addr) {
#if defined(__i386__) || defined(__x86_64__)
#ifdef CONFIG_X86_KERNEL_IBT
u64 ibt;
ibt = ibt_save();
#endif
flush_tlb_mm_range_func(get_mm(task_pid_nr(current)), addr, addr + real_page_size, real_page_shift, false);
#ifdef CONFIG_X86_KERNEL_IBT
ibt_restore(ibt);
#endif
#elif defined(__aarch64__)
struct vm_area_struct *vma = find_vma(current->mm, addr);
tlb_page_t tlb_page;
Expand Down Expand Up @@ -679,11 +729,16 @@ static int __init pteditor_init(void) {
#endif

#ifdef KPROBE_KALLSYMS_LOOKUP
register_kprobe(&kp);
kallsyms_lookup_name = (kallsyms_lookup_name_t) kp.addr;
r = register_kprobe(&kp);
if (r != 0) {
pr_alert("Could not register kprobe\n");
return -ENXIO;
}

kallsyms_lookup_name_func = (kallsyms_lookup_name_t) kp.addr;
unregister_kprobe(&kp);

if(!unlikely(kallsyms_lookup_name)) {
if(!unlikely(kallsyms_lookup_name_func)) {
pr_alert("Could not retrieve kallsyms_lookup_name address\n");
return -ENXIO;
}
Expand Down