Indirect Branch Tracking (IBT) provides an optional legacy code bitmap that allows execution of legacy, non-IBT compatible library by an IBT-enabled application. When set, each bit in the bitmap indicates one page of legacy code.
The bitmap is allocated and setup from the application. Signed-off-by: Yu-cheng Yu <[email protected]> --- arch/x86/include/asm/cet.h | 1 + arch/x86/kernel/cet.c | 23 +++++++++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h index 810d3e386fdb..db40fc54a905 100644 --- a/arch/x86/include/asm/cet.h +++ b/arch/x86/include/asm/cet.h @@ -29,6 +29,7 @@ void cet_disable_free_shstk(struct task_struct *p); int cet_restore_signal(unsigned long ssp); int cet_setup_signal(bool ia32, unsigned long rstor, unsigned long *new_ssp); int cet_setup_ibt(void); +int cet_setup_ibt_bitmap(unsigned long bitmap, unsigned long size); void cet_disable_ibt(void); #else static inline int prctl_cet(int option, unsigned long arg2) { return -EINVAL; } diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c index fd157a6208c3..18a92a92c50f 100644 --- a/arch/x86/kernel/cet.c +++ b/arch/x86/kernel/cet.c @@ -21,6 +21,7 @@ #include <asm/fpu/types.h> #include <asm/cet.h> #include <asm/special_insns.h> +#include <asm/elf.h> static int set_shstk_ptr(unsigned long addr) { @@ -333,3 +334,25 @@ void cet_disable_ibt(void) wrmsrl(MSR_IA32_U_CET, r); current->thread.cet.ibt_enabled = 0; } + +int cet_setup_ibt_bitmap(unsigned long bitmap, unsigned long size) +{ + u64 r; + + if (!current->thread.cet.ibt_enabled) + return -EINVAL; + + if (!PAGE_ALIGNED(bitmap) || (size > TASK_SIZE_MAX)) + return -EINVAL; + + current->thread.cet.ibt_bitmap_addr = bitmap; + current->thread.cet.ibt_bitmap_size = size; + + /* + * Turn on IBT legacy bitmap. + */ + rdmsrl(MSR_IA32_U_CET, r); + r |= (MSR_IA32_CET_LEG_IW_EN | bitmap); + wrmsrl(MSR_IA32_U_CET, r); + return 0; +} -- 2.17.1
