On Thu, 2 Jun 2016 23:26:22 -0400 David Long <[email protected]> wrote:
> From: William Cohen <[email protected]> > > The trampoline code is used by kretprobes to capture a return from a probed > function. This is done by saving the registers, calling the handler, and > restoring the registers. The code then returns to the original saved caller > return address. It is necessary to do this directly instead of using a > software breakpoint because the code used in processing that breakpoint > could itself be kprobe'd and cause a problematic reentry into the debug > exception handler. OK, I think we had discussed why this was not included to the next patch. (Not like to merge patches from different person?) Acked-by: Masami Hiramatsu <[email protected]> Thanks, > Signed-off-by: William Cohen <[email protected]> > Signed-off-by: David A. Long <[email protected]> > --- > arch/arm64/include/asm/kprobes.h | 2 + > arch/arm64/kernel/Makefile | 1 + > arch/arm64/kernel/asm-offsets.c | 11 +++++ > arch/arm64/kernel/kprobes.c | 5 ++ > arch/arm64/kernel/kprobes_trampoline.S | 85 > ++++++++++++++++++++++++++++++++++ > 5 files changed, 104 insertions(+) > create mode 100644 arch/arm64/kernel/kprobes_trampoline.S > > diff --git a/arch/arm64/include/asm/kprobes.h > b/arch/arm64/include/asm/kprobes.h > index 79c9511..61b4915 100644 > --- a/arch/arm64/include/asm/kprobes.h > +++ b/arch/arm64/include/asm/kprobes.h > @@ -56,5 +56,7 @@ int kprobe_exceptions_notify(struct notifier_block *self, > unsigned long val, void *data); > int kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr); > int kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr); > +void kretprobe_trampoline(void); > +void __kprobes *trampoline_probe_handler(struct pt_regs *regs); > > #endif /* _ARM_KPROBES_H */ > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile > index 46724a1..75751b7 100644 > --- a/arch/arm64/kernel/Makefile > +++ b/arch/arm64/kernel/Makefile > @@ -38,6 +38,7 @@ arm64-obj-$(CONFIG_CPU_IDLE) += cpuidle.o > arm64-obj-$(CONFIG_JUMP_LABEL) += jump_label.o > arm64-obj-$(CONFIG_KGDB) += kgdb.o > arm64-obj-$(CONFIG_KPROBES) += kprobes.o kprobes-arm64.o > \ > + kprobes_trampoline.o > \ > probes-simulate-insn.o > arm64-obj-$(CONFIG_EFI) += efi.o efi-entry.stub.o > arm64-obj-$(CONFIG_PCI) += pci.o > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c > index f8e5d47..03dfa27 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -51,6 +51,17 @@ int main(void) > DEFINE(S_X5, offsetof(struct pt_regs, regs[5])); > DEFINE(S_X6, offsetof(struct pt_regs, regs[6])); > DEFINE(S_X7, offsetof(struct pt_regs, regs[7])); > + DEFINE(S_X8, offsetof(struct pt_regs, regs[8])); > + DEFINE(S_X10, offsetof(struct pt_regs, regs[10])); > + DEFINE(S_X12, offsetof(struct pt_regs, regs[12])); > + DEFINE(S_X14, offsetof(struct pt_regs, regs[14])); > + DEFINE(S_X16, offsetof(struct pt_regs, regs[16])); > + DEFINE(S_X18, offsetof(struct pt_regs, regs[18])); > + DEFINE(S_X20, offsetof(struct pt_regs, regs[20])); > + DEFINE(S_X22, offsetof(struct pt_regs, regs[22])); > + DEFINE(S_X24, offsetof(struct pt_regs, regs[24])); > + DEFINE(S_X26, offsetof(struct pt_regs, regs[26])); > + DEFINE(S_X28, offsetof(struct pt_regs, regs[28])); > DEFINE(S_LR, offsetof(struct pt_regs, regs[30])); > DEFINE(S_SP, offsetof(struct pt_regs, sp)); > #ifdef CONFIG_COMPAT > diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c > index 9d0ad47..b35f76f 100644 > --- a/arch/arm64/kernel/kprobes.c > +++ b/arch/arm64/kernel/kprobes.c > @@ -575,6 +575,11 @@ bool arch_within_kprobe_blacklist(unsigned long addr) > return false; > } > > +void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) > +{ > + return NULL; > +} > + > int __init arch_init_kprobes(void) > { > return 0; > diff --git a/arch/arm64/kernel/kprobes_trampoline.S > b/arch/arm64/kernel/kprobes_trampoline.S > new file mode 100644 > index 0000000..ba37d85 > --- /dev/null > +++ b/arch/arm64/kernel/kprobes_trampoline.S > @@ -0,0 +1,85 @@ > +/* > + * trampoline entry and return code for kretprobes. > + */ > + > +#include <linux/linkage.h> > +#include <asm/asm-offsets.h> > +#include <asm/assembler.h> > + > + .text > + > +.macro save_all_base_regs > + stp x0, x1, [sp, #S_X0] > + stp x2, x3, [sp, #S_X2] > + stp x4, x5, [sp, #S_X4] > + stp x6, x7, [sp, #S_X6] > + stp x8, x9, [sp, #S_X8] > + stp x10, x11, [sp, #S_X10] > + stp x12, x13, [sp, #S_X12] > + stp x14, x15, [sp, #S_X14] > + stp x16, x17, [sp, #S_X16] > + stp x18, x19, [sp, #S_X18] > + stp x20, x21, [sp, #S_X20] > + stp x22, x23, [sp, #S_X22] > + stp x24, x25, [sp, #S_X24] > + stp x26, x27, [sp, #S_X26] > + stp x28, x29, [sp, #S_X28] > + add x0, sp, #S_FRAME_SIZE > + stp lr, x0, [sp, #S_LR] > +/* > + * Construct a useful saved PSTATE > + */ > + mrs x0, nzcv > + and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT) > + mrs x1, daif > + and x1, x1, #(PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT) > + orr x0, x0, x1 > + mrs x1, CurrentEL > + and x1, x1, #(3 << 2) > + orr x0, x1, x0 > + mrs x1, SPSel > + and x1, x1, #1 > + orr x0, x1, x0 > + str x0, [sp, #S_PSTATE] > +.endm > + > +.macro restore_all_base_regs > + ldr x0, [sp, #S_PSTATE] > + and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT) > + msr nzcv, x0 > + ldp x0, x1, [sp, #S_X0] > + ldp x2, x3, [sp, #S_X2] > + ldp x4, x5, [sp, #S_X4] > + ldp x6, x7, [sp, #S_X6] > + ldp x8, x9, [sp, #S_X8] > + ldp x10, x11, [sp, #S_X10] > + ldp x12, x13, [sp, #S_X12] > + ldp x14, x15, [sp, #S_X14] > + ldp x16, x17, [sp, #S_X16] > + ldp x18, x19, [sp, #S_X18] > + ldp x20, x21, [sp, #S_X20] > + ldp x22, x23, [sp, #S_X22] > + ldp x24, x25, [sp, #S_X24] > + ldp x26, x27, [sp, #S_X26] > + ldp x28, x29, [sp, #S_X28] > +.endm > + > +ENTRY(kretprobe_trampoline) > + > + sub sp, sp, #S_FRAME_SIZE > + > + save_all_base_regs > + > + mov x0, sp > + bl trampoline_probe_handler > + /* Replace trampoline address in lr with actual > + orig_ret_addr return address. */ > + mov lr, x0 > + > + restore_all_base_regs > + > + add sp, sp, #S_FRAME_SIZE > + > + ret > + > +ENDPROC(kretprobe_trampoline) > -- > 2.5.0 > -- Masami Hiramatsu <[email protected]>
