Messages in this thread | | | Subject | Re: [PATCH v13 08/10] arm64: Add trampoline code for kretprobes | From | David Long <> | Date | Mon, 13 Jun 2016 00:23:58 -0400 |
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On 06/07/2016 06:38 AM, Masami Hiramatsu wrote: > On Thu, 2 Jun 2016 23:26:22 -0400 > David Long <dave.long@linaro.org> wrote: > >> From: William Cohen <wcohen@redhat.com> >> >> 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?)
Yes, and adding the trampoline support before making use of it seemed OK to me even if it wasn't strictly necessary.
> > Acked-by: Masami Hiramatsu <mhiramat@kernel.org> > > Thanks, > > >> Signed-off-by: William Cohen <wcohen@redhat.com> >> Signed-off-by: David A. Long <dave.long@linaro.org> >> --- >> 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 >> > >
Thanks, -dl
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