diff options
| author | Tobias Huschle <huschle@linux.ibm.com> | 2022-02-21 12:55:52 +0100 |
|---|---|---|
| committer | Vasily Gorbik <gor@linux.ibm.com> | 2022-03-10 15:58:17 +0100 |
| commit | 63bf38ff5bc3d8cee6c6a089657876d0b669cae1 (patch) | |
| tree | 7551b4e8820713493acbf93a348fecd33535504a /arch/s390/kernel/mcount.S | |
| parent | 731efc9613ee073c8944d0d56616d421cf906b0b (diff) | |
s390/kprobes: Avoid additional kprobe in kretprobe handling
So far, s390 registered a krobe on __kretprobe_trampoline which is
called everytime a kretprobe fires. This kprobe would then determine
the correct return address and adjust the psw accordingly, such that
the kretprobe would branch to the appropriate address after completion.
Some other archs handle kretprobes without such an additional kprobe.
This approach is adopted to s390 with this patch.
Furthermore, the __kretprobe_trampoline now uses an assembler function
to correctly gather the register and psw content to be passed to the
registered kretprobe handler as struct pt_regs. After completion, the
register content and the psw are set based on the contents of said
pt_regs struct.
Note that a change to the psw address in struct pt_regs will not have
an impact, as the probe will still return to the original return
address of the probed function.
The return address is now recovered by using the appropriate function
arch_kretprobe_fixup_return.
The no longer needed kprobe is removed.
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Tobias Huschle <huschle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'arch/s390/kernel/mcount.S')
| -rw-r--r-- | arch/s390/kernel/mcount.S | 51 |
1 files changed, 43 insertions, 8 deletions
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S index 1326927a17b5..4786bfe02144 100644 --- a/arch/s390/kernel/mcount.S +++ b/arch/s390/kernel/mcount.S @@ -11,14 +11,6 @@ #include <asm/ptrace.h> #include <asm/export.h> - GEN_BR_THUNK %r1 - GEN_BR_THUNK %r14 - - .section .kprobes.text, "ax" - -ENTRY(ftrace_stub) - BR_EX %r14 -ENDPROC(ftrace_stub) #define STACK_FRAME_SIZE (STACK_FRAME_OVERHEAD + __PT_SIZE) #define STACK_PTREGS (STACK_FRAME_OVERHEAD) @@ -29,6 +21,17 @@ ENDPROC(ftrace_stub) /* packed stack: allocate just enough for r14, r15 and backchain */ #define TRACED_FUNC_FRAME_SIZE 24 +#ifdef CONFIG_FUNCTION_TRACER + + GEN_BR_THUNK %r1 + GEN_BR_THUNK %r14 + + .section .kprobes.text, "ax" + +ENTRY(ftrace_stub) + BR_EX %r14 +ENDPROC(ftrace_stub) + .macro ftrace_regs_entry, allregs=0 stg %r14,(__SF_GPRS+8*8)(%r15) # save traced function caller @@ -130,3 +133,35 @@ SYM_FUNC_START(return_to_handler) SYM_FUNC_END(return_to_handler) #endif +#endif /* CONFIG_FUNCTION_TRACER */ + +#ifdef CONFIG_KPROBES + +SYM_FUNC_START(__kretprobe_trampoline) + + stg %r14,(__SF_GPRS+8*8)(%r15) + lay %r15,-STACK_FRAME_SIZE(%r15) + stmg %r0,%r14,STACK_PTREGS_GPRS(%r15) + + # store original stack pointer in backchain and pt_regs + lay %r7,STACK_FRAME_SIZE(%r15) + stg %r7,__SF_BACKCHAIN(%r15) + stg %r7,STACK_PTREGS_GPRS+(15*8)(%r15) + + # store full psw + epsw %r2,%r3 + risbg %r3,%r2,0,31,32 + stg %r3,STACK_PTREGS_PSW(%r15) + larl %r1,__kretprobe_trampoline + stg %r1,STACK_PTREGS_PSW+8(%r15) + + lay %r2,STACK_PTREGS(%r15) + brasl %r14,trampoline_probe_handler + + mvc __SF_EMPTY(16,%r7),STACK_PTREGS_PSW(%r15) + lmg %r0,%r15,STACK_PTREGS_GPRS(%r15) + lpswe __SF_EMPTY(%r15) + +SYM_FUNC_END(__kretprobe_trampoline) + +#endif /* CONFIG_KPROBES */ |