powerpc/ftrace: Activate HAVE_DYNAMIC_FTRACE_WITH_REGS on PPC32

Unlike PPC64, PPC32 doesn't require any special compiler option
to get _mcount() call not clobbering registers.

Provide ftrace_regs_caller() and ftrace_regs_call() and activate
HAVE_DYNAMIC_FTRACE_WITH_REGS.

That's heavily copied from ftrace_64_mprofile.S

For the time being leave livepatching aside, it will come with
following patch.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1862dc7719855cc2a4eec80920d94c955877557e.1635423081.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index bb5e44e4d7c76468d656bdafc010bad598959f18..5c61f3511d5ae0ef91d1233e3c8d8cfcf3a26b64 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -206,7 +206,7 @@ config PPC
        select HAVE_DEBUG_KMEMLEAK
        select HAVE_DEBUG_STACKOVERFLOW
        select HAVE_DYNAMIC_FTRACE
-       select HAVE_DYNAMIC_FTRACE_WITH_REGS    if MPROFILE_KERNEL
+       select HAVE_DYNAMIC_FTRACE_WITH_REGS    if MPROFILE_KERNEL || PPC32
        select HAVE_EBPF_JIT
        select HAVE_EFFICIENT_UNALIGNED_ACCESS  if !(CPU_LITTLE_ENDIAN && POWER7_CPU)
        select HAVE_FAST_GUP
@@ -230,7 +230,7 @@ config PPC
        select HAVE_KPROBES_ON_FTRACE
        select HAVE_KRETPROBES
        select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
-       select HAVE_LIVEPATCH                   if HAVE_DYNAMIC_FTRACE_WITH_REGS
+       select HAVE_LIVEPATCH                   if HAVE_DYNAMIC_FTRACE_WITH_REGS && PPC64
        select HAVE_MOD_ARCH_SPECIFIC
        select HAVE_NMI                         if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
        select HAVE_OPTPROBES

diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c
index 5dedd76346b2e4b6a0a3f98c84091022d26f7770..a491ad481d85ea0a829f19e68467e191104a772a 100644 (file)
--- a/arch/powerpc/kernel/module_32.c
+++ b/arch/powerpc/kernel/module_32.c
@@ -306,6 +306,14 @@ int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
        if (!module->arch.tramp)
                return -ENOENT;
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+       module->arch.tramp_regs = do_plt_call(module->core_layout.base,
+                                             (unsigned long)ftrace_regs_caller,
+                                             sechdrs, module);
+       if (!module->arch.tramp_regs)
+               return -ENOENT;
+#endif
+
        return 0;
 }
 #endif

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index c1d54c18e912d3d7a9e79a0df5b464270699444f..faa0fa29ac20d556e51b005d5366b38e0e6096a3 100644 (file)
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -561,6 +561,8 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
        int err;
        struct ppc_inst op;
        u32 *ip = (u32 *)rec->ip;
+       struct module *mod = rec->arch.mod;
+       unsigned long tramp;
 
        /* read where this goes */
        if (copy_inst_from_kernel_nofault(&op, ip))
@@ -573,13 +575,23 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
        }
 
        /* If we never set up a trampoline to ftrace_caller, then bail */
-       if (!rec->arch.mod->arch.tramp) {
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+       if (!mod->arch.tramp || !mod->arch.tramp_regs) {
+#else
+       if (!mod->arch.tramp) {
+#endif
                pr_err("No ftrace trampoline\n");
                return -EINVAL;
        }
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+       if (rec->flags & FTRACE_FL_REGS)
+               tramp = mod->arch.tramp_regs;
+       else
+#endif
+               tramp = mod->arch.tramp;
        /* create the branch to the trampoline */
-       err = create_branch(&op, ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
+       err = create_branch(&op, ip, tramp, BRANCH_SET_LINK);
        if (err) {
                pr_err("REL24 out of range!\n");
                return -EINVAL;

diff --git a/arch/powerpc/kernel/trace/ftrace_32.S b/arch/powerpc/kernel/trace/ftrace_32.S
index c7d57124cc59cd2071af0ac9431af11903cebc58..0a02c0cb12d99c48b9de59d5d332dd265289627a 100644 (file)
--- a/arch/powerpc/kernel/trace/ftrace_32.S
+++ b/arch/powerpc/kernel/trace/ftrace_32.S
@@ -9,6 +9,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/ftrace.h>
 #include <asm/export.h>
+#include <asm/ptrace.h>
 
 _GLOBAL(mcount)
 _GLOBAL(_mcount)
@@ -29,17 +30,21 @@ _GLOBAL(ftrace_caller)
        MCOUNT_SAVE_FRAME
        /* r3 ends up with link register */
        subi    r3, r3, MCOUNT_INSN_SIZE
+       lis     r5,function_trace_op@ha
+       lwz     r5,function_trace_op@l(r5)
+       li      r6, 0
 .globl ftrace_call
 ftrace_call:
        bl      ftrace_stub
        nop
+       MCOUNT_RESTORE_FRAME
+ftrace_caller_common:
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 .globl ftrace_graph_call
 ftrace_graph_call:
        b       ftrace_graph_stub
 _GLOBAL(ftrace_graph_stub)
 #endif
-       MCOUNT_RESTORE_FRAME
        /* old link register ends up in ctr reg */
        bctr
 
@@ -47,16 +52,92 @@ _GLOBAL(ftrace_graph_stub)
 _GLOBAL(ftrace_stub)
        blr
 
+_GLOBAL(ftrace_regs_caller)
+       /* Save the original return address in A's stack frame */
+       stw     r0,LRSAVE(r1)
+
+       /* Create our stack frame + pt_regs */
+       stwu    r1,-INT_FRAME_SIZE(r1)
+
+       /* Save all gprs to pt_regs */
+       stw     r0, GPR0(r1)
+       stmw    r2, GPR2(r1)
+
+       /* Save previous stack pointer (r1) */
+       addi    r8, r1, INT_FRAME_SIZE
+       stw     r8, GPR1(r1)
+
+       /* Load special regs for save below */
+       mfmsr   r8
+       mfctr   r9
+       mfxer   r10
+       mfcr    r11
+
+       /* Get the _mcount() call site out of LR */
+       mflr    r7
+       /* Save it as pt_regs->nip */
+       stw     r7, _NIP(r1)
+       /* Save the read LR in pt_regs->link */
+       stw     r0, _LINK(r1)
+
+       lis     r3,function_trace_op@ha
+       lwz     r5,function_trace_op@l(r3)
+
+       /* Calculate ip from nip-4 into r3 for call below */
+       subi    r3, r7, MCOUNT_INSN_SIZE
+
+       /* Put the original return address in r4 as parent_ip */
+       mr      r4, r0
+
+       /* Save special regs */
+       stw     r8, _MSR(r1)
+       stw     r9, _CTR(r1)
+       stw     r10, _XER(r1)
+       stw     r11, _CCR(r1)
+
+       /* Load &pt_regs in r6 for call below */
+       addi    r6, r1, STACK_FRAME_OVERHEAD
+
+       /* ftrace_call(r3, r4, r5, r6) */
+.globl ftrace_regs_call
+ftrace_regs_call:
+       bl      ftrace_stub
+       nop
+
+       /* Load ctr with the possibly modified NIP */
+       lwz     r3, _NIP(r1)
+       mtctr   r3
+
+       /* Restore gprs */
+       lmw     r2, GPR2(r1)
+
+       /* Restore possibly modified LR */
+       lwz     r0, _LINK(r1)
+       mtlr    r0
+
+       /* Pop our stack frame */
+       addi r1, r1, INT_FRAME_SIZE
+
+       b       ftrace_caller_common
+
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 _GLOBAL(ftrace_graph_caller)
+       stwu    r1,-48(r1)
+       stw     r3, 12(r1)
+       stw     r4, 16(r1)
+       stw     r5, 20(r1)
+       stw     r6, 24(r1)
+       stw     r7, 28(r1)
+       stw     r8, 32(r1)
+       stw     r9, 36(r1)
+       stw     r10,40(r1)
+
        addi    r5, r1, 48
-       /* load r4 with local address */
-       lwz     r4, 44(r1)
+       mfctr   r4              /* ftrace_caller has moved local addr here */
+       stw     r4, 44(r1)
+       mflr    r3              /* ftrace_caller has restored LR from stack */
        subi    r4, r4, MCOUNT_INSN_SIZE
 
-       /* Grab the LR out of the caller stack frame */
-       lwz     r3,52(r1)
-
        bl      prepare_ftrace_return
        nop
 
@@ -65,9 +146,21 @@ _GLOBAL(ftrace_graph_caller)
          * Change the LR in the callers stack frame to this.
          */
        stw     r3,52(r1)
+       mtlr    r3
+       lwz     r0,44(r1)
+       mtctr   r0
+
+       lwz     r3, 12(r1)
+       lwz     r4, 16(r1)
+       lwz     r5, 20(r1)
+       lwz     r6, 24(r1)
+       lwz     r7, 28(r1)
+       lwz     r8, 32(r1)
+       lwz     r9, 36(r1)
+       lwz     r10,40(r1)
+
+       addi    r1, r1, 48
 
-       MCOUNT_RESTORE_FRAME
-       /* old link register ends up in ctr reg */
        bctr
 
 _GLOBAL(return_to_handler)