[PATCH v1 4/5] powerpc/ftrace: Activate HAVE_DYNAMIC_FTRACE_WITH_REGS on PPC32
From: Christophe Leroy
Date: Thu Oct 28 2021 - 08:24:45 EST
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@xxxxxxxxxx>
---
arch/powerpc/Kconfig | 4 +-
arch/powerpc/kernel/module_32.c | 8 ++
arch/powerpc/kernel/trace/ftrace.c | 16 +++-
arch/powerpc/kernel/trace/ftrace_32.S | 109 ++++++++++++++++++++++++--
4 files changed, 125 insertions(+), 12 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e43e17987b92..f66eb1984b00 100644
--- 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 5dedd76346b2..a491ad481d85 100644
--- 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 c1d54c18e912..faa0fa29ac20 100644
--- 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 c7d57124cc59..0a02c0cb12d9 100644
--- 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)
--
2.31.1