[PATCH v4 10/10] powerpc64/ftrace: Implement support for ftrace_regs_caller()
Naveen N. Rao
naveen.n.rao at linux.vnet.ibm.com
Wed Apr 4 06:12:25 AEST 2018
With -mprofile-kernel, we always save the full register state in
ftrace_caller(). While this works, this is inefficient if we're not
interested in the register state, such as when we're using the function
tracer.
Rename the existing ftrace_caller() as ftrace_regs_caller() and provide
a simpler implementation for ftrace_caller() that is used when registers
are not required to be saved.
Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
---
arch/powerpc/include/asm/ftrace.h | 2 -
arch/powerpc/include/asm/module.h | 3 +
arch/powerpc/kernel/module_64.c | 28 +++-
arch/powerpc/kernel/trace/ftrace.c | 184 +++++++++++++++++++++++--
arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 71 +++++++++-
5 files changed, 262 insertions(+), 26 deletions(-)
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 3b5e85a72e10..f0806a2fd451 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -49,8 +49,6 @@
extern void _mcount(void);
#ifdef CONFIG_DYNAMIC_FTRACE
-# define FTRACE_ADDR ((unsigned long)ftrace_caller)
-# define FTRACE_REGS_ADDR FTRACE_ADDR
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
/* reloction of mcount call site is the same as the address */
diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index 7e28442827f1..2d16b6d9147d 100644
--- a/arch/powerpc/include/asm/module.h
+++ b/arch/powerpc/include/asm/module.h
@@ -43,6 +43,9 @@ struct mod_arch_specific {
#ifdef CONFIG_DYNAMIC_FTRACE
unsigned long toc;
unsigned long tramp;
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ unsigned long tramp_regs;
+#endif
#endif
/* For module function descriptor dereference */
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 8413be31d6a4..f7667e2ebfcb 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -280,6 +280,10 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
#ifdef CONFIG_DYNAMIC_FTRACE
/* make the trampoline to the ftrace_caller */
relocs++;
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ /* an additional one for ftrace_regs_caller */
+ relocs++;
+#endif
#endif
pr_debug("Looks like a total of %lu stubs, max\n", relocs);
@@ -765,7 +769,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
* via the paca (in r13). The target (ftrace_caller()) is responsible for
* saving and restoring the toc before returning.
*/
-static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)
+static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs,
+ struct module *me, unsigned long addr)
{
struct ppc64_stub_entry *entry;
unsigned int i, num_stubs;
@@ -792,9 +797,10 @@ static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module
memcpy(entry->jump, stub_insns, sizeof(stub_insns));
/* Stub uses address relative to kernel toc (from the paca) */
- reladdr = (unsigned long)ftrace_caller - kernel_toc_addr();
+ reladdr = addr - kernel_toc_addr();
if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
- pr_err("%s: Address of ftrace_caller out of range of kernel_toc.\n", me->name);
+ pr_err("%s: Address of %ps out of range of kernel_toc.\n",
+ me->name, (void *)addr);
return 0;
}
@@ -802,22 +808,30 @@ static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module
entry->jump[2] |= PPC_LO(reladdr);
/* Eventhough we don't use funcdata in the stub, it's needed elsewhere. */
- entry->funcdata = func_desc((unsigned long)ftrace_caller);
+ entry->funcdata = func_desc(addr);
entry->magic = STUB_MAGIC;
return (unsigned long)entry;
}
#else
-static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)
+static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs,
+ struct module *me, unsigned long addr)
{
- return stub_for_addr(sechdrs, (unsigned long)ftrace_caller, me);
+ return stub_for_addr(sechdrs, addr, me);
}
#endif
int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
{
mod->arch.toc = my_r2(sechdrs, mod);
- mod->arch.tramp = create_ftrace_stub(sechdrs, mod);
+ mod->arch.tramp = create_ftrace_stub(sechdrs, mod,
+ (unsigned long)ftrace_caller);
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ mod->arch.tramp_regs = create_ftrace_stub(sechdrs, mod,
+ (unsigned long)ftrace_regs_caller);
+ if (!mod->arch.tramp_regs)
+ return -ENOENT;
+#endif
if (!mod->arch.tramp)
return -ENOENT;
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 80667128db3d..79d2924e75d5 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -357,6 +357,8 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op[2];
void *ip = (void *)rec->ip;
+ unsigned long entry, ptr, tramp;
+ struct module *mod = rec->arch.mod;
/* read where this goes */
if (probe_kernel_read(op, ip, sizeof(op)))
@@ -368,19 +370,44 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
return -EINVAL;
}
- /* If we never set up a trampoline to ftrace_caller, then bail */
- if (!rec->arch.mod->arch.tramp) {
+ /* If we never set up ftrace trampoline(s), then bail */
+#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;
+
+ if (module_trampoline_target(mod, tramp, &ptr)) {
+ pr_err("Failed to get trampoline target\n");
+ return -EFAULT;
+ }
+
+ pr_devel("trampoline target %lx", ptr);
+
+ entry = ppc_global_function_entry((void *)addr);
+ /* This should match what was called */
+ if (ptr != entry) {
+ pr_err("addr %lx does not match expected %lx\n", ptr, entry);
+ return -EINVAL;
+ }
+
/* Ensure branch is within 24 bits */
- if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
+ if (!create_branch(ip, tramp, BRANCH_SET_LINK)) {
pr_err("Branch out of range\n");
return -EINVAL;
}
- if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
+ if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
@@ -388,14 +415,6 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
return 0;
}
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
-int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
- unsigned long addr)
-{
- return ftrace_make_call(rec, addr);
-}
-#endif
-
#else /* !CONFIG_PPC64: */
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
@@ -472,6 +491,137 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
#endif /* CONFIG_MODULES */
}
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+#ifdef CONFIG_MODULES
+static int
+__ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ unsigned int op;
+ unsigned long ip = rec->ip;
+ unsigned long entry, ptr, tramp;
+ struct module *mod = rec->arch.mod;
+
+ /* If we never set up ftrace trampolines, then bail */
+ if (!mod->arch.tramp || !mod->arch.tramp_regs) {
+ pr_err("No ftrace trampoline\n");
+ return -EINVAL;
+ }
+
+ /* read where this goes */
+ if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
+ pr_err("Fetching opcode failed.\n");
+ return -EFAULT;
+ }
+
+ /* Make sure that that this is still a 24bit jump */
+ if (!is_bl_op(op)) {
+ pr_err("Not expected bl: opcode is %x\n", op);
+ return -EINVAL;
+ }
+
+ /* lets find where the pointer goes */
+ tramp = find_bl_target(ip, op);
+ entry = ppc_global_function_entry((void *)old_addr);
+
+ pr_devel("ip:%lx jumps to %lx", ip, tramp);
+
+ if (tramp != entry) {
+ /* old_addr is not within range, so we must have used a trampoline */
+ if (module_trampoline_target(mod, tramp, &ptr)) {
+ pr_err("Failed to get trampoline target\n");
+ return -EFAULT;
+ }
+
+ pr_devel("trampoline target %lx", ptr);
+
+ /* This should match what was called */
+ if (ptr != entry) {
+ pr_err("addr %lx does not match expected %lx\n", ptr, entry);
+ return -EINVAL;
+ }
+ }
+
+ /* The new target may be within range */
+ if (test_24bit_addr(ip, addr)) {
+ /* within range */
+ if (patch_branch((unsigned int *)ip, addr, BRANCH_SET_LINK)) {
+ pr_err("REL24 out of range!\n");
+ return -EINVAL;
+ }
+
+ return 0;
+ }
+
+ if (rec->flags & FTRACE_FL_REGS)
+ tramp = mod->arch.tramp_regs;
+ else
+ tramp = mod->arch.tramp;
+
+ if (module_trampoline_target(mod, tramp, &ptr)) {
+ pr_err("Failed to get trampoline target\n");
+ return -EFAULT;
+ }
+
+ pr_devel("trampoline target %lx", ptr);
+
+ entry = ppc_global_function_entry((void *)addr);
+ /* This should match what was called */
+ if (ptr != entry) {
+ pr_err("addr %lx does not match expected %lx\n", ptr, entry);
+ return -EINVAL;
+ }
+
+ /* Ensure branch is within 24 bits */
+ if (!create_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {
+ pr_err("Branch out of range\n");
+ return -EINVAL;
+ }
+
+ if (patch_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {
+ pr_err("REL24 out of range!\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+#endif
+
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ unsigned long ip = rec->ip;
+ unsigned int old, new;
+
+ /*
+ * If the calling address is more that 24 bits away,
+ * then we had to use a trampoline to make the call.
+ * Otherwise just update the call site.
+ */
+ if (test_24bit_addr(ip, addr) && test_24bit_addr(ip, old_addr)) {
+ /* within range */
+ old = ftrace_call_replace(ip, old_addr, 1);
+ new = ftrace_call_replace(ip, addr, 1);
+ return ftrace_modify_code(ip, old, new);
+ }
+
+#ifdef CONFIG_MODULES
+ /*
+ * Out of range jumps are called from modules.
+ */
+ if (!rec->arch.mod) {
+ pr_err("No module loaded\n");
+ return -EINVAL;
+ }
+
+ return __ftrace_modify_call(rec, old_addr, addr);
+#else
+ /* We should not get here without modules */
+ return -EINVAL;
+#endif /* CONFIG_MODULES */
+}
+#endif
+
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip = (unsigned long)(&ftrace_call);
@@ -482,6 +632,16 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
new = ftrace_call_replace(ip, (unsigned long)func, 1);
ret = ftrace_modify_code(ip, old, new);
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ /* Also update the regs callback function */
+ if (!ret) {
+ ip = (unsigned long)(&ftrace_regs_call);
+ old = *(unsigned int *)&ftrace_regs_call;
+ new = ftrace_call_replace(ip, (unsigned long)func, 1);
+ ret = ftrace_modify_code(ip, old, new);
+ }
+#endif
+
return ret;
}
diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
index ae1cbe783ab6..ed9d7a46c3af 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
@@ -20,8 +20,8 @@
#ifdef CONFIG_DYNAMIC_FTRACE
/*
*
- * ftrace_caller() is the function that replaces _mcount() when ftrace is
- * active.
+ * ftrace_caller()/ftrace_regs_caller() is the function that replaces _mcount()
+ * when ftrace is active.
*
* We arrive here after a function A calls function B, and we are the trace
* function for B. When we enter r1 points to A's stack frame, B has not yet
@@ -37,7 +37,7 @@
* Our job is to save the register state into a struct pt_regs (on the stack)
* and then arrange for the ftrace function to be called.
*/
-_GLOBAL(ftrace_caller)
+_GLOBAL(ftrace_regs_caller)
/* Save the original return address in A's stack frame */
std r0,LRSAVE(r1)
@@ -100,8 +100,8 @@ _GLOBAL(ftrace_caller)
addi r6, r1 ,STACK_FRAME_OVERHEAD
/* ftrace_call(r3, r4, r5, r6) */
-.globl ftrace_call
-ftrace_call:
+.globl ftrace_regs_call
+ftrace_regs_call:
bl ftrace_stub
nop
@@ -162,6 +162,7 @@ ftrace_call:
bne- livepatch_handler
#endif
+ftrace_caller_common:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl ftrace_graph_call
ftrace_graph_call:
@@ -182,6 +183,66 @@ ftrace_no_trace:
mtlr r0
bctr
+_GLOBAL(ftrace_caller)
+ /* Save the original return address in A's stack frame */
+ std r0, LRSAVE(r1)
+
+ /* Create our stack frame + pt_regs */
+ stdu r1, -SWITCH_FRAME_SIZE(r1)
+
+ /* Save all gprs to pt_regs */
+ SAVE_8GPRS(3, r1)
+
+ lbz r3, PACA_FTRACE_ENABLED(r13)
+ cmpdi r3, 0
+ beq ftrace_no_trace
+
+ /* Get the _mcount() call site out of LR */
+ mflr r7
+ std r7, _NIP(r1)
+
+ /* Save callee's TOC in the ABI compliant location */
+ std r2, 24(r1)
+ ld r2, PACATOC(r13) /* get kernel TOC in r2 */
+
+ addis r3, r2, function_trace_op at toc@ha
+ addi r3, r3, function_trace_op at toc@l
+ ld r5, 0(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
+
+ /* Set pt_regs to NULL */
+ li r6, 0
+
+ /* ftrace_call(r3, r4, r5, r6) */
+.globl ftrace_call
+ftrace_call:
+ bl ftrace_stub
+ nop
+
+ ld r3, _NIP(r1)
+ mtctr r3
+
+ /* Restore gprs */
+ REST_8GPRS(3,r1)
+
+ /* Restore callee's TOC */
+ ld r2, 24(r1)
+
+ /* Pop our stack frame */
+ addi r1, r1, SWITCH_FRAME_SIZE
+
+ /* Reload original LR */
+ ld r0, LRSAVE(r1)
+ mtlr r0
+
+ /* Handle function_graph or go back */
+ b ftrace_caller_common
+
#ifdef CONFIG_LIVEPATCH
/*
* This function runs in the mcount context, between two functions. As
--
2.16.2
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