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Subject[PATCH 5/7] ftrace, PPC64: handle module trampolines for dyn ftrace
Impact: Implement PPC64 module trampolines for dyn ftrace

This adds code to handle the PPC64 module trampolines, and allows for
PPC64 to use dynamic ftrace.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
arch/powerpc/include/asm/ftrace.h | 3 +-
arch/powerpc/include/asm/module.h | 11 ++
arch/powerpc/kernel/ftrace.c | 202 +++++++++++++++++++++++++++++++++++--
arch/powerpc/kernel/module_64.c | 13 +++
4 files changed, 220 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 17efecc..d57f5bc 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -16,7 +16,8 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
}

struct dyn_arch_ftrace {
- /* nothing yet */
+ struct module *mod;
+ unsigned long tramp;
};
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index e5f14b1..340bc69 100644
--- a/arch/powerpc/include/asm/module.h
+++ b/arch/powerpc/include/asm/module.h
@@ -34,6 +34,11 @@ struct mod_arch_specific {
#ifdef __powerpc64__
unsigned int stubs_section; /* Index of stubs section in module */
unsigned int toc_section; /* What section is the TOC? */
+#ifdef CONFIG_DYNAMIC_FTRACE
+ unsigned long toc;
+ unsigned long tramp;
+#endif
+
#else
/* Indices of PLT sections within module. */
unsigned int core_plt_section;
@@ -68,6 +73,12 @@ struct mod_arch_specific {
# endif /* MODULE */
#endif

+#ifdef CONFIG_DYNAMIC_FTRACE
+# ifdef MODULE
+ asm(".section .ftrace.tramp,\"ax\",@nobits; .align 3; .previous");
+# endif /* MODULE */
+#endif
+

struct exception_table_entry;
void sort_ex_table(struct exception_table_entry *start,
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 3852919..acbec66 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -10,22 +10,29 @@
#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/uaccess.h>
+#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/list.h>

#include <asm/cacheflush.h>
+#include <asm/code-patching.h>
#include <asm/ftrace.h>

+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(fmt , ...) do { } while (0)
+#endif

-static unsigned int ftrace_nop = 0x60000000;
+static unsigned int ftrace_nop = PPC_NOP_INSTR;

#ifdef CONFIG_PPC32
# define GET_ADDR(addr) addr
#else
/* PowerPC64's functions are data that points to the functions */
-# define GET_ADDR(addr) *(unsigned long *)addr
+# define GET_ADDR(addr) (*(unsigned long *)addr)
#endif


@@ -115,40 +122,219 @@ static int test_24bit_addr(unsigned long ip, unsigned long addr)
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
+ unsigned char replaced[MCOUNT_INSN_SIZE * 2];
+ unsigned int *op = (unsigned *)&replaced;
+ unsigned char jmp[8];
+ unsigned long *ptr = (unsigned long *)&jmp;
unsigned char *old, *new;
+ unsigned long ip = rec->ip;
+ unsigned long tramp;
+ int offset;

/*
* 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(rec->ip, addr)) {
+ if (test_24bit_addr(ip, addr)) {
/* within range */
- old = ftrace_call_replace(rec->ip, addr);
+ old = ftrace_call_replace(ip, addr);
new = ftrace_nop_replace();
- return ftrace_modify_code(rec->ip, old, new);
+ return ftrace_modify_code(ip, old, new);
}

+#ifndef CONFIG_PPC64
+ /* only supported for PPC64 for now */
return 0;
+#else
+
+ /*
+ * Out of range jumps are called from modules.
+ * We should either already have a pointer to the module
+ * or it has been passed in.
+ */
+ if (!rec->arch.mod) {
+ if (!mod) {
+ printk(KERN_ERR "No module loaded addr=%lx\n",
+ addr);
+ return -EFAULT;
+ }
+ rec->arch.mod = mod;
+ } else if (mod) {
+ printk(KERN_ERR
+ "Record mod %p not equal to passed in mod %p\n",
+ rec->arch.mod, mod);
+ return -EINVAL;
+ } else
+ mod = rec->arch.mod;
+
+ /* read where this goes */
+ if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
+ return -EFAULT;
+
+ /* Make sure that that this is still a 24bit jump */
+ if ((*op & 0xff000000) != 0x48000000) {
+ printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);
+ return -EINVAL;
+ }
+
+ /* lets find where the pointer goes */
+ offset = (*op & 0x03fffffc);
+ /* make it signed */
+ if (offset & 0x02000000)
+ offset |= 0xfe000000;
+
+ tramp = ip + (long)offset;
+
+ /*
+ * On PPC64 the trampoline looks like:
+ * 0x3d, 0x82, 0x00, 0x00, addis r12,r2, <high>
+ * 0x39, 0x8c, 0x00, 0x00, addi r12,r12, <low>
+ * Where the bytes 2,3,6 and 7 make up the 32bit offset
+ * to the TOC that holds the pointer.
+ * to jump to.
+ * 0xf8, 0x41, 0x00, 0x28, std r2,40(r1)
+ * 0xe9, 0x6c, 0x00, 0x20, ld r11,32(r12)
+ * The actually address is 32 bytes from the offset
+ * into the TOC.
+ * 0xe8, 0x4c, 0x00, 0x28, ld r2,40(r12)
+ */
+
+ DEBUGP("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);
+
+ /* Find where the trampoline jumps to */
+ if (probe_kernel_read(jmp, (void *)tramp, 8)) {
+ printk(KERN_ERR "Failed to read %lx\n", tramp);
+ return -EFAULT;
+ }
+
+ DEBUGP(" %08x %08x",
+ (unsigned)(*ptr >> 32),
+ (unsigned)*ptr);
+
+ offset = (unsigned)jmp[2] << 24 |
+ (unsigned)jmp[3] << 16 |
+ (unsigned)jmp[6] << 8 |
+ (unsigned)jmp[7];
+
+ DEBUGP(" %x ", offset);
+
+ /* get the address this jumps too */
+ tramp = mod->arch.toc + offset + 32;
+ DEBUGP("toc: %lx", tramp);
+
+ if (probe_kernel_read(jmp, (void *)tramp, 8)) {
+ printk(KERN_ERR "Failed to read %lx\n", tramp);
+ return -EFAULT;
+ }
+
+ DEBUGP(" %08x %08x\n",
+ (unsigned)(*ptr >> 32),
+ (unsigned)*ptr);
+
+ /* This should match what was called */
+ if (*ptr != GET_ADDR(addr)) {
+ printk(KERN_ERR "addr does not match %lx\n", *ptr);
+ return -EINVAL;
+ }
+
+ /*
+ * We want to nop the line, but the next line is
+ * 0xe8, 0x41, 0x00, 0x28 ld r2,40(r1)
+ * This needs to be turned to a nop too.
+ */
+ if (probe_kernel_read(replaced, (void *)(ip+4), MCOUNT_INSN_SIZE))
+ return -EFAULT;
+
+ if (*op != 0xe8410028) {
+ printk(KERN_ERR "Next line is not ld! (%08x)\n", *op);
+ return -EINVAL;
+ }
+
+ op[0] = PPC_NOP_INSTR;
+ op[1] = PPC_NOP_INSTR;
+
+ if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE * 2))
+ return -EPERM;
+
+ return 0;
+#endif /* CONFIG_PPC64 */
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
+ unsigned char replaced[MCOUNT_INSN_SIZE * 2];
+ unsigned int *op = (unsigned *)&replaced;
unsigned char *old, *new;
+ unsigned long ip = rec->ip;
+ unsigned long offset;

/*
* 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(rec->ip, addr)) {
+ if (test_24bit_addr(ip, addr)) {
/* within range */
old = ftrace_nop_replace();
- new = ftrace_call_replace(rec->ip, addr);
- return ftrace_modify_code(rec->ip, old, new);
+ new = ftrace_call_replace(ip, addr);
+ return ftrace_modify_code(ip, old, new);
}

+#ifndef CONFIG_PPC64
+ /* only supported for PPC64 for now */
+ return 0;
+#else
+
+ /*
+ * Out of range jumps are called from modules.
+ * Being that we are converting from nop, it had better
+ * already have a module defined.
+ */
+ if (!rec->arch.mod) {
+ printk(KERN_ERR "No module loaded\n");
+ return -EINVAL;
+ }
+
+ /* read where this goes */
+ if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE * 2))
+ return -EFAULT;
+
+ /* It should be pointing to two nops */
+ if ((op[0] != PPC_NOP_INSTR) ||
+ (op[1] != PPC_NOP_INSTR)) {
+ printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
+ return -EINVAL;
+ }
+
+ /* If we never set up a trampoline to ftrace_caller, then bail */
+ if (!rec->arch.mod->arch.tramp) {
+ printk(KERN_ERR "No ftrace trampoline\n");
+ return -EINVAL;
+ }
+
+ /* now calculate a jump to the ftrace caller trampoline */
+ offset = rec->arch.mod->arch.tramp - ip;
+
+ if (offset + 0x2000000 > 0x3ffffff || (offset & 3) != 0) {
+ printk(KERN_ERR "REL24 %li out of range!\n",
+ (long int)offset);
+ return -EINVAL;
+ }
+
+
+ /* Set to "bl addr" */
+ op[0] = 0x48000001 | (offset & 0x03fffffc);
+ /* ld r2,40(r1) */
+ op[1] = 0xe8410028;
+
+ DEBUGP("write to %lx\n", rec->ip);
+
+ if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE * 2))
+ return -EPERM;
+
return 0;
+#endif /* CONFIG_PPC64 */
}

int ftrace_update_ftrace_func(ftrace_func_t func)
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 1af2377..8992b03 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -20,6 +20,7 @@
#include <linux/moduleloader.h>
#include <linux/err.h>
#include <linux/vmalloc.h>
+#include <linux/ftrace.h>
#include <linux/bug.h>
#include <asm/module.h>
#include <asm/firmware.h>
@@ -163,6 +164,11 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
}
}

+#ifdef CONFIG_DYNAMIC_FTRACE
+ /* make the trampoline to the ftrace_caller */
+ relocs++;
+#endif
+
DEBUGP("Looks like a total of %lu stubs, max\n", relocs);
return relocs * sizeof(struct ppc64_stub_entry);
}
@@ -441,5 +447,12 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
}
}

+#ifdef CONFIG_DYNAMIC_FTRACE
+ me->arch.toc = my_r2(sechdrs, me);
+ me->arch.tramp = stub_for_addr(sechdrs,
+ (unsigned long)ftrace_caller,
+ me);
+#endif
+
return 0;
}
--
1.5.6.5
--


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