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Commit 7cc45e64 authored by Steven Rostedt's avatar Steven Rostedt
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powerpc/ppc32: ftrace, dynamic ftrace to handle modules



Impact: add ability to trace modules on 32 bit PowerPC

This patch performs the necessary trampoline calls to handle
modules with dynamic ftrace on 32 bit PowerPC.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent f48cb8b4
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+4 −1
Original line number Diff line number Diff line
@@ -39,11 +39,14 @@ struct mod_arch_specific {
	unsigned long tramp;
#endif

#else
#else /* powerpc64 */
	/* Indices of PLT sections within module. */
	unsigned int core_plt_section;
	unsigned int init_plt_section;
#ifdef CONFIG_DYNAMIC_FTRACE
	unsigned long tramp;
#endif
#endif /* powerpc64 */

	/* List of BUG addresses, source line numbers and filenames */
	struct list_head bug_list;
+95 −6
Original line number Diff line number Diff line
@@ -274,7 +274,63 @@ static int
__ftrace_make_nop(struct module *mod,
		  struct dyn_ftrace *rec, unsigned long addr)
{
	/* Ignore modules for PPC32 (for now) */
	unsigned char replaced[MCOUNT_INSN_SIZE];
	unsigned int *op = (unsigned *)&replaced;
	unsigned char jmp[8];
	unsigned int *ptr = (unsigned int *)&jmp;
	unsigned long ip = rec->ip;
	unsigned long tramp;
	int offset;

	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
		return -EFAULT;

	/* Make sure that that this is still a 24bit jump */
	if (!is_bl_op(*op)) {
		printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);
		return -EINVAL;
	}

	/* lets find where the pointer goes */
	tramp = find_bl_target(ip, *op);

	/*
	 * On PPC32 the trampoline looks like:
	 * lis r11,sym@ha
	 * addi r11,r11,sym@l
	 * mtctr r11
	 * bctr
	 */

	DEBUGP("ip:%lx jumps to %lx", ip, tramp);

	/* 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 ", ptr[0], ptr[1]);

	tramp = (ptr[1] & 0xffff) |
		((ptr[0] & 0xffff) << 16);
	if (tramp & 0x8000)
		tramp -= 0x10000;

	DEBUGP(" %x ", tramp);

	if (tramp != addr) {
		printk(KERN_ERR
		       "Trampoline location %08lx does not match addr\n",
		       tramp);
		return -EINVAL;
	}

	op[0] = PPC_NOP_INSTR;

	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
		return -EPERM;

	return 0;
}
#endif /* PPC64 */
@@ -297,7 +353,6 @@ int ftrace_make_nop(struct module *mod,
		return ftrace_modify_code(ip, old, new);
	}

#ifdef CONFIG_PPC64
	/*
	 * Out of range jumps are called from modules.
	 * We should either already have a pointer to the module
@@ -320,7 +375,6 @@ int ftrace_make_nop(struct module *mod,
		/* nothing to do if mod == rec->arch.mod */
	} else
		mod = rec->arch.mod;
#endif /* CONFIG_PPC64 */

	return __ftrace_make_nop(mod, rec, addr);

@@ -380,7 +434,44 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	/* PPC32 ignores modules for now */
	unsigned char replaced[MCOUNT_INSN_SIZE];
	unsigned int *op = (unsigned *)&replaced;
	unsigned long ip = rec->ip;
	unsigned long offset;

	/* read where this goes */
	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
		return -EFAULT;

	/* It should be pointing to a nop */
	if (op[0] != PPC_NOP_INSTR) {
		printk(KERN_ERR "Expected NOP but have %x\n", op[0]);
		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 (test_offset(offset)) {
		printk(KERN_ERR "REL24 %li out of range!\n",
		       (long int)offset);
		return -EINVAL;
	}

	/* Set to "bl addr" */
	op[0] = branch_offset(offset);

	DEBUGP("write to %lx\n", rec->ip);

	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
		return -EPERM;

	return 0;
}
#endif /* CONFIG_PPC64 */
@@ -402,7 +493,6 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
		return ftrace_modify_code(ip, old, new);
	}

#ifdef CONFIG_PPC64
	/*
	 * Out of range jumps are called from modules.
	 * Being that we are converting from nop, it had better
@@ -412,7 +502,6 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
		printk(KERN_ERR "No module loaded\n");
		return -EINVAL;
	}
#endif

	return __ftrace_make_call(rec, addr);
}
+10 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/ftrace.h>
#include <linux/cache.h>
#include <linux/bug.h>
#include <linux/sort.h>
@@ -53,6 +54,9 @@ static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
			r_addend = rela[i].r_addend;
		}

#ifdef CONFIG_DYNAMIC_FTRACE
	_count_relocs++;	/* add one for ftrace_caller */
#endif
	return _count_relocs;
}

@@ -306,5 +310,11 @@ int apply_relocate_add(Elf32_Shdr *sechdrs,
			return -ENOEXEC;
		}
	}
#ifdef CONFIG_DYNAMIC_FTRACE
	module->arch.tramp =
		do_plt_call(module->module_core,
			    (unsigned long)ftrace_caller,
			    sechdrs, module);
#endif
	return 0;
}