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Commit 7cc45e64 authored by Steven Rostedt's avatar Steven Rostedt
Browse files

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

arch/powerpc/include/asm/module.h

+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;

arch/powerpc/kernel/ftrace.c

+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);

}

arch/powerpc/kernel/module_32.c

+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;

}