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83e840c770
Currently, we assume that the function pointer we receive in
ppc_function_entry() points to a function descriptor. However, this is
not always the case. In particular, assembly symbols without the right
annotation do not have an associated function descriptor. Some of these
symbols are added to the kprobe blacklist using _ASM_NOKPROBE_SYMBOL().
When such addresses are subsequently processed through
arch_deref_entry_point() in populate_kprobe_blacklist(), we see the
below errors during bootup:
[ 0.663963] Failed to find blacklist at 7d9b02a648029b6c
[ 0.663970] Failed to find blacklist at a14d03d0394a0001
[ 0.663972] Failed to find blacklist at 7d5302a6f94d0388
[ 0.663973] Failed to find blacklist at 48027d11e8610178
[ 0.663974] Failed to find blacklist at f8010070f8410080
[ 0.663976] Failed to find blacklist at 386100704801f89d
[ 0.663977] Failed to find blacklist at 7d5302a6f94d00b0
Fix this by checking if the function pointer we receive in
ppc_function_entry() already points to kernel text. If so, we just
return it as is. If not, we assume that this is a function descriptor
and proceed to dereference it.
Suggested-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
173 lines
5.0 KiB
C
173 lines
5.0 KiB
C
#ifndef _ASM_POWERPC_CODE_PATCHING_H
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#define _ASM_POWERPC_CODE_PATCHING_H
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/*
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* Copyright 2008, Michael Ellerman, IBM Corporation.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <asm/types.h>
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#include <asm/ppc-opcode.h>
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#include <linux/string.h>
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#include <linux/kallsyms.h>
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/* Flags for create_branch:
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* "b" == create_branch(addr, target, 0);
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* "ba" == create_branch(addr, target, BRANCH_ABSOLUTE);
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* "bl" == create_branch(addr, target, BRANCH_SET_LINK);
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* "bla" == create_branch(addr, target, BRANCH_ABSOLUTE | BRANCH_SET_LINK);
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*/
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#define BRANCH_SET_LINK 0x1
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#define BRANCH_ABSOLUTE 0x2
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bool is_offset_in_branch_range(long offset);
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unsigned int create_branch(const unsigned int *addr,
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unsigned long target, int flags);
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unsigned int create_cond_branch(const unsigned int *addr,
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unsigned long target, int flags);
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int patch_branch(unsigned int *addr, unsigned long target, int flags);
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int patch_instruction(unsigned int *addr, unsigned int instr);
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int instr_is_relative_branch(unsigned int instr);
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int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr);
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unsigned long branch_target(const unsigned int *instr);
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unsigned int translate_branch(const unsigned int *dest,
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const unsigned int *src);
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extern bool is_conditional_branch(unsigned int instr);
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#ifdef CONFIG_PPC_BOOK3E_64
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void __patch_exception(int exc, unsigned long addr);
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#define patch_exception(exc, name) do { \
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extern unsigned int name; \
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__patch_exception((exc), (unsigned long)&name); \
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} while (0)
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#endif
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#define OP_RT_RA_MASK 0xffff0000UL
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#define LIS_R2 0x3c020000UL
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#define ADDIS_R2_R12 0x3c4c0000UL
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#define ADDI_R2_R2 0x38420000UL
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static inline unsigned long ppc_function_entry(void *func)
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{
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#ifdef PPC64_ELF_ABI_v2
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u32 *insn = func;
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/*
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* A PPC64 ABIv2 function may have a local and a global entry
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* point. We need to use the local entry point when patching
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* functions, so identify and step over the global entry point
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* sequence.
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*
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* The global entry point sequence is always of the form:
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*
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* addis r2,r12,XXXX
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* addi r2,r2,XXXX
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*
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* A linker optimisation may convert the addis to lis:
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*
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* lis r2,XXXX
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* addi r2,r2,XXXX
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*/
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if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) ||
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((*insn & OP_RT_RA_MASK) == LIS_R2)) &&
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((*(insn+1) & OP_RT_RA_MASK) == ADDI_R2_R2))
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return (unsigned long)(insn + 2);
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else
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return (unsigned long)func;
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#elif defined(PPC64_ELF_ABI_v1)
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/*
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* On PPC64 ABIv1 the function pointer actually points to the
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* function's descriptor. The first entry in the descriptor is the
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* address of the function text.
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*
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* However, we may also receive pointer to an assembly symbol. To
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* detect that, we first check if the function pointer we receive
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* already points to kernel/module text and we only dereference it
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* if it doesn't.
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*/
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if (kernel_text_address((unsigned long)func))
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return (unsigned long)func;
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else
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return ((func_descr_t *)func)->entry;
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#else
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return (unsigned long)func;
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#endif
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}
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static inline unsigned long ppc_global_function_entry(void *func)
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{
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#ifdef PPC64_ELF_ABI_v2
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/* PPC64 ABIv2 the global entry point is at the address */
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return (unsigned long)func;
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#else
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/* All other cases there is no change vs ppc_function_entry() */
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return ppc_function_entry(func);
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#endif
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}
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/*
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* Wrapper around kallsyms_lookup() to return function entry address:
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* - For ABIv1, we lookup the dot variant.
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* - For ABIv2, we return the local entry point.
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*/
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static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
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{
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unsigned long addr;
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#ifdef PPC64_ELF_ABI_v1
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/* check for dot variant */
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char dot_name[1 + KSYM_NAME_LEN];
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bool dot_appended = false;
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if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
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return 0;
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if (name[0] != '.') {
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dot_name[0] = '.';
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dot_name[1] = '\0';
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strlcat(dot_name, name, sizeof(dot_name));
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dot_appended = true;
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} else {
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dot_name[0] = '\0';
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strlcat(dot_name, name, sizeof(dot_name));
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}
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addr = kallsyms_lookup_name(dot_name);
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if (!addr && dot_appended)
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/* Let's try the original non-dot symbol lookup */
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addr = kallsyms_lookup_name(name);
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#elif defined(PPC64_ELF_ABI_v2)
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addr = kallsyms_lookup_name(name);
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if (addr)
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addr = ppc_function_entry((void *)addr);
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#else
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addr = kallsyms_lookup_name(name);
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#endif
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return addr;
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}
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#ifdef CONFIG_PPC64
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/*
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* Some instruction encodings commonly used in dynamic ftracing
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* and function live patching.
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*/
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/* This must match the definition of STK_GOT in <asm/ppc_asm.h> */
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#ifdef PPC64_ELF_ABI_v2
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#define R2_STACK_OFFSET 24
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#else
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#define R2_STACK_OFFSET 40
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#endif
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#define PPC_INST_LD_TOC (PPC_INST_LD | ___PPC_RT(__REG_R2) | \
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___PPC_RA(__REG_R1) | R2_STACK_OFFSET)
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/* usually preceded by a mflr r0 */
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#define PPC_INST_STD_LR (PPC_INST_STD | ___PPC_RS(__REG_R0) | \
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___PPC_RA(__REG_R1) | PPC_LR_STKOFF)
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#endif /* CONFIG_PPC64 */
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#endif /* _ASM_POWERPC_CODE_PATCHING_H */
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