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2a83afe72a
The ppc_inst_as_str() macro tries to make printing variable length,
aka "prefixed", instructions convenient. It mostly succeeds, but it does
hide an on-stack buffer, which triggers stack protector.
More problematically it doesn't compile at all with GCC 12,
with -Wdangling-pointer, due to the fact that it returns the char buffer
declared inside the macro:
arch/powerpc/kernel/trace/ftrace.c: In function '__ftrace_modify_call':
./include/linux/printk.h:475:44: error: using a dangling pointer to '__str' [-Werror=dangling-pointer=]
475 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
...
arch/powerpc/kernel/trace/ftrace.c:567:17: note: in expansion of macro 'pr_err'
567 | pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
| ^~~~~~
./arch/powerpc/include/asm/inst.h:156:14: note: '__str' declared here
156 | char __str[PPC_INST_STR_LEN]; \
| ^~~~~
This could be fixed by having the caller declare the buffer, but in some
places there'd need to be two buffers. In all cases where
ppc_inst_as_str() is used the output is not really meant for user
consumption, it's almost always indicative of a kernel bug.
A simpler solution is to just print the value as an unsigned long. For
normal instructions the output is identical. For prefixed instructions
the value is printed as a single 64-bit quantity, whereas previously the
low half was printed first. But that is good enough for debug output,
especially as prefixed instructions will be rare in kernel code in
practice.
Old:
c000000000111170 60420000 ori r2,r2,0
c000000000111174 04100001 e580fb00 .long 0xe580fb0004100001
New:
c00000000010f90c 60420000 ori r2,r2,0
c00000000010f910 e580fb0004100001 .long 0xe580fb0004100001
Reported-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reported-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20220531065936.3674348-1-mpe@ellerman.id.au
170 lines
3.9 KiB
C
170 lines
3.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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#ifndef _ASM_POWERPC_INST_H
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#define _ASM_POWERPC_INST_H
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#include <asm/ppc-opcode.h>
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#include <asm/reg.h>
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#include <asm/disassemble.h>
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#include <asm/uaccess.h>
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#define ___get_user_instr(gu_op, dest, ptr) \
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({ \
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long __gui_ret; \
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u32 __user *__gui_ptr = (u32 __user *)ptr; \
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ppc_inst_t __gui_inst; \
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unsigned int __prefix, __suffix; \
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\
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__chk_user_ptr(ptr); \
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__gui_ret = gu_op(__prefix, __gui_ptr); \
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if (__gui_ret == 0) { \
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if (IS_ENABLED(CONFIG_PPC64) && (__prefix >> 26) == OP_PREFIX) { \
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__gui_ret = gu_op(__suffix, __gui_ptr + 1); \
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__gui_inst = ppc_inst_prefix(__prefix, __suffix); \
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} else { \
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__gui_inst = ppc_inst(__prefix); \
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} \
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if (__gui_ret == 0) \
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(dest) = __gui_inst; \
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} \
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__gui_ret; \
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})
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#define get_user_instr(x, ptr) ___get_user_instr(get_user, x, ptr)
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#define __get_user_instr(x, ptr) ___get_user_instr(__get_user, x, ptr)
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/*
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* Instruction data type for POWER
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*/
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#if defined(CONFIG_PPC64) || defined(__CHECKER__)
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static inline u32 ppc_inst_val(ppc_inst_t x)
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{
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return x.val;
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}
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#define ppc_inst(x) ((ppc_inst_t){ .val = (x) })
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#else
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static inline u32 ppc_inst_val(ppc_inst_t x)
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{
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return x;
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}
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#define ppc_inst(x) (x)
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#endif
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static inline int ppc_inst_primary_opcode(ppc_inst_t x)
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{
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return ppc_inst_val(x) >> 26;
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}
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#ifdef CONFIG_PPC64
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#define ppc_inst_prefix(x, y) ((ppc_inst_t){ .val = (x), .suffix = (y) })
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static inline u32 ppc_inst_suffix(ppc_inst_t x)
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{
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return x.suffix;
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}
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#else
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#define ppc_inst_prefix(x, y) ((void)y, ppc_inst(x))
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static inline u32 ppc_inst_suffix(ppc_inst_t x)
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{
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return 0;
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}
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#endif /* CONFIG_PPC64 */
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static inline ppc_inst_t ppc_inst_read(const u32 *ptr)
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{
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if (IS_ENABLED(CONFIG_PPC64) && (*ptr >> 26) == OP_PREFIX)
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return ppc_inst_prefix(*ptr, *(ptr + 1));
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else
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return ppc_inst(*ptr);
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}
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static inline bool ppc_inst_prefixed(ppc_inst_t x)
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{
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return IS_ENABLED(CONFIG_PPC64) && ppc_inst_primary_opcode(x) == OP_PREFIX;
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}
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static inline ppc_inst_t ppc_inst_swab(ppc_inst_t x)
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{
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return ppc_inst_prefix(swab32(ppc_inst_val(x)), swab32(ppc_inst_suffix(x)));
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}
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static inline bool ppc_inst_equal(ppc_inst_t x, ppc_inst_t y)
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{
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if (ppc_inst_val(x) != ppc_inst_val(y))
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return false;
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if (!ppc_inst_prefixed(x))
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return true;
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return ppc_inst_suffix(x) == ppc_inst_suffix(y);
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}
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static inline int ppc_inst_len(ppc_inst_t x)
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{
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return ppc_inst_prefixed(x) ? 8 : 4;
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}
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/*
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* Return the address of the next instruction, if the instruction @value was
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* located at @location.
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*/
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static inline u32 *ppc_inst_next(u32 *location, u32 *value)
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{
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ppc_inst_t tmp;
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tmp = ppc_inst_read(value);
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return (void *)location + ppc_inst_len(tmp);
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}
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static inline unsigned long ppc_inst_as_ulong(ppc_inst_t x)
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{
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if (IS_ENABLED(CONFIG_PPC32))
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return ppc_inst_val(x);
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else if (IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN))
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return (u64)ppc_inst_suffix(x) << 32 | ppc_inst_val(x);
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else
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return (u64)ppc_inst_val(x) << 32 | ppc_inst_suffix(x);
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}
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static inline void ppc_inst_write(u32 *ptr, ppc_inst_t x)
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{
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if (!ppc_inst_prefixed(x))
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*ptr = ppc_inst_val(x);
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else
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*(u64 *)ptr = ppc_inst_as_ulong(x);
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}
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static inline int __copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
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{
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unsigned int val, suffix;
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/* See https://github.com/ClangBuiltLinux/linux/issues/1521 */
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#if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 140000
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val = suffix = 0;
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#endif
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__get_kernel_nofault(&val, src, u32, Efault);
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if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
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__get_kernel_nofault(&suffix, src + 1, u32, Efault);
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*inst = ppc_inst_prefix(val, suffix);
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} else {
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*inst = ppc_inst(val);
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}
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return 0;
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Efault:
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return -EFAULT;
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}
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static inline int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
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{
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if (unlikely(!is_kernel_addr((unsigned long)src)))
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return -ERANGE;
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return __copy_inst_from_kernel_nofault(inst, src);
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}
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#endif /* _ASM_POWERPC_INST_H */
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