[PATCH] powerpc/64: Drop ppc_inst_as_str()
Michael Ellerman
mpe at ellerman.id.au
Tue May 31 16:59:36 AEST 2022
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, 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 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 at gmail.com>
Reported-by: Petr Mladek <pmladek at suse.com>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
---
arch/powerpc/include/asm/inst.h | 19 -------------------
arch/powerpc/kernel/kprobes.c | 2 +-
arch/powerpc/kernel/trace/ftrace.c | 24 +++++++++++++-----------
arch/powerpc/lib/test_emulate_step.c | 6 +++---
arch/powerpc/xmon/xmon.c | 2 +-
5 files changed, 18 insertions(+), 35 deletions(-)
diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
index b49aae9f6f27..684d3f453282 100644
--- a/arch/powerpc/include/asm/inst.h
+++ b/arch/powerpc/include/asm/inst.h
@@ -139,25 +139,6 @@ static inline void ppc_inst_write(u32 *ptr, ppc_inst_t x)
*(u64 *)ptr = ppc_inst_as_ulong(x);
}
-#define PPC_INST_STR_LEN sizeof("00000000 00000000")
-
-static inline char *__ppc_inst_as_str(char str[PPC_INST_STR_LEN], ppc_inst_t x)
-{
- if (ppc_inst_prefixed(x))
- sprintf(str, "%08x %08x", ppc_inst_val(x), ppc_inst_suffix(x));
- else
- sprintf(str, "%08x", ppc_inst_val(x));
-
- return str;
-}
-
-#define ppc_inst_as_str(x) \
-({ \
- char __str[PPC_INST_STR_LEN]; \
- __ppc_inst_as_str(__str, x); \
- __str; \
-})
-
static inline int __copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
{
unsigned int val, suffix;
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 1c97c0f177ae..912d4f8a13be 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -269,7 +269,7 @@ static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
* So, we should never get here... but, its still
* good to catch them, just in case...
*/
- printk("Can't step on instruction %s\n", ppc_inst_as_str(insn));
+ printk("Can't step on instruction %08lx\n", ppc_inst_as_ulong(insn));
BUG();
} else {
/*
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 2a893e06e4f1..cab67b5120b9 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -69,8 +69,8 @@ ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
/* Make sure it is what we expect it to be */
if (!ppc_inst_equal(replaced, old)) {
- pr_err("%p: replaced (%s) != old (%s)",
- (void *)ip, ppc_inst_as_str(replaced), ppc_inst_as_str(old));
+ pr_err("%p: replaced (%08lx) != old (%08lx)", (void *)ip,
+ ppc_inst_as_ulong(replaced), ppc_inst_as_ulong(old));
return -EINVAL;
}
@@ -127,7 +127,7 @@ __ftrace_make_nop(struct module *mod,
/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
- pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
+ pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
return -EINVAL;
}
@@ -159,8 +159,8 @@ __ftrace_make_nop(struct module *mod,
/* We expect either a mflr r0, or a std r0, LRSAVE(r1) */
if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_MFLR(_R0))) &&
!ppc_inst_equal(op, ppc_inst(PPC_INST_STD_LR))) {
- pr_err("Unexpected instruction %s around bl _mcount\n",
- ppc_inst_as_str(op));
+ pr_err("Unexpected instruction %08lx around bl _mcount\n",
+ ppc_inst_as_ulong(op));
return -EINVAL;
}
} else if (IS_ENABLED(CONFIG_PPC64)) {
@@ -174,7 +174,8 @@ __ftrace_make_nop(struct module *mod,
}
if (!ppc_inst_equal(op, ppc_inst(PPC_INST_LD_TOC))) {
- pr_err("Expected %08lx found %s\n", PPC_INST_LD_TOC, ppc_inst_as_str(op));
+ pr_err("Expected %08lx found %08lx\n", PPC_INST_LD_TOC,
+ ppc_inst_as_ulong(op));
return -EINVAL;
}
}
@@ -312,7 +313,7 @@ static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr)
/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
- pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
+ pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
return -EINVAL;
}
@@ -416,8 +417,8 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
return -EFAULT;
if (!expected_nop_sequence(ip, op[0], op[1])) {
- pr_err("Unexpected call sequence at %p: %s %s\n",
- ip, ppc_inst_as_str(op[0]), ppc_inst_as_str(op[1]));
+ pr_err("Unexpected call sequence at %p: %08lx %08lx\n", ip,
+ ppc_inst_as_ulong(op[0]), ppc_inst_as_ulong(op[1]));
return -EINVAL;
}
@@ -486,7 +487,8 @@ static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
}
if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_NOP()))) {
- pr_err("Unexpected call sequence at %p: %s\n", ip, ppc_inst_as_str(op));
+ pr_err("Unexpected call sequence at %p: %08lx\n",
+ ip, ppc_inst_as_ulong(op));
return -EINVAL;
}
@@ -564,7 +566,7 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
- pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
+ pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
return -EINVAL;
}
diff --git a/arch/powerpc/lib/test_emulate_step.c b/arch/powerpc/lib/test_emulate_step.c
index 4f141daafcff..f2e47be05e8c 100644
--- a/arch/powerpc/lib/test_emulate_step.c
+++ b/arch/powerpc/lib/test_emulate_step.c
@@ -1616,11 +1616,11 @@ static int __init emulate_compute_instr(struct pt_regs *regs,
if (analysed != 1 || GETTYPE(op.type) != COMPUTE) {
if (negative)
return -EFAULT;
- pr_info("emulation failed, instruction = %s\n", ppc_inst_as_str(instr));
+ pr_info("emulation failed, instruction = %08lx\n", ppc_inst_as_ulong(instr));
return -EFAULT;
}
if (analysed == 1 && negative)
- pr_info("negative test failed, instruction = %s\n", ppc_inst_as_str(instr));
+ pr_info("negative test failed, instruction = %08lx\n", ppc_inst_as_ulong(instr));
if (!negative)
emulate_update_regs(regs, &op);
return 0;
@@ -1637,7 +1637,7 @@ static int __init execute_compute_instr(struct pt_regs *regs,
/* Patch the NOP with the actual instruction */
patch_instruction_site(&patch__exec_instr, instr);
if (exec_instr(regs)) {
- pr_info("execution failed, instruction = %s\n", ppc_inst_as_str(instr));
+ pr_info("execution failed, instruction = %08lx\n", ppc_inst_as_ulong(instr));
return -EFAULT;
}
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index fff81c2300fa..6043454842cb 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3048,7 +3048,7 @@ generic_inst_dump(unsigned long adr, long count, int praddr,
dotted = 0;
last_inst = inst;
if (praddr)
- printf(REG" %s", adr, ppc_inst_as_str(inst));
+ printf(REG" %08lx", adr, ppc_inst_as_ulong(inst));
printf("\t");
if (!ppc_inst_prefixed(inst))
dump_func(ppc_inst_val(inst), adr);
--
2.35.3
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