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s390/ftrace: verify opcode before applying patch

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commit 72b3942a17 ("scripts: ftrace - move the
sort-processing in ftrace_init") had the unexpected
side effect that wrong code locations were patched.
To prevent this from happening again, verify the
opcode before patching it.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Sven Schnelle 2022-01-23 20:20:09 +01:00 committed by Vasily Gorbik
parent f36e7c9845
commit 98c0d24d1e
1 changed files with 27 additions and 16 deletions
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43
arch/s390/kernel/ftrace.c
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@ -164,31 +164,32 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
return 0;
}
static void brcl_disable(void *brcl)
static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable)
{
u8 op = 0x04; /* set mask field to zero */
u16 old;
u8 op;
s390_kernel_write((char *)brcl + 1, &op, sizeof(op));
if (get_kernel_nofault(old, addr))
return -EFAULT;
if (old != expected)
return -EINVAL;
/* set mask field to all ones or zeroes */
op = enable ? 0xf4 : 0x04;
s390_kernel_write((char *)addr + 1, &op, sizeof(op));
return 0;
}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
brcl_disable((void *)rec->ip);
return 0;
}
static void brcl_enable(void *brcl)
{
u8 op = 0xf4; /* set mask field to all ones */
s390_kernel_write((char *)brcl + 1, &op, sizeof(op));
/* Expect brcl 0xf,... */
return ftrace_patch_branch_mask((void *)rec->ip, 0xc0f4, false);
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
brcl_enable((void *)rec->ip);
return 0;
/* Expect brcl 0x0,... */
return ftrace_patch_branch_mask((void *)rec->ip, 0xc004, true);
}
int ftrace_update_ftrace_func(ftrace_func_t func)
@ -261,14 +262,24 @@ NOKPROBE_SYMBOL(prepare_ftrace_return);
*/
int ftrace_enable_ftrace_graph_caller(void)
{
brcl_disable(ftrace_graph_caller);
int rc;
/* Expect brc 0xf,... */
rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);
if (rc)
return rc;
text_poke_sync_lock();
return 0;
}
int ftrace_disable_ftrace_graph_caller(void)
{
brcl_enable(ftrace_graph_caller);
int rc;
/* Expect brc 0x0,... */
rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);
if (rc)
return rc;
text_poke_sync_lock();
return 0;
}