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x86/ibt,ftrace: Search for __fentry__ location

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Currently a lot of ftrace code assumes __fentry__ is at sym+0. However
with Intel IBT enabled the first instruction of a function will most
likely be ENDBR.

Change ftrace_location() to not only return the __fentry__ location
when called for the __fentry__ location, but also when called for the
sym+0 location.

Then audit/update all callsites of this function to consistently use
these new semantics.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154318.227581603@infradead.org
This commit is contained in:
Peter Zijlstra
2022-03-15 10:32:37 +01:00
parent 6649fa876d
commit aebfd12521
4 changed files with 48 additions and 39 deletions
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kernel/trace/ftrace.c
+40 -8
View File
@@ -1568,17 +1568,34 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
}
/**
* ftrace_location - return true if the ip giving is a traced location
* ftrace_location - return the ftrace location
* @ip: the instruction pointer to check
*
* Returns rec->ip if @ip given is a pointer to a ftrace location.
* That is, the instruction that is either a NOP or call to
* the function tracer. It checks the ftrace internal tables to
* determine if the address belongs or not.
* If @ip matches the ftrace location, return @ip.
* If @ip matches sym+0, return sym's ftrace location.
* Otherwise, return 0.
*/
unsigned long ftrace_location(unsigned long ip)
{
return ftrace_location_range(ip, ip);
struct dyn_ftrace *rec;
unsigned long offset;
unsigned long size;
rec = lookup_rec(ip, ip);
if (!rec) {
if (!kallsyms_lookup_size_offset(ip, &size, &offset))
goto out;
/* map sym+0 to __fentry__ */
if (!offset)
rec = lookup_rec(ip, ip + size - 1);
}
if (rec)
return rec->ip;
out:
return 0;
}
/**
@@ -4962,7 +4979,8 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
{
struct ftrace_func_entry *entry;
if (!ftrace_location(ip))
ip = ftrace_location(ip);
if (!ip)
return -EINVAL;
if (remove) {
@@ -5110,11 +5128,16 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
struct ftrace_func_entry *entry;
struct ftrace_hash *free_hash = NULL;
struct dyn_ftrace *rec;
int ret = -EBUSY;
int ret = -ENODEV;
mutex_lock(&direct_mutex);
ip = ftrace_location(ip);
if (!ip)
goto out_unlock;
/* See if there's a direct function at @ip already */
ret = -EBUSY;
if (ftrace_find_rec_direct(ip))
goto out_unlock;
@@ -5222,6 +5245,10 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
mutex_lock(&direct_mutex);
ip = ftrace_location(ip);
if (!ip)
goto out_unlock;
entry = find_direct_entry(&ip, NULL);
if (!entry)
goto out_unlock;
@@ -5354,6 +5381,11 @@ int modify_ftrace_direct(unsigned long ip,
mutex_lock(&direct_mutex);
mutex_lock(&ftrace_lock);
ip = ftrace_location(ip);
if (!ip)
goto out_unlock;
entry = find_direct_entry(&ip, &rec);
if (!entry)
goto out_unlock;