From 6778948f9de86c3cfaf36725a7c87dcff9ba247f Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Mon, 11 Dec 2023 08:20:59 +0000
Subject: [PATCH] kernel_5.10 no rt
---
kernel/tools/objtool/Documentation/stack-validation.txt | 51 +++++++++++++++++++++++++++++++++++++++++++++++----
1 files changed, 47 insertions(+), 4 deletions(-)
diff --git a/kernel/tools/objtool/Documentation/stack-validation.txt b/kernel/tools/objtool/Documentation/stack-validation.txt
index 3995735..30f38fd 100644
--- a/kernel/tools/objtool/Documentation/stack-validation.txt
+++ b/kernel/tools/objtool/Documentation/stack-validation.txt
@@ -21,7 +21,7 @@
which gcc sometimes uses jump tables.
(Objtool also has an 'orc generate' subcommand which generates debuginfo
-for the ORC unwinder. See Documentation/x86/orc-unwinder.txt in the
+for the ORC unwinder. See Documentation/x86/orc-unwinder.rst in the
kernel tree for more details.)
@@ -101,7 +101,7 @@
band. So it doesn't affect runtime performance and it can be
reliable even when interrupts or exceptions are involved.
- For more details, see Documentation/x86/orc-unwinder.txt.
+ For more details, see Documentation/x86/orc-unwinder.rst.
c) Higher live patching compatibility rate
@@ -111,7 +111,7 @@
be detectable). Objtool makes that possible.
For more details, see the livepatch documentation in the Linux kernel
- source tree at Documentation/livepatch/livepatch.txt.
+ source tree at Documentation/livepatch/livepatch.rst.
Rules
-----
@@ -289,6 +289,49 @@
might be corrupt due to a gcc bug. For more details, see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646
+9. file.o: warning: objtool: funcA() call to funcB() with UACCESS enabled
+
+ This means that an unexpected call to a non-whitelisted function exists
+ outside of arch-specific guards.
+ X86: SMAP (stac/clac): __uaccess_begin()/__uaccess_end()
+ ARM: PAN: uaccess_enable()/uaccess_disable()
+
+ These functions should be called to denote a minimal critical section around
+ access to __user variables. See also: https://lwn.net/Articles/517475/
+
+ The intention of the warning is to prevent calls to funcB() from eventually
+ calling schedule(), potentially leaking the AC flags state, and not
+ restoring them correctly.
+
+ It also helps verify that there are no unexpected calls to funcB() which may
+ access user space pages with protections against doing so disabled.
+
+ To fix, either:
+ 1) remove explicit calls to funcB() from funcA().
+ 2) add the correct guards before and after calls to low level functions like
+ __get_user_size()/__put_user_size().
+ 3) add funcB to uaccess_safe_builtin whitelist in tools/objtool/check.c, if
+ funcB obviously does not call schedule(), and is marked notrace (since
+ function tracing inserts additional calls, which is not obvious from the
+ sources).
+
+10. file.o: warning: func()+0x5c: stack layout conflict in alternatives
+
+ This means that in the use of the alternative() or ALTERNATIVE()
+ macro, the code paths have conflicting modifications to the stack.
+ The problem is that there is only one ORC unwind table, which means
+ that the ORC unwind entries must be consistent for all possible
+ instruction boundaries regardless of which code has been patched.
+ This limitation can be overcome by massaging the alternatives with
+ NOPs to shift the stack changes around so they no longer conflict.
+
+11. file.o: warning: unannotated intra-function call
+
+ This warning means that a direct call is done to a destination which
+ is not at the beginning of a function. If this is a legit call, you
+ can remove this warning by putting the ANNOTATE_INTRA_FUNCTION_CALL
+ directive right before the call.
+
If the error doesn't seem to make sense, it could be a bug in objtool.
Feel free to ask the objtool maintainer for help.
@@ -306,7 +349,7 @@
- To skip validation of a file, add
- OBJECT_FILES_NON_STANDARD_filename.o := n
+ OBJECT_FILES_NON_STANDARD_filename.o := y
to the Makefile.
--
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