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From: Peter Zijlstra <peterz@infradead.org>
To: x86@kernel.org, joao@overdrivepizza.com, hjl.tools@gmail.com,
	jpoimboe@redhat.com, andrew.cooper3@citrix.com
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
	ndesaulniers@google.com, keescook@chromium.org,
	samitolvanen@google.com, mark.rutland@arm.com,
	alyssa.milburn@intel.com, mbenes@suse.cz, rostedt@goodmis.org,
	mhiramat@kernel.org, alexei.starovoitov@gmail.com
Subject: [PATCH v4 20/45] x86/ibt,ftrace: Make function-graph play nice
Date: Tue, 08 Mar 2022 16:30:31 +0100	[thread overview]
Message-ID: <20220308154318.347296408@infradead.org> (raw)
In-Reply-To: <20220308153011.021123062@infradead.org>

Return trampoline must not use indirect branch to return; while this
preserves the RSB, it is fundamentally incompatible with IBT. Instead
use a retpoline like ROP gadget that defeats IBT while not unbalancing
the RSB.

And since ftrace_stub is no longer a plain RET, don't use it to copy
from. Since RET is a trivial instruction, poke it directly.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/kernel/ftrace.c    |    9 ++-------
 arch/x86/kernel/ftrace_64.S |   21 +++++++++++++++++----
 2 files changed, 19 insertions(+), 11 deletions(-)

--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -316,12 +316,12 @@ create_trampoline(struct ftrace_ops *ops
 	unsigned long offset;
 	unsigned long npages;
 	unsigned long size;
-	unsigned long retq;
 	unsigned long *ptr;
 	void *trampoline;
 	void *ip;
 	/* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
 	unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
+	unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE };
 	union ftrace_op_code_union op_ptr;
 	int ret;
 
@@ -359,12 +359,7 @@ create_trampoline(struct ftrace_ops *ops
 		goto fail;
 
 	ip = trampoline + size;
-
-	/* The trampoline ends with ret(q) */
-	retq = (unsigned long)ftrace_stub;
-	ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE);
-	if (WARN_ON(ret < 0))
-		goto fail;
+	memcpy(ip, retq, RET_SIZE);
 
 	/* No need to test direct calls on created trampolines */
 	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -176,10 +176,10 @@ SYM_FUNC_END(ftrace_caller);
 SYM_FUNC_START(ftrace_epilogue)
 /*
  * This is weak to keep gas from relaxing the jumps.
- * It is also used to copy the RET for trampolines.
  */
 SYM_INNER_LABEL_ALIGN(ftrace_stub, SYM_L_WEAK)
 	UNWIND_HINT_FUNC
+	ENDBR
 	RET
 SYM_FUNC_END(ftrace_epilogue)
 
@@ -284,6 +284,7 @@ SYM_FUNC_START(__fentry__)
 	jnz trace
 
 SYM_INNER_LABEL(ftrace_stub, SYM_L_GLOBAL)
+	ENDBR
 	RET
 
 trace:
@@ -307,7 +308,7 @@ EXPORT_SYMBOL(__fentry__)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 SYM_FUNC_START(return_to_handler)
-	subq  $24, %rsp
+	subq  $16, %rsp
 
 	/* Save the return values */
 	movq %rax, (%rsp)
@@ -319,7 +320,19 @@ SYM_FUNC_START(return_to_handler)
 	movq %rax, %rdi
 	movq 8(%rsp), %rdx
 	movq (%rsp), %rax
-	addq $24, %rsp
-	JMP_NOSPEC rdi
+
+	addq $16, %rsp
+	/*
+	 * Jump back to the old return address. This cannot be JMP_NOSPEC rdi
+	 * since IBT would demand that contain ENDBR, which simply isn't so for
+	 * return addresses. Use a retpoline here to keep the RSB balanced.
+	 */
+	ANNOTATE_INTRA_FUNCTION_CALL
+	call .Ldo_rop
+	int3
+.Ldo_rop:
+	mov %rdi, (%rsp)
+	UNWIND_HINT_FUNC
+	RET
 SYM_FUNC_END(return_to_handler)
 #endif



  parent reply	other threads:[~2022-03-08 15:58 UTC|newest]

Thread overview: 193+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-08 15:30 [PATCH v4 00/45] x86: Kernel IBT Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 01/45] static_call: Avoid building empty .static_call_sites Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 02/45] objtool: Add --dry-run Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 03/45] objtool: Default ignore INT3 for unreachable Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 04/45] objtool,efi: Update __efi64_thunk annotation Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-09  8:35   ` [PATCH v4 04/45] " Miroslav Benes
2022-03-15 10:44   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 05/45] objtool: Have WARN_FUNC fall back to sym+off Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 06/45] x86/ibt: Base IBT bits Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 07/45] x86/ibt: Add ANNOTATE_NOENDBR Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 08/45] x86/text-patching: Make text_gen_insn() play nice with ANNOTATE_NOENDBR Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 09/45] x86/ibt,paravirt: Use text_gen_insn() for paravirt_patch() Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 10/45] x86/entry: Cleanup PARAVIRT Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 11/45] x86/entry,xen: Early rewrite of restore_regs_and_return_to_kernel() Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 12/45] x86/ibt,xen: Sprinkle the ENDBR Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 13/45] x86/ibt,entry: Sprinkle ENDBR dust Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 14/45] x86/linkage: Add ENDBR to SYM_FUNC_START*() Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 15/45] x86/ibt,paravirt: Sprinkle ENDBR Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 16/45] x86/ibt,crypto: Add ENDBR for the jump-table entries Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 17/45] x86/ibt,kvm: Add ENDBR to fastops Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 18/45] x86/ibt,ftrace: Search for __fentry__ location Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 19/45] x86/livepatch: Validate " Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-09  8:58   ` [PATCH v4 19/45] " Miroslav Benes
2022-03-15 10:44   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` Peter Zijlstra [this message]
2022-03-09  7:55   ` [tip: x86/core] x86/ibt,ftrace: Make function-graph play nice tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 21/45] x86/ibt,kprobes: Cure sym+0 equals fentry woes Peter Zijlstra
2022-03-09  7:55   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 22/45] x86/ibt,bpf: Add ENDBR instructions to prologue and trampoline Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:44   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 23/45] x86/ibt,ftrace: Add ENDBR to samples/ftrace Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 24/45] x86/ibt: Add IBT feature, MSR and #CP handling Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-09 13:56   ` [PATCH v4 24/45] " Andrew Cooper
2022-03-15 10:43   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 25/45] x86/ibt,kexec: Disable CET on kexec Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 26/45] x86/alternative: Simplify int3_selftest_ip Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 27/45] x86/ibt: Disable IBT around firmware Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 28/45] x86/bugs: Disable Retpoline when IBT Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 29/45] x86/ibt: Annotate text references Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-22  4:43   ` [PATCH v4 29/45] " Masami Hiramatsu
2022-03-22  4:45     ` Alexei Starovoitov
2022-03-08 15:30 ` [PATCH v4 30/45] x86/ibt,ftrace: Annotate ftrace code patching Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 31/45] x86/ibt,sev: Annotations Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 32/45] x86/ibt: Dont generate ENDBR in .discard.text Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 33/45] x86/ibt: Ensure module init/exit points have references Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 34/45] objtool: Rename --duplicate to --lto Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 35/45] objtool: Ignore extra-symbol code Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 36/45] x86: Mark stop_this_cpu() __noreturn Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 37/45] exit: Mark do_group_exit() __noreturn Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 38/45] objtool: Rework ASM_REACHABLE Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 39/45] x86: Annotate call_on_stack() Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 40/45] Kbuild: Allow whole module objtool runs Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 41/45] objtool: Read the NOENDBR annotation Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 42/45] objtool: Add IBT/ENDBR decoding Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 43/45] objtool: Validate IBT assumptions Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 44/45] objtool: Find unused ENDBR instructions Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-15 15:39     ` David Laight
2022-03-17 22:22       ` Josh Poimboeuf
2022-03-18 10:49         ` Peter Zijlstra
2022-03-08 15:30 ` [PATCH v4 45/45] x86/alternative: Use .ibt_endbr_seal to seal indirect calls Peter Zijlstra
2022-03-09  7:54   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-03-15 10:43   ` tip-bot2 for Peter Zijlstra
2022-03-08 20:00 ` [PATCH v4 00/45] x86: Kernel IBT Alexei Starovoitov
2022-03-08 22:01   ` Peter Zijlstra
2022-03-08 22:32     ` Peter Zijlstra
2022-03-09  1:02       ` Peter Zijlstra
2022-03-09 19:09         ` Alexei Starovoitov
2022-03-10  9:35           ` Peter Zijlstra
2022-03-10 13:47             ` Peter Zijlstra
2022-03-10 14:37               ` Steven Rostedt
2022-03-11 15:23                 ` Peter Zijlstra
2022-03-10 16:29               ` Peter Zijlstra
2022-03-11 10:40                 ` Peter Zijlstra
2022-03-11 17:09                   ` Alexei Starovoitov
2022-03-12 15:44                     ` Peter Zijlstra
2022-03-13  1:33                       ` Alexei Starovoitov
2022-03-13  8:52                         ` Peter Zijlstra
2022-03-14 14:59                           ` Peter Zijlstra
2022-03-15  8:15                             ` Peter Zijlstra
2022-03-15 16:28                               ` Masahiro Yamada
2022-03-17 19:44                                 ` Peter Zijlstra
2022-03-18  2:07                                   ` David Laight
2022-03-17 18:15                               ` Masahiro Yamada
2022-03-17 19:52                                 ` Peter Zijlstra
2022-03-18 15:36                                 ` [tip: x86/core] kbuild: Fixup the IBT kbuild changes tip-bot2 for Peter Zijlstra
2022-03-18 16:15                                   ` Masahiro Yamada
2022-03-22 20:24                                 ` tip-bot2 for Peter Zijlstra
2022-03-15 16:26                             ` [PATCH v4 00/45] x86: Kernel IBT Masahiro Yamada
2022-03-17 19:36                               ` Peter Zijlstra
2022-03-14 15:33                           ` Peter Zijlstra
2022-03-15 10:43                             ` [tip: x86/core] x86: Annotate idtentry_df() tip-bot2 for Peter Zijlstra
2022-03-15 10:43                             ` [tip: x86/core] x86,objtool: Move the ASM_REACHABLE annotation to objtool.h tip-bot2 for Peter Zijlstra
2022-03-15 10:43                             ` [tip: x86/core] x86: Mark __invalid_creds() __noreturn tip-bot2 for Peter Zijlstra
2022-03-14 20:44                         ` [PATCH v4 00/45] x86: Kernel IBT Kumar Kartikeya Dwivedi
2022-03-15  9:00                           ` Peter Zijlstra
2022-03-15 10:05                             ` Kumar Kartikeya Dwivedi
2022-03-15 10:07                             ` Peter Zijlstra
2022-03-15 10:39                               ` Peter Zijlstra
2022-03-16  9:35                             ` Peter Zijlstra
2022-03-16 11:12                               ` Kumar Kartikeya Dwivedi
2022-03-15 18:26                           ` Alexei Starovoitov
2022-03-17 20:27                             ` Peter Zijlstra
2022-03-11 14:40               ` [tip: x86/core] x86,ftrace: Fix modify_ftrace_direct() tip-bot2 for Peter Zijlstra
2022-03-10  0:30       ` [PATCH v4 00/45] x86: Kernel IBT Nick Desaulniers
2022-03-10  9:05         ` Peter Zijlstra
2022-03-10  9:22           ` David Laight
2022-03-10 10:16             ` Peter Zijlstra
2022-03-10 20:49               ` Nick Desaulniers
2022-03-11 14:40               ` [tip: x86/core] x86: Fix {int3,ibt}_selftest() vs LTO tip-bot2 for Peter Zijlstra
2022-03-08 20:06 ` [PATCH v4 00/45] x86: Kernel IBT Josh Poimboeuf
2022-03-09  6:57   ` Josh Poimboeuf
2022-03-09 13:37     ` David Laight
2022-03-10 14:27       ` Peter Zijlstra
2022-03-09 12:51 ` Miroslav Benes

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