From: Peter Zijlstra <peterz@infradead.org>
To: bpf@vger.kernel.org
Subject: [PATCH bpf-next 03/17] objtool: Explicitly avoid self modifying code in .altinstr_replacement
Date: Wed, 27 Oct 2021 10:52:46 +0200 [thread overview]
Message-ID: <20211027085520.232801925@infradead.org> (raw)
In-Reply-To: 20211027085243.008677168@infradead.org
Assume ALTERNATIVE()s know what they're doing and do not change, or
cause to change, instructions in .altinstr_replacement sections.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
tools/objtool/check.c | 42 +++++++++++++++++++++++++++++++-----------
1 file changed, 31 insertions(+), 11 deletions(-)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -993,18 +993,27 @@ static void remove_insn_ops(struct instr
}
}
-static void add_call_dest(struct objtool_file *file, struct instruction *insn,
- struct symbol *dest, bool sibling)
+static void annotate_call_site(struct objtool_file *file,
+ struct instruction *insn, bool sibling)
{
struct reloc *reloc = insn_reloc(file, insn);
+ struct symbol *sym = insn->call_dest;
- insn->call_dest = dest;
- if (!dest)
+ if (!sym)
+ sym = reloc->sym;
+
+ /*
+ * Alternative replacement code is just template code which is
+ * sometimes copied to the original instruction, For now, don't
+ * annotate it. (In the future we might consider annotating the
+ * original instruction if/when it ever makes sense to do so.).
+ */
+ if (!strcmp(insn->sec->name, ".altinstr_replacement"))
return;
- if (insn->call_dest->static_call_tramp) {
- list_add_tail(&insn->call_node,
- &file->static_call_list);
+ if (sym->static_call_tramp) {
+ list_add_tail(&insn->call_node, &file->static_call_list);
+ return;
}
/*
@@ -1012,7 +1021,7 @@ static void add_call_dest(struct objtool
* so they need a little help, NOP out any KCOV calls from noinstr
* text.
*/
- if (insn->sec->noinstr && insn->call_dest->kcov) {
+ if (insn->sec->noinstr && sym->kcov) {
if (reloc) {
reloc->type = R_NONE;
elf_write_reloc(file->elf, reloc);
@@ -1024,9 +1033,10 @@ static void add_call_dest(struct objtool
: arch_nop_insn(insn->len));
insn->type = sibling ? INSN_RETURN : INSN_NOP;
+ return;
}
- if (mcount && insn->call_dest->fentry) {
+ if (mcount && sym->fentry) {
if (sibling)
WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
@@ -1041,9 +1051,17 @@ static void add_call_dest(struct objtool
insn->type = INSN_NOP;
- list_add_tail(&insn->mcount_loc_node,
- &file->mcount_loc_list);
+ list_add_tail(&insn->mcount_loc_node, &file->mcount_loc_list);
+ return;
}
+}
+
+static void add_call_dest(struct objtool_file *file, struct instruction *insn,
+ struct symbol *dest, bool sibling)
+{
+ insn->call_dest = dest;
+ if (!dest)
+ return;
/*
* Whatever stack impact regular CALLs have, should be undone
@@ -1053,6 +1071,8 @@ static void add_call_dest(struct objtool
* are converted to JUMP, see read_intra_function_calls().
*/
remove_insn_ops(insn);
+
+ annotate_call_site(file, insn, sibling);
}
/*
next prev parent reply other threads:[~2021-10-27 8:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-27 8:52 [PATCH bpf-next 00/17] x86: Rewrite the retpoline rewrite logic Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 01/17] objtool: Handle __sanitize_cov*() tail calls Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 02/17] objtool: Classify symbols Peter Zijlstra
2021-10-27 8:52 ` Peter Zijlstra [this message]
2021-10-27 8:52 ` [PATCH bpf-next 04/17] objtool: Shrink struct instruction Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 05/17] objtool,x86: Replace alternatives with .retpoline_sites Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 06/17] x86/retpoline: Remove unused replacement symbols Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 07/17] x86/asm: Fix register order Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 08/17] x86/asm: Fixup odd GEN-for-each-reg.h usage Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 09/17] x86/retpoline: Move the retpoline thunk declarations to nospec-branch.h Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 10/17] x86/retpoline: Create a retpoline thunk array Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 11/17] x86/alternative: Implement .retpoline_sites support Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 12/17] x86/alternative: Handle Jcc __x86_indirect_thunk_\reg Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 13/17] x86/alternative: Try inline spectre_v2=retpoline,amd Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 14/17] x86/alternative: Add debug prints to apply_retpolines() Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 15/17] x86,bugs: Unconditionally allow spectre_v2=retpoline,amd Peter Zijlstra
2021-10-27 8:52 ` [PATCH bpf-next 16/17] bpf, x86: Simplify computing label offsets Peter Zijlstra
2021-10-27 8:53 ` [PATCH bpf-next 17/17] bpf,x86: Respect X86_FEATURE_RETPOLINE* Peter Zijlstra
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