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Message-ID: <20241011170847.334429-14-ardb+git@google.com>
Date: Fri, 11 Oct 2024 19:08:52 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: llvm@...ts.linux.dev, keescook@...omium.org,
linux-hardening@...r.kernel.org, nathan@...nel.org,
Ard Biesheuvel <ardb@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, Jan Beulich <jbeulich@...e.com>,
"Jose E. Marchesi" <jemarch@....org>, Kees Cook <kees@...nel.org>
Subject: [PATCH v3 4/8] objtool: Move jump table heuristics to a x86 specific
source file
From: Ard Biesheuvel <ardb@...nel.org>
In preparation for implementing support for the use of compiler emitted
jump table annotations, move the existing code out of the generic
sources. This will permit a clean separation between the two approaches,
where the old one will not be wired up for architectures other than x86.
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
tools/objtool/arch/loongarch/special.c | 7 --
tools/objtool/arch/powerpc/special.c | 7 --
tools/objtool/arch/x86/special.c | 114 +++++++++++++++++++-
tools/objtool/check.c | 112 +------------------
tools/objtool/include/objtool/special.h | 9 +-
5 files changed, 122 insertions(+), 127 deletions(-)
diff --git a/tools/objtool/arch/loongarch/special.c b/tools/objtool/arch/loongarch/special.c
index 87230ed570fd..acf3a391a2f9 100644
--- a/tools/objtool/arch/loongarch/special.c
+++ b/tools/objtool/arch/loongarch/special.c
@@ -7,10 +7,3 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
{
return false;
}
-
-struct reloc *arch_find_switch_table(struct objtool_file *file,
- struct instruction *insn,
- unsigned long *table_size)
-{
- return NULL;
-}
diff --git a/tools/objtool/arch/powerpc/special.c b/tools/objtool/arch/powerpc/special.c
index 51610689abf7..3a108437cfa6 100644
--- a/tools/objtool/arch/powerpc/special.c
+++ b/tools/objtool/arch/powerpc/special.c
@@ -11,10 +11,3 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
{
exit(-1);
}
-
-struct reloc *arch_find_switch_table(struct objtool_file *file,
- struct instruction *insn,
- unsigned long *table_size)
-{
- exit(-1);
-}
diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
index f8fb67636384..cd964b85e2b1 100644
--- a/tools/objtool/arch/x86/special.c
+++ b/tools/objtool/arch/x86/special.c
@@ -108,9 +108,9 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
*
* NOTE: MITIGATION_RETPOLINE made it harder still to decode dynamic jumps.
*/
-struct reloc *arch_find_switch_table(struct objtool_file *file,
- struct instruction *insn,
- unsigned long *table_size)
+static struct reloc *find_switch_table(struct objtool_file *file,
+ struct instruction *insn,
+ unsigned long *table_size)
{
struct reloc *text_reloc, *rodata_reloc;
struct section *table_sec;
@@ -154,3 +154,111 @@ struct reloc *arch_find_switch_table(struct objtool_file *file,
*table_size = 0;
return rodata_reloc;
}
+
+/*
+ * find_jump_table() - Given a dynamic jump, find the switch jump table
+ * associated with it.
+ */
+static void find_jump_table(struct objtool_file *file,
+ struct symbol *func,
+ struct instruction *insn)
+{
+ struct reloc *table_reloc;
+ struct instruction *dest_insn, *orig_insn = insn;
+ unsigned long table_size;
+
+ /*
+ * Backward search using the @first_jump_src links, these help avoid
+ * much of the 'in between' code. Which avoids us getting confused by
+ * it.
+ */
+ for (;
+ insn && insn_func(insn) && insn_func(insn)->pfunc == func;
+ insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
+
+ if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
+ break;
+
+ /* allow small jumps within the range */
+ if (insn->type == INSN_JUMP_UNCONDITIONAL &&
+ insn->jump_dest &&
+ (insn->jump_dest->offset <= insn->offset ||
+ insn->jump_dest->offset > orig_insn->offset))
+ break;
+
+ table_reloc = find_switch_table(file, insn, &table_size);
+ if (!table_reloc)
+ continue;
+ dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
+ if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
+ continue;
+
+ orig_insn->_jump_table = table_reloc;
+ orig_insn->_jump_table_size = table_size;
+ break;
+ }
+}
+
+/*
+ * First pass: Mark the head of each jump table so that in the next pass,
+ * we know when a given jump table ends and the next one starts.
+ */
+static void mark_func_jump_tables(struct objtool_file *file,
+ struct symbol *func)
+{
+ struct instruction *insn, *last = NULL;
+
+ func_for_each_insn(file, func, insn) {
+ if (!last)
+ last = insn;
+
+ /*
+ * Store back-pointers for unconditional forward jumps such
+ * that find_jump_table() can back-track using those and
+ * avoid some potentially confusing code.
+ */
+ if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
+ insn->offset > last->offset &&
+ insn->jump_dest->offset > insn->offset &&
+ !insn->jump_dest->first_jump_src) {
+
+ insn->jump_dest->first_jump_src = insn;
+ last = insn->jump_dest;
+ }
+
+ if (insn->type == INSN_JUMP_DYNAMIC)
+ find_jump_table(file, func, insn);
+ }
+}
+
+int add_func_jump_tables(struct objtool_file *file,
+ struct symbol *func)
+{
+ struct instruction *insn, *insn_t1 = NULL, *insn_t2;
+ int ret = 0;
+
+ mark_func_jump_tables(file, func);
+
+ func_for_each_insn(file, func, insn) {
+ if (!insn_jump_table(insn))
+ continue;
+
+ if (!insn_t1) {
+ insn_t1 = insn;
+ continue;
+ }
+
+ insn_t2 = insn;
+
+ ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
+ if (ret)
+ return ret;
+
+ insn_t1 = insn_t2;
+ }
+
+ if (insn_t1)
+ ret = add_jump_table(file, insn_t1, NULL);
+
+ return ret;
+}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index fbb05e973acc..389475dde47c 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2091,8 +2091,8 @@ static int add_special_section_alts(struct objtool_file *file)
return ret;
}
-static int add_jump_table(struct objtool_file *file, struct instruction *insn,
- struct reloc *next_table)
+int add_jump_table(struct objtool_file *file, struct instruction *insn,
+ struct reloc *next_table)
{
unsigned long table_size = insn_jump_table_size(insn);
struct symbol *pfunc = insn_func(insn)->pfunc;
@@ -2169,111 +2169,10 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
return 0;
}
-/*
- * find_jump_table() - Given a dynamic jump, find the switch jump table
- * associated with it.
- */
-static void find_jump_table(struct objtool_file *file, struct symbol *func,
- struct instruction *insn)
+int __weak add_func_jump_tables(struct objtool_file *file,
+ struct symbol *func)
{
- struct reloc *table_reloc;
- struct instruction *dest_insn, *orig_insn = insn;
- unsigned long table_size;
-
- /*
- * Backward search using the @first_jump_src links, these help avoid
- * much of the 'in between' code. Which avoids us getting confused by
- * it.
- */
- for (;
- insn && insn_func(insn) && insn_func(insn)->pfunc == func;
- insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
-
- if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
- break;
-
- /* allow small jumps within the range */
- if (insn->type == INSN_JUMP_UNCONDITIONAL &&
- insn->jump_dest &&
- (insn->jump_dest->offset <= insn->offset ||
- insn->jump_dest->offset > orig_insn->offset))
- break;
-
- table_reloc = arch_find_switch_table(file, insn, &table_size);
- if (!table_reloc)
- continue;
- dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
- if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
- continue;
-
- orig_insn->_jump_table = table_reloc;
- orig_insn->_jump_table_size = table_size;
- break;
- }
-}
-
-/*
- * First pass: Mark the head of each jump table so that in the next pass,
- * we know when a given jump table ends and the next one starts.
- */
-static void mark_func_jump_tables(struct objtool_file *file,
- struct symbol *func)
-{
- struct instruction *insn, *last = NULL;
-
- func_for_each_insn(file, func, insn) {
- if (!last)
- last = insn;
-
- /*
- * Store back-pointers for unconditional forward jumps such
- * that find_jump_table() can back-track using those and
- * avoid some potentially confusing code.
- */
- if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
- insn->offset > last->offset &&
- insn->jump_dest->offset > insn->offset &&
- !insn->jump_dest->first_jump_src) {
-
- insn->jump_dest->first_jump_src = insn;
- last = insn->jump_dest;
- }
-
- if (insn->type != INSN_JUMP_DYNAMIC)
- continue;
-
- find_jump_table(file, func, insn);
- }
-}
-
-static int add_func_jump_tables(struct objtool_file *file,
- struct symbol *func)
-{
- struct instruction *insn, *insn_t1 = NULL, *insn_t2;
- int ret = 0;
-
- func_for_each_insn(file, func, insn) {
- if (!insn_jump_table(insn))
- continue;
-
- if (!insn_t1) {
- insn_t1 = insn;
- continue;
- }
-
- insn_t2 = insn;
-
- ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
- if (ret)
- return ret;
-
- insn_t1 = insn_t2;
- }
-
- if (insn_t1)
- ret = add_jump_table(file, insn_t1, NULL);
-
- return ret;
+ return 0;
}
/*
@@ -2293,7 +2192,6 @@ static int add_jump_table_alts(struct objtool_file *file)
if (func->type != STT_FUNC)
continue;
- mark_func_jump_tables(file, func);
ret = add_func_jump_tables(file, func);
if (ret)
return ret;
diff --git a/tools/objtool/include/objtool/special.h b/tools/objtool/include/objtool/special.h
index e7ee7ffccefd..019b511eca6e 100644
--- a/tools/objtool/include/objtool/special.h
+++ b/tools/objtool/include/objtool/special.h
@@ -37,7 +37,10 @@ void arch_handle_alternative(unsigned short feature, struct special_alt *alt);
bool arch_support_alt_relocation(struct special_alt *special_alt,
struct instruction *insn,
struct reloc *reloc);
-struct reloc *arch_find_switch_table(struct objtool_file *file,
- struct instruction *insn,
- unsigned long *table_size);
+
+int add_func_jump_tables(struct objtool_file *file, struct symbol *func);
+
+int add_jump_table(struct objtool_file *file, struct instruction *insn,
+ struct reloc *next_table);
+
#endif /* _SPECIAL_H */
--
2.47.0.rc1.288.g06298d1525-goog
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