[PATCH v8 4/5] jump_label: adjust inline asm to be consistent

Alice Ryhl
2024-08-22T12:05:01Z

To avoid duplication of inline asm between C and Rust, we need to
import the inline asm from the relevant `jump_label.h` header into Rust.
To make that easier, this patch updates the header files to expose the
inline asm via a new ARCH_STATIC_BRANCH_ASM macro.

The header files are all updated to define a ARCH_STATIC_BRANCH_ASM that
takes the same arguments in a consistent order so that Rust can use the
same logic for every architecture.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
arch/arm/include/asm/jump_label.h | 14 +++++----
arch/arm64/include/asm/jump_label.h | 20 ++++++++-----
arch/loongarch/include/asm/jump_label.h | 16 +++++++----
arch/riscv/include/asm/jump_label.h | 50 ++++++++++++++++++---------------
arch/x86/include/asm/jump_label.h | 38 ++++++++++---------------
5 files changed, 75 insertions(+), 63 deletions(-)

diff --git a/arch/arm/include/asm/jump_label.h b/arch/arm/include/asm/jump_label.h
index e4eb54f6cd9f..a35aba7f548c 100644
--- a/arch/arm/include/asm/jump_label.h
+++ b/arch/arm/include/asm/jump_label.h
@@ -9,13 +9,17 @@

#define JUMP_LABEL_NOP_SIZE 4

+/* This macro is also expanded on the Rust side. */
+#define ARCH_STATIC_BRANCH_ASM(key, label) \
+ "1:\n\t" \
+ WASM(nop) "\n\t" \
+ ".pushsection __jump_table, \"aw\"\n\t" \
+ ".word 1b, " label ", " key "\n\t" \
+ ".popsection\n\t" \
+
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
- asm goto("1:\n\t"
- WASM(nop) "\n\t"
- ".pushsection __jump_table, \"aw\"\n\t"
- ".word 1b, %l[l_yes], %c0\n\t"
- ".popsection\n\t"
+ asm goto(ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
: : "i" (&((char *)key)[branch]) : : l_yes);

return false;
diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
index a0a5bbae7229..424ed421cd97 100644
--- a/arch/arm64/include/asm/jump_label.h
+++ b/arch/arm64/include/asm/jump_label.h
@@ -19,10 +19,14 @@
#define JUMP_TABLE_ENTRY(key, label) \
".pushsection __jump_table, \"aw\"\n\t" \
".align 3\n\t" \
- ".long 1b - ., %l["#label"] - .\n\t" \
- ".quad %c0 - .\n\t" \
- ".popsection\n\t" \
- : : "i"(key) : : label
+ ".long 1b - ., " label " - .\n\t" \
+ ".quad " key " - .\n\t" \
+ ".popsection\n\t"
+
+/* This macro is also expanded on the Rust side. */
+#define ARCH_STATIC_BRANCH_ASM(key, label) \
+ "1: nop\n\t" \
+ JUMP_TABLE_ENTRY(key, label)

static __always_inline bool arch_static_branch(struct static_key * const key,
const bool branch)
@@ -30,8 +34,8 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
char *k = &((char *)key)[branch];

asm goto(
- "1: nop \n\t"
- JUMP_TABLE_ENTRY(k, l_yes)
+ ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
+ : : "i"(k) : : l_yes
);

return false;
@@ -43,9 +47,11 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
const bool branch)
{
char *k = &((char *)key)[branch];
+
asm goto(
"1: b %l[l_yes] \n\t"
- JUMP_TABLE_ENTRY(k, l_yes)
+ JUMP_TABLE_ENTRY("%c0", "%l[l_yes]")
+ : : "i"(k) : : l_yes
);
return false;
l_yes:
diff --git a/arch/loongarch/include/asm/jump_label.h b/arch/loongarch/include/asm/jump_label.h
index 29acfe3de3fa..8a924bd69d19 100644
--- a/arch/loongarch/include/asm/jump_label.h
+++ b/arch/loongarch/include/asm/jump_label.h
@@ -13,18 +13,22 @@

#define JUMP_LABEL_NOP_SIZE 4

-#define JUMP_TABLE_ENTRY \
+/* This macro is also expanded on the Rust side. */
+#define JUMP_TABLE_ENTRY(key, label) \
".pushsection __jump_table, \"aw\" \n\t" \
".align 3 \n\t" \
- ".long 1b - ., %l[l_yes] - . \n\t" \
- ".quad %0 - . \n\t" \
+ ".long 1b - ., " label " - . \n\t" \
+ ".quad " key " - . \n\t" \
".popsection \n\t"

+#define ARCH_STATIC_BRANCH_ASM(key, label) \
+ "1: nop \n\t" \
+ JUMP_TABLE_ENTRY(key, label)
+
static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
{
asm goto(
- "1: nop \n\t"
- JUMP_TABLE_ENTRY
+ ARCH_STATIC_BRANCH_ASM("%0", "%l[l_yes]")
: : "i"(&((char *)key)[branch]) : : l_yes);

return false;
@@ -37,7 +41,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
{
asm goto(
"1: b %l[l_yes] \n\t"
- JUMP_TABLE_ENTRY
+ JUMP_TABLE_ENTRY("%0", "%l[l_yes]")
: : "i"(&((char *)key)[branch]) : : l_yes);

return false;
diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
index 1c768d02bd0c..87a71cc6d146 100644
--- a/arch/riscv/include/asm/jump_label.h
+++ b/arch/riscv/include/asm/jump_label.h
@@ -16,21 +16,28 @@

#define JUMP_LABEL_NOP_SIZE 4

+#define JUMP_TABLE_ENTRY(key, label) \
+ ".pushsection __jump_table, \"aw\" \n\t" \
+ ".align " RISCV_LGPTR " \n\t" \
+ ".long 1b - ., " label " - . \n\t" \
+ "" RISCV_PTR " " key " - . \n\t" \
+ ".popsection \n\t"
+
+/* This macro is also expanded on the Rust side. */
+#define ARCH_STATIC_BRANCH_ASM(key, label) \
+ " .align 2 \n\t" \
+ " .option push \n\t" \
+ " .option norelax \n\t" \
+ " .option norvc \n\t" \
+ "1: nop \n\t" \
+ " .option pop \n\t" \
+ JUMP_TABLE_ENTRY(key, label)
+
static __always_inline bool arch_static_branch(struct static_key * const key,
const bool branch)
{
asm goto(
- " .align 2 \n\t"
- " .option push \n\t"
- " .option norelax \n\t"
- " .option norvc \n\t"
- "1: nop \n\t"
- " .option pop \n\t"
- " .pushsection __jump_table, \"aw\" \n\t"
- " .align " RISCV_LGPTR " \n\t"
- " .long 1b - ., %l[label] - . \n\t"
- " " RISCV_PTR " %0 - . \n\t"
- " .popsection \n\t"
+ ARCH_STATIC_BRANCH_ASM("%0", "%l[label]")
: : "i"(&((char *)key)[branch]) : : label);

return false;
@@ -38,21 +45,20 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
return true;
}

+#define ARCH_STATIC_BRANCH_JUMP_ASM(key, label) \
+ " .align 2 \n\t" \
+ " .option push \n\t" \
+ " .option norelax \n\t" \
+ " .option norvc \n\t" \
+ "1: j " label " \n\t" \
+ " .option pop \n\t" \
+ JUMP_TABLE_ENTRY(key, label)
+
static __always_inline bool arch_static_branch_jump(struct static_key * const key,
const bool branch)
{
asm goto(
- " .align 2 \n\t"
- " .option push \n\t"
- " .option norelax \n\t"
- " .option norvc \n\t"
- "1: j %l[label] \n\t"
- " .option pop \n\t"
- " .pushsection __jump_table, \"aw\" \n\t"
- " .align " RISCV_LGPTR " \n\t"
- " .long 1b - ., %l[label] - . \n\t"
- " " RISCV_PTR " %0 - . \n\t"
- " .popsection \n\t"
+ ARCH_STATIC_BRANCH_JUMP_ASM("%0", "%l[label]")
: : "i"(&((char *)key)[branch]) : : label);

return false;
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index cbbef32517f0..fb79fa1cf70a 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -12,49 +12,41 @@
#include <linux/stringify.h>
#include <linux/types.h>

-#define JUMP_TABLE_ENTRY \
+#define JUMP_TABLE_ENTRY(key, label) \
".pushsection __jump_table, \"aw\" \n\t" \
_ASM_ALIGN "\n\t" \
".long 1b - . \n\t" \
- ".long %l[l_yes] - . \n\t" \
- _ASM_PTR "%c0 + %c1 - .\n\t" \
+ ".long " label " - . \n\t" \
+ _ASM_PTR " " key " - . \n\t" \
".popsection \n\t"

+/* This macro is also expanded on the Rust side. */
#ifdef CONFIG_HAVE_JUMP_LABEL_HACK
-
-static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
-{
- asm goto("1:"
- "jmp %l[l_yes] # objtool NOPs this \n\t"
- JUMP_TABLE_ENTRY
- : : "i" (key), "i" (2 | branch) : : l_yes);
-
- return false;
-l_yes:
- return true;
-}
-
+#define ARCH_STATIC_BRANCH_ASM(key, label) \
+ "1: jmp " label " # objtool NOPs this \n\t" \
+ JUMP_TABLE_ENTRY(key, label)
#else /* !CONFIG_HAVE_JUMP_LABEL_HACK */
+#define ARCH_STATIC_BRANCH_ASM(key, label) \
+ "1: .byte " __stringify(BYTES_NOP5) "\n\t" \
+ JUMP_TABLE_ENTRY(key, label)
+#endif /* CONFIG_HAVE_JUMP_LABEL_HACK */

static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
{
- asm goto("1:"
- ".byte " __stringify(BYTES_NOP5) "\n\t"
- JUMP_TABLE_ENTRY
- : : "i" (key), "i" (branch) : : l_yes);
+ int hack_bit = IS_ENABLED(CONFIG_HAVE_JUMP_LABEL_HACK) ? 2 : 0;
+ asm goto(ARCH_STATIC_BRANCH_ASM("%c0 + %c1", "%l[l_yes]")
+ : : "i" (key), "i" (hack_bit | branch) : : l_yes);

return false;
l_yes:
return true;
}

-#endif /* CONFIG_HAVE_JUMP_LABEL_HACK */
-
static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch)
{
asm goto("1:"
"jmp %l[l_yes]\n\t"
- JUMP_TABLE_ENTRY
+ JUMP_TABLE_ENTRY("%c0 + %c1", "%l[l_yes]")
: : "i" (key), "i" (branch) : : l_yes);

return false;

--
2.46.0.184.g6999bdac58-goog