[PATCH] ARM: Use conditionals for CFI branches

Linus Walleij linus.walleij at linaro.org
Tue Apr 30 01:26:10 PDT 2024 

Commit 9385/2 introduced a few branches inside function
prototypes when using CFI in order to deal with the situation
where CFI inserts a few bytes of function information in front
of the symbol.

This is not good for older CPUs where every cycle counts.

Commit 9386/2 alleviated the situation a bit by using aliases
for the cache functions with identical signatures.

This leaves the coherent cache flush functions
*_coherent_kern_range() with these branches to the corresponing
*_coherent_user_range() around, since their return type differ and
they therefore cannot be aliased.

Solve this by a simple ifdef so at least we can use fallthroughs
when compiling without CFI enabled.

Suggested-by: Ard Biesheuvel <ardb at kernel.org>
Link: https://lore.kernel.org/linux-arm-kernel/Zi+e9M%2Ff5b%2FSto9H@shell.armlinux.org.uk/
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
 arch/arm/mm/cache-fa.S      | 2 ++
 arch/arm/mm/cache-v4.S      | 2 ++
 arch/arm/mm/cache-v4wb.S    | 4 ++++
 arch/arm/mm/cache-v4wt.S    | 2 ++
 arch/arm/mm/cache-v6.S      | 2 ++
 arch/arm/mm/cache-v7.S      | 2 ++
 arch/arm/mm/cache-v7m.S     | 2 ++
 arch/arm/mm/proc-arm1020.S  | 2 ++
 arch/arm/mm/proc-arm1020e.S | 2 ++
 arch/arm/mm/proc-arm1022.S  | 2 ++
 arch/arm/mm/proc-arm1026.S  | 2 ++
 arch/arm/mm/proc-arm920.S   | 2 ++
 arch/arm/mm/proc-arm922.S   | 2 ++
 arch/arm/mm/proc-arm925.S   | 2 ++
 arch/arm/mm/proc-arm926.S   | 2 ++
 arch/arm/mm/proc-arm940.S   | 2 ++
 arch/arm/mm/proc-arm946.S   | 2 ++
 arch/arm/mm/proc-feroceon.S | 2 ++
 arch/arm/mm/proc-mohawk.S   | 2 ++
 arch/arm/mm/proc-xsc3.S     | 2 ++
 20 files changed, 42 insertions(+)

diff --git a/arch/arm/mm/cache-fa.S b/arch/arm/mm/cache-fa.S
index db454033b76f..4a3668b52a2d 100644
--- a/arch/arm/mm/cache-fa.S
+++ b/arch/arm/mm/cache-fa.S
@@ -112,7 +112,9 @@ SYM_FUNC_END(fa_flush_user_cache_range)
  *	- end	 - virtual end address
  */
 SYM_TYPED_FUNC_START(fa_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	fa_coherent_user_range
+#endif
 SYM_FUNC_END(fa_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/cache-v4.S b/arch/arm/mm/cache-v4.S
index 0df97a610026..0e94e5193dbd 100644
--- a/arch/arm/mm/cache-v4.S
+++ b/arch/arm/mm/cache-v4.S
@@ -104,7 +104,9 @@ SYM_FUNC_END(v4_coherent_user_range)
  *	- size	- region size
  */
 SYM_TYPED_FUNC_START(v4_flush_kern_dcache_area)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	v4_dma_flush_range
+#endif
 SYM_FUNC_END(v4_flush_kern_dcache_area)
 
 /*
diff --git a/arch/arm/mm/cache-v4wb.S b/arch/arm/mm/cache-v4wb.S
index 1912f559968c..ce55a2eef5da 100644
--- a/arch/arm/mm/cache-v4wb.S
+++ b/arch/arm/mm/cache-v4wb.S
@@ -136,7 +136,9 @@ SYM_FUNC_END(v4wb_flush_user_cache_range)
  */
 SYM_TYPED_FUNC_START(v4wb_flush_kern_dcache_area)
 	add	r1, r0, r1
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	v4wb_coherent_user_range
+#endif
 SYM_FUNC_END(v4wb_flush_kern_dcache_area)
 
 /*
@@ -150,7 +152,9 @@ SYM_FUNC_END(v4wb_flush_kern_dcache_area)
  *	- end	 - virtual end address
  */
 SYM_TYPED_FUNC_START(v4wb_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	v4wb_coherent_user_range
+#endif
 SYM_FUNC_END(v4wb_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/cache-v4wt.S b/arch/arm/mm/cache-v4wt.S
index 43b4275ab680..a97dc267b3b0 100644
--- a/arch/arm/mm/cache-v4wt.S
+++ b/arch/arm/mm/cache-v4wt.S
@@ -108,7 +108,9 @@ SYM_FUNC_END(v4wt_flush_user_cache_range)
  *	- end	 - virtual end address
  */
 SYM_TYPED_FUNC_START(v4wt_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	v4wt_coherent_user_range
+#endif
 SYM_FUNC_END(v4wt_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/cache-v6.S b/arch/arm/mm/cache-v6.S
index 86affd60d6d4..9f415476e218 100644
--- a/arch/arm/mm/cache-v6.S
+++ b/arch/arm/mm/cache-v6.S
@@ -117,7 +117,9 @@ SYM_FUNC_END(v6_flush_user_cache_range)
  *	- the Icache does not read data from the write buffer
  */
 SYM_TYPED_FUNC_START(v6_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	v6_coherent_user_range
+#endif
 SYM_FUNC_END(v6_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
index 170b9ac72331..201ca05436fa 100644
--- a/arch/arm/mm/cache-v7.S
+++ b/arch/arm/mm/cache-v7.S
@@ -261,7 +261,9 @@ SYM_FUNC_END(v7_flush_user_cache_range)
  *	- the Icache does not read data from the write buffer
  */
 SYM_TYPED_FUNC_START(v7_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	v7_coherent_user_range
+#endif
 SYM_FUNC_END(v7_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/cache-v7m.S b/arch/arm/mm/cache-v7m.S
index 4e670697eabc..14d719eba729 100644
--- a/arch/arm/mm/cache-v7m.S
+++ b/arch/arm/mm/cache-v7m.S
@@ -286,7 +286,9 @@ SYM_FUNC_END(v7m_flush_user_cache_range)
  *	- the Icache does not read data from the write buffer
  */
 SYM_TYPED_FUNC_START(v7m_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	v7m_coherent_user_range
+#endif
 SYM_FUNC_END(v7m_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm1020.S b/arch/arm/mm/proc-arm1020.S
index ddda04929dae..d0ce3414a13e 100644
--- a/arch/arm/mm/proc-arm1020.S
+++ b/arch/arm/mm/proc-arm1020.S
@@ -203,7 +203,9 @@ SYM_FUNC_END(arm1020_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm1020_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm1020_coherent_user_range
+#endif
 SYM_FUNC_END(arm1020_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm1020e.S b/arch/arm/mm/proc-arm1020e.S
index 60169f4ca391..64f031bf6eff 100644
--- a/arch/arm/mm/proc-arm1020e.S
+++ b/arch/arm/mm/proc-arm1020e.S
@@ -200,7 +200,9 @@ SYM_FUNC_END(arm1020e_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm1020e_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm1020e_coherent_user_range
+#endif
 SYM_FUNC_END(arm1020e_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm1022.S b/arch/arm/mm/proc-arm1022.S
index 30b0e4d05a05..42ed5ed07252 100644
--- a/arch/arm/mm/proc-arm1022.S
+++ b/arch/arm/mm/proc-arm1022.S
@@ -199,7 +199,9 @@ SYM_FUNC_END(arm1022_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm1022_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm1022_coherent_user_range
+#endif
 SYM_FUNC_END(arm1022_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm1026.S b/arch/arm/mm/proc-arm1026.S
index ae06262ca779..b3ae62cd553a 100644
--- a/arch/arm/mm/proc-arm1026.S
+++ b/arch/arm/mm/proc-arm1026.S
@@ -194,7 +194,9 @@ SYM_FUNC_END(arm1026_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm1026_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm1026_coherent_user_range
+#endif
 SYM_FUNC_END(arm1026_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm920.S b/arch/arm/mm/proc-arm920.S
index e47411243b08..a30df54ad5fa 100644
--- a/arch/arm/mm/proc-arm920.S
+++ b/arch/arm/mm/proc-arm920.S
@@ -180,7 +180,9 @@ SYM_FUNC_END(arm920_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm920_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm920_coherent_user_range
+#endif
 SYM_FUNC_END(arm920_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm922.S b/arch/arm/mm/proc-arm922.S
index 092f8b7656a7..aac4e048100d 100644
--- a/arch/arm/mm/proc-arm922.S
+++ b/arch/arm/mm/proc-arm922.S
@@ -182,7 +182,9 @@ SYM_FUNC_END(arm922_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm922_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm922_coherent_user_range
+#endif
 SYM_FUNC_END(arm922_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm925.S b/arch/arm/mm/proc-arm925.S
index a06039a3b2a8..035941faeb2e 100644
--- a/arch/arm/mm/proc-arm925.S
+++ b/arch/arm/mm/proc-arm925.S
@@ -229,7 +229,9 @@ SYM_FUNC_END(arm925_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm925_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm925_coherent_user_range
+#endif
 SYM_FUNC_END(arm925_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm926.S b/arch/arm/mm/proc-arm926.S
index 2c8b93d446a9..6f43d6af2d9a 100644
--- a/arch/arm/mm/proc-arm926.S
+++ b/arch/arm/mm/proc-arm926.S
@@ -192,7 +192,9 @@ SYM_FUNC_END(arm926_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm926_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm926_coherent_user_range
+#endif
 SYM_FUNC_END(arm926_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm940.S b/arch/arm/mm/proc-arm940.S
index fbe168213ec1..0d30bb25c42b 100644
--- a/arch/arm/mm/proc-arm940.S
+++ b/arch/arm/mm/proc-arm940.S
@@ -153,7 +153,9 @@ SYM_FUNC_END(arm940_coherent_kern_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm940_coherent_user_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm940_flush_kern_dcache_area
+#endif
 SYM_FUNC_END(arm940_coherent_user_range)
 
 /*
diff --git a/arch/arm/mm/proc-arm946.S b/arch/arm/mm/proc-arm946.S
index 4772b46064e6..27750ace2ced 100644
--- a/arch/arm/mm/proc-arm946.S
+++ b/arch/arm/mm/proc-arm946.S
@@ -173,7 +173,9 @@ SYM_FUNC_END(arm946_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(arm946_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	arm946_coherent_user_range
+#endif
 SYM_FUNC_END(arm946_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-feroceon.S b/arch/arm/mm/proc-feroceon.S
index 8519ff60e512..f67b2ffac854 100644
--- a/arch/arm/mm/proc-feroceon.S
+++ b/arch/arm/mm/proc-feroceon.S
@@ -208,7 +208,9 @@ SYM_FUNC_END(feroceon_flush_user_cache_range)
  */
 	.align	5
 SYM_TYPED_FUNC_START(feroceon_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	feroceon_coherent_user_range
+#endif
 SYM_FUNC_END(feroceon_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-mohawk.S b/arch/arm/mm/proc-mohawk.S
index 091f6c6719a8..8e9f38da863a 100644
--- a/arch/arm/mm/proc-mohawk.S
+++ b/arch/arm/mm/proc-mohawk.S
@@ -163,7 +163,9 @@ SYM_FUNC_END(mohawk_flush_user_cache_range)
  *	- end	- virtual end address
  */
 SYM_TYPED_FUNC_START(mohawk_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	mohawk_coherent_user_range
+#endif
 SYM_FUNC_END(mohawk_coherent_kern_range)
 
 /*
diff --git a/arch/arm/mm/proc-xsc3.S b/arch/arm/mm/proc-xsc3.S
index f4889911eca2..14927b380452 100644
--- a/arch/arm/mm/proc-xsc3.S
+++ b/arch/arm/mm/proc-xsc3.S
@@ -223,7 +223,9 @@ SYM_FUNC_END(xsc3_flush_user_cache_range)
  *	it also trashes the mini I-cache used by JTAG debuggers.
  */
 SYM_TYPED_FUNC_START(xsc3_coherent_kern_range)
+#ifdef CONFIG_CFI_CLANG /* Fallthrough if !CFI */
 	b	xsc3_coherent_user_range
+#endif
 SYM_FUNC_END(xsc3_coherent_kern_range)
 
 SYM_TYPED_FUNC_START(xsc3_coherent_user_range)

---
base-commit: b42bf708a0c9d6c7303bd623a6b615b6d599dc75
change-id: 20240430-arm32-cfi-topping-3253b11d3600

Best regards,
-- 
Linus Walleij <linus.walleij at linaro.org>

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