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authorWill Deacon <will@kernel.org>2021-06-24 16:04:00 +0300
committerWill Deacon <will@kernel.org>2021-06-24 16:04:00 +0300
commit2c9bd9d806757bc84e9d744044d6937a85df5f60 (patch)
tree289f534b5da17a07e40f01a7e993869a72108e70
parent181a126979307a0192f41a4a1fac235d6f4ac9f0 (diff)
parent1cbdf60bd1b74e397d48aa877367cfc621f45ffe (diff)
downloadlinux-2c9bd9d806757bc84e9d744044d6937a85df5f60.tar.xz
Merge branch 'for-next/kasan' into for-next/core
Optimise out-of-line KASAN checking when using software tagging. * for-next/kasan: kasan: arm64: support specialized outlined tag mismatch checks
-rw-r--r--arch/arm64/include/asm/asm-prototypes.h6
-rw-r--r--arch/arm64/include/asm/module.lds.h17
-rw-r--r--arch/arm64/lib/Makefile2
-rw-r--r--arch/arm64/lib/kasan_sw_tags.S76
-rw-r--r--mm/kasan/sw_tags.c7
-rw-r--r--scripts/Makefile.kasan1
6 files changed, 107 insertions, 2 deletions
diff --git a/arch/arm64/include/asm/asm-prototypes.h b/arch/arm64/include/asm/asm-prototypes.h
index 1c9a3a0c5fa5..ec1d9655f885 100644
--- a/arch/arm64/include/asm/asm-prototypes.h
+++ b/arch/arm64/include/asm/asm-prototypes.h
@@ -23,4 +23,10 @@ long long __ashlti3(long long a, int b);
long long __ashrti3(long long a, int b);
long long __lshrti3(long long a, int b);
+/*
+ * This function uses a custom calling convention and cannot be called from C so
+ * this prototype is not entirely accurate.
+ */
+void __hwasan_tag_mismatch(unsigned long addr, unsigned long access_info);
+
#endif /* __ASM_PROTOTYPES_H */
diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
index 810045628c66..a11ccadd47d2 100644
--- a/arch/arm64/include/asm/module.lds.h
+++ b/arch/arm64/include/asm/module.lds.h
@@ -1,7 +1,20 @@
-#ifdef CONFIG_ARM64_MODULE_PLTS
SECTIONS {
+#ifdef CONFIG_ARM64_MODULE_PLTS
.plt 0 (NOLOAD) : { BYTE(0) }
.init.plt 0 (NOLOAD) : { BYTE(0) }
.text.ftrace_trampoline 0 (NOLOAD) : { BYTE(0) }
-}
#endif
+
+#ifdef CONFIG_KASAN_SW_TAGS
+ /*
+ * Outlined checks go into comdat-deduplicated sections named .text.hot.
+ * Because they are in comdats they are not combined by the linker and
+ * we otherwise end up with multiple sections with the same .text.hot
+ * name in the .ko file. The kernel module loader warns if it sees
+ * multiple sections with the same name so we use this sections
+ * directive to force them into a single section and silence the
+ * warning.
+ */
+ .text.hot : { *(.text.hot) }
+#endif
+}
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index c97b10de5e87..6dd56a49790a 100644
--- a/arch/arm64/lib/Makefile
+++ b/arch/arm64/lib/Makefile
@@ -18,3 +18,5 @@ obj-$(CONFIG_CRC32) += crc32.o
obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
obj-$(CONFIG_ARM64_MTE) += mte.o
+
+obj-$(CONFIG_KASAN_SW_TAGS) += kasan_sw_tags.o
diff --git a/arch/arm64/lib/kasan_sw_tags.S b/arch/arm64/lib/kasan_sw_tags.S
new file mode 100644
index 000000000000..5b04464c045e
--- /dev/null
+++ b/arch/arm64/lib/kasan_sw_tags.S
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Google LLC
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * Report a tag mismatch detected by tag-based KASAN.
+ *
+ * A compiler-generated thunk calls this with a non-AAPCS calling
+ * convention. Upon entry to this function, registers are as follows:
+ *
+ * x0: fault address (see below for restore)
+ * x1: fault description (see below for restore)
+ * x2 to x15: callee-saved
+ * x16 to x17: safe to clobber
+ * x18 to x30: callee-saved
+ * sp: pre-decremented by 256 bytes (see below for restore)
+ *
+ * The caller has decremented the SP by 256 bytes, and created a
+ * structure on the stack as follows:
+ *
+ * sp + 0..15: x0 and x1 to be restored
+ * sp + 16..231: free for use
+ * sp + 232..247: x29 and x30 (same as in GPRs)
+ * sp + 248..255: free for use
+ *
+ * Note that this is not a struct pt_regs.
+ *
+ * To call a regular AAPCS function we must save x2 to x15 (which we can
+ * store in the gaps), and create a frame record (for which we can use
+ * x29 and x30 spilled by the caller as those match the GPRs).
+ *
+ * The caller expects x0 and x1 to be restored from the structure, and
+ * for the structure to be removed from the stack (i.e. the SP must be
+ * incremented by 256 prior to return).
+ */
+SYM_CODE_START(__hwasan_tag_mismatch)
+#ifdef BTI_C
+ BTI_C
+#endif
+ add x29, sp, #232
+ stp x2, x3, [sp, #8 * 2]
+ stp x4, x5, [sp, #8 * 4]
+ stp x6, x7, [sp, #8 * 6]
+ stp x8, x9, [sp, #8 * 8]
+ stp x10, x11, [sp, #8 * 10]
+ stp x12, x13, [sp, #8 * 12]
+ stp x14, x15, [sp, #8 * 14]
+#ifndef CONFIG_SHADOW_CALL_STACK
+ str x18, [sp, #8 * 18]
+#endif
+
+ mov x2, x30
+ bl kasan_tag_mismatch
+
+ ldp x0, x1, [sp]
+ ldp x2, x3, [sp, #8 * 2]
+ ldp x4, x5, [sp, #8 * 4]
+ ldp x6, x7, [sp, #8 * 6]
+ ldp x8, x9, [sp, #8 * 8]
+ ldp x10, x11, [sp, #8 * 10]
+ ldp x12, x13, [sp, #8 * 12]
+ ldp x14, x15, [sp, #8 * 14]
+#ifndef CONFIG_SHADOW_CALL_STACK
+ ldr x18, [sp, #8 * 18]
+#endif
+ ldp x29, x30, [sp, #8 * 29]
+
+ /* remove the structure from the stack */
+ add sp, sp, #256
+ ret
+SYM_CODE_END(__hwasan_tag_mismatch)
+EXPORT_SYMBOL(__hwasan_tag_mismatch)
diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c
index 9df8e7f69e87..9362938abbfa 100644
--- a/mm/kasan/sw_tags.c
+++ b/mm/kasan/sw_tags.c
@@ -207,3 +207,10 @@ struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
return &alloc_meta->free_track[i];
}
+
+void kasan_tag_mismatch(unsigned long addr, unsigned long access_info,
+ unsigned long ret_ip)
+{
+ kasan_report(addr, 1 << (access_info & 0xf), access_info & 0x10,
+ ret_ip);
+}
diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 3d791908ed36..801c415bac59 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -50,6 +50,7 @@ endif
CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
$(call cc-param,hwasan-instrument-stack=$(stack_enable)) \
$(call cc-param,hwasan-use-short-granules=0) \
+ $(call cc-param,hwasan-inline-all-checks=0) \
$(instrumentation_flags)
endif # CONFIG_KASAN_SW_TAGS