Alignment cleanup for arch code and parasite args

LibertyGlobal · Dec 21, 2023 · c1fde68 · c1fde68
1 parent 4f288ab
commit c1fde68
Show file tree

Hide file tree

Showing 6 changed files with 29 additions and 19 deletions.
diff --git a/arch/arm/enter.c b/arch/arm/enter.c
@@ -29,7 +29,7 @@ static void __attribute__((used)) container(void)
 	/* rt_sigprocmask(), expects pointer to area for masks in r8 */
 	asm volatile(
 		".global sigprocmask_blob			\n"
-		".align 3					\n"
+		".align 2					\n"
 		"sigprocmask_blob:				\n"
 		"mov r7, #175					\n" /* __NR_rt_sigprocmask */
 		"mov r0, %0					\n" /* @how */
@@ -39,7 +39,7 @@ static void __attribute__((used)) container(void)
 		"svc 0x0					\n"
 		"udf #16					\n" /* SIGTRAP */
 		".global sigprocmask_blob_size			\n"
-		".align 3					\n"
+		".align 2					\n"
 		"sigprocmask_blob_size:				\n"
 		".int sigprocmask_blob_size - sigprocmask_blob	\n"
 		:: "i" (SIG_SETMASK)
@@ -48,7 +48,7 @@ static void __attribute__((used)) container(void)
 	/* mmaps anon area for parasite_blob */
 	asm volatile(
 		".global mmap_blob				\n"
-		".align 3					\n"
+		".align 2					\n"
 		"mmap_blob:					\n"
 		"mov r7, #192					\n" /* __NR_mmap2 */
 		"mov r0, #0					\n" /* @addr */
@@ -60,7 +60,7 @@ static void __attribute__((used)) container(void)
 		"svc 0x0					\n"
 		"udf #16					\n" /* SIGTRAP */
 		".global mmap_blob_size				\n"
-		".align 3					\n"
+		".align 2					\n"
 		"mmap_blob_size:				\n"
 		".int mmap_blob_size - mmap_blob		\n"
 		:: "i" (PROT_EXEC | PROT_READ | PROT_WRITE),
@@ -70,7 +70,7 @@ static void __attribute__((used)) container(void)
 	/* clones parasite, expects parasite address in r8 */
 	asm volatile(
 		".global clone_blob				\n"
-		".align 3					\n"
+		".align 2					\n"
 		"clone_blob:					\n"
 		"mov r7, #120					\n" /* __NR_clone */
 		"ldr r0, CLONE_FLAGS				\n"
@@ -84,23 +84,23 @@ static void __attribute__((used)) container(void)
 		"CLONE_FLAGS:					\n"
 		".word 0x80050f00				\n" /* (CLONE_FILES | CLONE_FS | CLONE_IO | CLONE_SIGHAND | CLONE_SYSVSEM | CLONE_THREAD | CLONE_VM) */
 		".global clone_blob_size			\n"
-		".align 3					\n"
+		".align 2					\n"
 		"clone_blob_size:				\n"
 		".int clone_blob_size - clone_blob		\n"
 	);
 
 	/* munmap anon area for parasite_blob, expects addr in r8 and len in r9 */
 	asm volatile(
 		".global munmap_blob				\n"
-		".align 3					\n"
+		".align 2					\n"
 		"munmap_blob:					\n"
 		"mov r7, #91					\n" /* __NR_munmap */
 		"mov r0, r8					\n" /* @addr */
 		"mov r1, r9					\n" /* @len */
 		"svc 0x0					\n"
 		"udf #16					\n" /* SIGTRAP */
 		".global munmap_blob_size			\n"
-		".align 3					\n"
+		".align 2					\n"
 		"munmap_blob_size:				\n"
 		".int munmap_blob_size - munmap_blob		\n"
 	);

diff --git a/arch/arm/parasite-head.S b/arch/arm/parasite-head.S
@@ -20,19 +20,20 @@
 #define PARASITE_ARG_SIZE   4096
 
 .section .head.text, "ax"
-	.globl __parasite_head_start
-	.align 4, 0x00
+.globl __parasite_head_start
 
+.align 2
 __parasite_head_start:
 	adr sp, __parasite_stack
 	adr r0, __parasite_args
 	bl service
 	udf #16 @ SIGTRAP
-	.align 4, 0x00
 
+.align 2
 __parasite_args:
 	.space PARASITE_ARG_SIZE, 0
 	.space 56, 0 /* 8+4 fill */
 
+.align 2 /* sp must be 4-byte aligned */
 __parasite_stack:
 	.space PARASITE_STACK_SIZE, 0
diff --git a/arch/arm64/enter.c b/arch/arm64/enter.c
@@ -20,6 +20,9 @@
 #include <sys/mman.h>
 #include <linux/sched.h>
 
+/*
+ * blobs are 2^3 aligned (rather than 2^2) for ptrace() peek/poke
+ */
 static void __attribute__((used)) container(void)
 {
 	/*

diff --git a/arch/arm64/parasite-head.S b/arch/arm64/parasite-head.S
@@ -20,19 +20,20 @@
 #define PARASITE_ARG_SIZE   4096
 
 .section .head.text, "ax"
-	.globl __parasite_head_start
-	.align 4, 0x00
+.globl __parasite_head_start
 
+.align 2
 __parasite_head_start:
 	adr x0, __parasite_stack
 	mov sp, x0
 	adr x0, __parasite_args
 	bl service
 	brk #0 /* SIGTRAP */
-	.align 4, 0x00
 
+.align 2
 __parasite_args:
 	.space PARASITE_ARG_SIZE, 0
 
+.align 4 /* sp must be 16-byte aligned */
 __parasite_stack:
 	.space PARASITE_STACK_SIZE, 0
diff --git a/arch/x86_64/parasite-head.S b/arch/x86_64/parasite-head.S
@@ -20,18 +20,19 @@
 #define PARASITE_ARG_SIZE   4096
 
 .section .head.text, "ax"
-	.global __parasite_head_start;
-	.align 8, 0x90; /* nop */
+.global __parasite_head_start;
 
+.align 8
 __parasite_head_start:
 	leaq __parasite_stack(%rip), %rsp
 	leaq __parasite_args(%rip), %rdi
 	call service
 	int $0x03 /* SIGTRAP */
-	.align 8, 0x90
 
+.align 8
 __parasite_args:
 	.space PARASITE_ARG_SIZE, 0
 
+.align 16 /* sp must be 16-byte aligned */
 __parasite_stack:
 	.space PARASITE_STACK_SIZE, 0
diff --git a/memcr.h b/memcr.h
@@ -20,15 +20,19 @@
 #define __MEMCR_H__
 
 #include <stdint.h>
+#include <assert.h>
 
 #ifndef PAGE_SIZE
 #define PAGE_SIZE 4096
 #endif
 
-/* size is CPU word aligned for ptrace() peek/poke */
 struct parasite_args {
 	struct sockaddr_un addr;
-} __attribute__((aligned(sizeof(unsigned long))));
+	char padding[2];
+};
+
+/* size must be CPU word aligned for ptrace() peek/poke */
+static_assert(sizeof(struct parasite_args) % sizeof(unsigned long) == 0, "invalid size");
 
 typedef enum {
 	CMD_MPROTECT = 1,