Merge patch series "riscv: Introduce compat-mode helpers & improve arch_get_mmap_end()"

Leonardo Bras <leobras@redhat.com> says:

I just saw the opportunity of optimizing the helper is_compat_task() by
introducing a compile-time test, and it made possible to remove some
 #ifdef's without any loss of performance.

I also saw the possibility of removing the direct check of task flags from
general code, and concentrated it in asm/compat.h by creating a few more
helpers, which in the end helped optimize code.

arch_get_mmap_end() just got a simple improvement and some extra docs.

* b4-shazam-merge:
  riscv: Introduce set_compat_task() in asm/compat.h
  riscv: Introduce is_compat_thread() into compat.h
  riscv: add compile-time test into is_compat_task()
  riscv: Replace direct thread flag check with is_compat_task()
  riscv: Improve arch_get_mmap_end() macro

Link: https://lore.kernel.org/r/20240103160024.70305-2-leobras@redhat.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

5 files changed, 34 insertions, 24 deletions

diff --git a/arch/riscv/include/asm/compat.h b/arch/riscv/include/asm/compat.h
index 2ac955b51148..aa103530a5c8 100644
--- a/arch/riscv/include/asm/compat.h
+++ b/arch/riscv/include/asm/compat.h
@@ -14,9 +14,28 @@
 
 static inline int is_compat_task(void)
 {
+	if (!IS_ENABLED(CONFIG_COMPAT))
+		return 0;
+
 	return test_thread_flag(TIF_32BIT);
 }
 
+static inline int is_compat_thread(struct thread_info *thread)
+{
+	if (!IS_ENABLED(CONFIG_COMPAT))
+		return 0;
+
+	return test_ti_thread_flag(thread, TIF_32BIT);
+}
+
+static inline void set_compat_task(bool is_compat)
+{
+	if (is_compat)
+		set_thread_flag(TIF_32BIT);
+	else
+		clear_thread_flag(TIF_32BIT);
+}
+
 struct compat_user_regs_struct {
 	compat_ulong_t pc;
 	compat_ulong_t ra;
diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
index 06c236bfab53..c7aea7886d22 100644
--- a/arch/riscv/include/asm/elf.h
+++ b/arch/riscv/include/asm/elf.h
@@ -53,13 +53,9 @@ extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
 #define ELF_ET_DYN_BASE		((DEFAULT_MAP_WINDOW / 3) * 2)
 
 #ifdef CONFIG_64BIT
-#ifdef CONFIG_COMPAT
-#define STACK_RND_MASK		(test_thread_flag(TIF_32BIT) ? \
+#define STACK_RND_MASK		(is_compat_task() ? \
 				 0x7ff >> (PAGE_SHIFT - 12) : \
 				 0x3ffff >> (PAGE_SHIFT - 12))
-#else
-#define STACK_RND_MASK		(0x3ffff >> (PAGE_SHIFT - 12))
-#endif
 #endif
 
 /*
@@ -139,10 +135,7 @@ do {							\
 #ifdef CONFIG_COMPAT
 
 #define SET_PERSONALITY(ex)					\
-do {    if ((ex).e_ident[EI_CLASS] == ELFCLASS32)		\
-		set_thread_flag(TIF_32BIT);			\
-	else							\
-		clear_thread_flag(TIF_32BIT);			\
+do {	set_compat_task((ex).e_ident[EI_CLASS] == ELFCLASS32);	\
 	if (personality(current->personality) != PER_LINUX32)	\
 		set_personality(PER_LINUX |			\
 			(current->personality & (~PER_MASK)));	\
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 3e9177f40c68..9c45810806ff 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -127,17 +127,11 @@
 #define VA_USER_SV48 (UL(1) << (VA_BITS_SV48 - 1))
 #define VA_USER_SV57 (UL(1) << (VA_BITS_SV57 - 1))
 
-#ifdef CONFIG_COMPAT
 #define MMAP_VA_BITS_64 ((VA_BITS >= VA_BITS_SV48) ? VA_BITS_SV48 : VA_BITS)
 #define MMAP_MIN_VA_BITS_64 (VA_BITS_SV39)
 #define MMAP_VA_BITS (is_compat_task() ? VA_BITS_SV32 : MMAP_VA_BITS_64)
 #define MMAP_MIN_VA_BITS (is_compat_task() ? VA_BITS_SV32 : MMAP_MIN_VA_BITS_64)
 #else
-#define MMAP_VA_BITS ((VA_BITS >= VA_BITS_SV48) ? VA_BITS_SV48 : VA_BITS)
-#define MMAP_MIN_VA_BITS (VA_BITS_SV39)
-#endif /* CONFIG_COMPAT */
-
-#else
 #include <asm/pgtable-32.h>
 #endif /* CONFIG_64BIT */
 
@@ -877,8 +871,8 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
 #define TASK_SIZE_MIN	(PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
 
 #ifdef CONFIG_COMPAT
-#define TASK_SIZE_32	(_AC(0x80000000, UL))
-#define TASK_SIZE	(test_thread_flag(TIF_32BIT) ? \
+#define TASK_SIZE_32	(_AC(0x80000000, UL) - PAGE_SIZE)
+#define TASK_SIZE	(is_compat_task() ? \
 			 TASK_SIZE_32 : TASK_SIZE_64)
 #else
 #define TASK_SIZE	TASK_SIZE_64
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 0d13b4497b01..0faf5f161f1e 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -14,12 +14,17 @@
 
 #include <asm/ptrace.h>
 
+/*
+ * addr is a hint to the maximum userspace address that mmap should provide, so
+ * this macro needs to return the largest address space available so that
+ * mmap_end < addr, being mmap_end the top of that address space.
+ * See Documentation/arch/riscv/vm-layout.rst for more details.
+ */
 #define arch_get_mmap_end(addr, len, flags)			\
 ({								\
 	unsigned long mmap_end;					\
 	typeof(addr) _addr = (addr);				\
-	if ((_addr) == 0 ||					\
-	    (IS_ENABLED(CONFIG_COMPAT) && is_compat_task()) ||	\
+	if ((_addr) == 0 || is_compat_task() ||			\
 	    ((_addr + len) > BIT(VA_BITS - 1)))			\
 		mmap_end = STACK_TOP_MAX;			\
 	else							\
@@ -33,8 +38,7 @@
 	typeof(addr) _addr = (addr);				\
 	typeof(base) _base = (base);				\
 	unsigned long rnd_gap = DEFAULT_MAP_WINDOW - (_base);	\
-	if ((_addr) == 0 ||					\
-	    (IS_ENABLED(CONFIG_COMPAT) && is_compat_task()) ||	\
+	if ((_addr) == 0 || is_compat_task() || 		\
 	    ((_addr + len) > BIT(VA_BITS - 1)))			\
 		mmap_base = (_base);				\
 	else							\
diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
index e8515aa9d80b..92731ff8c79a 100644
--- a/arch/riscv/kernel/ptrace.c
+++ b/arch/riscv/kernel/ptrace.c
@@ -377,14 +377,14 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 
 	return ret;
 }
+#else
+static const struct user_regset_view compat_riscv_user_native_view = {};
 #endif /* CONFIG_COMPAT */
 
 const struct user_regset_view *task_user_regset_view(struct task_struct *task)
 {
-#ifdef CONFIG_COMPAT
-	if (test_tsk_thread_flag(task, TIF_32BIT))
+	if (is_compat_thread(&task->thread_info))
 		return &compat_riscv_user_native_view;
 	else
-#endif
 		return &riscv_user_native_view;
 }