[PATCH 12/16] parisc: mm: Support MAP_BELOW_HINT

Charlie Jenkins
2024-08-28T05:50:07Z

Add support for MAP_BELOW_HINT to mmap by restricting high_limit to addr
when the flag is enabled.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
arch/parisc/include/uapi/asm/mman.h | 1 +
arch/parisc/kernel/sys_parisc.c | 9 +++++++++
tools/arch/parisc/include/uapi/asm/mman.h | 1 +
3 files changed, 11 insertions(+)

diff --git a/arch/parisc/include/uapi/asm/mman.h b/arch/parisc/include/uapi/asm/mman.h
index 68c44f99bc93..44925ef8ac44 100644
--- a/arch/parisc/include/uapi/asm/mman.h
+++ b/arch/parisc/include/uapi/asm/mman.h
@@ -26,6 +26,7 @@
#define MAP_HUGETLB 0x80000 /* create a huge page mapping */
#define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */
#define MAP_UNINITIALIZED 0 /* uninitialized anonymous mmap */
+#define MAP_BELOW_HINT 0x200000 /* give out address that is below (inclusive) hint address */

#define MS_SYNC 1 /* synchronous memory sync */
#define MS_ASYNC 2 /* sync memory asynchronously */
diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
index f7722451276e..feccb60cf746 100644
--- a/arch/parisc/kernel/sys_parisc.c
+++ b/arch/parisc/kernel/sys_parisc.c
@@ -148,6 +148,13 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.low_limit = PAGE_SIZE;
info.high_limit = mm->mmap_base;
+ if (flags & MAP_BELOW_HINT)
+ /*
+ * Subtract (STACK_TOP - mm->mmap_base) to get random
+ * offset defined in mmap_base() in mm/util.c
+ */
+ info.high_limit = MIN(info.high_limit,
+ (addr + len) - (STACK_TOP - mm->mmap_base));
addr = vm_unmapped_area(&info);
if (!(addr & ~PAGE_MASK))
return addr;
@@ -163,6 +170,8 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,

info.low_limit = mm->mmap_base;
info.high_limit = mmap_upper_limit(NULL);
+ if (flags & MAP_BELOW_HINT)
+ info.high_limit = MIN(info.high_limit, addr + len);
return vm_unmapped_area(&info);
}

diff --git a/tools/arch/parisc/include/uapi/asm/mman.h b/tools/arch/parisc/include/uapi/asm/mman.h
index 4cc88a642e10..297acc0f7b2a 100644
--- a/tools/arch/parisc/include/uapi/asm/mman.h
+++ b/tools/arch/parisc/include/uapi/asm/mman.h
@@ -40,4 +40,5 @@
/* MAP_32BIT is undefined on parisc, fix it for perf */
#define MAP_32BIT 0
#define MAP_UNINITIALIZED 0
+#define MAP_BELOW_MAP 0x200000
#endif

--
2.45.0