[PATCH 3/5] uprobes: introduce uprobe_xol_slots[NR_CPUS]

[Oleg Nesterov]

This patch adds uprobe_xol_slots[UPROBES_XOL_SLOT_BYTES][NR_CPUS] array.
Each CPU has its own slot for xol (used in the next patch).

We "export" this data to the user-space via set_fixmap(PAGE_KERNEL_VSYSCALL).

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
 arch/x86/include/asm/fixmap.h |    9 +++++++++
 arch/x86/kernel/uprobes.c     |   10 ++++++++++
 include/linux/uprobes.h       |    1 +
 kernel/uprobes.c              |    4 ++++
 4 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index 460c74e..a902e19 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -81,6 +81,15 @@ enum fixed_addresses {
 	VVAR_PAGE,
 	VSYSCALL_HPET,
 #endif
+
+#ifdef CONFIG_UPROBES
+	#define UPROBES_XOL_SLOT_BYTES  128
+
+	UPROBE_XOL_LAST_PAGE,
+	UPROBE_XOL_FIRST_PAGE = UPROBE_XOL_LAST_PAGE
+			      + NR_CPUS * UPROBES_XOL_SLOT_BYTES / PAGE_SIZE,
+#endif
+
 	FIX_DBGP_BASE,
 	FIX_EARLYCON_MEM_BASE,
 #ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 4140137..ebb280c 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -664,3 +664,13 @@ bool can_skip_xol(struct pt_regs *regs, struct uprobe *u)
 	u->flags &= ~UPROBES_SKIP_SSTEP;
 	return false;
 }
+
+void __init map_uprobe_xol_slots(void *pages)
+{
+	int idx = UPROBE_XOL_FIRST_PAGE;
+
+	do {
+		__set_fixmap(idx, __pa(pages), PAGE_KERNEL_VSYSCALL);
+		pages += PAGE_SIZE;
+	} while (idx-- != UPROBE_XOL_LAST_PAGE);
+}
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index d590d66..bb59a66 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -142,6 +142,7 @@ extern bool uprobe_deny_signal(void);
 extern bool __weak can_skip_xol(struct pt_regs *regs, struct uprobe *u);
 extern void __weak set_xol_ip(struct pt_regs *regs);
 extern void uprobe_switch_to(struct task_struct *);
+extern void map_uprobe_xol_slots(void *);
 #else /* CONFIG_UPROBES is not defined */
 static inline int register_uprobe(struct inode *inode, loff_t offset,
 				struct uprobe_consumer *consumer)
diff --git a/kernel/uprobes.c b/kernel/uprobes.c
index 9c509dc..20007da 100644
--- a/kernel/uprobes.c
+++ b/kernel/uprobes.c
@@ -1342,6 +1342,9 @@ bool __weak can_skip_xol(struct pt_regs *regs, struct uprobe *u)
 	return false;
 }
 
+static unsigned char
+uprobe_xol_slots[UPROBES_XOL_SLOT_BYTES][NR_CPUS] __page_aligned_bss;
+
 void __weak set_xol_ip(struct pt_regs *regs)
 {
 	set_instruction_pointer(regs, current->utask->xol_vaddr);
@@ -1490,6 +1493,7 @@ static int __init init_uprobes(void)
 		mutex_init(&uprobes_mmap_mutex[i]);
 	}
 	init_bulkref(&uprobes_srcu);
+	map_uprobe_xol_slots(uprobe_xol_slots);
 	return register_die_notifier(&uprobe_exception_nb);
 }
 
-- 
1.5.5.1


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