linux-kernel - [PATCH RFC] riscv/mm: Add handling for VM_FAULT_SIGSEGV in mm_fault

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Message-ID: <20240730073822.27732-1-qiaozhe@iscas.ac.cn>
Date: Tue, 30 Jul 2024 15:38:22 +0800
From: Zhe Qiao <qiaozhe@...as.ac.cn>
To: paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	surenb@...gle.com,
	alexghiti@...osinc.com,
	akpm@...ux-foundation.org,
	wangkefeng.wang@...wei.com,
	willy@...radead.org,
	qiaozhe@...as.ac.cn
Cc: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH RFC] riscv/mm: Add handling for VM_FAULT_SIGSEGV in mm_fault_error()

Hello everyone, recently while learning about the Riscv architecture's
handling of page fault exceptions in the Linux kernel, I found that
there is no handling of VM_CAULT_SIGSEGV in mm_fault_erroneous (), but
rather a BUG() is executed directly. Therefore, I simultaneously analyzed
the processing procedures of arm64, powerpc, and sh architectures for
this area and found that all three architectures have processing for
VM_CAULT_SIGSEGV. Therefore, I added relevant processing methods for
VM_CAULT_SIGSEGV on the riscv architecture.

As a beginner, I am not sure if this processing method is correct and
would like to hear the opinions of my seniors.

Signed-off-by: Zhe Qiao <qiaozhe@...as.ac.cn>
---
 arch/riscv/mm/fault.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 5224f3733802..868163b904e2 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -61,26 +61,27 @@ static inline void no_context(struct pt_regs *regs, unsigned long addr)
 
 static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
 {
+	if (!user_mode(regs)) {
+		no_context(regs, addr);
+		return;
+	}
+
 	if (fault & VM_FAULT_OOM) {
 		/*
 		 * We ran out of memory, call the OOM killer, and return the userspace
 		 * (which will retry the fault, or kill us if we got oom-killed).
 		 */
-		if (!user_mode(regs)) {
-			no_context(regs, addr);
-			return;
-		}
 		pagefault_out_of_memory();
 		return;
 	} else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) {
 		/* Kernel mode? Handle exceptions or die */
-		if (!user_mode(regs)) {
-			no_context(regs, addr);
-			return;
-		}
 		do_trap(regs, SIGBUS, BUS_ADRERR, addr);
 		return;
+	} else if (fault & VM_FAULT_SIGSEGV) {
+		do_trap(regs, SIGSEGV, SEGV_MAPERR, addr);
+		return;
 	}
+
 	BUG();
 }
 
-- 
2.43.0