6.6-stable review patch. If anyone has any objections, please let me know.
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From: Nam Cao namcaov@gmail.com
[ Upstream commit b701f9e726f0a30a94ea6af596b74c1f07b95b6b ]
uprobes expects is_trap_insn() to return true for any trap instructions, not just the one used for installing uprobe. The current default implementation only returns true for 16-bit c.ebreak if C extension is enabled. This can confuse uprobes if a 32-bit ebreak generates a trap exception from userspace: uprobes asks is_trap_insn() who says there is no trap, so uprobes assume a probe was there before but has been removed, and return to the trap instruction. This causes an infinite loop of entering and exiting trap handler.
Instead of using the default implementation, implement this function speficially for riscv with checks for both ebreak and c.ebreak.
Fixes: 74784081aac8 ("riscv: Add uprobes supported") Signed-off-by: Nam Cao namcaov@gmail.com Tested-by: Björn Töpel bjorn@rivosinc.com Reviewed-by: Guo Ren guoren@kernel.org Link: https://lore.kernel.org/r/20230829083614.117748-1-namcaov@gmail.com Signed-off-by: Palmer Dabbelt palmer@rivosinc.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/kernel/probes/uprobes.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c index 194f166b2cc40..4b3dc8beaf77d 100644 --- a/arch/riscv/kernel/probes/uprobes.c +++ b/arch/riscv/kernel/probes/uprobes.c @@ -3,6 +3,7 @@ #include <linux/highmem.h> #include <linux/ptrace.h> #include <linux/uprobes.h> +#include <asm/insn.h>
#include "decode-insn.h"
@@ -17,6 +18,11 @@ bool is_swbp_insn(uprobe_opcode_t *insn) #endif }
+bool is_trap_insn(uprobe_opcode_t *insn) +{ + return riscv_insn_is_ebreak(*insn) || riscv_insn_is_c_ebreak(*insn); +} + unsigned long uprobe_get_swbp_addr(struct pt_regs *regs) { return instruction_pointer(regs);