x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 184 insertions, 0 deletions

diff --git a/drivers/firmware/trusted_foundations.c b/drivers/firmware/trusted_foundations.c
new file mode 100644
index 000000000..1389fa941
--- /dev/null
+++ b/drivers/firmware/trusted_foundations.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Trusted Foundations support for ARM CPUs
+ *
+ * Copyright (c) 2013, NVIDIA Corporation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/of.h>
+
+#include <linux/firmware/trusted_foundations.h>
+
+#include <asm/firmware.h>
+#include <asm/hardware/cache-l2x0.h>
+#include <asm/outercache.h>
+
+#define TF_CACHE_MAINT		0xfffff100
+
+#define TF_CACHE_ENABLE		1
+#define TF_CACHE_DISABLE	2
+#define TF_CACHE_REENABLE	4
+
+#define TF_SET_CPU_BOOT_ADDR_SMC 0xfffff200
+
+#define TF_CPU_PM		0xfffffffc
+#define TF_CPU_PM_S3		0xffffffe3
+#define TF_CPU_PM_S2		0xffffffe6
+#define TF_CPU_PM_S2_NO_MC_CLK	0xffffffe5
+#define TF_CPU_PM_S1		0xffffffe4
+#define TF_CPU_PM_S1_NOFLUSH_L2	0xffffffe7
+
+static unsigned long tf_idle_mode = TF_PM_MODE_NONE;
+static unsigned long cpu_boot_addr;
+
+static void tf_generic_smc(u32 type, u32 arg1, u32 arg2)
+{
+	register u32 r0 asm("r0") = type;
+	register u32 r1 asm("r1") = arg1;
+	register u32 r2 asm("r2") = arg2;
+
+	asm volatile(
+		".arch_extension	sec\n\t"
+		"stmfd	sp!, {r4 - r11}\n\t"
+		__asmeq("%0", "r0")
+		__asmeq("%1", "r1")
+		__asmeq("%2", "r2")
+		"mov	r3, #0\n\t"
+		"mov	r4, #0\n\t"
+		"smc	#0\n\t"
+		"ldmfd	sp!, {r4 - r11}\n\t"
+		:
+		: "r" (r0), "r" (r1), "r" (r2)
+		: "memory", "r3", "r12", "lr");
+}
+
+static int tf_set_cpu_boot_addr(int cpu, unsigned long boot_addr)
+{
+	cpu_boot_addr = boot_addr;
+	tf_generic_smc(TF_SET_CPU_BOOT_ADDR_SMC, cpu_boot_addr, 0);
+
+	return 0;
+}
+
+static int tf_prepare_idle(unsigned long mode)
+{
+	switch (mode) {
+	case TF_PM_MODE_LP0:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S3, cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_LP1:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S2, cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_LP1_NO_MC_CLK:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S2_NO_MC_CLK,
+			       cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_LP2:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S1, cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_LP2_NOFLUSH_L2:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S1_NOFLUSH_L2,
+			       cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_NONE:
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	tf_idle_mode = mode;
+
+	return 0;
+}
+
+#ifdef CONFIG_CACHE_L2X0
+static void tf_cache_write_sec(unsigned long val, unsigned int reg)
+{
+	u32 enable_op, l2x0_way_mask = 0xff;
+
+	switch (reg) {
+	case L2X0_CTRL:
+		if (l2x0_saved_regs.aux_ctrl & L310_AUX_CTRL_ASSOCIATIVITY_16)
+			l2x0_way_mask = 0xffff;
+
+		switch (tf_idle_mode) {
+		case TF_PM_MODE_LP2:
+			enable_op = TF_CACHE_REENABLE;
+			break;
+
+		default:
+			enable_op = TF_CACHE_ENABLE;
+			break;
+		}
+
+		if (val == L2X0_CTRL_EN)
+			tf_generic_smc(TF_CACHE_MAINT, enable_op,
+				       l2x0_saved_regs.aux_ctrl);
+		else
+			tf_generic_smc(TF_CACHE_MAINT, TF_CACHE_DISABLE,
+				       l2x0_way_mask);
+		break;
+
+	default:
+		break;
+	}
+}
+
+static int tf_init_cache(void)
+{
+	outer_cache.write_sec = tf_cache_write_sec;
+
+	return 0;
+}
+#endif /* CONFIG_CACHE_L2X0 */
+
+static const struct firmware_ops trusted_foundations_ops = {
+	.set_cpu_boot_addr = tf_set_cpu_boot_addr,
+	.prepare_idle = tf_prepare_idle,
+#ifdef CONFIG_CACHE_L2X0
+	.l2x0_init = tf_init_cache,
+#endif
+};
+
+void register_trusted_foundations(struct trusted_foundations_platform_data *pd)
+{
+	/*
+	 * we are not using version information for now since currently
+	 * supported SMCs are compatible with all TF releases
+	 */
+	register_firmware_ops(&trusted_foundations_ops);
+}
+
+void of_register_trusted_foundations(void)
+{
+	struct device_node *node;
+	struct trusted_foundations_platform_data pdata;
+	int err;
+
+	node = of_find_compatible_node(NULL, NULL, "tlm,trusted-foundations");
+	if (!node)
+		return;
+
+	err = of_property_read_u32(node, "tlm,version-major",
+				   &pdata.version_major);
+	if (err != 0)
+		panic("Trusted Foundation: missing version-major property\n");
+	err = of_property_read_u32(node, "tlm,version-minor",
+				   &pdata.version_minor);
+	if (err != 0)
+		panic("Trusted Foundation: missing version-minor property\n");
+	register_trusted_foundations(&pdata);
+}
+
+bool trusted_foundations_registered(void)
+{
+	return firmware_ops == &trusted_foundations_ops;
+}