[RFC PATCH 03/12] powerpc/prom_init: Add the ESM call to prom_init

[Thiago Jung Bauermann]

From: Ram Pai <linuxram@xxxxxxxxxx>

Make the Enter-Secure-Mode (ESM) ultravisor call to switch the VM to secure
mode. Add "svm=" command line option to turn off switching to secure mode.
Introduce CONFIG_PPC_SVM to control support for secure guests.

Signed-off-by: Ram Pai <linuxram@xxxxxxxxxx>
[ Generate an RTAS os-term hcall when the ESM ucall fails. ]
Signed-off-by: Michael Anderson <andmike@xxxxxxxxxxxxx>
[ Cleaned up the code a bit. ]
Signed-off-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
---
 .../admin-guide/kernel-parameters.txt         |   5 +
 arch/powerpc/include/asm/ultravisor-api.h     |   1 +
 arch/powerpc/kernel/prom_init.c               | 124 ++++++++++++++++++
 3 files changed, 130 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c45a19d654f3..7237d86b25c6 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4501,6 +4501,11 @@
 			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
 			is set. Default value is 5.
 
+	svm=		[PPC]
+			Format: { on | off | y | n | 1 | 0 }
+			This parameter controls use of the Protected
+			Execution Facility on pSeries.
+
 	swapaccount=[0|1]
 			[KNL] Enable accounting of swap in memory resource
 			controller if no parameter or 1 is given or disable
diff --git a/arch/powerpc/include/asm/ultravisor-api.h b/arch/powerpc/include/asm/ultravisor-api.h
index 15e6ce77a131..0e8b72081718 100644
--- a/arch/powerpc/include/asm/ultravisor-api.h
+++ b/arch/powerpc/include/asm/ultravisor-api.h
@@ -19,6 +19,7 @@
 
 /* opcodes */
 #define UV_WRITE_PATE			0xF104
+#define UV_ESM				0xF110
 #define UV_RETURN			0xF11C
 
 #endif /* _ASM_POWERPC_ULTRAVISOR_API_H */
diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index 523bb99d7676..5d8a3efb54f2 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -44,6 +44,7 @@
 #include <asm/sections.h>
 #include <asm/machdep.h>
 #include <asm/asm-prototypes.h>
+#include <asm/ultravisor-api.h>
 
 #include <linux/linux_logo.h>
 
@@ -174,6 +175,10 @@ static unsigned long __prombss prom_tce_alloc_end;
 static bool __prombss prom_radix_disable;
 #endif
 
+#ifdef CONFIG_PPC_SVM
+static bool __prombss prom_svm_disable;
+#endif
+
 struct platform_support {
 	bool hash_mmu;
 	bool radix_mmu;
@@ -809,6 +814,17 @@ static void __init early_cmdline_parse(void)
 	if (prom_radix_disable)
 		prom_debug("Radix disabled from cmdline\n");
 #endif /* CONFIG_PPC_PSERIES */
+
+#ifdef CONFIG_PPC_SVM
+	opt = prom_strstr(prom_cmd_line, "svm=");
+	if (opt) {
+		bool val;
+
+		opt += sizeof("svm=") - 1;
+		if (!prom_strtobool(opt, &val))
+			prom_svm_disable = !val;
+	}
+#endif /* CONFIG_PPC_SVM */
 }
 
 #ifdef CONFIG_PPC_PSERIES
@@ -1707,6 +1723,43 @@ static void __init prom_close_stdin(void)
 	}
 }
 
+#ifdef CONFIG_PPC_SVM
+static int prom_rtas_os_term_hcall(uint64_t args)
+{
+	register uint64_t arg1 asm("r3") = 0xf000;
+	register uint64_t arg2 asm("r4") = args;
+
+	asm volatile("sc 1\n" : "=r" (arg1) :
+			"r" (arg1),
+			"r" (arg2) :);
+	return arg1;
+}
+
+static struct rtas_args __prombss os_term_args;
+
+static void __init prom_rtas_os_term(char *str)
+{
+	phandle rtas_node;
+	__be32 val;
+	u32 token;
+
+	prom_printf("%s: start...\n", __func__);
+	rtas_node = call_prom("finddevice", 1, 1, ADDR("/rtas"));
+	prom_printf("rtas_node: %x\n", rtas_node);
+	if (!PHANDLE_VALID(rtas_node))
+		return;
+
+	val = 0;
+	prom_getprop(rtas_node, "ibm,os-term", &val, sizeof(val));
+	token = be32_to_cpu(val);
+	prom_printf("ibm,os-term: %x\n", token);
+	if (token == 0)
+		prom_panic("Could not get token for ibm,os-term\n");
+	os_term_args.token = cpu_to_be32(token);
+	prom_rtas_os_term_hcall((uint64_t)&os_term_args);
+}
+#endif /* CONFIG_PPC_SVM */
+
 /*
  * Allocate room for and instantiate RTAS
  */
@@ -3162,6 +3215,74 @@ static void unreloc_toc(void)
 #endif
 #endif
 
+#ifdef CONFIG_PPC_SVM
+/*
+ * The ESM blob is a data structure with information needed by the Ultravisor to
+ * validate the integrity of the secure guest.
+ */
+static void *get_esm_blob(void)
+{
+	/*
+	 * FIXME: We are still finalizing the details on how prom_init will grab
+	 * the ESM blob. When that is done, this function will be updated.
+	 */
+	return (void *)0xdeadbeef;
+}
+
+/*
+ * Perform the Enter Secure Mode ultracall.
+ */
+static int enter_secure_mode(void *esm_blob, void *retaddr, void *fdt)
+{
+	register uint64_t func asm("r0") = UV_ESM;
+	register uint64_t arg1 asm("r3") = (uint64_t)esm_blob;
+	register uint64_t arg2 asm("r4") = (uint64_t)retaddr;
+	register uint64_t arg3 asm("r5") = (uint64_t)fdt;
+
+	asm volatile("sc 2\n"
+		     : "=r"(arg1)
+		     : "r"(func), "0"(arg1), "r"(arg2), "r"(arg3)
+		     :);
+
+	return (int)arg1;
+}
+
+/*
+ * Call the Ultravisor to transfer us to secure memory if we have an ESM blob.
+ */
+static void setup_secure_guest(void *fdt)
+{
+	void *esm_blob;
+	int ret;
+
+	if (prom_svm_disable) {
+		prom_printf("Secure mode is OFF\n");
+		return;
+	}
+
+	esm_blob = get_esm_blob();
+	if (esm_blob == NULL)
+		/*
+		 * Absence of an ESM blob isn't an error, it just means we
+		 * shouldn't switch to secure mode.
+		 */
+		return;
+
+	/* Switch to secure mode. */
+	prom_printf("Switching to secure mode.\n");
+
+	ret = enter_secure_mode(esm_blob, NULL, fdt);
+	if (ret != U_SUCCESS) {
+		prom_printf("Returned %d from switching to secure mode.\n", ret);
+		prom_rtas_os_term("Switch to secure mode failed.\n");
+	}
+}
+#else
+static void setup_secure_guest(void *fdt)
+{
+}
+#endif /* CONFIG_PPC_SVM */
+
 /*
  * We enter here early on, when the Open Firmware prom is still
  * handling exceptions and the MMU hash table for us.
@@ -3360,6 +3481,9 @@ unsigned long __init prom_init(unsigned long r3, unsigned long r4,
 	unreloc_toc();
 #endif
 
+	/* Move to secure memory if we're supposed to be secure guests. */
+	setup_secure_guest((void *)hdr);
+
 	__start(hdr, kbase, 0, 0, 0, 0, 0);
 
 	return 0;