[PATCH 0/7] CVE-2020-4788: Speculation on incompletely validated data on IBM Power9

[PATCH 0/7] CVE-2020-4788: Speculation on incompletely validated data on IBM Power9

[Daniel Axtens]

IBM Power9 processors can speculatively operate on data in the L1
cache before it has been completely validated, via a way-prediction
mechanism. It is not possible for an attacker to determine the
contents of impermissible memory using this method, since these
systems implement a combination of hardware and software security
measures to prevent scenarios where protected data could be leaked.

However these measures don't address the scenario where an attacker
induces the operating system to speculatively execute instructions
using data that the attacker controls. This can be used for example to
speculatively bypass "kernel user access prevention" techniques, as
discovered by Anthony Steinhauser of Google's Safeside Project. This
is not an attack by itself, but there is a possibility it could be
used in conjunction with side-channels or other weaknesses in the
privileged code to construct an attack.

This issue can be mitigated by flushing the L1 cache between privilege
boundaries of concern. This series flushes the cache on kernel entry and
after kernel user accesses.

Thanks to Nick Piggin, Russell Currey, Christopher M. Riedl, Michael
Ellerman and Spoorthy S for their work in developing, optimising,
testing and backporting these fixes, and to the many others who helped
behind the scenes.

Daniel Axtens (3):
  selftests/powerpc: entry flush test
  selftests/powerpc: refactor entry and rfi_flush tests
  powerpc/64s: rename pnv|pseries_setup_rfi_flush to
    _setup_security_mitigations

Michael Ellerman (1):
  powerpc: Only include kup-radix.h for 64-bit Book3S

Nicholas Piggin (2):
  powerpc/64s: flush L1D on kernel entry
  powerpc/64s: flush L1D after user accesses

Russell Currey (1):
  selftests/powerpc: rfi_flush: disable entry flush if present

 .../admin-guide/kernel-parameters.txt         |   7 +
 .../powerpc/include/asm/book3s/64/kup-radix.h |  66 ++++++---
 arch/powerpc/include/asm/exception-64s.h      |  12 +-
 arch/powerpc/include/asm/feature-fixups.h     |  19 +++
 arch/powerpc/include/asm/kup.h                |  26 +++-
 arch/powerpc/include/asm/security_features.h  |   7 +
 arch/powerpc/include/asm/setup.h              |   4 +
 arch/powerpc/kernel/exceptions-64s.S          |  80 +++++-----
 arch/powerpc/kernel/setup_64.c                | 122 ++++++++++++++-
 arch/powerpc/kernel/syscall_64.c              |   2 +-
 arch/powerpc/kernel/vmlinux.lds.S             |  14 ++
 arch/powerpc/lib/feature-fixups.c             | 104 +++++++++++++
 arch/powerpc/platforms/powernv/setup.c        |  24 ++-
 arch/powerpc/platforms/pseries/mobility.c     |   4 +-
 arch/powerpc/platforms/pseries/pseries.h      |   2 +-
 arch/powerpc/platforms/pseries/setup.c        |  15 +-
 .../testing/selftests/powerpc/include/utils.h |   5 +
 .../selftests/powerpc/security/.gitignore     |   1 +
 .../selftests/powerpc/security/Makefile       |   4 +-
 .../selftests/powerpc/security/entry_flush.c  | 139 ++++++++++++++++++
 .../selftests/powerpc/security/flush_utils.c  |  70 +++++++++
 .../selftests/powerpc/security/flush_utils.h  |  17 +++
 .../selftests/powerpc/security/rfi_flush.c    |  96 ++++--------
 23 files changed, 693 insertions(+), 147 deletions(-)
 create mode 100644 tools/testing/selftests/powerpc/security/entry_flush.c
 create mode 100644 tools/testing/selftests/powerpc/security/flush_utils.c
 create mode 100644 tools/testing/selftests/powerpc/security/flush_utils.h

-- 
2.25.1

[PATCH 1/7] selftests/powerpc: rfi_flush: disable entry flush if present

[Daniel Axtens]

From: Russell Currey <ruscur@russell.cc>

We are about to add an entry flush. The rfi (exit) flush test measures
the number of L1D flushes over a syscall with the RFI flush enabled and
disabled. But if the entry flush is also enabled, the effect of enabling
and disabling the RFI flush is masked.

If there is a debugfs entry for the entry flush, disable it during the RFI
flush and restore it later.

Reported-by: Spoorthy S <spoorts2@in.ibm.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 .../selftests/powerpc/security/rfi_flush.c    | 35 +++++++++++++++----
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/powerpc/security/rfi_flush.c b/tools/testing/selftests/powerpc/security/rfi_flush.c
index 93a65bd1f231..4e7b2776c367 100644
--- a/tools/testing/selftests/powerpc/security/rfi_flush.c
+++ b/tools/testing/selftests/powerpc/security/rfi_flush.c
@@ -85,19 +85,33 @@ int rfi_flush_test(void)
 	__u64 l1d_misses_total = 0;
 	unsigned long iterations = 100000, zero_size = 24 * 1024;
 	unsigned long l1d_misses_expected;
-	int rfi_flush_org, rfi_flush;
+	int rfi_flush_orig, rfi_flush;
+	int have_entry_flush, entry_flush_orig;
 
 	SKIP_IF(geteuid() != 0);
 
 	// The PMU event we use only works on Power7 or later
 	SKIP_IF(!have_hwcap(PPC_FEATURE_ARCH_2_06));
 
-	if (read_debugfs_file("powerpc/rfi_flush", &rfi_flush_org)) {
+	if (read_debugfs_file("powerpc/rfi_flush", &rfi_flush_orig) < 0) {
 		perror("Unable to read powerpc/rfi_flush debugfs file");
 		SKIP_IF(1);
 	}
 
-	rfi_flush = rfi_flush_org;
+	if (read_debugfs_file("powerpc/entry_flush", &entry_flush_orig) < 0) {
+		have_entry_flush = 0;
+	} else {
+		have_entry_flush = 1;
+
+		if (entry_flush_orig != 0) {
+			if (write_debugfs_file("powerpc/entry_flush", 0) < 0) {
+				perror("error writing to powerpc/entry_flush debugfs file");
+				return 1;
+			}
+		}
+	}
+
+	rfi_flush = rfi_flush_orig;
 
 	fd = perf_event_open_counter(PERF_TYPE_RAW, /* L1d miss */ 0x400f0, -1);
 	FAIL_IF(fd < 0);
@@ -106,6 +120,7 @@ int rfi_flush_test(void)
 
 	FAIL_IF(perf_event_enable(fd));
 
+	// disable L1 prefetching
 	set_dscr(1);
 
 	iter = repetitions;
@@ -147,8 +162,8 @@ again:
 		       repetitions * l1d_misses_expected / 2,
 		       passes, repetitions);
 
-	if (rfi_flush == rfi_flush_org) {
-		rfi_flush = !rfi_flush_org;
+	if (rfi_flush == rfi_flush_orig) {
+		rfi_flush = !rfi_flush_orig;
 		if (write_debugfs_file("powerpc/rfi_flush", rfi_flush) < 0) {
 			perror("error writing to powerpc/rfi_flush debugfs file");
 			return 1;
@@ -164,11 +179,19 @@ again:
 
 	set_dscr(0);
 
-	if (write_debugfs_file("powerpc/rfi_flush", rfi_flush_org) < 0) {
+	if (write_debugfs_file("powerpc/rfi_flush", rfi_flush_orig) < 0) {
 		perror("unable to restore original value of powerpc/rfi_flush debugfs file");
 		return 1;
 	}
 
+	if (have_entry_flush) {
+		if (write_debugfs_file("powerpc/entry_flush", entry_flush_orig) < 0) {
+			perror("unable to restore original value of powerpc/entry_flush "
+			       "debugfs file");
+			return 1;
+		}
+	}
+
 	return rc;
 }
 
-- 
2.25.1

[PATCH 2/7] powerpc/64s: flush L1D on kernel entry

[Daniel Axtens]

From: Nicholas Piggin <npiggin@gmail.com>

IBM Power9 processors can speculatively operate on data in the L1 cache
before it has been completely validated, via a way-prediction mechanism. It
is not possible for an attacker to determine the contents of impermissible
memory using this method, since these systems implement a combination of
hardware and software security measures to prevent scenarios where
protected data could be leaked.

However these measures don't address the scenario where an attacker induces
the operating system to speculatively execute instructions using data that
the attacker controls. This can be used for example to speculatively bypass
"kernel user access prevention" techniques, as discovered by Anthony
Steinhauser of Google's Safeside Project. This is not an attack by itself,
but there is a possibility it could be used in conjunction with
side-channels or other weaknesses in the privileged code to construct an
attack.

This issue can be mitigated by flushing the L1 cache between privilege
boundaries of concern. This patch flushes the L1 cache on kernel entry.

This is part of the fix for CVE-2020-4788.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 .../admin-guide/kernel-parameters.txt         |  3 +
 arch/powerpc/include/asm/exception-64s.h      |  9 ++-
 arch/powerpc/include/asm/feature-fixups.h     | 10 ++++
 arch/powerpc/include/asm/security_features.h  |  4 ++
 arch/powerpc/include/asm/setup.h              |  3 +
 arch/powerpc/kernel/exceptions-64s.S          | 37 ++++++++++++
 arch/powerpc/kernel/setup_64.c                | 60 ++++++++++++++++++-
 arch/powerpc/kernel/vmlinux.lds.S             |  7 +++
 arch/powerpc/lib/feature-fixups.c             | 54 +++++++++++++++++
 arch/powerpc/platforms/powernv/setup.c        | 11 ++++
 arch/powerpc/platforms/pseries/setup.c        |  4 ++
 11 files changed, 200 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index af4ec2a8f32a..282789cfa1dc 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2875,6 +2875,7 @@
 					       mds=off [X86]
 					       tsx_async_abort=off [X86]
 					       kvm.nx_huge_pages=off [X86]
+					       no_entry_flush [PPC]
 
 				Exceptions:
 					       This does not have any effect on
@@ -3203,6 +3204,8 @@
 
 	noefi		Disable EFI runtime services support.
 
+	no_entry_flush  [PPC] Don't flush the L1-D cache when entering the kernel.
+
 	noexec		[IA-64]
 
 	noexec		[X86]
diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index ebe95aa04d53..83fa88bc9935 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -57,11 +57,18 @@
 	nop;								\
 	nop
 
+#define ENTRY_FLUSH_SLOT						\
+	ENTRY_FLUSH_FIXUP_SECTION;					\
+	nop;								\
+	nop;								\
+	nop;
+
 /*
  * r10 must be free to use, r13 must be paca
  */
 #define INTERRUPT_TO_KERNEL						\
-	STF_ENTRY_BARRIER_SLOT
+	STF_ENTRY_BARRIER_SLOT;						\
+	ENTRY_FLUSH_SLOT
 
 /*
  * Macros for annotating the expected destination of (h)rfid
diff --git a/arch/powerpc/include/asm/feature-fixups.h b/arch/powerpc/include/asm/feature-fixups.h
index b0af97add751..06a48219bbf2 100644
--- a/arch/powerpc/include/asm/feature-fixups.h
+++ b/arch/powerpc/include/asm/feature-fixups.h
@@ -205,6 +205,14 @@ label##3:					       	\
 	FTR_ENTRY_OFFSET 955b-956b;			\
 	.popsection;
 
+#define ENTRY_FLUSH_FIXUP_SECTION			\
+957:							\
+	.pushsection __entry_flush_fixup,"a";		\
+	.align 2;					\
+958:							\
+	FTR_ENTRY_OFFSET 957b-958b;			\
+	.popsection;
+
 #define RFI_FLUSH_FIXUP_SECTION				\
 951:							\
 	.pushsection __rfi_flush_fixup,"a";		\
@@ -237,8 +245,10 @@ label##3:					       	\
 #include <linux/types.h>
 
 extern long stf_barrier_fallback;
+extern long entry_flush_fallback;
 extern long __start___stf_entry_barrier_fixup, __stop___stf_entry_barrier_fixup;
 extern long __start___stf_exit_barrier_fixup, __stop___stf_exit_barrier_fixup;
+extern long __start___entry_flush_fixup, __stop___entry_flush_fixup;
 extern long __start___rfi_flush_fixup, __stop___rfi_flush_fixup;
 extern long __start___barrier_nospec_fixup, __stop___barrier_nospec_fixup;
 extern long __start__btb_flush_fixup, __stop__btb_flush_fixup;
diff --git a/arch/powerpc/include/asm/security_features.h b/arch/powerpc/include/asm/security_features.h
index fbb8fa32150f..9e7459d2edca 100644
--- a/arch/powerpc/include/asm/security_features.h
+++ b/arch/powerpc/include/asm/security_features.h
@@ -86,12 +86,16 @@ static inline bool security_ftr_enabled(u64 feature)
 // Software required to flush link stack on context switch
 #define SEC_FTR_FLUSH_LINK_STACK	0x0000000000001000ull
 
+// The L1-D cache should be flushed when entering the kernel
+#define SEC_FTR_L1D_FLUSH_ENTRY		0x0000000000004000ull
+
 
 // Features enabled by default
 #define SEC_FTR_DEFAULT \
 	(SEC_FTR_L1D_FLUSH_HV | \
 	 SEC_FTR_L1D_FLUSH_PR | \
 	 SEC_FTR_BNDS_CHK_SPEC_BAR | \
+	 SEC_FTR_L1D_FLUSH_ENTRY | \
 	 SEC_FTR_FAVOUR_SECURITY)
 
 #endif /* _ASM_POWERPC_SECURITY_FEATURES_H */
diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
index 9efbddee2bca..e2fcd3e874f8 100644
--- a/arch/powerpc/include/asm/setup.h
+++ b/arch/powerpc/include/asm/setup.h
@@ -52,12 +52,15 @@ enum l1d_flush_type {
 };
 
 void setup_rfi_flush(enum l1d_flush_type, bool enable);
+void setup_entry_flush(bool enable);
+void setup_uaccess_flush(bool enable);
 void do_rfi_flush_fixups(enum l1d_flush_type types);
 #ifdef CONFIG_PPC_BARRIER_NOSPEC
 void setup_barrier_nospec(void);
 #else
 static inline void setup_barrier_nospec(void) { };
 #endif
+void do_entry_flush_fixups(enum l1d_flush_type types);
 void do_barrier_nospec_fixups(bool enable);
 extern bool barrier_nospec_enabled;
 
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index f7d748b88705..5577dd887d37 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -2951,6 +2951,43 @@ TRAMP_REAL_BEGIN(stf_barrier_fallback)
 	.endr
 	blr
 
+TRAMP_REAL_BEGIN(entry_flush_fallback)
+	std	r9,PACA_EXRFI+EX_R9(r13)
+	std	r10,PACA_EXRFI+EX_R10(r13)
+	std	r11,PACA_EXRFI+EX_R11(r13)
+	mfctr	r9
+	ld	r10,PACA_RFI_FLUSH_FALLBACK_AREA(r13)
+	ld	r11,PACA_L1D_FLUSH_SIZE(r13)
+	srdi	r11,r11,(7 + 3) /* 128 byte lines, unrolled 8x */
+	mtctr	r11
+	DCBT_BOOK3S_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */
+
+	/* order ld/st prior to dcbt stop all streams with flushing */
+	sync
+
+	/*
+	 * The load addresses are at staggered offsets within cachelines,
+	 * which suits some pipelines better (on others it should not
+	 * hurt).
+	 */
+1:
+	ld	r11,(0x80 + 8)*0(r10)
+	ld	r11,(0x80 + 8)*1(r10)
+	ld	r11,(0x80 + 8)*2(r10)
+	ld	r11,(0x80 + 8)*3(r10)
+	ld	r11,(0x80 + 8)*4(r10)
+	ld	r11,(0x80 + 8)*5(r10)
+	ld	r11,(0x80 + 8)*6(r10)
+	ld	r11,(0x80 + 8)*7(r10)
+	addi	r10,r10,0x80*8
+	bdnz	1b
+
+	mtctr	r9
+	ld	r9,PACA_EXRFI+EX_R9(r13)
+	ld	r10,PACA_EXRFI+EX_R10(r13)
+	ld	r11,PACA_EXRFI+EX_R11(r13)
+	blr
+
 TRAMP_REAL_BEGIN(rfi_flush_fallback)
 	SET_SCRATCH0(r13);
 	GET_PACA(r13);
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index bb9cab3641d7..7d447b43ad13 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -945,7 +945,9 @@ early_initcall(disable_hardlockup_detector);
 static enum l1d_flush_type enabled_flush_types;
 static void *l1d_flush_fallback_area;
 static bool no_rfi_flush;
+static bool no_entry_flush;
 bool rfi_flush;
+bool entry_flush;
 
 static int __init handle_no_rfi_flush(char *p)
 {
@@ -955,6 +957,14 @@ static int __init handle_no_rfi_flush(char *p)
 }
 early_param("no_rfi_flush", handle_no_rfi_flush);
 
+static int __init handle_no_entry_flush(char *p)
+{
+	pr_info("entry-flush: disabled on command line.");
+	no_entry_flush = true;
+	return 0;
+}
+early_param("no_entry_flush", handle_no_entry_flush);
+
 /*
  * The RFI flush is not KPTI, but because users will see doco that says to use
  * nopti we hijack that option here to also disable the RFI flush.
@@ -986,6 +996,18 @@ void rfi_flush_enable(bool enable)
 	rfi_flush = enable;
 }
 
+void entry_flush_enable(bool enable)
+{
+	if (enable) {
+		do_entry_flush_fixups(enabled_flush_types);
+		on_each_cpu(do_nothing, NULL, 1);
+	} else {
+		do_entry_flush_fixups(L1D_FLUSH_NONE);
+	}
+
+	entry_flush = enable;
+}
+
 static void __ref init_fallback_flush(void)
 {
 	u64 l1d_size, limit;
@@ -1044,10 +1066,19 @@ void setup_rfi_flush(enum l1d_flush_type types, bool enable)
 
 	enabled_flush_types = types;
 
-	if (!no_rfi_flush && !cpu_mitigations_off())
+	if (!cpu_mitigations_off() && !no_rfi_flush)
 		rfi_flush_enable(enable);
 }
 
+void setup_entry_flush(bool enable)
+{
+	if (cpu_mitigations_off())
+		return;
+
+	if (!no_entry_flush)
+		entry_flush_enable(enable);
+}
+
 #ifdef CONFIG_DEBUG_FS
 static int rfi_flush_set(void *data, u64 val)
 {
@@ -1075,9 +1106,36 @@ static int rfi_flush_get(void *data, u64 *val)
 
 DEFINE_SIMPLE_ATTRIBUTE(fops_rfi_flush, rfi_flush_get, rfi_flush_set, "%llu\n");
 
+static int entry_flush_set(void *data, u64 val)
+{
+	bool enable;
+
+	if (val == 1)
+		enable = true;
+	else if (val == 0)
+		enable = false;
+	else
+		return -EINVAL;
+
+	/* Only do anything if we're changing state */
+	if (enable != entry_flush)
+		entry_flush_enable(enable);
+
+	return 0;
+}
+
+static int entry_flush_get(void *data, u64 *val)
+{
+	*val = entry_flush ? 1 : 0;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_entry_flush, entry_flush_get, entry_flush_set, "%llu\n");
+
 static __init int rfi_flush_debugfs_init(void)
 {
 	debugfs_create_file("rfi_flush", 0600, powerpc_debugfs_root, NULL, &fops_rfi_flush);
+	debugfs_create_file("entry_flush", 0600, powerpc_debugfs_root, NULL, &fops_entry_flush);
 	return 0;
 }
 device_initcall(rfi_flush_debugfs_init);
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index e0548b4950de..715ec4d4614a 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -131,6 +131,13 @@ SECTIONS
 		__stop___stf_entry_barrier_fixup = .;
 	}
 
+	. = ALIGN(8);
+	__entry_flush_fixup : AT(ADDR(__entry_flush_fixup) - LOAD_OFFSET) {
+		__start___entry_flush_fixup = .;
+		*(__entry_flush_fixup)
+		__stop___entry_flush_fixup = .;
+	}
+
 	. = ALIGN(8);
 	__stf_exit_barrier_fixup : AT(ADDR(__stf_exit_barrier_fixup) - LOAD_OFFSET) {
 		__start___stf_exit_barrier_fixup = .;
diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
index 4c0a7ee9fa00..70e83cfd74aa 100644
--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -234,6 +234,60 @@ void do_stf_barrier_fixups(enum stf_barrier_type types)
 	do_stf_exit_barrier_fixups(types);
 }
 
+void do_entry_flush_fixups(enum l1d_flush_type types)
+{
+	unsigned int instrs[3], *dest;
+	long *start, *end;
+	int i;
+
+	start = PTRRELOC(&__start___entry_flush_fixup);
+	end = PTRRELOC(&__stop___entry_flush_fixup);
+
+	instrs[0] = 0x60000000; /* nop */
+	instrs[1] = 0x60000000; /* nop */
+	instrs[2] = 0x60000000; /* nop */
+
+	i = 0;
+	if (types == L1D_FLUSH_FALLBACK) {
+		instrs[i++] = 0x7d4802a6; /* mflr r10		*/
+		instrs[i++] = 0x60000000; /* branch patched below */
+		instrs[i++] = 0x7d4803a6; /* mtlr r10		*/
+	}
+
+	if (types & L1D_FLUSH_ORI) {
+		instrs[i++] = 0x63ff0000; /* ori 31,31,0 speculation barrier */
+		instrs[i++] = 0x63de0000; /* ori 30,30,0 L1d flush*/
+	}
+
+	if (types & L1D_FLUSH_MTTRIG)
+		instrs[i++] = 0x7c12dba6; /* mtspr TRIG2,r0 (SPR #882) */
+
+	for (i = 0; start < end; start++, i++) {
+		dest = (void *)start + *start;
+
+		pr_devel("patching dest %lx\n", (unsigned long)dest);
+
+		patch_instruction((struct ppc_inst *)dest, ppc_inst(instrs[0]));
+
+		if (types == L1D_FLUSH_FALLBACK)
+			patch_branch((struct ppc_inst *)(dest + 1), (unsigned long)&entry_flush_fallback,
+				     BRANCH_SET_LINK);
+		else
+			patch_instruction((struct ppc_inst *)(dest + 1), ppc_inst(instrs[1]));
+
+		patch_instruction((struct ppc_inst *)(dest + 2), ppc_inst(instrs[2]));
+	}
+
+	printk(KERN_DEBUG "entry-flush: patched %d locations (%s flush)\n", i,
+		(types == L1D_FLUSH_NONE)       ? "no" :
+		(types == L1D_FLUSH_FALLBACK)   ? "fallback displacement" :
+		(types &  L1D_FLUSH_ORI)        ? (types & L1D_FLUSH_MTTRIG)
+							? "ori+mttrig type"
+							: "ori type" :
+		(types &  L1D_FLUSH_MTTRIG)     ? "mttrig type"
+						: "unknown");
+}
+
 void do_rfi_flush_fixups(enum l1d_flush_type types)
 {
 	unsigned int instrs[3], *dest;
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 9acaa0f131b9..d04a085c423d 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -122,12 +122,23 @@ static void pnv_setup_rfi_flush(void)
 			type = L1D_FLUSH_ORI;
 	}
 
+	/*
+	 * If we are non-Power9 bare metal, we don't need to flush on kernel
+	 * entry: it fixes a P9 specific vulnerability.
+	 */
+	if (!pvr_version_is(PVR_POWER9))
+		security_ftr_clear(SEC_FTR_L1D_FLUSH_ENTRY);
+
 	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && \
 		 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR)   || \
 		  security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV));
 
 	setup_rfi_flush(type, enable);
 	setup_count_cache_flush();
+
+	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
+		 security_ftr_enabled(SEC_FTR_L1D_FLUSH_ENTRY);
+	setup_entry_flush(enable);
 }
 
 static void __init pnv_check_guarded_cores(void)
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 633c45ec406d..8136c5368ee4 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -579,6 +579,10 @@ void pseries_setup_rfi_flush(void)
 
 	setup_rfi_flush(types, enable);
 	setup_count_cache_flush();
+
+	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
+		 security_ftr_enabled(SEC_FTR_L1D_FLUSH_ENTRY);
+	setup_entry_flush(enable);
 }
 
 #ifdef CONFIG_PCI_IOV
-- 
2.25.1

[PATCH 3/7] powerpc/64s: flush L1D after user accesses

[Daniel Axtens]

From: Nicholas Piggin <npiggin@gmail.com>

IBM Power9 processors can speculatively operate on data in the L1 cache
before it has been completely validated, via a way-prediction mechanism. It
is not possible for an attacker to determine the contents of impermissible
memory using this method, since these systems implement a combination of
hardware and software security measures to prevent scenarios where
protected data could be leaked.

However these measures don't address the scenario where an attacker induces
the operating system to speculatively execute instructions using data that
the attacker controls. This can be used for example to speculatively bypass
"kernel user access prevention" techniques, as discovered by Anthony
Steinhauser of Google's Safeside Project. This is not an attack by itself,
but there is a possibility it could be used in conjunction with
side-channels or other weaknesses in the privileged code to construct an
attack.

This issue can be mitigated by flushing the L1 cache between privilege
boundaries of concern. This patch flushes the L1 cache after user accesses.

This is part of the fix for CVE-2020-4788.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 .../admin-guide/kernel-parameters.txt         |  4 +
 .../powerpc/include/asm/book3s/64/kup-radix.h | 66 ++++++++------
 arch/powerpc/include/asm/exception-64s.h      |  3 +
 arch/powerpc/include/asm/feature-fixups.h     |  9 ++
 arch/powerpc/include/asm/kup.h                | 19 +++--
 arch/powerpc/include/asm/security_features.h  |  3 +
 arch/powerpc/include/asm/setup.h              |  1 +
 arch/powerpc/kernel/exceptions-64s.S          | 85 ++++++-------------
 arch/powerpc/kernel/setup_64.c                | 62 ++++++++++++++
 arch/powerpc/kernel/vmlinux.lds.S             |  7 ++
 arch/powerpc/lib/feature-fixups.c             | 50 +++++++++++
 arch/powerpc/platforms/powernv/setup.c        | 10 ++-
 arch/powerpc/platforms/pseries/setup.c        |  4 +
 13 files changed, 233 insertions(+), 90 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 282789cfa1dc..d1b417dd1266 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2876,6 +2876,7 @@
 					       tsx_async_abort=off [X86]
 					       kvm.nx_huge_pages=off [X86]
 					       no_entry_flush [PPC]
+					       no_uaccess_flush [PPC]
 
 				Exceptions:
 					       This does not have any effect on
@@ -3255,6 +3256,9 @@
 	nospec_store_bypass_disable
 			[HW] Disable all mitigations for the Speculative Store Bypass vulnerability
 
+	no_uaccess_flush
+	                [PPC] Don't flush the L1-D cache after accessing user data.
+
 	noxsave		[BUGS=X86] Disables x86 extended register state save
 			and restore using xsave. The kernel will fallback to
 			enabling legacy floating-point and sse state.
diff --git a/arch/powerpc/include/asm/book3s/64/kup-radix.h b/arch/powerpc/include/asm/book3s/64/kup-radix.h
index 3ee1ec60be84..97c2394e7dea 100644
--- a/arch/powerpc/include/asm/book3s/64/kup-radix.h
+++ b/arch/powerpc/include/asm/book3s/64/kup-radix.h
@@ -61,6 +61,8 @@
 
 #else /* !__ASSEMBLY__ */
 
+DECLARE_STATIC_KEY_FALSE(uaccess_flush_key);
+
 #ifdef CONFIG_PPC_KUAP
 
 #include <asm/mmu.h>
@@ -103,8 +105,16 @@ static inline void kuap_check_amr(void)
 
 static inline unsigned long get_kuap(void)
 {
+	/*
+	 * We return AMR_KUAP_BLOCKED when we don't support KUAP because
+	 * prevent_user_access_return needs to return AMR_KUAP_BLOCKED to
+	 * cause restore_user_access to do a flush.
+	 *
+	 * This has no effect in terms of actually blocking things on hash,
+	 * so it doesn't break anything.
+	 */
 	if (!early_mmu_has_feature(MMU_FTR_RADIX_KUAP))
-		return 0;
+		return AMR_KUAP_BLOCKED;
 
 	return mfspr(SPRN_AMR);
 }
@@ -123,6 +133,31 @@ static inline void set_kuap(unsigned long value)
 	isync();
 }
 
+static inline bool
+bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
+{
+	return WARN(mmu_has_feature(MMU_FTR_RADIX_KUAP) &&
+		    (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),
+		    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
+}
+#else /* CONFIG_PPC_KUAP */
+static inline void kuap_restore_amr(struct pt_regs *regs, unsigned long amr) { }
+
+static inline unsigned long kuap_get_and_check_amr(void)
+{
+	return 0UL;
+}
+
+static inline void kuap_check_amr(void) { }
+
+static inline unsigned long get_kuap(void)
+{
+	return AMR_KUAP_BLOCKED;
+}
+
+static inline void set_kuap(unsigned long value) { }
+#endif /* !CONFIG_PPC_KUAP */
+
 static __always_inline void allow_user_access(void __user *to, const void __user *from,
 					      unsigned long size, unsigned long dir)
 {
@@ -142,6 +177,8 @@ static inline void prevent_user_access(void __user *to, const void __user *from,
 				       unsigned long size, unsigned long dir)
 {
 	set_kuap(AMR_KUAP_BLOCKED);
+	if (static_branch_unlikely(&uaccess_flush_key))
+		do_uaccess_flush();
 }
 
 static inline unsigned long prevent_user_access_return(void)
@@ -149,6 +186,8 @@ static inline unsigned long prevent_user_access_return(void)
 	unsigned long flags = get_kuap();
 
 	set_kuap(AMR_KUAP_BLOCKED);
+	if (static_branch_unlikely(&uaccess_flush_key))
+		do_uaccess_flush();
 
 	return flags;
 }
@@ -156,30 +195,9 @@ static inline unsigned long prevent_user_access_return(void)
 static inline void restore_user_access(unsigned long flags)
 {
 	set_kuap(flags);
+	if (static_branch_unlikely(&uaccess_flush_key) && flags == AMR_KUAP_BLOCKED)
+		do_uaccess_flush();
 }
-
-static inline bool
-bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
-{
-	return WARN(mmu_has_feature(MMU_FTR_RADIX_KUAP) &&
-		    (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),
-		    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
-}
-#else /* CONFIG_PPC_KUAP */
-static inline void kuap_restore_amr(struct pt_regs *regs, unsigned long amr)
-{
-}
-
-static inline void kuap_check_amr(void)
-{
-}
-
-static inline unsigned long kuap_get_and_check_amr(void)
-{
-	return 0;
-}
-#endif /* CONFIG_PPC_KUAP */
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_BOOK3S_64_KUP_RADIX_H */
diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 83fa88bc9935..1d32b174ab6a 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -144,6 +144,9 @@
 	RFSCV;								\
 	b	rfscv_flush_fallback
 
+#else /* __ASSEMBLY__ */
+/* Prototype for function defined in exceptions-64s.S */
+void do_uaccess_flush(void);
 #endif /* __ASSEMBLY__ */
 
 #endif	/* _ASM_POWERPC_EXCEPTION_H */
diff --git a/arch/powerpc/include/asm/feature-fixups.h b/arch/powerpc/include/asm/feature-fixups.h
index 06a48219bbf2..fbd406cd6916 100644
--- a/arch/powerpc/include/asm/feature-fixups.h
+++ b/arch/powerpc/include/asm/feature-fixups.h
@@ -205,6 +205,14 @@ label##3:					       	\
 	FTR_ENTRY_OFFSET 955b-956b;			\
 	.popsection;
 
+#define UACCESS_FLUSH_FIXUP_SECTION			\
+959:							\
+	.pushsection __uaccess_flush_fixup,"a";		\
+	.align 2;					\
+960:							\
+	FTR_ENTRY_OFFSET 959b-960b;			\
+	.popsection;
+
 #define ENTRY_FLUSH_FIXUP_SECTION			\
 957:							\
 	.pushsection __entry_flush_fixup,"a";		\
@@ -248,6 +256,7 @@ extern long stf_barrier_fallback;
 extern long entry_flush_fallback;
 extern long __start___stf_entry_barrier_fixup, __stop___stf_entry_barrier_fixup;
 extern long __start___stf_exit_barrier_fixup, __stop___stf_exit_barrier_fixup;
+extern long __start___uaccess_flush_fixup, __stop___uaccess_flush_fixup;
 extern long __start___entry_flush_fixup, __stop___entry_flush_fixup;
 extern long __start___rfi_flush_fixup, __stop___rfi_flush_fixup;
 extern long __start___barrier_nospec_fixup, __stop___barrier_nospec_fixup;
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index 1d0f7d838b2e..0f5c606ae057 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h
@@ -53,17 +53,26 @@ static inline void setup_kuep(bool disabled) { }
 void setup_kuap(bool disabled);
 #else
 static inline void setup_kuap(bool disabled) { }
+
+static inline bool
+bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
+{
+	return false;
+}
+
+/*
+ * book3s/64/kup-radix.h defines these functions for the !KUAP case to flush
+ * the L1D cache after user accesses. Only include the empty stubs for other
+ * platforms.
+ */
+#ifndef CONFIG_PPC64
 static inline void allow_user_access(void __user *to, const void __user *from,
 				     unsigned long size, unsigned long dir) { }
 static inline void prevent_user_access(void __user *to, const void __user *from,
 				       unsigned long size, unsigned long dir) { }
 static inline unsigned long prevent_user_access_return(void) { return 0UL; }
 static inline void restore_user_access(unsigned long flags) { }
-static inline bool
-bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
-{
-	return false;
-}
+#endif /* CONFIG_PPC64 */
 #endif /* CONFIG_PPC_KUAP */
 
 static inline void allow_read_from_user(const void __user *from, unsigned long size)
diff --git a/arch/powerpc/include/asm/security_features.h b/arch/powerpc/include/asm/security_features.h
index 9e7459d2edca..b774a4477d5f 100644
--- a/arch/powerpc/include/asm/security_features.h
+++ b/arch/powerpc/include/asm/security_features.h
@@ -89,6 +89,8 @@ static inline bool security_ftr_enabled(u64 feature)
 // The L1-D cache should be flushed when entering the kernel
 #define SEC_FTR_L1D_FLUSH_ENTRY		0x0000000000004000ull
 
+// The L1-D cache should be flushed after user accesses from the kernel
+#define SEC_FTR_L1D_FLUSH_UACCESS	0x0000000000008000ull
 
 // Features enabled by default
 #define SEC_FTR_DEFAULT \
@@ -96,6 +98,7 @@ static inline bool security_ftr_enabled(u64 feature)
 	 SEC_FTR_L1D_FLUSH_PR | \
 	 SEC_FTR_BNDS_CHK_SPEC_BAR | \
 	 SEC_FTR_L1D_FLUSH_ENTRY | \
+	 SEC_FTR_L1D_FLUSH_UACCESS | \
 	 SEC_FTR_FAVOUR_SECURITY)
 
 #endif /* _ASM_POWERPC_SECURITY_FEATURES_H */
diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
index e2fcd3e874f8..a466749703f1 100644
--- a/arch/powerpc/include/asm/setup.h
+++ b/arch/powerpc/include/asm/setup.h
@@ -60,6 +60,7 @@ void setup_barrier_nospec(void);
 #else
 static inline void setup_barrier_nospec(void) { };
 #endif
+void do_uaccess_flush_fixups(enum l1d_flush_type types);
 void do_entry_flush_fixups(enum l1d_flush_type types);
 void do_barrier_nospec_fixups(bool enable);
 extern bool barrier_nospec_enabled;
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 5577dd887d37..f63a3d3bca3d 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -2951,11 +2951,8 @@ TRAMP_REAL_BEGIN(stf_barrier_fallback)
 	.endr
 	blr
 
-TRAMP_REAL_BEGIN(entry_flush_fallback)
-	std	r9,PACA_EXRFI+EX_R9(r13)
-	std	r10,PACA_EXRFI+EX_R10(r13)
-	std	r11,PACA_EXRFI+EX_R11(r13)
-	mfctr	r9
+/* Clobbers r10, r11, ctr */
+.macro L1D_DISPLACEMENT_FLUSH
 	ld	r10,PACA_RFI_FLUSH_FALLBACK_AREA(r13)
 	ld	r11,PACA_L1D_FLUSH_SIZE(r13)
 	srdi	r11,r11,(7 + 3) /* 128 byte lines, unrolled 8x */
@@ -2981,7 +2978,14 @@ TRAMP_REAL_BEGIN(entry_flush_fallback)
 	ld	r11,(0x80 + 8)*7(r10)
 	addi	r10,r10,0x80*8
 	bdnz	1b
+.endm
 
+TRAMP_REAL_BEGIN(entry_flush_fallback)
+	std	r9,PACA_EXRFI+EX_R9(r13)
+	std	r10,PACA_EXRFI+EX_R10(r13)
+	std	r11,PACA_EXRFI+EX_R11(r13)
+	mfctr	r9
+	L1D_DISPLACEMENT_FLUSH
 	mtctr	r9
 	ld	r9,PACA_EXRFI+EX_R9(r13)
 	ld	r10,PACA_EXRFI+EX_R10(r13)
@@ -2997,32 +3001,7 @@ TRAMP_REAL_BEGIN(rfi_flush_fallback)
 	std	r10,PACA_EXRFI+EX_R10(r13)
 	std	r11,PACA_EXRFI+EX_R11(r13)
 	mfctr	r9
-	ld	r10,PACA_RFI_FLUSH_FALLBACK_AREA(r13)
-	ld	r11,PACA_L1D_FLUSH_SIZE(r13)
-	srdi	r11,r11,(7 + 3) /* 128 byte lines, unrolled 8x */
-	mtctr	r11
-	DCBT_BOOK3S_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */
-
-	/* order ld/st prior to dcbt stop all streams with flushing */
-	sync
-
-	/*
-	 * The load adresses are at staggered offsets within cachelines,
-	 * which suits some pipelines better (on others it should not
-	 * hurt).
-	 */
-1:
-	ld	r11,(0x80 + 8)*0(r10)
-	ld	r11,(0x80 + 8)*1(r10)
-	ld	r11,(0x80 + 8)*2(r10)
-	ld	r11,(0x80 + 8)*3(r10)
-	ld	r11,(0x80 + 8)*4(r10)
-	ld	r11,(0x80 + 8)*5(r10)
-	ld	r11,(0x80 + 8)*6(r10)
-	ld	r11,(0x80 + 8)*7(r10)
-	addi	r10,r10,0x80*8
-	bdnz	1b
-
+	L1D_DISPLACEMENT_FLUSH
 	mtctr	r9
 	ld	r9,PACA_EXRFI+EX_R9(r13)
 	ld	r10,PACA_EXRFI+EX_R10(r13)
@@ -3040,32 +3019,7 @@ TRAMP_REAL_BEGIN(hrfi_flush_fallback)
 	std	r10,PACA_EXRFI+EX_R10(r13)
 	std	r11,PACA_EXRFI+EX_R11(r13)
 	mfctr	r9
-	ld	r10,PACA_RFI_FLUSH_FALLBACK_AREA(r13)
-	ld	r11,PACA_L1D_FLUSH_SIZE(r13)
-	srdi	r11,r11,(7 + 3) /* 128 byte lines, unrolled 8x */
-	mtctr	r11
-	DCBT_BOOK3S_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */
-
-	/* order ld/st prior to dcbt stop all streams with flushing */
-	sync
-
-	/*
-	 * The load adresses are at staggered offsets within cachelines,
-	 * which suits some pipelines better (on others it should not
-	 * hurt).
-	 */
-1:
-	ld	r11,(0x80 + 8)*0(r10)
-	ld	r11,(0x80 + 8)*1(r10)
-	ld	r11,(0x80 + 8)*2(r10)
-	ld	r11,(0x80 + 8)*3(r10)
-	ld	r11,(0x80 + 8)*4(r10)
-	ld	r11,(0x80 + 8)*5(r10)
-	ld	r11,(0x80 + 8)*6(r10)
-	ld	r11,(0x80 + 8)*7(r10)
-	addi	r10,r10,0x80*8
-	bdnz	1b
-
+	L1D_DISPLACEMENT_FLUSH
 	mtctr	r9
 	ld	r9,PACA_EXRFI+EX_R9(r13)
 	ld	r10,PACA_EXRFI+EX_R10(r13)
@@ -3116,8 +3070,21 @@ TRAMP_REAL_BEGIN(rfscv_flush_fallback)
 	RFSCV
 
 USE_TEXT_SECTION()
-	MASKED_INTERRUPT
-	MASKED_INTERRUPT hsrr=1
+
+_GLOBAL(do_uaccess_flush)
+	UACCESS_FLUSH_FIXUP_SECTION
+	nop
+	nop
+	nop
+	blr
+	L1D_DISPLACEMENT_FLUSH
+	blr
+_ASM_NOKPROBE_SYMBOL(do_uaccess_flush)
+EXPORT_SYMBOL(do_uaccess_flush)
+
+
+MASKED_INTERRUPT
+MASKED_INTERRUPT hsrr=1
 
 #ifdef CONFIG_KVM_BOOK3S_64_HANDLER
 kvmppc_skip_interrupt:
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 7d447b43ad13..74fd47f46fa5 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -946,8 +946,12 @@ static enum l1d_flush_type enabled_flush_types;
 static void *l1d_flush_fallback_area;
 static bool no_rfi_flush;
 static bool no_entry_flush;
+static bool no_uaccess_flush;
 bool rfi_flush;
 bool entry_flush;
+bool uaccess_flush;
+DEFINE_STATIC_KEY_FALSE(uaccess_flush_key);
+EXPORT_SYMBOL(uaccess_flush_key);
 
 static int __init handle_no_rfi_flush(char *p)
 {
@@ -965,6 +969,14 @@ static int __init handle_no_entry_flush(char *p)
 }
 early_param("no_entry_flush", handle_no_entry_flush);
 
+static int __init handle_no_uaccess_flush(char *p)
+{
+	pr_info("uaccess-flush: disabled on command line.");
+	no_uaccess_flush = true;
+	return 0;
+}
+early_param("no_uaccess_flush", handle_no_uaccess_flush);
+
 /*
  * The RFI flush is not KPTI, but because users will see doco that says to use
  * nopti we hijack that option here to also disable the RFI flush.
@@ -1008,6 +1020,20 @@ void entry_flush_enable(bool enable)
 	entry_flush = enable;
 }
 
+void uaccess_flush_enable(bool enable)
+{
+	if (enable) {
+		do_uaccess_flush_fixups(enabled_flush_types);
+		static_branch_enable(&uaccess_flush_key);
+		on_each_cpu(do_nothing, NULL, 1);
+	} else {
+		static_branch_disable(&uaccess_flush_key);
+		do_uaccess_flush_fixups(L1D_FLUSH_NONE);
+	}
+
+	uaccess_flush = enable;
+}
+
 static void __ref init_fallback_flush(void)
 {
 	u64 l1d_size, limit;
@@ -1079,6 +1105,15 @@ void setup_entry_flush(bool enable)
 		entry_flush_enable(enable);
 }
 
+void setup_uaccess_flush(bool enable)
+{
+	if (cpu_mitigations_off())
+		return;
+
+	if (!no_uaccess_flush)
+		uaccess_flush_enable(enable);
+}
+
 #ifdef CONFIG_DEBUG_FS
 static int rfi_flush_set(void *data, u64 val)
 {
@@ -1132,10 +1167,37 @@ static int entry_flush_get(void *data, u64 *val)
 
 DEFINE_SIMPLE_ATTRIBUTE(fops_entry_flush, entry_flush_get, entry_flush_set, "%llu\n");
 
+static int uaccess_flush_set(void *data, u64 val)
+{
+	bool enable;
+
+	if (val == 1)
+		enable = true;
+	else if (val == 0)
+		enable = false;
+	else
+		return -EINVAL;
+
+	/* Only do anything if we're changing state */
+	if (enable != uaccess_flush)
+		uaccess_flush_enable(enable);
+
+	return 0;
+}
+
+static int uaccess_flush_get(void *data, u64 *val)
+{
+	*val = uaccess_flush ? 1 : 0;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_uaccess_flush, uaccess_flush_get, uaccess_flush_set, "%llu\n");
+
 static __init int rfi_flush_debugfs_init(void)
 {
 	debugfs_create_file("rfi_flush", 0600, powerpc_debugfs_root, NULL, &fops_rfi_flush);
 	debugfs_create_file("entry_flush", 0600, powerpc_debugfs_root, NULL, &fops_entry_flush);
+	debugfs_create_file("uaccess_flush", 0600, powerpc_debugfs_root, NULL, &fops_uaccess_flush);
 	return 0;
 }
 device_initcall(rfi_flush_debugfs_init);
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 715ec4d4614a..6db90cdf11da 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -131,6 +131,13 @@ SECTIONS
 		__stop___stf_entry_barrier_fixup = .;
 	}
 
+	. = ALIGN(8);
+	__uaccess_flush_fixup : AT(ADDR(__uaccess_flush_fixup) - LOAD_OFFSET) {
+		__start___uaccess_flush_fixup = .;
+		*(__uaccess_flush_fixup)
+		__stop___uaccess_flush_fixup = .;
+	}
+
 	. = ALIGN(8);
 	__entry_flush_fixup : AT(ADDR(__entry_flush_fixup) - LOAD_OFFSET) {
 		__start___entry_flush_fixup = .;
diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
index 70e83cfd74aa..321c12a9ef6b 100644
--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -234,6 +234,56 @@ void do_stf_barrier_fixups(enum stf_barrier_type types)
 	do_stf_exit_barrier_fixups(types);
 }
 
+void do_uaccess_flush_fixups(enum l1d_flush_type types)
+{
+	unsigned int instrs[4], *dest;
+	long *start, *end;
+	int i;
+
+	start = PTRRELOC(&__start___uaccess_flush_fixup);
+	end = PTRRELOC(&__stop___uaccess_flush_fixup);
+
+	instrs[0] = 0x60000000; /* nop */
+	instrs[1] = 0x60000000; /* nop */
+	instrs[2] = 0x60000000; /* nop */
+	instrs[3] = 0x4e800020; /* blr */
+
+	i = 0;
+	if (types == L1D_FLUSH_FALLBACK) {
+		instrs[3] = 0x60000000; /* nop */
+		/* fallthrough to fallback flush */
+	}
+
+	if (types & L1D_FLUSH_ORI) {
+		instrs[i++] = 0x63ff0000; /* ori 31,31,0 speculation barrier */
+		instrs[i++] = 0x63de0000; /* ori 30,30,0 L1d flush*/
+	}
+
+	if (types & L1D_FLUSH_MTTRIG)
+		instrs[i++] = 0x7c12dba6; /* mtspr TRIG2,r0 (SPR #882) */
+
+	for (i = 0; start < end; start++, i++) {
+		dest = (void *)start + *start;
+
+		pr_devel("patching dest %lx\n", (unsigned long)dest);
+
+		patch_instruction((struct ppc_inst *)dest, ppc_inst(instrs[0]));
+
+		patch_instruction((struct ppc_inst *)(dest + 1), ppc_inst(instrs[1]));
+		patch_instruction((struct ppc_inst *)(dest + 2), ppc_inst(instrs[2]));
+		patch_instruction((struct ppc_inst *)(dest + 3), ppc_inst(instrs[3]));
+	}
+
+	printk(KERN_DEBUG "uaccess-flush: patched %d locations (%s flush)\n", i,
+		(types == L1D_FLUSH_NONE)       ? "no" :
+		(types == L1D_FLUSH_FALLBACK)   ? "fallback displacement" :
+		(types &  L1D_FLUSH_ORI)        ? (types & L1D_FLUSH_MTTRIG)
+							? "ori+mttrig type"
+							: "ori type" :
+		(types &  L1D_FLUSH_MTTRIG)     ? "mttrig type"
+						: "unknown");
+}
+
 void do_entry_flush_fixups(enum l1d_flush_type types)
 {
 	unsigned int instrs[3], *dest;
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index d04a085c423d..087ec92acfc4 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -124,10 +124,12 @@ static void pnv_setup_rfi_flush(void)
 
 	/*
 	 * If we are non-Power9 bare metal, we don't need to flush on kernel
-	 * entry: it fixes a P9 specific vulnerability.
+	 * entry or after user access: they fix a P9 specific vulnerability.
 	 */
-	if (!pvr_version_is(PVR_POWER9))
+	if (!pvr_version_is(PVR_POWER9)) {
 		security_ftr_clear(SEC_FTR_L1D_FLUSH_ENTRY);
+		security_ftr_clear(SEC_FTR_L1D_FLUSH_UACCESS);
+	}
 
 	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && \
 		 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR)   || \
@@ -139,6 +141,10 @@ static void pnv_setup_rfi_flush(void)
 	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 		 security_ftr_enabled(SEC_FTR_L1D_FLUSH_ENTRY);
 	setup_entry_flush(enable);
+
+	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
+		 security_ftr_enabled(SEC_FTR_L1D_FLUSH_UACCESS);
+	setup_uaccess_flush(enable);
 }
 
 static void __init pnv_check_guarded_cores(void)
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 8136c5368ee4..3617cdb079f6 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -583,6 +583,10 @@ void pseries_setup_rfi_flush(void)
 	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 		 security_ftr_enabled(SEC_FTR_L1D_FLUSH_ENTRY);
 	setup_entry_flush(enable);
+
+	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
+		 security_ftr_enabled(SEC_FTR_L1D_FLUSH_UACCESS);
+	setup_uaccess_flush(enable);
 }
 
 #ifdef CONFIG_PCI_IOV
-- 
2.25.1

[PATCH 4/7] powerpc: Only include kup-radix.h for 64-bit Book3S

[Daniel Axtens]

From: Michael Ellerman <mpe@ellerman.id.au>

In kup.h we currently include kup-radix.h for all 64-bit builds, which
includes Book3S and Book3E. The latter doesn't make sense, Book3E
never uses the Radix MMU.

This has worked up until now, but almost by accident, and the recent
uaccess flush changes introduced a build breakage on Book3E because of
the bad structure of the code.

So disentangle things so that we only use kup-radix.h for Book3S. This
requires some more stubs in kup.h and fixing an include in
syscall_64.c.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 arch/powerpc/include/asm/book3s/64/kup-radix.h |  4 ++--
 arch/powerpc/include/asm/kup.h                 | 11 ++++++++---
 arch/powerpc/kernel/syscall_64.c               |  2 +-
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/kup-radix.h b/arch/powerpc/include/asm/book3s/64/kup-radix.h
index 97c2394e7dea..28716e2f13e3 100644
--- a/arch/powerpc/include/asm/book3s/64/kup-radix.h
+++ b/arch/powerpc/include/asm/book3s/64/kup-radix.h
@@ -27,6 +27,7 @@
 #endif
 .endm
 
+#ifdef CONFIG_PPC_KUAP
 .macro kuap_check_amr gpr1, gpr2
 #ifdef CONFIG_PPC_KUAP_DEBUG
 	BEGIN_MMU_FTR_SECTION_NESTED(67)
@@ -38,6 +39,7 @@
 	END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_RADIX_KUAP, 67)
 #endif
 .endm
+#endif
 
 .macro kuap_save_amr_and_lock gpr1, gpr2, use_cr, msr_pr_cr
 #ifdef CONFIG_PPC_KUAP
@@ -148,8 +150,6 @@ static inline unsigned long kuap_get_and_check_amr(void)
 	return 0UL;
 }
 
-static inline void kuap_check_amr(void) { }
-
 static inline unsigned long get_kuap(void)
 {
 	return AMR_KUAP_BLOCKED;
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index 0f5c606ae057..0d93331d0fab 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h
@@ -14,7 +14,7 @@
 #define KUAP_CURRENT_WRITE	8
 #define KUAP_CURRENT		(KUAP_CURRENT_READ | KUAP_CURRENT_WRITE)
 
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_BOOK3S_64
 #include <asm/book3s/64/kup-radix.h>
 #endif
 #ifdef CONFIG_PPC_8xx
@@ -35,6 +35,9 @@
 .macro kuap_check	current, gpr
 .endm
 
+.macro kuap_check_amr	gpr1, gpr2
+.endm
+
 #endif
 
 #else /* !__ASSEMBLY__ */
@@ -60,19 +63,21 @@ bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
 	return false;
 }
 
+static inline void kuap_check_amr(void) { }
+
 /*
  * book3s/64/kup-radix.h defines these functions for the !KUAP case to flush
  * the L1D cache after user accesses. Only include the empty stubs for other
  * platforms.
  */
-#ifndef CONFIG_PPC64
+#ifndef CONFIG_PPC_BOOK3S_64
 static inline void allow_user_access(void __user *to, const void __user *from,
 				     unsigned long size, unsigned long dir) { }
 static inline void prevent_user_access(void __user *to, const void __user *from,
 				       unsigned long size, unsigned long dir) { }
 static inline unsigned long prevent_user_access_return(void) { return 0UL; }
 static inline void restore_user_access(unsigned long flags) { }
-#endif /* CONFIG_PPC64 */
+#endif /* CONFIG_PPC_BOOK3S_64 */
 #endif /* CONFIG_PPC_KUAP */
 
 static inline void allow_read_from_user(const void __user *from, unsigned long size)
diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
index 8e50818aa50b..310bcd768cd5 100644
--- a/arch/powerpc/kernel/syscall_64.c
+++ b/arch/powerpc/kernel/syscall_64.c
@@ -2,7 +2,7 @@
 
 #include <linux/err.h>
 #include <asm/asm-prototypes.h>
-#include <asm/book3s/64/kup-radix.h>
+#include <asm/kup.h>
 #include <asm/cputime.h>
 #include <asm/hw_irq.h>
 #include <asm/kprobes.h>
-- 
2.25.1

[PATCH 5/7] selftests/powerpc: entry flush test

[Daniel Axtens]

Add a test modelled on the RFI flush test which counts the number
of L1D misses doing a simple syscall with the entry flush on and off.

For simplicity of backporting, this test duplicates a lot of code from
rfi_flush. We clean that up in the next patch.

Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 .../selftests/powerpc/security/.gitignore     |   1 +
 .../selftests/powerpc/security/Makefile       |   2 +-
 .../selftests/powerpc/security/entry_flush.c  | 198 ++++++++++++++++++
 3 files changed, 200 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/powerpc/security/entry_flush.c

diff --git a/tools/testing/selftests/powerpc/security/.gitignore b/tools/testing/selftests/powerpc/security/.gitignore
index f795e06f5ae3..4257a1f156bb 100644
--- a/tools/testing/selftests/powerpc/security/.gitignore
+++ b/tools/testing/selftests/powerpc/security/.gitignore
@@ -1,2 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 rfi_flush
+entry_flush
diff --git a/tools/testing/selftests/powerpc/security/Makefile b/tools/testing/selftests/powerpc/security/Makefile
index eadbbff50be6..921152caf1dc 100644
--- a/tools/testing/selftests/powerpc/security/Makefile
+++ b/tools/testing/selftests/powerpc/security/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0+
 
-TEST_GEN_PROGS := rfi_flush spectre_v2
+TEST_GEN_PROGS := rfi_flush entry_flush spectre_v2
 top_srcdir = ../../../../..
 
 CFLAGS += -I../../../../../usr/include
diff --git a/tools/testing/selftests/powerpc/security/entry_flush.c b/tools/testing/selftests/powerpc/security/entry_flush.c
new file mode 100644
index 000000000000..7ae7e37204c5
--- /dev/null
+++ b/tools/testing/selftests/powerpc/security/entry_flush.c
@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * Copyright 2018 IBM Corporation.
+ */
+
+#define __SANE_USERSPACE_TYPES__
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <malloc.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include "utils.h"
+
+#define CACHELINE_SIZE 128
+
+struct perf_event_read {
+	__u64 nr;
+	__u64 l1d_misses;
+};
+
+static inline __u64 load(void *addr)
+{
+	__u64 tmp;
+
+	asm volatile("ld %0,0(%1)" : "=r"(tmp) : "b"(addr));
+
+	return tmp;
+}
+
+static void syscall_loop(char *p, unsigned long iterations,
+			 unsigned long zero_size)
+{
+	for (unsigned long i = 0; i < iterations; i++) {
+		for (unsigned long j = 0; j < zero_size; j += CACHELINE_SIZE)
+			load(p + j);
+		getppid();
+	}
+}
+
+static void sigill_handler(int signr, siginfo_t *info, void *unused)
+{
+	static int warned;
+	ucontext_t *ctx = (ucontext_t *)unused;
+	unsigned long *pc = &UCONTEXT_NIA(ctx);
+
+	/* mtspr 3,RS to check for move to DSCR below */
+	if ((*((unsigned int *)*pc) & 0xfc1fffff) == 0x7c0303a6) {
+		if (!warned++)
+			printf("WARNING: Skipping over dscr setup. Consider running 'ppc64_cpu --dscr=1' manually.\n");
+		*pc += 4;
+	} else {
+		printf("SIGILL at %p\n", pc);
+		abort();
+	}
+}
+
+static void set_dscr(unsigned long val)
+{
+	static int init;
+	struct sigaction sa;
+
+	if (!init) {
+		memset(&sa, 0, sizeof(sa));
+		sa.sa_sigaction = sigill_handler;
+		sa.sa_flags = SA_SIGINFO;
+		if (sigaction(SIGILL, &sa, NULL))
+			perror("sigill_handler");
+		init = 1;
+	}
+
+	asm volatile("mtspr %1,%0" : : "r" (val), "i" (SPRN_DSCR));
+}
+
+int entry_flush_test(void)
+{
+	char *p;
+	int repetitions = 10;
+	int fd, passes = 0, iter, rc = 0;
+	struct perf_event_read v;
+	__u64 l1d_misses_total = 0;
+	unsigned long iterations = 100000, zero_size = 24 * 1024;
+	unsigned long l1d_misses_expected;
+	int rfi_flush_orig;
+	int entry_flush, entry_flush_orig;
+
+	SKIP_IF(geteuid() != 0);
+
+	// The PMU event we use only works on Power7 or later
+	SKIP_IF(!have_hwcap(PPC_FEATURE_ARCH_2_06));
+
+	if (read_debugfs_file("powerpc/rfi_flush", &rfi_flush_orig) < 0) {
+		perror("Unable to read powerpc/rfi_flush debugfs file");
+		SKIP_IF(1);
+	}
+
+	if (read_debugfs_file("powerpc/entry_flush", &entry_flush_orig) < 0) {
+		perror("Unable to read powerpc/entry_flush debugfs file");
+		SKIP_IF(1);
+	}
+
+	if (rfi_flush_orig != 0) {
+		if (write_debugfs_file("powerpc/rfi_flush", 0) < 0) {
+			perror("error writing to powerpc/rfi_flush debugfs file");
+			FAIL_IF(1);
+		}
+	}
+
+	entry_flush = entry_flush_orig;
+
+	fd = perf_event_open_counter(PERF_TYPE_RAW, /* L1d miss */ 0x400f0, -1);
+	FAIL_IF(fd < 0);
+
+	p = (char *)memalign(zero_size, CACHELINE_SIZE);
+
+	FAIL_IF(perf_event_enable(fd));
+
+	// disable L1 prefetching
+	set_dscr(1);
+
+	iter = repetitions;
+
+	/*
+	 * We expect to see l1d miss for each cacheline access when entry_flush
+	 * is set. Allow a small variation on this.
+	 */
+	l1d_misses_expected = iterations * (zero_size / CACHELINE_SIZE - 2);
+
+again:
+	FAIL_IF(perf_event_reset(fd));
+
+	syscall_loop(p, iterations, zero_size);
+
+	FAIL_IF(read(fd, &v, sizeof(v)) != sizeof(v));
+
+	if (entry_flush && v.l1d_misses >= l1d_misses_expected)
+		passes++;
+	else if (!entry_flush && v.l1d_misses < (l1d_misses_expected / 2))
+		passes++;
+
+	l1d_misses_total += v.l1d_misses;
+
+	while (--iter)
+		goto again;
+
+	if (passes < repetitions) {
+		printf("FAIL (L1D misses with entry_flush=%d: %llu %c %lu) [%d/%d failures]\n",
+		       entry_flush, l1d_misses_total, entry_flush ? '<' : '>',
+		       entry_flush ? repetitions * l1d_misses_expected :
+		       repetitions * l1d_misses_expected / 2,
+		       repetitions - passes, repetitions);
+		rc = 1;
+	} else {
+		printf("PASS (L1D misses with entry_flush=%d: %llu %c %lu) [%d/%d pass]\n",
+		       entry_flush, l1d_misses_total, entry_flush ? '>' : '<',
+		       entry_flush ? repetitions * l1d_misses_expected :
+		       repetitions * l1d_misses_expected / 2,
+		       passes, repetitions);
+	}
+
+	if (entry_flush == entry_flush_orig) {
+		entry_flush = !entry_flush_orig;
+		if (write_debugfs_file("powerpc/entry_flush", entry_flush) < 0) {
+			perror("error writing to powerpc/entry_flush debugfs file");
+			return 1;
+		}
+		iter = repetitions;
+		l1d_misses_total = 0;
+		passes = 0;
+		goto again;
+	}
+
+	perf_event_disable(fd);
+	close(fd);
+
+	set_dscr(0);
+
+	if (write_debugfs_file("powerpc/rfi_flush", rfi_flush_orig) < 0) {
+		perror("unable to restore original value of powerpc/rfi_flush debugfs file");
+		return 1;
+	}
+
+	if (write_debugfs_file("powerpc/entry_flush", entry_flush_orig) < 0) {
+		perror("unable to restore original value of powerpc/entry_flush debugfs file");
+		return 1;
+	}
+
+	return rc;
+}
+
+int main(int argc, char *argv[])
+{
+	return test_harness(entry_flush_test, "entry_flush_test");
+}
-- 
2.25.1

[PATCH 6/7] selftests/powerpc: refactor entry and rfi_flush tests

[Daniel Axtens]

For simplicity in backporting, the original entry_flush test contained
a lot of duplicated code from the rfi_flush test. De-duplicate that code.

Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 .../testing/selftests/powerpc/include/utils.h |  5 ++
 .../selftests/powerpc/security/Makefile       |  2 +
 .../selftests/powerpc/security/entry_flush.c  | 61 +---------------
 .../selftests/powerpc/security/flush_utils.c  | 70 +++++++++++++++++++
 .../selftests/powerpc/security/flush_utils.h  | 17 +++++
 .../selftests/powerpc/security/rfi_flush.c    | 61 +---------------
 6 files changed, 96 insertions(+), 120 deletions(-)
 create mode 100644 tools/testing/selftests/powerpc/security/flush_utils.c
 create mode 100644 tools/testing/selftests/powerpc/security/flush_utils.h

diff --git a/tools/testing/selftests/powerpc/include/utils.h b/tools/testing/selftests/powerpc/include/utils.h
index 052b5a775dc2..b7d188fc87c7 100644
--- a/tools/testing/selftests/powerpc/include/utils.h
+++ b/tools/testing/selftests/powerpc/include/utils.h
@@ -42,6 +42,11 @@ int perf_event_enable(int fd);
 int perf_event_disable(int fd);
 int perf_event_reset(int fd);
 
+struct perf_event_read {
+	__u64 nr;
+	__u64 l1d_misses;
+};
+
 #if !defined(__GLIBC_PREREQ) || !__GLIBC_PREREQ(2, 30)
 #include <unistd.h>
 #include <sys/syscall.h>
diff --git a/tools/testing/selftests/powerpc/security/Makefile b/tools/testing/selftests/powerpc/security/Makefile
index 921152caf1dc..f25e854fe370 100644
--- a/tools/testing/selftests/powerpc/security/Makefile
+++ b/tools/testing/selftests/powerpc/security/Makefile
@@ -11,3 +11,5 @@ $(TEST_GEN_PROGS): ../harness.c ../utils.c
 
 $(OUTPUT)/spectre_v2: CFLAGS += -m64
 $(OUTPUT)/spectre_v2: ../pmu/event.c branch_loops.S
+$(OUTPUT)/rfi_flush: flush_utils.c
+$(OUTPUT)/entry_flush: flush_utils.c
diff --git a/tools/testing/selftests/powerpc/security/entry_flush.c b/tools/testing/selftests/powerpc/security/entry_flush.c
index 7ae7e37204c5..78cf914fa321 100644
--- a/tools/testing/selftests/powerpc/security/entry_flush.c
+++ b/tools/testing/selftests/powerpc/security/entry_flush.c
@@ -15,66 +15,7 @@
 #include <string.h>
 #include <stdio.h>
 #include "utils.h"
-
-#define CACHELINE_SIZE 128
-
-struct perf_event_read {
-	__u64 nr;
-	__u64 l1d_misses;
-};
-
-static inline __u64 load(void *addr)
-{
-	__u64 tmp;
-
-	asm volatile("ld %0,0(%1)" : "=r"(tmp) : "b"(addr));
-
-	return tmp;
-}
-
-static void syscall_loop(char *p, unsigned long iterations,
-			 unsigned long zero_size)
-{
-	for (unsigned long i = 0; i < iterations; i++) {
-		for (unsigned long j = 0; j < zero_size; j += CACHELINE_SIZE)
-			load(p + j);
-		getppid();
-	}
-}
-
-static void sigill_handler(int signr, siginfo_t *info, void *unused)
-{
-	static int warned;
-	ucontext_t *ctx = (ucontext_t *)unused;
-	unsigned long *pc = &UCONTEXT_NIA(ctx);
-
-	/* mtspr 3,RS to check for move to DSCR below */
-	if ((*((unsigned int *)*pc) & 0xfc1fffff) == 0x7c0303a6) {
-		if (!warned++)
-			printf("WARNING: Skipping over dscr setup. Consider running 'ppc64_cpu --dscr=1' manually.\n");
-		*pc += 4;
-	} else {
-		printf("SIGILL at %p\n", pc);
-		abort();
-	}
-}
-
-static void set_dscr(unsigned long val)
-{
-	static int init;
-	struct sigaction sa;
-
-	if (!init) {
-		memset(&sa, 0, sizeof(sa));
-		sa.sa_sigaction = sigill_handler;
-		sa.sa_flags = SA_SIGINFO;
-		if (sigaction(SIGILL, &sa, NULL))
-			perror("sigill_handler");
-		init = 1;
-	}
-
-	asm volatile("mtspr %1,%0" : : "r" (val), "i" (SPRN_DSCR));
-}
+#include "flush_utils.h"
 
 int entry_flush_test(void)
 {
diff --git a/tools/testing/selftests/powerpc/security/flush_utils.c b/tools/testing/selftests/powerpc/security/flush_utils.c
new file mode 100644
index 000000000000..0c3c4c40c7fb
--- /dev/null
+++ b/tools/testing/selftests/powerpc/security/flush_utils.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * Copyright 2018 IBM Corporation.
+ */
+
+#define __SANE_USERSPACE_TYPES__
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include "utils.h"
+#include "flush_utils.h"
+
+static inline __u64 load(void *addr)
+{
+	__u64 tmp;
+
+	asm volatile("ld %0,0(%1)" : "=r"(tmp) : "b"(addr));
+
+	return tmp;
+}
+
+void syscall_loop(char *p, unsigned long iterations,
+		  unsigned long zero_size)
+{
+	for (unsigned long i = 0; i < iterations; i++) {
+		for (unsigned long j = 0; j < zero_size; j += CACHELINE_SIZE)
+			load(p + j);
+		getppid();
+	}
+}
+
+static void sigill_handler(int signr, siginfo_t *info, void *unused)
+{
+	static int warned;
+	ucontext_t *ctx = (ucontext_t *)unused;
+	unsigned long *pc = &UCONTEXT_NIA(ctx);
+
+	/* mtspr 3,RS to check for move to DSCR below */
+	if ((*((unsigned int *)*pc) & 0xfc1fffff) == 0x7c0303a6) {
+		if (!warned++)
+			printf("WARNING: Skipping over dscr setup. Consider running 'ppc64_cpu --dscr=1' manually.\n");
+		*pc += 4;
+	} else {
+		printf("SIGILL at %p\n", pc);
+		abort();
+	}
+}
+
+void set_dscr(unsigned long val)
+{
+	static int init;
+	struct sigaction sa;
+
+	if (!init) {
+		memset(&sa, 0, sizeof(sa));
+		sa.sa_sigaction = sigill_handler;
+		sa.sa_flags = SA_SIGINFO;
+		if (sigaction(SIGILL, &sa, NULL))
+			perror("sigill_handler");
+		init = 1;
+	}
+
+	asm volatile("mtspr %1,%0" : : "r" (val), "i" (SPRN_DSCR));
+}
diff --git a/tools/testing/selftests/powerpc/security/flush_utils.h b/tools/testing/selftests/powerpc/security/flush_utils.h
new file mode 100644
index 000000000000..07a5eb301466
--- /dev/null
+++ b/tools/testing/selftests/powerpc/security/flush_utils.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+/*
+ * Copyright 2018 IBM Corporation.
+ */
+
+#ifndef _SELFTESTS_POWERPC_SECURITY_FLUSH_UTILS_H
+#define _SELFTESTS_POWERPC_SECURITY_FLUSH_UTILS_H
+
+#define CACHELINE_SIZE 128
+
+void syscall_loop(char *p, unsigned long iterations,
+		  unsigned long zero_size);
+
+void set_dscr(unsigned long val);
+
+#endif /* _SELFTESTS_POWERPC_SECURITY_FLUSH_UTILS_H */
diff --git a/tools/testing/selftests/powerpc/security/rfi_flush.c b/tools/testing/selftests/powerpc/security/rfi_flush.c
index 4e7b2776c367..7565fd786640 100644
--- a/tools/testing/selftests/powerpc/security/rfi_flush.c
+++ b/tools/testing/selftests/powerpc/security/rfi_flush.c
@@ -10,71 +10,12 @@
 #include <stdint.h>
 #include <malloc.h>
 #include <unistd.h>
-#include <signal.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 #include "utils.h"
+#include "flush_utils.h"
 
-#define CACHELINE_SIZE 128
-
-struct perf_event_read {
-	__u64 nr;
-	__u64 l1d_misses;
-};
-
-static inline __u64 load(void *addr)
-{
-	__u64 tmp;
-
-	asm volatile("ld %0,0(%1)" : "=r"(tmp) : "b"(addr));
-
-	return tmp;
-}
-
-static void syscall_loop(char *p, unsigned long iterations,
-			 unsigned long zero_size)
-{
-	for (unsigned long i = 0; i < iterations; i++) {
-		for (unsigned long j = 0; j < zero_size; j += CACHELINE_SIZE)
-			load(p + j);
-		getppid();
-	}
-}
-
-static void sigill_handler(int signr, siginfo_t *info, void *unused)
-{
-	static int warned = 0;
-	ucontext_t *ctx = (ucontext_t *)unused;
-	unsigned long *pc = &UCONTEXT_NIA(ctx);
-
-	/* mtspr 3,RS to check for move to DSCR below */
-	if ((*((unsigned int *)*pc) & 0xfc1fffff) == 0x7c0303a6) {
-		if (!warned++)
-			printf("WARNING: Skipping over dscr setup. Consider running 'ppc64_cpu --dscr=1' manually.\n");
-		*pc += 4;
-	} else {
-		printf("SIGILL at %p\n", pc);
-		abort();
-	}
-}
-
-static void set_dscr(unsigned long val)
-{
-	static int init = 0;
-	struct sigaction sa;
-
-	if (!init) {
-		memset(&sa, 0, sizeof(sa));
-		sa.sa_sigaction = sigill_handler;
-		sa.sa_flags = SA_SIGINFO;
-		if (sigaction(SIGILL, &sa, NULL))
-			perror("sigill_handler");
-		init = 1;
-	}
-
-	asm volatile("mtspr %1,%0" : : "r" (val), "i" (SPRN_DSCR));
-}
 
 int rfi_flush_test(void)
 {
-- 
2.25.1

[PATCH 7/7] powerpc/64s: rename pnv|pseries_setup_rfi_flush to _setup_security_mitigations

[Daniel Axtens]

pseries|pnv_setup_rfi_flush already does the count cache flush setup, and
we just added entry and uaccess flushes. So the name is not very accurate
any more. In both platforms we then also immediately setup the STF flush.

Rename them to _setup_security_mitigations and fold the STF flush in.

Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 arch/powerpc/platforms/powernv/setup.c    | 7 ++++---
 arch/powerpc/platforms/pseries/mobility.c | 4 ++--
 arch/powerpc/platforms/pseries/pseries.h  | 2 +-
 arch/powerpc/platforms/pseries/setup.c    | 7 ++++---
 4 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 087ec92acfc4..46115231a3b2 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -98,7 +98,7 @@ static void init_fw_feat_flags(struct device_node *np)
 		security_ftr_clear(SEC_FTR_BNDS_CHK_SPEC_BAR);
 }
 
-static void pnv_setup_rfi_flush(void)
+static void pnv_setup_security_mitigations(void)
 {
 	struct device_node *np, *fw_features;
 	enum l1d_flush_type type;
@@ -145,6 +145,8 @@ static void pnv_setup_rfi_flush(void)
 	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 		 security_ftr_enabled(SEC_FTR_L1D_FLUSH_UACCESS);
 	setup_uaccess_flush(enable);
+
+	setup_stf_barrier();
 }
 
 static void __init pnv_check_guarded_cores(void)
@@ -173,8 +175,7 @@ static void __init pnv_setup_arch(void)
 {
 	set_arch_panic_timeout(10, ARCH_PANIC_TIMEOUT);
 
-	pnv_setup_rfi_flush();
-	setup_stf_barrier();
+	pnv_setup_security_mitigations();
 
 	/* Initialize SMP */
 	pnv_smp_init();
diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index d6f4162478a5..2f73cb5bf12d 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -349,8 +349,8 @@ void post_mobility_fixup(void)
 
 	cpus_read_unlock();
 
-	/* Possibly switch to a new RFI flush type */
-	pseries_setup_rfi_flush();
+	/* Possibly switch to a new L1 flush type */
+	pseries_setup_security_mitigations();
 
 	/* Reinitialise system information for hv-24x7 */
 	read_24x7_sys_info();
diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h
index 13fa370a87e4..593840847cd3 100644
--- a/arch/powerpc/platforms/pseries/pseries.h
+++ b/arch/powerpc/platforms/pseries/pseries.h
@@ -111,7 +111,7 @@ static inline unsigned long cmo_get_page_size(void)
 
 int dlpar_workqueue_init(void);
 
-void pseries_setup_rfi_flush(void);
+void pseries_setup_security_mitigations(void);
 void pseries_lpar_read_hblkrm_characteristics(void);
 
 #endif /* _PSERIES_PSERIES_H */
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 3617cdb079f6..090c13f6c881 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -542,7 +542,7 @@ static void init_cpu_char_feature_flags(struct h_cpu_char_result *result)
 		security_ftr_clear(SEC_FTR_BNDS_CHK_SPEC_BAR);
 }
 
-void pseries_setup_rfi_flush(void)
+void pseries_setup_security_mitigations(void)
 {
 	struct h_cpu_char_result result;
 	enum l1d_flush_type types;
@@ -587,6 +587,8 @@ void pseries_setup_rfi_flush(void)
 	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 		 security_ftr_enabled(SEC_FTR_L1D_FLUSH_UACCESS);
 	setup_uaccess_flush(enable);
+
+	setup_stf_barrier();
 }
 
 #ifdef CONFIG_PCI_IOV
@@ -776,8 +778,7 @@ static void __init pSeries_setup_arch(void)
 
 	fwnmi_init();
 
-	pseries_setup_rfi_flush();
-	setup_stf_barrier();
+	pseries_setup_security_mitigations();
 	pseries_lpar_read_hblkrm_characteristics();
 
 	/* By default, only probe PCI (can be overridden by rtas_pci) */
-- 
2.25.1

Re: [PATCH 3/7] powerpc/64s: flush L1D after user accesses

[Qian Cai]

On Fri, 2020-11-20 at 10:13 +1100, Daniel Axtens wrote:
> From: Nicholas Piggin <npiggin@gmail.com>
> 
> IBM Power9 processors can speculatively operate on data in the L1 cache
> before it has been completely validated, via a way-prediction mechanism. It
> is not possible for an attacker to determine the contents of impermissible
> memory using this method, since these systems implement a combination of
> hardware and software security measures to prevent scenarios where
> protected data could be leaked.
> 
> However these measures don't address the scenario where an attacker induces
> the operating system to speculatively execute instructions using data that
> the attacker controls. This can be used for example to speculatively bypass
> "kernel user access prevention" techniques, as discovered by Anthony
> Steinhauser of Google's Safeside Project. This is not an attack by itself,
> but there is a possibility it could be used in conjunction with
> side-channels or other weaknesses in the privileged code to construct an
> attack.
> 
> This issue can be mitigated by flushing the L1 cache between privilege
> boundaries of concern. This patch flushes the L1 cache after user accesses.
> 
> This is part of the fix for CVE-2020-4788.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> ---
>  .../admin-guide/kernel-parameters.txt         |  4 +
>  .../powerpc/include/asm/book3s/64/kup-radix.h | 66 ++++++++------
>  arch/powerpc/include/asm/exception-64s.h      |  3 +
>  arch/powerpc/include/asm/feature-fixups.h     |  9 ++
>  arch/powerpc/include/asm/kup.h                | 19 +++--
>  arch/powerpc/include/asm/security_features.h  |  3 +
>  arch/powerpc/include/asm/setup.h              |  1 +
>  arch/powerpc/kernel/exceptions-64s.S          | 85 ++++++-------------
>  arch/powerpc/kernel/setup_64.c                | 62 ++++++++++++++
>  arch/powerpc/kernel/vmlinux.lds.S             |  7 ++
>  arch/powerpc/lib/feature-fixups.c             | 50 +++++++++++
>  arch/powerpc/platforms/powernv/setup.c        | 10 ++-
>  arch/powerpc/platforms/pseries/setup.c        |  4 +
>  13 files changed, 233 insertions(+), 90 deletions(-)
[]
> diff --git a/arch/powerpc/include/asm/book3s/64/kup-radix.h b/arch/powerpc/include/asm/book3s/64/kup-radix.h
> index 3ee1ec60be84..97c2394e7dea 100644
> --- a/arch/powerpc/include/asm/book3s/64/kup-radix.h
> +++ b/arch/powerpc/include/asm/book3s/64/kup-radix.h
[]
> +static inline bool
> +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
> +{
> +	return WARN(mmu_has_feature(MMU_FTR_RADIX_KUAP) &&
> +		    (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),
> +		    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
> +}

A simple "echo t > /proc/sysrq-trigger" will trigger this warning almost
endlessly on Power8 NV.

.config: 
https://cailca.coding.net/public/linux/mm/git/files/master/powerpc.config

[  391.734028][ T1986] Bug: Read fault blocked by AMR!
[  391.734032][ T1986] WARNING: CPU: 80 PID: 1986 at arch/powerpc/include/asm/book3s/64/kup-radix.h:145 do_page_fault+0x8fc/0xb70
[  391.734232][ T1986] Modules linked in: kvm_hv kvm ip_tables x_tables sd_mod ahci libahci tg3 libata firmware_class libphy dm_mirror dm_region_hash dm_log dm_mod
[  391.734425][ T1986] CPU: 80 PID: 1986 Comm: bash Tainted: G        W         5.10.0-rc6-next-20201203+ #3
[  391.734535][ T1986] NIP:  c00000000004dd1c LR: c00000000004dd18 CTR: 0000000000000000
[  391.734648][ T1986] REGS: c00020003a0bf3a0 TRAP: 0700   Tainted: G        W          (5.10.0-rc6-next-20201203+)
[  391.734768][ T1986] MSR:  9000000000021033 <SF,HV,ME,IR,DR,RI,LE>  CR: 48222284  XER: 00000000
[  391.734906][ T1986] CFAR: c0000000000bb05c IRQMASK: 1 
[  391.734906][ T1986] GPR00: c00000000004dd18 c00020003a0bf630 c000000007fe0d00 000000000000001f 
[  391.734906][ T1986] GPR04: c000000000f1cc58 0000000000000003 0000000000000027 c000201cc6207218 
[  391.734906][ T1986] GPR08: 0000000000000023 0000000000000002 c00020004753bd80 c000000007f1cee8 
[  391.734906][ T1986] GPR12: 0000000000002000 c000201fff7f8380 0000000040000000 0000000110929798 
[  391.734906][ T1986] GPR16: 0000000110929724 00000001108c6988 000000011085f290 000000011092d568 
[  391.734906][ T1986] GPR20: 00000001229f1f80 0000000000000001 0000000000000001 c000000000aa8dc8 
[  391.734906][ T1986] GPR24: c000000000ab4a00 c00020001cc8c880 0000000000000000 0000000000000000 
[  391.734906][ T1986] GPR28: c00000000801aa18 0000000000000160 c00020003a0bf760 0000000000000300 
[  391.735865][ T1986] NIP [c00000000004dd1c] do_page_fault+0x8fc/0xb70
[  391.735947][ T1986] LR [c00000000004dd18] do_page_fault+0x8f8/0xb70
[  391.736033][ T1986] Call Trace:
[  391.736072][ T1986] [c00020003a0bf630] [c00000000004dd18] do_page_fault+0x8f8/0xb70 (unreliable)
[  391.736181][ T1986] [c00020003a0bf6f0] [c00000000000c1b8] handle_page_fault+0x10/0x2c
[  391.736294][ T1986] --- interrupt: 300 at copy_from_kernel_nofault+0x68/0x190
[  391.736294][ T1986]     LR = copy_from_kernel_nofault+0x40/0x190
[  391.736441][ T1986] [c00020003a0bf9f0] [c00020003a0bfa30] 0xc00020003a0bfa30 (unreliable)
[  391.736565][ T1986] [c00020003a0bfa30] [c0000000000edd98] print_worker_info+0xe8/0x1c0
[  391.736672][ T1986] [c00020003a0bfaf0] [c000000000104b0c] sched_show_task+0x2dc/0x350
[  391.736807][ T1986] [c00020003a0bfb70] [c000000000112cd8] show_state_filter+0x148/0x320
[  391.736899][ T1986] [c00020003a0bfbe0] [c00000000070a3f4] sysrq_handle_showstate+0x24/0x40
[  391.736995][ T1986] [c00020003a0bfc00] [c00000000070add4] __handle_sysrq+0x164/0x280
[  391.737111][ T1986] [c00020003a0bfca0] [c00000000070b03c] write_sysrq_trigger+0xfc/0x13c
[  391.737233][ T1986] [c00020003a0bfce0] [c0000000004c579c] proc_reg_write+0x10c/0x1b0
[  391.737327][ T1986] [c00020003a0bfd10] [c0000000003e5ec4] vfs_write+0xf4/0x480
[  391.737431][ T1986] [c00020003a0bfd70] [c0000000003e642c] ksys_write+0x7c/0x140
[  391.737536][ T1986] [c00020003a0bfdc0] [c00000000002c578] system_call_exception+0xf8/0x1d0
[  391.737623][ T1986] [c00020003a0bfe20] [c00000000000d1c8] system_call_common+0xe8/0x218
[  391.737708][ T1986] Instruction dump:
[  391.737777][ T1986] 60000000 2fbb0000 e93e0168 419e007c 2fa90000 3c82f8ac 388467a0 409cfed4 
[  391.737913][ T1986] 3c62f8ac 386368a8 4806d2e1 60000000 <0fe00000> e80100d0 3ae0000b eb410090 
[  391.738041][ T1986] irq event stamp: 126198
[  391.738077][ T1986] hardirqs last  enabled at (126197): [<c00000000002cbf4>] interrupt_exit_kernel_prepare+0xb4/0x250
[  391.738196][ T1986] hardirqs last disabled at (126198): [<c00000000000897c>] data_access_common_virt+0x16c/0x180
[  391.738327][ T1986] softirqs last  enabled at (126196): [<c000000000948f08>] __do_softirq+0x388/0x704
[  391.738427][ T1986] softirqs last disabled at (126191): [<c0000000000c75b8>] irq_exit+0x198/0x1c0
[  392.177827][ T1986] ---[ end trace 8eaf99b33f09def0 ]---
[  392.177934][ T1986] Workqueue:  0x0 (mm_percpu_wq)
[  392.177994][ T1986] Call Trace:
[  392.178048][ T1986] [c00000002afbf9d0] [c000000000ab0ee8] __func__.4060+0x125178/0x185

Re: [PATCH 3/7] powerpc/64s: flush L1D after user accesses

[Qian Cai]

On Thu, 2020-12-03 at 12:17 -0500, Qian Cai wrote:
> A simple "echo t > /proc/sysrq-trigger" will trigger this warning almost
> endlessly on Power8 NV.

Correction -- POWER9 NV.

Re: [PATCH 3/7] powerpc/64s: flush L1D after user accesses

[Qian Cai]

On Thu, 2020-12-03 at 12:17 -0500, Qian Cai wrote:
> []
> > +static inline bool
> > +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
> > +{
> > +	return WARN(mmu_has_feature(MMU_FTR_RADIX_KUAP) &&
> > +		    (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),
> > +		    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
> > +}
> 
> A simple "echo t > /proc/sysrq-trigger" will trigger this warning almost
> endlessly on POWER9 NV.

I have just realized the patch just moved this warning around, so the issue was
pre-existent. Since I have not tested sysrq-t regularly, I am not sure when it
started to break. So far, I have reverted some of those for testing which did
not help, i.e., the sysrq-t issue remains.

16852975f0f  Revert "powerpc/64s: Use early_mmu_has_feature() in set_kuap()"
129e240ead32 Revert "powerpc: Implement user_access_save() and user_access_restore()"
edb0046c842c Revert "powerpc/64s/kuap: Add missing isync to KUAP restore paths"
2d46ee87ce44 Revert "powerpc/64/kuap: Conditionally restore AMR in interrupt exit"
c1e0e805fc57 Revert "powerpc/64s/kuap: Conditionally restore AMR in kuap_restore_amr asm"
7f30b7aaf23a Revert "selftests/powerpc: rfi_flush: disable entry flush if present"
bc9b9967a100 Revert "powerpc/64s: flush L1D on kernel entry"
b77e7b54f5eb Revert "powerpc/64s: flush L1D after user accesses"
22dddf532c64 Revert "powerpc: Only include kup-radix.h for 64-bit Book3S"
2679d155c46a Revert "selftests/powerpc: entry flush test"
87954b9b4243 Revert "selftests/powerpc: refactor entry and rfi_flush tests"
342d82bd4c5d Revert "powerpc/64s: rename pnv|pseries_setup_rfi_flush to _setup_security_mitigations"

Re: [PATCH 3/7] powerpc/64s: flush L1D after user accesses

[Christophe Leroy]

Quoting Qian Cai <qcai@redhat.com>:

> On Thu, 2020-12-03 at 12:17 -0500, Qian Cai wrote:
>> []
>> > +static inline bool
>> > +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool  
>> is_write)
>> > +{
>> > +	return WARN(mmu_has_feature(MMU_FTR_RADIX_KUAP) &&
>> > +		    (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE :  
>> AMR_KUAP_BLOCK_READ)),
>> > +		    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
>> > +}
>>
>> A simple "echo t > /proc/sysrq-trigger" will trigger this warning almost
>> endlessly on POWER9 NV.
>
> I have just realized the patch just moved this warning around, so  
> the issue was
> pre-existent. Since I have not tested sysrq-t regularly, I am not  
> sure when it
> started to break. So far, I have reverted some of those for testing which did
> not help, i.e., the sysrq-t issue remains.
>
> 16852975f0f  Revert "powerpc/64s: Use early_mmu_has_feature() in set_kuap()"
> 129e240ead32 Revert "powerpc: Implement user_access_save() and  
> user_access_restore()"
> edb0046c842c Revert "powerpc/64s/kuap: Add missing isync to KUAP  
> restore paths"
> 2d46ee87ce44 Revert "powerpc/64/kuap: Conditionally restore AMR in  
> interrupt exit"
> c1e0e805fc57 Revert "powerpc/64s/kuap: Conditionally restore AMR in  
> kuap_restore_amr asm"
> 7f30b7aaf23a Revert "selftests/powerpc: rfi_flush: disable entry  
> flush if present"
> bc9b9967a100 Revert "powerpc/64s: flush L1D on kernel entry"
> b77e7b54f5eb Revert "powerpc/64s: flush L1D after user accesses"
> 22dddf532c64 Revert "powerpc: Only include kup-radix.h for 64-bit Book3S"
> 2679d155c46a Revert "selftests/powerpc: entry flush test"
> 87954b9b4243 Revert "selftests/powerpc: refactor entry and rfi_flush tests"
> 342d82bd4c5d Revert "powerpc/64s: rename pnv|pseries_setup_rfi_flush  
> to _setup_security_mitigations"

I also hit that WARNING in the same way earlier this week.

I think it has been broken by commit c33165253492 ("powerpc: use  
non-set_fs based maccess routines")

IIUC we should provide copy_from_kernel_nofault_allowed() to avoid that.

Christophe