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-rw-r--r--arch/x86/include/asm/cfi.h110
-rw-r--r--arch/x86/kernel/alternative.c47
-rw-r--r--arch/x86/net/bpf_jit_comp.c82
-rw-r--r--include/linux/bpf.h12
-rw-r--r--include/linux/cfi.h7
-rw-r--r--kernel/bpf/core.c25
6 files changed, 269 insertions, 14 deletions
diff --git a/arch/x86/include/asm/cfi.h b/arch/x86/include/asm/cfi.h
index 2a494643089d..7a7b0b823a98 100644
--- a/arch/x86/include/asm/cfi.h
+++ b/arch/x86/include/asm/cfi.h
@@ -9,15 +9,125 @@
*/
#include <linux/bug.h>
+/*
+ * An overview of the various calling conventions...
+ *
+ * Traditional:
+ *
+ * foo:
+ * ... code here ...
+ * ret
+ *
+ * direct caller:
+ * call foo
+ *
+ * indirect caller:
+ * lea foo(%rip), %r11
+ * ...
+ * call *%r11
+ *
+ *
+ * IBT:
+ *
+ * foo:
+ * endbr64
+ * ... code here ...
+ * ret
+ *
+ * direct caller:
+ * call foo / call foo+4
+ *
+ * indirect caller:
+ * lea foo(%rip), %r11
+ * ...
+ * call *%r11
+ *
+ *
+ * kCFI:
+ *
+ * __cfi_foo:
+ * movl $0x12345678, %eax
+ * # 11 nops when CONFIG_CALL_PADDING
+ * foo:
+ * endbr64 # when IBT
+ * ... code here ...
+ * ret
+ *
+ * direct call:
+ * call foo # / call foo+4 when IBT
+ *
+ * indirect call:
+ * lea foo(%rip), %r11
+ * ...
+ * movl $(-0x12345678), %r10d
+ * addl -4(%r11), %r10d # -15 when CONFIG_CALL_PADDING
+ * jz 1f
+ * ud2
+ * 1:call *%r11
+ *
+ *
+ * FineIBT (builds as kCFI + CALL_PADDING + IBT + RETPOLINE and runtime patches into):
+ *
+ * __cfi_foo:
+ * endbr64
+ * subl 0x12345678, %r10d
+ * jz foo
+ * ud2
+ * nop
+ * foo:
+ * osp nop3 # was endbr64
+ * ... code here ...
+ * ret
+ *
+ * direct caller:
+ * call foo / call foo+4
+ *
+ * indirect caller:
+ * lea foo(%rip), %r11
+ * ...
+ * movl $0x12345678, %r10d
+ * subl $16, %r11
+ * nop4
+ * call *%r11
+ *
+ */
+enum cfi_mode {
+ CFI_DEFAULT, /* FineIBT if hardware has IBT, otherwise kCFI */
+ CFI_OFF, /* Taditional / IBT depending on .config */
+ CFI_KCFI, /* Optionally CALL_PADDING, IBT, RETPOLINE */
+ CFI_FINEIBT, /* see arch/x86/kernel/alternative.c */
+};
+
+extern enum cfi_mode cfi_mode;
+
struct pt_regs;
#ifdef CONFIG_CFI_CLANG
enum bug_trap_type handle_cfi_failure(struct pt_regs *regs);
+#define __bpfcall
+extern u32 cfi_bpf_hash;
+
+static inline int cfi_get_offset(void)
+{
+ switch (cfi_mode) {
+ case CFI_FINEIBT:
+ return 16;
+ case CFI_KCFI:
+ if (IS_ENABLED(CONFIG_CALL_PADDING))
+ return 16;
+ return 5;
+ default:
+ return 0;
+ }
+}
+#define cfi_get_offset cfi_get_offset
+
#else
static inline enum bug_trap_type handle_cfi_failure(struct pt_regs *regs)
{
return BUG_TRAP_TYPE_NONE;
}
+#define cfi_bpf_hash 0U
#endif /* CONFIG_CFI_CLANG */
#endif /* _ASM_X86_CFI_H */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 73be3931e4f0..d808d3aaec7e 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -30,6 +30,7 @@
#include <asm/fixmap.h>
#include <asm/paravirt.h>
#include <asm/asm-prototypes.h>
+#include <asm/cfi.h>
int __read_mostly alternatives_patched;
@@ -832,15 +833,43 @@ void __init_or_module apply_seal_endbr(s32 *start, s32 *end) { }
#endif /* CONFIG_X86_KERNEL_IBT */
#ifdef CONFIG_FINEIBT
+#define __CFI_DEFAULT CFI_DEFAULT
+#elif defined(CONFIG_CFI_CLANG)
+#define __CFI_DEFAULT CFI_KCFI
+#else
+#define __CFI_DEFAULT CFI_OFF
+#endif
-enum cfi_mode {
- CFI_DEFAULT,
- CFI_OFF,
- CFI_KCFI,
- CFI_FINEIBT,
-};
+enum cfi_mode cfi_mode __ro_after_init = __CFI_DEFAULT;
+
+#ifdef CONFIG_CFI_CLANG
+struct bpf_insn;
+
+/* Must match bpf_func_t / DEFINE_BPF_PROG_RUN() */
+extern unsigned int __bpf_prog_runX(const void *ctx,
+ const struct bpf_insn *insn);
+
+/*
+ * Force a reference to the external symbol so the compiler generates
+ * __kcfi_typid.
+ */
+__ADDRESSABLE(__bpf_prog_runX);
+
+/* u32 __ro_after_init cfi_bpf_hash = __kcfi_typeid___bpf_prog_runX; */
+asm (
+" .pushsection .data..ro_after_init,\"aw\",@progbits \n"
+" .type cfi_bpf_hash,@object \n"
+" .globl cfi_bpf_hash \n"
+" .p2align 2, 0x0 \n"
+"cfi_bpf_hash: \n"
+" .long __kcfi_typeid___bpf_prog_runX \n"
+" .size cfi_bpf_hash, 4 \n"
+" .popsection \n"
+);
+#endif
+
+#ifdef CONFIG_FINEIBT
-static enum cfi_mode cfi_mode __ro_after_init = CFI_DEFAULT;
static bool cfi_rand __ro_after_init = true;
static u32 cfi_seed __ro_after_init;
@@ -1149,8 +1178,10 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
goto err;
if (cfi_rand) {
- if (builtin)
+ if (builtin) {
cfi_seed = get_random_u32();
+ cfi_bpf_hash = cfi_rehash(cfi_bpf_hash);
+ }
ret = cfi_rand_preamble(start_cfi, end_cfi);
if (ret)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index af4a5de7d93a..5d5b967b111d 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -17,6 +17,7 @@
#include <asm/nospec-branch.h>
#include <asm/text-patching.h>
#include <asm/unwind.h>
+#include <asm/cfi.h>
static bool all_callee_regs_used[4] = {true, true, true, true};
@@ -51,9 +52,11 @@ static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len)
do { EMIT4(b1, b2, b3, b4); EMIT(off, 4); } while (0)
#ifdef CONFIG_X86_KERNEL_IBT
-#define EMIT_ENDBR() EMIT(gen_endbr(), 4)
+#define EMIT_ENDBR() EMIT(gen_endbr(), 4)
+#define EMIT_ENDBR_POISON() EMIT(gen_endbr_poison(), 4)
#else
#define EMIT_ENDBR()
+#define EMIT_ENDBR_POISON()
#endif
static bool is_imm8(int value)
@@ -305,6 +308,69 @@ static void pop_callee_regs(u8 **pprog, bool *callee_regs_used)
}
/*
+ * Emit the various CFI preambles, see asm/cfi.h and the comments about FineIBT
+ * in arch/x86/kernel/alternative.c
+ */
+
+static void emit_fineibt(u8 **pprog)
+{
+ u8 *prog = *pprog;
+
+ EMIT_ENDBR();
+ EMIT3_off32(0x41, 0x81, 0xea, cfi_bpf_hash); /* subl $hash, %r10d */
+ EMIT2(0x74, 0x07); /* jz.d8 +7 */
+ EMIT2(0x0f, 0x0b); /* ud2 */
+ EMIT1(0x90); /* nop */
+ EMIT_ENDBR_POISON();
+
+ *pprog = prog;
+}
+
+static void emit_kcfi(u8 **pprog)
+{
+ u8 *prog = *pprog;
+
+ EMIT1_off32(0xb8, cfi_bpf_hash); /* movl $hash, %eax */
+#ifdef CONFIG_CALL_PADDING
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+ EMIT1(0x90);
+#endif
+ EMIT_ENDBR();
+
+ *pprog = prog;
+}
+
+static void emit_cfi(u8 **pprog)
+{
+ u8 *prog = *pprog;
+
+ switch (cfi_mode) {
+ case CFI_FINEIBT:
+ emit_fineibt(&prog);
+ break;
+
+ case CFI_KCFI:
+ emit_kcfi(&prog);
+ break;
+
+ default:
+ EMIT_ENDBR();
+ break;
+ }
+
+ *pprog = prog;
+}
+
+/*
* Emit x86-64 prologue code for BPF program.
* bpf_tail_call helper will skip the first X86_TAIL_CALL_OFFSET bytes
* while jumping to another program
@@ -315,10 +381,10 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf,
{
u8 *prog = *pprog;
+ emit_cfi(&prog);
/* BPF trampoline can be made to work without these nops,
* but let's waste 5 bytes for now and optimize later
*/
- EMIT_ENDBR();
memcpy(prog, x86_nops[5], X86_PATCH_SIZE);
prog += X86_PATCH_SIZE;
if (!ebpf_from_cbpf) {
@@ -3013,9 +3079,16 @@ out_image:
jit_data->header = header;
jit_data->rw_header = rw_header;
}
- prog->bpf_func = (void *)image;
+ /*
+ * ctx.prog_offset is used when CFI preambles put code *before*
+ * the function. See emit_cfi(). For FineIBT specifically this code
+ * can also be executed and bpf_prog_kallsyms_add() will
+ * generate an additional symbol to cover this, hence also
+ * decrement proglen.
+ */
+ prog->bpf_func = (void *)image + cfi_get_offset();
prog->jited = 1;
- prog->jited_len = proglen;
+ prog->jited_len = proglen - cfi_get_offset();
} else {
prog = orig_prog;
}
@@ -3070,6 +3143,7 @@ void bpf_jit_free(struct bpf_prog *prog)
kvfree(jit_data->addrs);
kfree(jit_data);
}
+ prog->bpf_func = (void *)prog->bpf_func - cfi_get_offset();
hdr = bpf_jit_binary_pack_hdr(prog);
bpf_jit_binary_pack_free(hdr, NULL);
WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog));
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c87c608a3689..9d84c376851a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -29,6 +29,7 @@
#include <linux/rcupdate_trace.h>
#include <linux/static_call.h>
#include <linux/memcontrol.h>
+#include <linux/cfi.h>
struct bpf_verifier_env;
struct bpf_verifier_log;
@@ -1211,7 +1212,11 @@ struct bpf_dispatcher {
#endif
};
-static __always_inline __nocfi unsigned int bpf_dispatcher_nop_func(
+#ifndef __bpfcall
+#define __bpfcall __nocfi
+#endif
+
+static __always_inline __bpfcall unsigned int bpf_dispatcher_nop_func(
const void *ctx,
const struct bpf_insn *insnsi,
bpf_func_t bpf_func)
@@ -1303,7 +1308,7 @@ int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_func
#define DEFINE_BPF_DISPATCHER(name) \
__BPF_DISPATCHER_SC(name); \
- noinline __nocfi unsigned int bpf_dispatcher_##name##_func( \
+ noinline __bpfcall unsigned int bpf_dispatcher_##name##_func( \
const void *ctx, \
const struct bpf_insn *insnsi, \
bpf_func_t bpf_func) \
@@ -1453,6 +1458,9 @@ struct bpf_prog_aux {
struct bpf_kfunc_desc_tab *kfunc_tab;
struct bpf_kfunc_btf_tab *kfunc_btf_tab;
u32 size_poke_tab;
+#ifdef CONFIG_FINEIBT
+ struct bpf_ksym ksym_prefix;
+#endif
struct bpf_ksym ksym;
const struct bpf_prog_ops *ops;
struct bpf_map **used_maps;
diff --git a/include/linux/cfi.h b/include/linux/cfi.h
index 2309d74e77e6..1ed2d96c0cfc 100644
--- a/include/linux/cfi.h
+++ b/include/linux/cfi.h
@@ -11,6 +11,13 @@
#include <linux/module.h>
#include <asm/cfi.h>
+#ifndef cfi_get_offset
+static inline int cfi_get_offset(void)
+{
+ return 0;
+}
+#endif
+
#ifdef CONFIG_CFI_CLANG
enum bug_trap_type report_cfi_failure(struct pt_regs *regs, unsigned long addr,
unsigned long *target, u32 type);
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index c34513d645c4..5aa6863ac33b 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -121,6 +121,9 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flag
#endif
INIT_LIST_HEAD_RCU(&fp->aux->ksym.lnode);
+#ifdef CONFIG_FINEIBT
+ INIT_LIST_HEAD_RCU(&fp->aux->ksym_prefix.lnode);
+#endif
mutex_init(&fp->aux->used_maps_mutex);
mutex_init(&fp->aux->dst_mutex);
@@ -683,6 +686,23 @@ void bpf_prog_kallsyms_add(struct bpf_prog *fp)
fp->aux->ksym.prog = true;
bpf_ksym_add(&fp->aux->ksym);
+
+#ifdef CONFIG_FINEIBT
+ /*
+ * When FineIBT, code in the __cfi_foo() symbols can get executed
+ * and hence unwinder needs help.
+ */
+ if (cfi_mode != CFI_FINEIBT)
+ return;
+
+ snprintf(fp->aux->ksym_prefix.name, KSYM_NAME_LEN,
+ "__cfi_%s", fp->aux->ksym.name);
+
+ fp->aux->ksym_prefix.start = (unsigned long) fp->bpf_func - 16;
+ fp->aux->ksym_prefix.end = (unsigned long) fp->bpf_func;
+
+ bpf_ksym_add(&fp->aux->ksym_prefix);
+#endif
}
void bpf_prog_kallsyms_del(struct bpf_prog *fp)
@@ -691,6 +711,11 @@ void bpf_prog_kallsyms_del(struct bpf_prog *fp)
return;
bpf_ksym_del(&fp->aux->ksym);
+#ifdef CONFIG_FINEIBT
+ if (cfi_mode != CFI_FINEIBT)
+ return;
+ bpf_ksym_del(&fp->aux->ksym_prefix);
+#endif
}
static struct bpf_ksym *bpf_ksym_find(unsigned long addr)
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