Merge branch 'for-next/bti-user' into for-next/bti

Merge in user support for Branch Target Identification, which narrowly
missed the cut for 5.7 after a late ABI concern.

* for-next/bti-user:
  arm64: bti: Document behaviour for dynamically linked binaries
  arm64: elf: Fix allnoconfig kernel build with !ARCH_USE_GNU_PROPERTY
  arm64: BTI: Add Kconfig entry for userspace BTI
  mm: smaps: Report arm64 guarded pages in smaps
  arm64: mm: Display guarded pages in ptdump
  KVM: arm64: BTI: Reset BTYPE when skipping emulated instructions
  arm64: BTI: Reset BTYPE when skipping emulated instructions
  arm64: traps: Shuffle code to eliminate forward declarations
  arm64: unify native/compat instruction skipping
  arm64: BTI: Decode BYTPE bits when printing PSTATE
  arm64: elf: Enable BTI at exec based on ELF program properties
  elf: Allow arch to tweak initial mmap prot flags
  arm64: Basic Branch Target Identification support
  ELF: Add ELF program property parsing support
  ELF: UAPI and Kconfig additions for ELF program properties

1 files changed, 139 insertions, 6 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 13f25e241ac4..4adb963cdb83 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -40,12 +40,18 @@
 #include <linux/sched/coredump.h>
 #include <linux/sched/task_stack.h>
 #include <linux/sched/cputime.h>
+#include <linux/sizes.h>
+#include <linux/types.h>
 #include <linux/cred.h>
 #include <linux/dax.h>
 #include <linux/uaccess.h>
 #include <asm/param.h>
 #include <asm/page.h>
 
+#ifndef ELF_COMPAT
+#define ELF_COMPAT 0
+#endif
+
 #ifndef user_long_t
 #define user_long_t long
 #endif
@@ -539,7 +545,8 @@ static inline int arch_check_elf(struct elfhdr *ehdr, bool has_interp,
 
 #endif /* !CONFIG_ARCH_BINFMT_ELF_STATE */
 
-static inline int make_prot(u32 p_flags)
+static inline int make_prot(u32 p_flags, struct arch_elf_state *arch_state,
+			    bool has_interp, bool is_interp)
 {
 	int prot = 0;
 
@@ -549,7 +556,8 @@ static inline int make_prot(u32 p_flags)
 		prot |= PROT_WRITE;
 	if (p_flags & PF_X)
 		prot |= PROT_EXEC;
-	return prot;
+
+	return arch_elf_adjust_prot(prot, arch_state, has_interp, is_interp);
 }
 
 /* This is much more generalized than the library routine read function,
@@ -559,7 +567,8 @@ static inline int make_prot(u32 p_flags)
 
 static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
 		struct file *interpreter,
-		unsigned long no_base, struct elf_phdr *interp_elf_phdata)
+		unsigned long no_base, struct elf_phdr *interp_elf_phdata,
+		struct arch_elf_state *arch_state)
 {
 	struct elf_phdr *eppnt;
 	unsigned long load_addr = 0;
@@ -591,7 +600,8 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
 	for (i = 0; i < interp_elf_ex->e_phnum; i++, eppnt++) {
 		if (eppnt->p_type == PT_LOAD) {
 			int elf_type = MAP_PRIVATE | MAP_DENYWRITE;
-			int elf_prot = make_prot(eppnt->p_flags);
+			int elf_prot = make_prot(eppnt->p_flags, arch_state,
+						 true, true);
 			unsigned long vaddr = 0;
 			unsigned long k, map_addr;
 
@@ -682,6 +692,111 @@ out:
  * libraries.  There is no binary dependent code anywhere else.
  */
 
+static int parse_elf_property(const char *data, size_t *off, size_t datasz,
+			      struct arch_elf_state *arch,
+			      bool have_prev_type, u32 *prev_type)
+{
+	size_t o, step;
+	const struct gnu_property *pr;
+	int ret;
+
+	if (*off == datasz)
+		return -ENOENT;
+
+	if (WARN_ON_ONCE(*off > datasz || *off % ELF_GNU_PROPERTY_ALIGN))
+		return -EIO;
+	o = *off;
+	datasz -= *off;
+
+	if (datasz < sizeof(*pr))
+		return -ENOEXEC;
+	pr = (const struct gnu_property *)(data + o);
+	o += sizeof(*pr);
+	datasz -= sizeof(*pr);
+
+	if (pr->pr_datasz > datasz)
+		return -ENOEXEC;
+
+	WARN_ON_ONCE(o % ELF_GNU_PROPERTY_ALIGN);
+	step = round_up(pr->pr_datasz, ELF_GNU_PROPERTY_ALIGN);
+	if (step > datasz)
+		return -ENOEXEC;
+
+	/* Properties are supposed to be unique and sorted on pr_type: */
+	if (have_prev_type && pr->pr_type <= *prev_type)
+		return -ENOEXEC;
+	*prev_type = pr->pr_type;
+
+	ret = arch_parse_elf_property(pr->pr_type, data + o,
+				      pr->pr_datasz, ELF_COMPAT, arch);
+	if (ret)
+		return ret;
+
+	*off = o + step;
+	return 0;
+}
+
+#define NOTE_DATA_SZ SZ_1K
+#define GNU_PROPERTY_TYPE_0_NAME "GNU"
+#define NOTE_NAME_SZ (sizeof(GNU_PROPERTY_TYPE_0_NAME))
+
+static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
+				struct arch_elf_state *arch)
+{
+	union {
+		struct elf_note nhdr;
+		char data[NOTE_DATA_SZ];
+	} note;
+	loff_t pos;
+	ssize_t n;
+	size_t off, datasz;
+	int ret;
+	bool have_prev_type;
+	u32 prev_type;
+
+	if (!IS_ENABLED(CONFIG_ARCH_USE_GNU_PROPERTY) || !phdr)
+		return 0;
+
+	/* load_elf_binary() shouldn't call us unless this is true... */
+	if (WARN_ON_ONCE(phdr->p_type != PT_GNU_PROPERTY))
+		return -ENOEXEC;
+
+	/* If the properties are crazy large, that's too bad (for now): */
+	if (phdr->p_filesz > sizeof(note))
+		return -ENOEXEC;
+
+	pos = phdr->p_offset;
+	n = kernel_read(f, &note, phdr->p_filesz, &pos);
+
+	BUILD_BUG_ON(sizeof(note) < sizeof(note.nhdr) + NOTE_NAME_SZ);
+	if (n < 0 || n < sizeof(note.nhdr) + NOTE_NAME_SZ)
+		return -EIO;
+
+	if (note.nhdr.n_type != NT_GNU_PROPERTY_TYPE_0 ||
+	    note.nhdr.n_namesz != NOTE_NAME_SZ ||
+	    strncmp(note.data + sizeof(note.nhdr),
+		    GNU_PROPERTY_TYPE_0_NAME, n - sizeof(note.nhdr)))
+		return -ENOEXEC;
+
+	off = round_up(sizeof(note.nhdr) + NOTE_NAME_SZ,
+		       ELF_GNU_PROPERTY_ALIGN);
+	if (off > n)
+		return -ENOEXEC;
+
+	if (note.nhdr.n_descsz > n - off)
+		return -ENOEXEC;
+	datasz = off + note.nhdr.n_descsz;
+
+	have_prev_type = false;
+	do {
+		ret = parse_elf_property(note.data, &off, datasz, arch,
+					 have_prev_type, &prev_type);
+		have_prev_type = true;
+	} while (!ret);
+
+	return ret == -ENOENT ? 0 : ret;
+}
+
 static int load_elf_binary(struct linux_binprm *bprm)
 {
 	struct file *interpreter = NULL; /* to shut gcc up */
@@ -689,6 +804,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	int load_addr_set = 0;
 	unsigned long error;
 	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
+	struct elf_phdr *elf_property_phdata = NULL;
 	unsigned long elf_bss, elf_brk;
 	int bss_prot = 0;
 	int retval, i;
@@ -726,6 +842,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) {
 		char *elf_interpreter;
 
+		if (elf_ppnt->p_type == PT_GNU_PROPERTY) {
+			elf_property_phdata = elf_ppnt;
+			continue;
+		}
+
 		if (elf_ppnt->p_type != PT_INTERP)
 			continue;
 
@@ -819,9 +940,14 @@ out_free_interp:
 			goto out_free_dentry;
 
 		/* Pass PT_LOPROC..PT_HIPROC headers to arch code */
+		elf_property_phdata = NULL;
 		elf_ppnt = interp_elf_phdata;
 		for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++)
 			switch (elf_ppnt->p_type) {
+			case PT_GNU_PROPERTY:
+				elf_property_phdata = elf_ppnt;
+				break;
+
 			case PT_LOPROC ... PT_HIPROC:
 				retval = arch_elf_pt_proc(interp_elf_ex,
 							  elf_ppnt, interpreter,
@@ -832,6 +958,11 @@ out_free_interp:
 			}
 	}
 
+	retval = parse_elf_properties(interpreter ?: bprm->file,
+				      elf_property_phdata, &arch_state);
+	if (retval)
+		goto out_free_dentry;
+
 	/*
 	 * Allow arch code to reject the ELF at this point, whilst it's
 	 * still possible to return an error to the code that invoked
@@ -913,7 +1044,8 @@ out_free_interp:
 			}
 		}
 
-		elf_prot = make_prot(elf_ppnt->p_flags);
+		elf_prot = make_prot(elf_ppnt->p_flags, &arch_state,
+				     !!interpreter, false);
 
 		elf_flags = MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE;
 
@@ -1056,7 +1188,8 @@ out_free_interp:
 	if (interpreter) {
 		elf_entry = load_elf_interp(interp_elf_ex,
 					    interpreter,
-					    load_bias, interp_elf_phdata);
+					    load_bias, interp_elf_phdata,
+					    &arch_state);
 		if (!IS_ERR((void *)elf_entry)) {
 			/*
 			 * load_elf_interp() returns relocation