Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 199 insertions, 0 deletions

diff --git a/scripts/mod/symsearch.c b/scripts/mod/symsearch.c
new file mode 100644
index 000000000..b9737b92f
--- /dev/null
+++ b/scripts/mod/symsearch.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Helper functions for finding the symbol in an ELF which is "nearest"
+ * to a given address.
+ */
+#include <xalloc.h>
+#include "modpost.h"
+
+struct syminfo {
+	unsigned int symbol_index;
+	unsigned int section_index;
+	Elf_Addr addr;
+};
+
+/*
+ * Container used to hold an entire binary search table.
+ * Entries in table are ascending, sorted first by section_index,
+ * then by addr, and last by symbol_index.  The sorting by
+ * symbol_index is used to ensure predictable behavior when
+ * multiple symbols are present with the same address; all
+ * symbols past the first are effectively ignored, by eliding
+ * them in symsearch_fixup().
+ */
+struct symsearch {
+	unsigned int table_size;
+	struct syminfo table[];
+};
+
+static int syminfo_compare(const void *s1, const void *s2)
+{
+	const struct syminfo *sym1 = s1;
+	const struct syminfo *sym2 = s2;
+
+	if (sym1->section_index > sym2->section_index)
+		return 1;
+	if (sym1->section_index < sym2->section_index)
+		return -1;
+	if (sym1->addr > sym2->addr)
+		return 1;
+	if (sym1->addr < sym2->addr)
+		return -1;
+	if (sym1->symbol_index > sym2->symbol_index)
+		return 1;
+	if (sym1->symbol_index < sym2->symbol_index)
+		return -1;
+	return 0;
+}
+
+static unsigned int symbol_count(struct elf_info *elf)
+{
+	unsigned int result = 0;
+
+	for (Elf_Sym *sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
+		if (is_valid_name(elf, sym))
+			result++;
+	}
+	return result;
+}
+
+/*
+ * Populate the search array that we just allocated.
+ * Be slightly paranoid here.  The ELF file is mmap'd and could
+ * conceivably change between symbol_count() and symsearch_populate().
+ * If we notice any difference, bail out rather than potentially
+ * propagating errors or crashing.
+ */
+static void symsearch_populate(struct elf_info *elf,
+			       struct syminfo *table,
+			       unsigned int table_size)
+{
+	bool is_arm = (elf->hdr->e_machine == EM_ARM);
+
+	for (Elf_Sym *sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
+		if (is_valid_name(elf, sym)) {
+			if (table_size-- == 0)
+				fatal("%s: size mismatch\n", __func__);
+			table->symbol_index = sym - elf->symtab_start;
+			table->section_index = get_secindex(elf, sym);
+			table->addr = sym->st_value;
+
+			/*
+			 * For ARM Thumb instruction, the bit 0 of st_value is
+			 * set if the symbol is STT_FUNC type. Mask it to get
+			 * the address.
+			 */
+			if (is_arm && ELF_ST_TYPE(sym->st_info) == STT_FUNC)
+				table->addr &= ~1;
+
+			table++;
+		}
+	}
+
+	if (table_size != 0)
+		fatal("%s: size mismatch\n", __func__);
+}
+
+/*
+ * Do any fixups on the table after sorting.
+ * For now, this just finds adjacent entries which have
+ * the same section_index and addr, and it propagates
+ * the first symbol_index over the subsequent entries,
+ * so that only one symbol_index is seen for any given
+ * section_index and addr.  This ensures that whether
+ * we're looking at an address from "above" or "below"
+ * that we see the same symbol_index.
+ * This does leave some duplicate entries in the table;
+ * in practice, these are a small fraction of the
+ * total number of entries, and they are harmless to
+ * the binary search algorithm other than a few occasional
+ * unnecessary comparisons.
+ */
+static void symsearch_fixup(struct syminfo *table, unsigned int table_size)
+{
+	/* Don't look at index 0, it will never change. */
+	for (unsigned int i = 1; i < table_size; i++) {
+		if (table[i].addr == table[i - 1].addr &&
+		    table[i].section_index == table[i - 1].section_index) {
+			table[i].symbol_index = table[i - 1].symbol_index;
+		}
+	}
+}
+
+void symsearch_init(struct elf_info *elf)
+{
+	unsigned int table_size = symbol_count(elf);
+
+	elf->symsearch = xmalloc(sizeof(struct symsearch) +
+				       sizeof(struct syminfo) * table_size);
+	elf->symsearch->table_size = table_size;
+
+	symsearch_populate(elf, elf->symsearch->table, table_size);
+	qsort(elf->symsearch->table, table_size,
+	      sizeof(struct syminfo), syminfo_compare);
+
+	symsearch_fixup(elf->symsearch->table, table_size);
+}
+
+void symsearch_finish(struct elf_info *elf)
+{
+	free(elf->symsearch);
+	elf->symsearch = NULL;
+}
+
+/*
+ * Find the syminfo which is in secndx and "nearest" to addr.
+ * allow_negative: allow returning a symbol whose address is > addr.
+ * min_distance: ignore symbols which are further away than this.
+ *
+ * Returns a pointer into the symbol table for success.
+ * Returns NULL if no legal symbol is found within the requested range.
+ */
+Elf_Sym *symsearch_find_nearest(struct elf_info *elf, Elf_Addr addr,
+				unsigned int secndx, bool allow_negative,
+				Elf_Addr min_distance)
+{
+	unsigned int hi = elf->symsearch->table_size;
+	unsigned int lo = 0;
+	struct syminfo *table = elf->symsearch->table;
+	struct syminfo target;
+
+	target.addr = addr;
+	target.section_index = secndx;
+	target.symbol_index = ~0;  /* compares greater than any actual index */
+	while (hi > lo) {
+		unsigned int mid = lo + (hi - lo) / 2;  /* Avoids overflow */
+
+		if (syminfo_compare(&table[mid], &target) > 0)
+			hi = mid;
+		else
+			lo = mid + 1;
+	}
+
+	/*
+	 * table[hi], if it exists, is the first entry in the array which
+	 * lies beyond target.  table[hi - 1], if it exists, is the last
+	 * entry in the array which comes before target, including the
+	 * case where it perfectly matches the section and the address.
+	 *
+	 * Note -- if the address we're looking up falls perfectly
+	 * in the middle of two symbols, this is written to always
+	 * prefer the symbol with the lower address.
+	 */
+	Elf_Sym *result = NULL;
+
+	if (allow_negative &&
+	    hi < elf->symsearch->table_size &&
+	    table[hi].section_index == secndx &&
+	    table[hi].addr - addr <= min_distance) {
+		min_distance = table[hi].addr - addr;
+		result = &elf->symtab_start[table[hi].symbol_index];
+	}
+	if (hi > 0 &&
+	    table[hi - 1].section_index == secndx &&
+	    addr - table[hi - 1].addr <= min_distance) {
+		result = &elf->symtab_start[table[hi - 1].symbol_index];
+	}
+	return result;
+}