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Message-ID: <79d29ed011f2afda285691a47b157363ab547204.1592510545.git.mhelsley@vmware.com>
Date: Thu, 18 Jun 2020 13:38:12 -0700
From: Matt Helsley <mhelsley@...are.com>
To: <linux-kernel@...r.kernel.org>
CC: Josh Poimboeuf <jpoimboe@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Julien Thierry <jthierry@...hat.com>,
Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
Matt Helsley <mhelsley@...are.com>
Subject: [RFC][PATCH v5 26/51] objtool: mcount: Remove unused file mapping
The ELF data is now accessed completely through objtool's
ELF code. We can remove the mapping of the original ELF
file and propagate elf_open_read(), elf_close(), and malloc()
up in place of mmap_file(), mmap_cleanup(), and umalloc()
respectively. This also eliminates the last use of the
umalloc() wrapper, reduces the number of global
variables, and limits the use of globals to:
The struct elf for the file we're working on. This
saves passing it to nearly every function as a parameter.
Variables set depending on the ELF file endian, wordsize,
and arch so that the appropriate relocation structures,
offset sizes, architecture quirks, and nop encodings will
be used.
One command-line option
Note that we're still using the recordmcount wrapper to change
variable sizes and structure definitions we use to build the
mcount relocation data and call instruction offsets.
Signed-off-by: Matt Helsley <mhelsley@...are.com>
---
tools/objtool/recordmcount.c | 99 +++---------------------------------
tools/objtool/recordmcount.h | 4 +-
2 files changed, 9 insertions(+), 94 deletions(-)
diff --git a/tools/objtool/recordmcount.c b/tools/objtool/recordmcount.c
index f8699e52e7e5..a263062c9c64 100644
--- a/tools/objtool/recordmcount.c
+++ b/tools/objtool/recordmcount.c
@@ -41,104 +41,14 @@
#define R_AARCH64_ABS64 257
#endif
-#define R_ARM_PC24 1
#define R_ARM_THM_CALL 10
-#define R_ARM_CALL 28
-static int fd_map; /* File descriptor for file being modified. */
-static int mmap_failed; /* Boolean flag. */
static char gpfx; /* prefix for global symbol name (sometimes '_') */
static const char *altmcount; /* alternate mcount symbol name */
extern int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
-static void *file_map; /* pointer of the mapped file */
-static size_t file_map_size; /* original ELF file size */
static struct elf *lf;
-static void mmap_cleanup(void)
-{
- if (!mmap_failed)
- munmap(file_map, file_map_size);
- else
- free(file_map);
- file_map = NULL;
- if (lf)
- elf_close(lf);
- lf = NULL;
-}
-
-static void * umalloc(size_t size)
-{
- void *const addr = malloc(size);
- if (addr == 0) {
- fprintf(stderr, "malloc failed: %zu bytes\n", size);
- mmap_cleanup();
- return NULL;
- }
- return addr;
-}
-
-/*
- * Get the whole file as a programming convenience in order to avoid
- * malloc+lseek+read+free of many pieces. If successful, then mmap
- * avoids copying unused pieces; else just read the whole file.
- * Open for both read and write; new info will be appended to the file.
- * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
- * do not propagate to the file until an explicit overwrite at the last.
- * This preserves most aspects of consistency (all except .st_size)
- * for simultaneous readers of the file while we are appending to it.
- * However, multiple writers still are bad. We choose not to use
- * locking because it is expensive and the use case of kernel build
- * makes multiple writers unlikely.
- */
-static void *mmap_file(char const *fname)
-{
- struct stat sb;
-
- /* Avoid problems if early cleanup() */
- fd_map = -1;
- mmap_failed = 1;
- file_map = NULL;
- file_map_size = 0;
-
- lf = elf_open_read(fname, O_RDWR);
- if (!lf) {
- perror(fname);
- return NULL;
- }
- fd_map = lf->fd;
- if (fstat(fd_map, &sb) < 0) {
- perror(fname);
- goto out;
- }
- if (!S_ISREG(sb.st_mode)) {
- fprintf(stderr, "not a regular file: %s\n", fname);
- goto out;
- }
- file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
- fd_map, 0);
- if (file_map == MAP_FAILED) {
- mmap_failed = 1;
- file_map = umalloc(sb.st_size);
- if (!file_map) {
- perror(fname);
- goto out;
- }
- if (read(fd_map, file_map, sb.st_size) != sb.st_size) {
- perror(fname);
- mmap_cleanup();
- goto out;
- }
- } else
- mmap_failed = 0;
- file_map_size = sb.st_size;
-out:
- fd_map = -1;
-
- return file_map;
-}
-
-
static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
static unsigned char *ideal_nop;
@@ -527,8 +437,11 @@ static int do_file(char const *const fname)
unsigned int reltype = 0;
int rc = -1;
- if (!mmap_file(fname))
+ lf = elf_open_read(fname, O_RDWR);
+ if (!lf) {
+ perror(fname);
goto out;
+ }
w = w4nat;
w2 = w2nat;
@@ -658,7 +571,9 @@ static int do_file(char const *const fname)
} /* end switch */
out:
- mmap_cleanup();
+ if (lf)
+ elf_close(lf);
+ lf = NULL;
return rc;
}
diff --git a/tools/objtool/recordmcount.h b/tools/objtool/recordmcount.h
index 5ca488f3471c..fcc4f1a74d60 100644
--- a/tools/objtool/recordmcount.h
+++ b/tools/objtool/recordmcount.h
@@ -184,13 +184,13 @@ static int do_func(unsigned const reltype)
totrelsz = tot_relsize(&rel_entsize);
if (totrelsz == 0)
return 0;
- mrel0 = umalloc(totrelsz);
+ mrel0 = malloc(totrelsz);
mrelp = mrel0;
if (!mrel0)
return -1;
/* 2*sizeof(address) <= sizeof(Elf_Rel) */
- mloc0 = umalloc(totrelsz>>1);
+ mloc0 = malloc(totrelsz>>1);
mlocp = mloc0;
if (!mloc0) {
free(mrel0);
--
2.20.1
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