Messages in this thread Patch in this message | | | From | Matt Helsley <> | Subject | [RFC][PATCH v4 23/32] objtool: mcount: Remove unused file mapping | Date | Tue, 2 Jun 2020 12:50:16 -0700 |
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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@vmware.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 bfed27f53f75..5ec44c9f2884 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; @@ -525,8 +435,11 @@ 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; @@ -656,7 +569,9 @@ 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 352d2042be35..e1be7243742b 100644 --- a/tools/objtool/recordmcount.h +++ b/tools/objtool/recordmcount.h @@ -188,13 +188,13 @@ 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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