Re: [PATCH v2 10/10] gcov: Remove old GCC 3.4 support

[Nick Desaulniers <ndesaulniers@google.com>]

On Thu, Jan 23, 2020 at 7:34 AM Will Deacon <will@kernel.org> wrote:
>
> The kernel requires at least GCC 4.8 in order to build, and so there is
> no need to cater for the pre-4.7 gcov format.

Thanks for the cleanup! Deleting such a large volume of code is great!

>
> Remove the obsolete code.
>
> Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  kernel/gcov/Kconfig   |  24 --
>  kernel/gcov/Makefile  |   3 +-
>  kernel/gcov/gcc_3_4.c | 573 ------------------------------------------
>  3 files changed, 1 insertion(+), 599 deletions(-)
>  delete mode 100644 kernel/gcov/gcc_3_4.c
>
> diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
> index 060e8e726755..8df7fad82df8 100644
> --- a/kernel/gcov/Kconfig
> +++ b/kernel/gcov/Kconfig
> @@ -51,28 +51,4 @@ config GCOV_PROFILE_ALL
>         larger and run slower. Also be sure to exclude files from profiling
>         which are not linked to the kernel image to prevent linker errors.
>
> -choice
> -       prompt "Specify GCOV format"
> -       depends on GCOV_KERNEL
> -       depends on CC_IS_GCC
> -       ---help---
> -       The gcov format is usually determined by the GCC version, and the
> -       default is chosen according to your GCC version. However, there are
> -       exceptions where format changes are integrated in lower-version GCCs.
> -       In such a case, change this option to adjust the format used in the
> -       kernel accordingly.
> -
> -config GCOV_FORMAT_3_4
> -       bool "GCC 3.4 format"
> -       depends on GCC_VERSION < 40700

I was thinking this patch could be independant of the series, until I
saw this; before the series GCC 4.6+ is still supported, after GCC
4.8+ is.  So NVM.

> -       ---help---
> -       Select this option to use the format defined by GCC 3.4.
> -
> -config GCOV_FORMAT_4_7
> -       bool "GCC 4.7 format"
> -       ---help---
> -       Select this option to use the format defined by GCC 4.7.
> -
> -endchoice
> -
>  endmenu
> diff --git a/kernel/gcov/Makefile b/kernel/gcov/Makefile
> index d66a74b0f100..16f8ecc7d882 100644
> --- a/kernel/gcov/Makefile
> +++ b/kernel/gcov/Makefile
> @@ -2,6 +2,5 @@
>  ccflags-y := -DSRCTREE='"$(srctree)"' -DOBJTREE='"$(objtree)"'
>
>  obj-y := base.o fs.o
> -obj-$(CONFIG_GCOV_FORMAT_3_4) += gcc_base.o gcc_3_4.o
> -obj-$(CONFIG_GCOV_FORMAT_4_7) += gcc_base.o gcc_4_7.o
> +obj-$(CONFIG_CC_IS_GCC) += gcc_base.o gcc_4_7.o

For further refactoring/cleanups, the split between gcc_base.c and
gcc_4_7.c can now be combined into one source file.  gcc_base.c just
shared code with either 3.4 or 4.7, but I'll leave that as work that
can be done another day.  Thanks for the patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

>  obj-$(CONFIG_CC_IS_CLANG) += clang.o
> diff --git a/kernel/gcov/gcc_3_4.c b/kernel/gcov/gcc_3_4.c
> deleted file mode 100644
> index 801ee4b0b969..000000000000
> --- a/kernel/gcov/gcc_3_4.c
> +++ /dev/null
> @@ -1,573 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -/*
> - *  This code provides functions to handle gcc's profiling data format
> - *  introduced with gcc 3.4. Future versions of gcc may change the gcov
> - *  format (as happened before), so all format-specific information needs
> - *  to be kept modular and easily exchangeable.
> - *
> - *  This file is based on gcc-internal definitions. Functions and data
> - *  structures are defined to be compatible with gcc counterparts.
> - *  For a better understanding, refer to gcc source: gcc/gcov-io.h.
> - *
> - *    Copyright IBM Corp. 2009
> - *    Author(s): Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
> - *
> - *    Uses gcc-internal data definitions.
> - */
> -
> -#include <linux/errno.h>
> -#include <linux/slab.h>
> -#include <linux/string.h>
> -#include <linux/seq_file.h>
> -#include <linux/vmalloc.h>
> -#include "gcov.h"
> -
> -#define GCOV_COUNTERS          5
> -
> -static struct gcov_info *gcov_info_head;
> -
> -/**
> - * struct gcov_fn_info - profiling meta data per function
> - * @ident: object file-unique function identifier
> - * @checksum: function checksum
> - * @n_ctrs: number of values per counter type belonging to this function
> - *
> - * This data is generated by gcc during compilation and doesn't change
> - * at run-time.
> - */
> -struct gcov_fn_info {
> -       unsigned int ident;
> -       unsigned int checksum;
> -       unsigned int n_ctrs[0];
> -};
> -
> -/**
> - * struct gcov_ctr_info - profiling data per counter type
> - * @num: number of counter values for this type
> - * @values: array of counter values for this type
> - * @merge: merge function for counter values of this type (unused)
> - *
> - * This data is generated by gcc during compilation and doesn't change
> - * at run-time with the exception of the values array.
> - */
> -struct gcov_ctr_info {
> -       unsigned int    num;
> -       gcov_type       *values;
> -       void            (*merge)(gcov_type *, unsigned int);
> -};
> -
> -/**
> - * struct gcov_info - profiling data per object file
> - * @version: gcov version magic indicating the gcc version used for compilation
> - * @next: list head for a singly-linked list
> - * @stamp: time stamp
> - * @filename: name of the associated gcov data file
> - * @n_functions: number of instrumented functions
> - * @functions: function data
> - * @ctr_mask: mask specifying which counter types are active
> - * @counts: counter data per counter type
> - *
> - * This data is generated by gcc during compilation and doesn't change
> - * at run-time with the exception of the next pointer.
> - */
> -struct gcov_info {
> -       unsigned int                    version;
> -       struct gcov_info                *next;
> -       unsigned int                    stamp;
> -       const char                      *filename;
> -       unsigned int                    n_functions;
> -       const struct gcov_fn_info       *functions;
> -       unsigned int                    ctr_mask;
> -       struct gcov_ctr_info            counts[0];
> -};
> -
> -/**
> - * gcov_info_filename - return info filename
> - * @info: profiling data set
> - */
> -const char *gcov_info_filename(struct gcov_info *info)
> -{
> -       return info->filename;
> -}
> -
> -/**
> - * gcov_info_version - return info version
> - * @info: profiling data set
> - */
> -unsigned int gcov_info_version(struct gcov_info *info)
> -{
> -       return info->version;
> -}
> -
> -/**
> - * gcov_info_next - return next profiling data set
> - * @info: profiling data set
> - *
> - * Returns next gcov_info following @info or first gcov_info in the chain if
> - * @info is %NULL.
> - */
> -struct gcov_info *gcov_info_next(struct gcov_info *info)
> -{
> -       if (!info)
> -               return gcov_info_head;
> -
> -       return info->next;
> -}
> -
> -/**
> - * gcov_info_link - link/add profiling data set to the list
> - * @info: profiling data set
> - */
> -void gcov_info_link(struct gcov_info *info)
> -{
> -       info->next = gcov_info_head;
> -       gcov_info_head = info;
> -}
> -
> -/**
> - * gcov_info_unlink - unlink/remove profiling data set from the list
> - * @prev: previous profiling data set
> - * @info: profiling data set
> - */
> -void gcov_info_unlink(struct gcov_info *prev, struct gcov_info *info)
> -{
> -       if (prev)
> -               prev->next = info->next;
> -       else
> -               gcov_info_head = info->next;
> -}
> -
> -/**
> - * gcov_info_within_module - check if a profiling data set belongs to a module
> - * @info: profiling data set
> - * @mod: module
> - *
> - * Returns true if profiling data belongs module, false otherwise.
> - */
> -bool gcov_info_within_module(struct gcov_info *info, struct module *mod)
> -{
> -       return within_module((unsigned long)info, mod);
> -}
> -
> -/* Symbolic links to be created for each profiling data file. */
> -const struct gcov_link gcov_link[] = {
> -       { OBJ_TREE, "gcno" },   /* Link to .gcno file in $(objtree). */
> -       { 0, NULL},
> -};
> -
> -/*
> - * Determine whether a counter is active. Based on gcc magic. Doesn't change
> - * at run-time.
> - */
> -static int counter_active(struct gcov_info *info, unsigned int type)
> -{
> -       return (1 << type) & info->ctr_mask;
> -}
> -
> -/* Determine number of active counters. Based on gcc magic. */
> -static unsigned int num_counter_active(struct gcov_info *info)
> -{
> -       unsigned int i;
> -       unsigned int result = 0;
> -
> -       for (i = 0; i < GCOV_COUNTERS; i++) {
> -               if (counter_active(info, i))
> -                       result++;
> -       }
> -       return result;
> -}
> -
> -/**
> - * gcov_info_reset - reset profiling data to zero
> - * @info: profiling data set
> - */
> -void gcov_info_reset(struct gcov_info *info)
> -{
> -       unsigned int active = num_counter_active(info);
> -       unsigned int i;
> -
> -       for (i = 0; i < active; i++) {
> -               memset(info->counts[i].values, 0,
> -                      info->counts[i].num * sizeof(gcov_type));
> -       }
> -}
> -
> -/**
> - * gcov_info_is_compatible - check if profiling data can be added
> - * @info1: first profiling data set
> - * @info2: second profiling data set
> - *
> - * Returns non-zero if profiling data can be added, zero otherwise.
> - */
> -int gcov_info_is_compatible(struct gcov_info *info1, struct gcov_info *info2)
> -{
> -       return (info1->stamp == info2->stamp);
> -}
> -
> -/**
> - * gcov_info_add - add up profiling data
> - * @dest: profiling data set to which data is added
> - * @source: profiling data set which is added
> - *
> - * Adds profiling counts of @source to @dest.
> - */
> -void gcov_info_add(struct gcov_info *dest, struct gcov_info *source)
> -{
> -       unsigned int i;
> -       unsigned int j;
> -
> -       for (i = 0; i < num_counter_active(dest); i++) {
> -               for (j = 0; j < dest->counts[i].num; j++) {
> -                       dest->counts[i].values[j] +=
> -                               source->counts[i].values[j];
> -               }
> -       }
> -}
> -
> -/* Get size of function info entry. Based on gcc magic. */
> -static size_t get_fn_size(struct gcov_info *info)
> -{
> -       size_t size;
> -
> -       size = sizeof(struct gcov_fn_info) + num_counter_active(info) *
> -              sizeof(unsigned int);
> -       if (__alignof__(struct gcov_fn_info) > sizeof(unsigned int))
> -               size = ALIGN(size, __alignof__(struct gcov_fn_info));
> -       return size;
> -}
> -
> -/* Get address of function info entry. Based on gcc magic. */
> -static struct gcov_fn_info *get_fn_info(struct gcov_info *info, unsigned int fn)
> -{
> -       return (struct gcov_fn_info *)
> -               ((char *) info->functions + fn * get_fn_size(info));
> -}
> -
> -/**
> - * gcov_info_dup - duplicate profiling data set
> - * @info: profiling data set to duplicate
> - *
> - * Return newly allocated duplicate on success, %NULL on error.
> - */
> -struct gcov_info *gcov_info_dup(struct gcov_info *info)
> -{
> -       struct gcov_info *dup;
> -       unsigned int i;
> -       unsigned int active;
> -
> -       /* Duplicate gcov_info. */
> -       active = num_counter_active(info);
> -       dup = kzalloc(struct_size(dup, counts, active), GFP_KERNEL);
> -       if (!dup)
> -               return NULL;
> -       dup->version            = info->version;
> -       dup->stamp              = info->stamp;
> -       dup->n_functions        = info->n_functions;
> -       dup->ctr_mask           = info->ctr_mask;
> -       /* Duplicate filename. */
> -       dup->filename           = kstrdup(info->filename, GFP_KERNEL);
> -       if (!dup->filename)
> -               goto err_free;
> -       /* Duplicate table of functions. */
> -       dup->functions = kmemdup(info->functions, info->n_functions *
> -                                get_fn_size(info), GFP_KERNEL);
> -       if (!dup->functions)
> -               goto err_free;
> -       /* Duplicate counter arrays. */
> -       for (i = 0; i < active ; i++) {
> -               struct gcov_ctr_info *ctr = &info->counts[i];
> -               size_t size = ctr->num * sizeof(gcov_type);
> -
> -               dup->counts[i].num = ctr->num;
> -               dup->counts[i].merge = ctr->merge;
> -               dup->counts[i].values = vmalloc(size);
> -               if (!dup->counts[i].values)
> -                       goto err_free;
> -               memcpy(dup->counts[i].values, ctr->values, size);
> -       }
> -       return dup;
> -
> -err_free:
> -       gcov_info_free(dup);
> -       return NULL;
> -}
> -
> -/**
> - * gcov_info_free - release memory for profiling data set duplicate
> - * @info: profiling data set duplicate to free
> - */
> -void gcov_info_free(struct gcov_info *info)
> -{
> -       unsigned int active = num_counter_active(info);
> -       unsigned int i;
> -
> -       for (i = 0; i < active ; i++)
> -               vfree(info->counts[i].values);
> -       kfree(info->functions);
> -       kfree(info->filename);
> -       kfree(info);
> -}
> -
> -/**
> - * struct type_info - iterator helper array
> - * @ctr_type: counter type
> - * @offset: index of the first value of the current function for this type
> - *
> - * This array is needed to convert the in-memory data format into the in-file
> - * data format:
> - *
> - * In-memory:
> - *   for each counter type
> - *     for each function
> - *       values
> - *
> - * In-file:
> - *   for each function
> - *     for each counter type
> - *       values
> - *
> - * See gcc source gcc/gcov-io.h for more information on data organization.
> - */
> -struct type_info {
> -       int ctr_type;
> -       unsigned int offset;
> -};
> -
> -/**
> - * struct gcov_iterator - specifies current file position in logical records
> - * @info: associated profiling data
> - * @record: record type
> - * @function: function number
> - * @type: counter type
> - * @count: index into values array
> - * @num_types: number of counter types
> - * @type_info: helper array to get values-array offset for current function
> - */
> -struct gcov_iterator {
> -       struct gcov_info *info;
> -
> -       int record;
> -       unsigned int function;
> -       unsigned int type;
> -       unsigned int count;
> -
> -       int num_types;
> -       struct type_info type_info[0];
> -};
> -
> -static struct gcov_fn_info *get_func(struct gcov_iterator *iter)
> -{
> -       return get_fn_info(iter->info, iter->function);
> -}
> -
> -static struct type_info *get_type(struct gcov_iterator *iter)
> -{
> -       return &iter->type_info[iter->type];
> -}
> -
> -/**
> - * gcov_iter_new - allocate and initialize profiling data iterator
> - * @info: profiling data set to be iterated
> - *
> - * Return file iterator on success, %NULL otherwise.
> - */
> -struct gcov_iterator *gcov_iter_new(struct gcov_info *info)
> -{
> -       struct gcov_iterator *iter;
> -
> -       iter = kzalloc(struct_size(iter, type_info, num_counter_active(info)),
> -                      GFP_KERNEL);
> -       if (iter)
> -               iter->info = info;
> -
> -       return iter;
> -}
> -
> -/**
> - * gcov_iter_free - release memory for iterator
> - * @iter: file iterator to free
> - */
> -void gcov_iter_free(struct gcov_iterator *iter)
> -{
> -       kfree(iter);
> -}
> -
> -/**
> - * gcov_iter_get_info - return profiling data set for given file iterator
> - * @iter: file iterator
> - */
> -struct gcov_info *gcov_iter_get_info(struct gcov_iterator *iter)
> -{
> -       return iter->info;
> -}
> -
> -/**
> - * gcov_iter_start - reset file iterator to starting position
> - * @iter: file iterator
> - */
> -void gcov_iter_start(struct gcov_iterator *iter)
> -{
> -       int i;
> -
> -       iter->record = 0;
> -       iter->function = 0;
> -       iter->type = 0;
> -       iter->count = 0;
> -       iter->num_types = 0;
> -       for (i = 0; i < GCOV_COUNTERS; i++) {
> -               if (counter_active(iter->info, i)) {
> -                       iter->type_info[iter->num_types].ctr_type = i;
> -                       iter->type_info[iter->num_types++].offset = 0;
> -               }
> -       }
> -}
> -
> -/* Mapping of logical record number to actual file content. */
> -#define RECORD_FILE_MAGIC      0
> -#define RECORD_GCOV_VERSION    1
> -#define RECORD_TIME_STAMP      2
> -#define RECORD_FUNCTION_TAG    3
> -#define RECORD_FUNCTON_TAG_LEN 4
> -#define RECORD_FUNCTION_IDENT  5
> -#define RECORD_FUNCTION_CHECK  6
> -#define RECORD_COUNT_TAG       7
> -#define RECORD_COUNT_LEN       8
> -#define RECORD_COUNT           9
> -
> -/**
> - * gcov_iter_next - advance file iterator to next logical record
> - * @iter: file iterator
> - *
> - * Return zero if new position is valid, non-zero if iterator has reached end.
> - */
> -int gcov_iter_next(struct gcov_iterator *iter)
> -{
> -       switch (iter->record) {
> -       case RECORD_FILE_MAGIC:
> -       case RECORD_GCOV_VERSION:
> -       case RECORD_FUNCTION_TAG:
> -       case RECORD_FUNCTON_TAG_LEN:
> -       case RECORD_FUNCTION_IDENT:
> -       case RECORD_COUNT_TAG:
> -               /* Advance to next record */
> -               iter->record++;
> -               break;
> -       case RECORD_COUNT:
> -               /* Advance to next count */
> -               iter->count++;
> -               /* fall through */
> -       case RECORD_COUNT_LEN:
> -               if (iter->count < get_func(iter)->n_ctrs[iter->type]) {
> -                       iter->record = 9;
> -                       break;
> -               }
> -               /* Advance to next counter type */
> -               get_type(iter)->offset += iter->count;
> -               iter->count = 0;
> -               iter->type++;
> -               /* fall through */
> -       case RECORD_FUNCTION_CHECK:
> -               if (iter->type < iter->num_types) {
> -                       iter->record = 7;
> -                       break;
> -               }
> -               /* Advance to next function */
> -               iter->type = 0;
> -               iter->function++;
> -               /* fall through */
> -       case RECORD_TIME_STAMP:
> -               if (iter->function < iter->info->n_functions)
> -                       iter->record = 3;
> -               else
> -                       iter->record = -1;
> -               break;
> -       }
> -       /* Check for EOF. */
> -       if (iter->record == -1)
> -               return -EINVAL;
> -       else
> -               return 0;
> -}
> -
> -/**
> - * seq_write_gcov_u32 - write 32 bit number in gcov format to seq_file
> - * @seq: seq_file handle
> - * @v: value to be stored
> - *
> - * Number format defined by gcc: numbers are recorded in the 32 bit
> - * unsigned binary form of the endianness of the machine generating the
> - * file.
> - */
> -static int seq_write_gcov_u32(struct seq_file *seq, u32 v)
> -{
> -       return seq_write(seq, &v, sizeof(v));
> -}
> -
> -/**
> - * seq_write_gcov_u64 - write 64 bit number in gcov format to seq_file
> - * @seq: seq_file handle
> - * @v: value to be stored
> - *
> - * Number format defined by gcc: numbers are recorded in the 32 bit
> - * unsigned binary form of the endianness of the machine generating the
> - * file. 64 bit numbers are stored as two 32 bit numbers, the low part
> - * first.
> - */
> -static int seq_write_gcov_u64(struct seq_file *seq, u64 v)
> -{
> -       u32 data[2];
> -
> -       data[0] = (v & 0xffffffffUL);
> -       data[1] = (v >> 32);
> -       return seq_write(seq, data, sizeof(data));
> -}
> -
> -/**
> - * gcov_iter_write - write data for current pos to seq_file
> - * @iter: file iterator
> - * @seq: seq_file handle
> - *
> - * Return zero on success, non-zero otherwise.
> - */
> -int gcov_iter_write(struct gcov_iterator *iter, struct seq_file *seq)
> -{
> -       int rc = -EINVAL;
> -
> -       switch (iter->record) {
> -       case RECORD_FILE_MAGIC:
> -               rc = seq_write_gcov_u32(seq, GCOV_DATA_MAGIC);
> -               break;
> -       case RECORD_GCOV_VERSION:
> -               rc = seq_write_gcov_u32(seq, iter->info->version);
> -               break;
> -       case RECORD_TIME_STAMP:
> -               rc = seq_write_gcov_u32(seq, iter->info->stamp);
> -               break;
> -       case RECORD_FUNCTION_TAG:
> -               rc = seq_write_gcov_u32(seq, GCOV_TAG_FUNCTION);
> -               break;
> -       case RECORD_FUNCTON_TAG_LEN:
> -               rc = seq_write_gcov_u32(seq, 2);
> -               break;
> -       case RECORD_FUNCTION_IDENT:
> -               rc = seq_write_gcov_u32(seq, get_func(iter)->ident);
> -               break;
> -       case RECORD_FUNCTION_CHECK:
> -               rc = seq_write_gcov_u32(seq, get_func(iter)->checksum);
> -               break;
> -       case RECORD_COUNT_TAG:
> -               rc = seq_write_gcov_u32(seq,
> -                       GCOV_TAG_FOR_COUNTER(get_type(iter)->ctr_type));
> -               break;
> -       case RECORD_COUNT_LEN:
> -               rc = seq_write_gcov_u32(seq,
> -                               get_func(iter)->n_ctrs[iter->type] * 2);
> -               break;
> -       case RECORD_COUNT:
> -               rc = seq_write_gcov_u64(seq,
> -                       iter->info->counts[iter->type].
> -                               values[iter->count + get_type(iter)->offset]);
> -               break;
> -       }
> -       return rc;
> -}
> --
> 2.25.0.341.g760bfbb309-goog
>


-- 
Thanks,
~Nick Desaulniers