97096bed83
The lowest bit of the thumb instruction is 1 by default, which is used to distinguish arm instructions and thumb instructions.
Fixed the problem of misalignment of symbol table when performing binary search
In arm, the lowest bit of the instruction is 1, which is a thumb instruction, and 0, which is an arm instruction.
The nm command was used in mkallsym.sh before, and the result it will return will set the lowest bit of the thumb instruction to 0. There will be a one-byte deviation during binary search, so mkallsyms.py will also set the lowest bit to 0 according to the previous format.
```sh
arm-none-eabi-nm -Cn nuttx | grep hello
0801c384 T hello_main
arm-none-eabi-objdump nuttx -t |grep hello
0801c384 g F .text 0000004c hello_main
arm-none-eabi-readelf nuttx -s |grep hello
4558: 0801c385 76 FUNC GLOBAL DEFAULT 1 hello_main
```
However, in the following case, when you need to find the function address according to the symbol name and execute the corresponding function, the lowest address obtained is 0. It will follow the arm instruction, causing an exception.
```c
void sym_test(void)
{
printf("call sym_test\n");
}
int main(int argc, FAR char *argv[])
{
FAR void *addr = sym_test;
printf("sym_test:%p %pS\n",addr, addr);
printf("sym_test - 1: %pS\n", (char *)addr - 1);
printf("sym_test + 1: %pS\n", (char *)addr + 1);
size_t size;
void (*func)(void);
const struct symtab_s *sym = allsyms_findbyname("sym_test", &size);
printf("sym_test:%p %pS\n",sym, sym);
func = sym->sym_value;
func();
return 0;
}
```
Therefore, you need to change mkallsyms.py back to the correct result and correct the binary search.
Signed-off-by: yinshengkai <yinshengkai@xiaomi.com>
144 lines
4.0 KiB
C
144 lines
4.0 KiB
C
/****************************************************************************
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* libs/libc/symtab/symtab_findbyvalue.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stddef.h>
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#include <debug.h>
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#include <assert.h>
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#include <errno.h>
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#include <nuttx/symtab.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: symtab_findbyvalue
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*
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* Description:
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* Find the symbol in the symbol table whose value closest (but not greater
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* than), the provided value. This version assumes that table is not
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* ordered with respect to symbol value and, hence, access time will be
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* linear with respect to nsyms.
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*
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* Returned Value:
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* A reference to the symbol table entry if an entry with the matching
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* value is found; NULL is returned if the entry is not found.
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*
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****************************************************************************/
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FAR const struct symtab_s *
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symtab_findbyvalue(FAR const struct symtab_s *symtab,
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FAR void *value, int nsyms)
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{
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#ifndef CONFIG_SYMTAB_ORDEREDBYVALUE
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FAR const struct symtab_s *retval = NULL;
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#else
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int high = nsyms - 1;
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int mid = high >> 1;
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int low = 0;
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#endif
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if (symtab == NULL)
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{
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DEBUGASSERT(nsyms == 0);
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return NULL;
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}
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#ifdef CONFIG_SYMTAB_ORDEREDBYVALUE
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while (high >= low)
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{
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mid = (low + high) >> 1;
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if (symtab[mid].sym_value == value)
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{
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break;
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}
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else if (symtab[mid].sym_value > value)
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{
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if (symtab[mid - 1].sym_value <= value)
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{
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mid -= 1;
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break;
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}
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else
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{
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high = mid - 1;
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}
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}
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else if (symtab[mid].sym_value < value)
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{
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if (symtab[mid + 1].sym_value > value)
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{
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break;
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}
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else
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{
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low = mid + 1;
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}
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}
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}
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return &symtab[mid];
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#else /* CONFIG_SYMTAB_ORDEREDBYVALUE */
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for (; nsyms > 0; symtab++, nsyms--)
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{
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/* Look for symbols of lesser or equal value (probably address) to
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* value
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*/
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if (symtab->sym_value <= value)
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{
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/* Found one. Is it the largest we have found so far? */
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if (!retval || symtab->sym_value > retval->sym_value)
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{
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/* Yes, then it is the new candidate for the symbol whose value
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* just below 'value'
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*/
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retval = symtab;
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/* If it is exactly equal to the search 'value', then we might
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* as well terminate early because we can't do any better than
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* that.
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*/
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if (retval->sym_value == value)
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{
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break;
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}
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}
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}
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}
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return retval;
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#endif /* CONFIG_SYMTAB_ORDEREDBYVALUE */
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}
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