1 files changed, 145 insertions, 0 deletions
diff --git a/stm32/stlink/elfsym.c b/stm32/stlink/elfsym.c
new file mode 100644
index 0000000..b764bf5
--- /dev/null
+++ b/stm32/stlink/elfsym.c
@@ -0,0 +1,145 @@
+/*
+  elfsym.c
+
+  Read symbol addresses from a .elf file.
+
+  Based on libelf-howto.c from: http://em386.blogspot.com
+
+  Unit test with:
+
+  gcc elfsym.c -o elfsym -D__UNITTEST__ -Wall -lelf
+  ./elfsym elf_file.elf
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <libelf.h>
+#include <gelf.h>
+#include "elfsym.h"
+
+#define ERR -1
+
+int elfsym_open(char file[]) {
+    int fd; 		        /* File Descriptor             */
+    char *base_ptr;		/* ptr to our object in memory */
+    struct stat elf_stats;	/* fstat struct                */
+
+    if((fd = open(file, O_RDWR)) == ERR) {
+        printf("couldn't open %s\n", file);
+        return ERR;
+    }
+
+    if((fstat(fd, &elf_stats))) {
+        printf("could not fstat %s\n", file);
+        close(fd);
+        return ERR;
+    }
+
+    if((base_ptr = (char *) malloc(elf_stats.st_size)) == NULL) {
+        fprintf(stderr, "could not malloc\n");
+        close(fd);
+        return ERR;
+    }
+
+    if((read(fd, base_ptr, elf_stats.st_size)) < elf_stats.st_size) {
+        fprintf(stderr, "could not read %s\n", file);
+        free(base_ptr);
+        close(fd);
+        return ERR;
+    }
+
+    /* Check libelf version first */
+
+    if(elf_version(EV_CURRENT) == EV_NONE) {
+        fprintf(stderr, "WARNING Elf Library is out of date!\n");
+    }
+
+    free(base_ptr);
+
+    return fd;
+}
+
+
+void elfsym_close(int fd) {
+    close(fd);
+}
+
+unsigned int elfsym_get_symbol_address(int fd, char symbol_name[])
+{
+    Elf_Scn     *scn;              /* Section Descriptor          */
+    Elf_Data    *edata;            /* Data Descriptor             */
+    GElf_Sym     sym;		   /* Symbol                      */
+    GElf_Shdr    shdr;             /* Section Header              */
+    Elf         *elf;              /* Our Elf pointer for libelf  */
+    unsigned int symbol_address;
+    int          symbol_count;
+    int          i;
+
+    /* Iterate through section headers, stop when we find symbols,
+       and check for match */
+
+    elf = elf_begin(fd, ELF_C_READ, NULL);
+    if (elf == 0) {
+        fprintf(stderr, "could not elf_begin\n");
+    }
+    symbol_address = 0;
+    scn = NULL;
+
+    while((scn = elf_nextscn(elf, scn)) != 0) {
+        gelf_getshdr(scn, &shdr);
+
+        // When we find a section header marked SHT_SYMTAB stop and get symbols
+        edata = NULL;
+        if(shdr.sh_type == SHT_SYMTAB) {
+            // edata points to our symbol table
+            edata = elf_getdata(scn, edata);
+
+            // how many symbols are there? this number comes from the size of
+            // the section divided by the entry size
+            symbol_count = shdr.sh_size / shdr.sh_entsize;
+
+            // loop through to grab all symbols
+            for(i = 0; i < symbol_count; i++) {
+                // libelf grabs the symbol data using gelf_getsym()
+                gelf_getsym(edata, i, &sym);
+
+                if (strcmp(symbol_name,
+                           elf_strptr(elf, shdr.sh_link, sym.st_name)) == 0) {
+                    symbol_address = sym.st_value;
+                }
+            }
+
+        }
+    }
+
+    return symbol_address;
+}
+
+#ifdef __UNITTEST__
+
+int main(int argc, char *argv[])
+{
+    int           fd;
+    unsigned int  flag_addr, ptr_addr, file_addr, len_addr;
+
+    fd = elfsym_open(argv[1]);
+    flag_addr = elfsym_get_symbol_address(fd, "syscalls_gdb_flag");
+    ptr_addr = elfsym_get_symbol_address(fd, "syscalls_gdb_ptr");
+    file_addr = elfsym_get_symbol_address(fd, "syscalls_gdb_file");
+    len_addr = elfsym_get_symbol_address(fd, "syscalls_gdb_len");
+    elfsym_close(fd);
+
+    printf("flag_addr: 0x%x\n", flag_addr);
+    printf("ptr_addr: 0x%x\n", ptr_addr);
+    printf("file_addr: 0x%x\n", file_addr);
+    printf("len_addr: 0x%x\n", len_addr);
+
+    return 0;
+}
+
+#endif