https://github.com/michaeljclark/riscv-qemu/commit/17272f5c66adf8532f196d660d2a593c2178ac95
hw/core/loader.c | 18 ++++++++++++++++-- include/hw/elf_ops.h | 28 ++++++++++++++++------------ include/hw/loader.h | 17 ++++++++++++++++- 3 files changed, 48 insertions(+), 15 deletions(-) On Fri, Feb 9, 2018 at 9:09 PM, Michael Clark <m...@sifive.com> wrote: > > > On Fri, Feb 9, 2018 at 8:33 PM, Michael Clark <m...@sifive.com> wrote: > >> >> >> On Fri, Feb 9, 2018 at 5:35 AM, Richard Henderson < >> richard.hender...@linaro.org> wrote: >> >>> On 02/07/2018 05:28 PM, Michael Clark wrote: >>> > +++ b/hw/riscv/riscv_elf.c >>> > @@ -0,0 +1,244 @@ >>> > +/* >>> > + * elf.c - A simple package for manipulating symbol tables in elf >>> binaries. >>> > + * >>> > + * Taken from >>> > + * https://www.cs.cmu.edu/afs/cs.cmu.edu/academic/class/15213-f >>> 03/www/ >>> > + * ftrace/elf.c >>> > + * >>> > + */ >>> > +#include <stdio.h> >>> > +#include <stdlib.h> >>> > +#include <unistd.h> >>> > +#include <string.h> >>> > +#include <sys/stat.h> >>> > +#include <sys/types.h> >>> > +#include <sys/mman.h> >>> > +#include <errno.h> >>> > +#include <fcntl.h> >>> > +#include <glib.h> >>> > + >>> > +#include "hw/riscv/riscv_elf.h" >>> > + >>> > +/* >>> > + * elf_open - Map a binary into the address space and extract the >>> > + * locations of the static and dynamic symbol tables and their string >>> > + * tables. Return this information in a Elf object file handle that >>> will >>> > + * be passed to all of the other elf functions. >>> > + */ >>> > +Elf_obj64 *elf_open64(const char *filename) >>> > +{ >>> > + int i, fd; >>> > + struct stat sbuf; >>> > + Elf_obj64 *ep; >>> > + Elf64_Shdr *shdr; >>> > + >>> > + ep = g_new(Elf_obj64, 1); >>> > + >>> > + /* Do some consistency checks on the binary */ >>> > + fd = open(filename, O_RDONLY); >>> > + if (fd == -1) { >>> > + fprintf(stderr, "Can't open \"%s\": %s\n", filename, >>> strerror(errno)); >>> > + exit(1); >>> > + } >>> > + if (fstat(fd, &sbuf) == -1) { >>> > + fprintf(stderr, "Can't stat \"%s\": %s\n", filename, >>> strerror(errno)); >>> > + exit(1); >>> > + } >>> > + if (sbuf.st_size < sizeof(Elf64_Ehdr)) { >>> > + fprintf(stderr, "\"%s\" is not an ELF binary object\n", >>> filename); >>> > + exit(1); >>> > + } >>> > + >>> > + /* It looks OK, so map the Elf binary into our address space */ >>> > + ep->mlen = sbuf.st_size; >>> > + ep->maddr = mmap(NULL, ep->mlen, PROT_READ, MAP_SHARED, fd, 0); >>> > + if (ep->maddr == (void *)-1) { >>> > + fprintf(stderr, "Can't mmap \"%s\": %s\n", filename, >>> strerror(errno)); >>> > + exit(1); >>> > + } >>> > + close(fd); >>> > + >>> > + /* The Elf binary begins with the Elf header */ >>> > + ep->ehdr = ep->maddr; >>> > + >>> > + /* check we have a 64-bit little-endian RISC-V ELF object */ >>> > + if (ep->ehdr->e_ident[EI_MAG0] != ELFMAG0 || >>> > + ep->ehdr->e_ident[EI_MAG1] != ELFMAG1 || >>> > + ep->ehdr->e_ident[EI_MAG2] != ELFMAG2 || >>> > + ep->ehdr->e_ident[EI_MAG3] != ELFMAG3 || >>> > + ep->ehdr->e_ident[EI_CLASS] != ELFCLASS64 || >>> > + ep->ehdr->e_ident[EI_DATA] != ELFDATA2LSB || >>> > + ep->ehdr->e_machine != EM_RISCV) >>> > + { >>> > + fprintf(stderr, "\"%s\" is not a 64-bit RISC-V ELF object\n", >>> filename); >>> > + exit(1); >>> > + } >>> > + >>> > + /* >>> > + * Find the static and dynamic symbol tables and their string >>> > + * tables in the the mapped binary. The sh_link field in symbol >>> > + * table section headers gives the section index of the string >>> > + * table for that symbol table. >>> > + */ >>> > + shdr = (Elf64_Shdr *)(ep->maddr + ep->ehdr->e_shoff); >>> >>> This duplicates, badly, existing code within include/hw/elf_ops.h. >>> >>> In particular, this fails to bswap these fields. As such, this code >>> will only >>> work on little-endian hosts. >>> >> >> There is enough information in the structures held in the syminfo table >> used by the disassembler however elf_ops.h currently throws away all >> symbols that are not STT_FUNC, and we are after STT_OBJECT symbols. We >> would need to add an option to load_elf to load the entire symbol table. >> Also, it runs qsort on the table by address, so we'd need to do a linear >> scan for the HTIF symbols by name. There are only two symbols we need: >> 'fromhost' and 'tohost'. >> >> /* We are only interested in function symbols. >> Throw everything else away. */ >> if (syms[i].st_shndx == SHN_UNDEF || >> syms[i].st_shndx >= SHN_LORESERVE || >> ELF_ST_TYPE(syms[i].st_info) != STT_FUNC) { >> nsyms--; >> if (i < nsyms) { >> syms[i] = syms[nsyms]; >> } >> continue; >> } >> >> It would be really nice if HTIF just specified registers in device-tree; >> alas it doesn't; and there is still quite a bit of code that depend on >> using these magic HTIF 'fromhost' and 'tohost' symbols. riscv-tests for one >> uses the HTIF mechanism and spike the official ISA simulator uses HTIF for >> IO. >> > > Luckily elf_ops.h load_elf32 and load_elf64 are wrapped by load_elf, and > several load_elf_* variants. > > We need the symbol name, type, address and size to find and validate the > HTIF symbols. The current thought is to pass a callback function pointer to > a new load_elf_sym variant, where the new function pointer, in the common > case, won't be called by load_elf32 and load_elf64 as it will be NULL for > all present users. We could use uint64_t to abstract the caller from > the elf32_sym/elf64_sym address and size types. This approach would likely > require less code than adding a new /linear/ search by name method, along > with a retain all symbols argument to load_symbols and associated plumbing. > It's also inherently one pass e.g. > > typedef void (*symbol_fn_t)(const char *st_name, int st_info, > uint64_t st_value, uint64_t st_size); > > static int glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int > must_swab, > int clear_lsb, symbol_fn_t sym_cb) > { > > .... > > if (sym_cb) { > sym_cb(strtab + syms[i].st_name, syms[i].st_info, > syms[i].st_value, syms[i].st_size) > } > > ... > > } > > static int glue(load_elf, SZ)(const char *name, int fd, > uint64_t (*translate_fn)(void *, uint64_t), > void *translate_opaque, > int must_swab, uint64_t *pentry, > uint64_t *lowaddr, uint64_t *highaddr, > int elf_machine, int clear_lsb, int > data_swab, > AddressSpace *as, bool load_rom, > symbol_fn_t sym_cb) > { > .... > > glue(load_symbols, SZ)(&ehdr, fd, must_swab, clear_lsb, sym_cb); > > .... > } > >
