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authorLaurent ALFONSI <laurent.alfonsi@st.com>2011-06-20 08:43:13 +0200
committerRiku Voipio <riku.voipio@iki.fi>2011-06-21 20:30:09 +0300
commit14322bad88c46e41b962ff8f4a6f524dd883670c (patch)
tree0ee597cebc6ded214c1b771458aea3dc1a3b1c4b /linux-user/sparc/termbits.h
parent055e090687d31429b4cd080626d2bf9ce8bbfe59 (diff)
linux-user: Define AT_RANDOM to support target stack protection mechanism.
The dynamic linker from the GNU C library v2.10+ uses the ELF auxiliary vector AT_RANDOM [1] as a pointer to 16 bytes with random values to initialize the stack protection mechanism. Technically the emulated GNU dynamic linker crashes due to a NULL pointer derefencement if it is built with stack protection enabled and if AT_RANDOM is not defined by the QEMU ELF loader. [1] This ELF auxiliary vector was introduced in Linux v2.6.29. This patch can be tested with the code above: #include <elf.h> /* Elf*_auxv_t, AT_RANDOM, */ #include <stdio.h> /* printf(3), */ #include <stdlib.h> /* exit(3), EXIT_*, */ #include <stdint.h> /* uint8_t, */ #include <string.h> /* memcpy(3), */ #if defined(__LP64__) || defined(__ILP64__) || defined(__LLP64__) # define Elf_auxv_t Elf64_auxv_t #else # define Elf_auxv_t Elf32_auxv_t #endif main(int argc, char* argv[], char* envp[]) { Elf_auxv_t *auxv; /* *envp = NULL marks end of envp. */ while (*envp++ != NULL); /* auxv->a_type = AT_NULL marks the end of auxv. */ for (auxv = (Elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) { if (auxv->a_type == AT_RANDOM) { int i; uint8_t rand_bytes[16]; printf("AT_RANDOM is: 0x%x\n", auxv->a_un.a_val); memcpy(rand_bytes, (const uint8_t *)auxv->a_un.a_val, sizeof(rand_bytes)); printf("it points to: "); for (i = 0; i < 16; i++) { printf("0x%02x ", rand_bytes[i]); } printf("\n"); exit(EXIT_SUCCESS); } } exit(EXIT_FAILURE); } Changes introduced in v2 and v3: * Fix typos + thinko (AT_RANDOM is used for stack canary, not for ASLR) * AT_RANDOM points to 16 random bytes stored inside the user stack. * Add a small test program. Signed-off-by: Cédric VINCENT <cedric.vincent@st.com> Signed-off-by: Laurent ALFONSI <laurent.alfonsi@st.com> Signed-off-by: Riku Voipio <riku.voipio@iki.fi>
Diffstat (limited to 'linux-user/sparc/termbits.h')
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