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stand: Avoid unaligned access in smbios code

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This code was written on x86 where unaligned accesses were
easy. LinuxBoot running on aarch64 uses mmap of /dev/mem to read the
smbios table. Linux's mapping of this memory doesn't allow the normal
unaligned fixup, so we get a bus error instead. We can't use the more
natural le16dec and friends because they optimize into a single,
unaligned memory load. We don't see this issue on aarch64 UEFI because
memory is mapped such that unaligned accesses are fixed up.

Sponsored by:		Netflix
Differential Revision:	https://reviews.freebsd.org/D39793
This commit is contained in:
Warner Losh 2023-05-01 15:12:34 -06:00
parent a083d08676
commit c5e433b99e
1 changed files with 42 additions and 5 deletions
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47
stand/libsa/smbios.c
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@ -96,10 +96,47 @@ __FBSDID("$FreeBSD$");
#define SMBIOS3_SIG "_SM3_"
#define SMBIOS_DMI_SIG "_DMI_"
#define SMBIOS_GET8(base, off) (*(uint8_t *)((base) + (off)))
#define SMBIOS_GET16(base, off) (*(uint16_t *)((base) + (off)))
#define SMBIOS_GET32(base, off) (*(uint32_t *)((base) + (off)))
#define SMBIOS_GET64(base, off) (*(uint64_t *)((base) + (off)))
/*
* 5.1 General
*...
* NOTE The Entry Point Structure and all SMBIOS structures assume a
* little-endian ordering convention...
* ...
*
* We use memcpy to avoid unaligned access to memory. To normal memory, this is
* fine, but the memory we are using might be mmap'd /dev/mem which under Linux
* on aarch64 doesn't allow unaligned access. leXdec and friends can't be used
* because those can optimize to an unaligned load (which often is fine, but not
* for mmap'd /dev/mem which has special memory attributes).
*/
static inline uint8_t SMBIOS_GET8(const caddr_t base, int off) { return (base[off]); }
static inline uint16_t
SMBIOS_GET16(const caddr_t base, int off)
{
uint16_t v;
memcpy(&v, base + off, sizeof(v));
return (le16toh(v));
}
static inline uint32_t
SMBIOS_GET32(const caddr_t base, int off)
{
uint32_t v;
memcpy(&v, base + off, sizeof(v));
return (le32toh(v));
}
static inline uint64_t
SMBIOS_GET64(const caddr_t base, int off)
{
uint64_t v;
memcpy(&v, base + off, sizeof(v));
return (le64toh(v));
}
#define SMBIOS_GETLEN(base) SMBIOS_GET8(base, 0x01)
#define SMBIOS_GETSTR(base) ((base) + SMBIOS_GETLEN(base))
@ -195,7 +232,7 @@ smbios_setenv(const char *name, caddr_t addr, const int offset)
#define UUID_TYPE uint32_t
#define UUID_STEP sizeof(UUID_TYPE)
#define UUID_ALL_BITS (UUID_SIZE / UUID_STEP)
#define UUID_GET(base, off) (*(UUID_TYPE *)((base) + (off)))
#define UUID_GET(base, off) SMBIOS_GET32(base, off)
static void
smbios_setuuid(const char *name, const caddr_t addr, const int ver __unused)