Commit 8c87df45 authored by Jan Beulich's avatar Jan Beulich Committed by Linus Torvalds
Browse files

BUILD_BUG_ON(): fix it and a couple of bogus uses of it 



gcc permitting variable length arrays makes the current construct used for
BUILD_BUG_ON() useless, as that doesn't produce any diagnostic if the
controlling expression isn't really constant.  Instead, this patch makes
it so that a bit field gets used here.  Consequently, those uses where the
condition isn't really constant now also need fixing.

Note that in the gfp.h, kmemcheck.h, and virtio_config.h cases
MAYBE_BUILD_BUG_ON() really just serves documentation purposes - even if
the expression is compile time constant (__builtin_constant_p() yields
true), the array is still deemed of variable length by gcc, and hence the
whole expression doesn't have the intended effect.

[akpm@linux-foundation.org: make arch/sparc/include/asm/vio.h compile]
[akpm@linux-foundation.org: more nonsensical assertions in tpm.c..]
Signed-off-by: default avatarJan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Rajiv Andrade <srajiv@linux.vnet.ibm.com>
Cc: Mimi Zohar <zohar@us.ibm.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1fe72eaa

arch/sparc/include/asm/vio.h

+1 −1
Original line number Diff line number Diff line
@@ -258,7 +258,7 @@ static inline void *vio_dring_entry(struct vio_dring_state *dr, 
static inline u32 vio_dring_avail(struct vio_dring_state *dr,

				  unsigned int ring_size)

{

	BUILD_BUG_ON(!is_power_of_2(ring_size));

	MAYBE_BUILD_BUG_ON(!is_power_of_2(ring_size));



	return (dr->pending -

		((dr->prod - dr->cons) & (ring_size - 1)));

drivers/char/tpm/tpm.c

+2 −2
Original line number Diff line number Diff line
@@ -696,7 +696,7 @@ int __tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf) 


	cmd.header.in = pcrread_header;

	cmd.params.pcrread_in.pcr_idx = cpu_to_be32(pcr_idx);

	BUILD_BUG_ON(cmd.header.in.length > READ_PCR_RESULT_SIZE);

	BUG_ON(cmd.header.in.length > READ_PCR_RESULT_SIZE);

	rc = transmit_cmd(chip, &cmd, cmd.header.in.length,

			  "attempting to read a pcr value");
@@ -760,7 +760,7 @@ int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash) 
		return -ENODEV;



	cmd.header.in = pcrextend_header;

	BUILD_BUG_ON(be32_to_cpu(cmd.header.in.length) > EXTEND_PCR_SIZE);

	BUG_ON(be32_to_cpu(cmd.header.in.length) > EXTEND_PCR_SIZE);

	cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);

	memcpy(cmd.params.pcrextend_in.hash, hash, TPM_DIGEST_SIZE);

	rc = transmit_cmd(chip, &cmd, cmd.header.in.length,

drivers/net/niu.c

+1 −1
Original line number Diff line number Diff line
@@ -5615,7 +5615,7 @@ static void niu_init_tx_mac(struct niu *np) 
	/* The XMAC_MIN register only accepts values for TX min which

	 * have the low 3 bits cleared.

	 */

	BUILD_BUG_ON(min & 0x7);

	BUG_ON(min & 0x7);



	if (np->flags & NIU_FLAGS_XMAC)

		niu_init_tx_xmac(np, min, max);

include/linux/gfp.h

+1 −1
Original line number Diff line number Diff line
@@ -220,7 +220,7 @@ static inline enum zone_type gfp_zone(gfp_t flags) 
					 ((1 << ZONES_SHIFT) - 1);



	if (__builtin_constant_p(bit))

		BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);

		MAYBE_BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);

	else {

#ifdef CONFIG_DEBUG_VM

		BUG_ON((GFP_ZONE_BAD >> bit) & 1);

include/linux/kernel.h

+6 −2
Original line number Diff line number Diff line
@@ -678,13 +678,17 @@ struct sysinfo { 
};



/* Force a compilation error if condition is true */

#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))

#define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition))



/* Force a compilation error if condition is constant and true */

#define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)]))



/* Force a compilation error if condition is true, but also produce a

   result (of value 0 and type size_t), so the expression can be used

   e.g. in a structure initializer (or where-ever else comma expressions

   aren't permitted). */

#define BUILD_BUG_ON_ZERO(e) (sizeof(char[1 - 2 * !!(e)]) - 1)

#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))

#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))



/* Trap pasters of __FUNCTION__ at compile-time */

#define __FUNCTION__ (__func__)

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