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| author | Marc Zyngier <maz@kernel.org> | 2020-12-17 14:11:35 +0300 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2020-12-17 14:46:20 +0300 |
| commit | 9fd339a45be5c06e239d45a042eab9d25de87882 (patch) | |
| tree | a5c3d1eb0e47cc2f099fe072688fb93e83fb818f /arch | |
| parent | 31f80a4e9603c3d1668bc3a1401d49321d547d54 (diff) | |
| download | linux-9fd339a45be5c06e239d45a042eab9d25de87882.tar.xz | |
arm64: Work around broken GCC 4.9 handling of "S" constraint
GCC 4.9 seems to have a problem with the "S" asm constraint
when the symbol lives in the same compilation unit, and pretends
the constraint is impossible:
$ cat x.c
void *foo(void)
{
static int x;
int *addr;
asm("adrp %0, %1" : "=r" (addr) : "S" (&x));
return addr;
}
$ ~/Work/gcc-linaro-aarch64-linux-gnu-4.9-2014.09_linux/bin/aarch64-linux-gnu-gcc -S -x c -O2 x.c
x.c: In function ‘foo’:
x.c:5:2: error: impossible constraint in ‘asm’
asm("adrp %0, %1" : "=r" (addr) : "S" (&x));
^
Boo. Following revisions of the compiler work just fine, though.
We can fallback to the "i" constraint for GCC version prior to 5.0,
which *seems* to do the right thing. Hopefully we will be able to
remove this at some point, but in the meantime this gets us going.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20201217111135.1536658-1-maz@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/include/asm/kvm_asm.h | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index 54387ccd1ab2..8e5fa28b78c2 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -200,6 +200,12 @@ extern u32 __kvm_get_mdcr_el2(void); extern char __smccc_workaround_1_smc[__SMCCC_WORKAROUND_1_SMC_SZ]; +#if defined(GCC_VERSION) && GCC_VERSION < 50000 +#define SYM_CONSTRAINT "i" +#else +#define SYM_CONSTRAINT "S" +#endif + /* * Obtain the PC-relative address of a kernel symbol * s: symbol @@ -216,7 +222,7 @@ extern char __smccc_workaround_1_smc[__SMCCC_WORKAROUND_1_SMC_SZ]; typeof(s) *addr; \ asm("adrp %0, %1\n" \ "add %0, %0, :lo12:%1\n" \ - : "=r" (addr) : "S" (&s)); \ + : "=r" (addr) : SYM_CONSTRAINT (&s)); \ addr; \ }) |