Files
linux-bredos/arch/riscv/include/asm/hwcap.h
Linus Torvalds aaff74d886 work around gcc bugs with 'asm goto' with outputs
commit 4356e9f841 upstream.

We've had issues with gcc and 'asm goto' before, and we created a
'asm_volatile_goto()' macro for that in the past: see commits
3f0116c323 ("compiler/gcc4: Add quirk for 'asm goto' miscompilation
bug") and a9f180345f ("compiler/gcc4: Make quirk for
asm_volatile_goto() unconditional").

Then, much later, we ended up removing the workaround in commit
43c249ea0b ("compiler-gcc.h: remove ancient workaround for gcc PR
58670") because we no longer supported building the kernel with the
affected gcc versions, but we left the macro uses around.

Now, Sean Christopherson reports a new version of a very similar
problem, which is fixed by re-applying that ancient workaround.  But the
problem in question is limited to only the 'asm goto with outputs'
cases, so instead of re-introducing the old workaround as-is, let's
rename and limit the workaround to just that much less common case.

It looks like there are at least two separate issues that all hit in
this area:

 (a) some versions of gcc don't mark the asm goto as 'volatile' when it
     has outputs:

        https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98619
        https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110420

     which is easy to work around by just adding the 'volatile' by hand.

 (b) Internal compiler errors:

        https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110422

     which are worked around by adding the extra empty 'asm' as a
     barrier, as in the original workaround.

but the problem Sean sees may be a third thing since it involves bad
code generation (not an ICE) even with the manually added 'volatile'.

but the same old workaround works for this case, even if this feels a
bit like voodoo programming and may only be hiding the issue.

Reported-and-tested-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Andrew Pinski <quic_apinski@quicinc.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-02-23 09:24:47 +01:00

143 lines
3.6 KiB
C

/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copied from arch/arm64/include/asm/hwcap.h
*
* Copyright (C) 2012 ARM Ltd.
* Copyright (C) 2017 SiFive
*/
#ifndef _ASM_RISCV_HWCAP_H
#define _ASM_RISCV_HWCAP_H
#include <asm/alternative-macros.h>
#include <asm/errno.h>
#include <linux/bits.h>
#include <uapi/asm/hwcap.h>
#define RISCV_ISA_EXT_a ('a' - 'a')
#define RISCV_ISA_EXT_b ('b' - 'a')
#define RISCV_ISA_EXT_c ('c' - 'a')
#define RISCV_ISA_EXT_d ('d' - 'a')
#define RISCV_ISA_EXT_f ('f' - 'a')
#define RISCV_ISA_EXT_h ('h' - 'a')
#define RISCV_ISA_EXT_i ('i' - 'a')
#define RISCV_ISA_EXT_j ('j' - 'a')
#define RISCV_ISA_EXT_k ('k' - 'a')
#define RISCV_ISA_EXT_m ('m' - 'a')
#define RISCV_ISA_EXT_p ('p' - 'a')
#define RISCV_ISA_EXT_q ('q' - 'a')
#define RISCV_ISA_EXT_s ('s' - 'a')
#define RISCV_ISA_EXT_u ('u' - 'a')
#define RISCV_ISA_EXT_v ('v' - 'a')
/*
* These macros represent the logical IDs of each multi-letter RISC-V ISA
* extension and are used in the ISA bitmap. The logical IDs start from
* RISCV_ISA_EXT_BASE, which allows the 0-25 range to be reserved for single
* letter extensions. The maximum, RISCV_ISA_EXT_MAX, is defined in order
* to allocate the bitmap and may be increased when necessary.
*
* New extensions should just be added to the bottom, rather than added
* alphabetically, in order to avoid unnecessary shuffling.
*/
#define RISCV_ISA_EXT_BASE 26
#define RISCV_ISA_EXT_SSCOFPMF 26
#define RISCV_ISA_EXT_SSTC 27
#define RISCV_ISA_EXT_SVINVAL 28
#define RISCV_ISA_EXT_SVPBMT 29
#define RISCV_ISA_EXT_ZBB 30
#define RISCV_ISA_EXT_ZICBOM 31
#define RISCV_ISA_EXT_ZIHINTPAUSE 32
#define RISCV_ISA_EXT_SVNAPOT 33
#define RISCV_ISA_EXT_ZICBOZ 34
#define RISCV_ISA_EXT_SMAIA 35
#define RISCV_ISA_EXT_SSAIA 36
#define RISCV_ISA_EXT_ZBA 37
#define RISCV_ISA_EXT_ZBS 38
#define RISCV_ISA_EXT_ZICNTR 39
#define RISCV_ISA_EXT_ZICSR 40
#define RISCV_ISA_EXT_ZIFENCEI 41
#define RISCV_ISA_EXT_ZIHPM 42
#define RISCV_ISA_EXT_MAX 64
#ifdef CONFIG_RISCV_M_MODE
#define RISCV_ISA_EXT_SxAIA RISCV_ISA_EXT_SMAIA
#else
#define RISCV_ISA_EXT_SxAIA RISCV_ISA_EXT_SSAIA
#endif
#ifndef __ASSEMBLY__
#include <linux/jump_label.h>
unsigned long riscv_get_elf_hwcap(void);
struct riscv_isa_ext_data {
const unsigned int id;
const char *name;
const char *property;
};
extern const struct riscv_isa_ext_data riscv_isa_ext[];
extern const size_t riscv_isa_ext_count;
extern bool riscv_isa_fallback;
unsigned long riscv_isa_extension_base(const unsigned long *isa_bitmap);
#define riscv_isa_extension_mask(ext) BIT_MASK(RISCV_ISA_EXT_##ext)
bool __riscv_isa_extension_available(const unsigned long *isa_bitmap, int bit);
#define riscv_isa_extension_available(isa_bitmap, ext) \
__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_##ext)
static __always_inline bool
riscv_has_extension_likely(const unsigned long ext)
{
compiletime_assert(ext < RISCV_ISA_EXT_MAX,
"ext must be < RISCV_ISA_EXT_MAX");
if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
asm goto(
ALTERNATIVE("j %l[l_no]", "nop", 0, %[ext], 1)
:
: [ext] "i" (ext)
:
: l_no);
} else {
if (!__riscv_isa_extension_available(NULL, ext))
goto l_no;
}
return true;
l_no:
return false;
}
static __always_inline bool
riscv_has_extension_unlikely(const unsigned long ext)
{
compiletime_assert(ext < RISCV_ISA_EXT_MAX,
"ext must be < RISCV_ISA_EXT_MAX");
if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
asm goto(
ALTERNATIVE("nop", "j %l[l_yes]", 0, %[ext], 1)
:
: [ext] "i" (ext)
:
: l_yes);
} else {
if (__riscv_isa_extension_available(NULL, ext))
goto l_yes;
}
return false;
l_yes:
return true;
}
#endif
#endif /* _ASM_RISCV_HWCAP_H */