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work around gcc bugs with 'asm goto' with outputs

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commit 68fb3ca0e408e00db1c3f8fccdfa19e274c033be 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'.

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>
This commit is contained in:
Linus Torvalds
2024-02-09 12:39:31 -08:00
committed by Greg Kroah-Hartman
parent 8b4118fabd
commit f70efe54b9
30 changed files with 86 additions and 67 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
arch/arc/include/asm/jump_label.h
View File

@@ -31,7 +31,7 @@
static __always_inline bool arch_static_branch(struct static_key *key,
bool branch)
{
asm_volatile_goto(".balign "__stringify(JUMP_LABEL_NOP_SIZE)" \n"
asm goto(".balign "__stringify(JUMP_LABEL_NOP_SIZE)" \n"
"1: \n"
"nop \n"
".pushsection __jump_table, \"aw\" \n"
@@ -47,7 +47,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key *key,
bool branch)
{
asm_volatile_goto(".balign "__stringify(JUMP_LABEL_NOP_SIZE)" \n"
asm goto(".balign "__stringify(JUMP_LABEL_NOP_SIZE)" \n"
"1: \n"
"b %l[l_yes] \n"
".pushsection __jump_table, \"aw\" \n"

4
arch/arm/include/asm/jump_label.h
View File

@@ -11,7 +11,7 @@
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\n\t"
asm goto("1:\n\t"
WASM(nop) "\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".word 1b, %l[l_yes], %c0\n\t"
@@ -25,7 +25,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\n\t"
asm goto("1:\n\t"
WASM(b) " %l[l_yes]\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".word 1b, %l[l_yes], %c0\n\t"

4
arch/arm64/include/asm/alternative-macros.h
View File

@@ -229,7 +229,7 @@ alternative_has_feature_likely(unsigned long feature)
compiletime_assert(feature < ARM64_NCAPS,
"feature must be < ARM64_NCAPS");
asm_volatile_goto(
asm goto(
ALTERNATIVE_CB("b %l[l_no]", %[feature], alt_cb_patch_nops)
:
: [feature] "i" (feature)
@@ -247,7 +247,7 @@ alternative_has_feature_unlikely(unsigned long feature)
compiletime_assert(feature < ARM64_NCAPS,
"feature must be < ARM64_NCAPS");
asm_volatile_goto(
asm goto(
ALTERNATIVE("nop", "b %l[l_yes]", %[feature])
:
: [feature] "i" (feature)

4
arch/arm64/include/asm/jump_label.h
View File

@@ -18,7 +18,7 @@
static __always_inline bool arch_static_branch(struct static_key *key,
bool branch)
{
asm_volatile_goto(
asm goto(
"1: nop \n\t"
" .pushsection __jump_table, \"aw\" \n\t"
" .align 3 \n\t"
@@ -35,7 +35,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key *key,
bool branch)
{
asm_volatile_goto(
asm goto(
"1: b %l[l_yes] \n\t"
" .pushsection __jump_table, \"aw\" \n\t"
" .align 3 \n\t"

4
arch/csky/include/asm/jump_label.h
View File

@@ -12,7 +12,7 @@
static __always_inline bool arch_static_branch(struct static_key *key,
bool branch)
{
asm_volatile_goto(
asm goto(
"1: nop32 \n"
" .pushsection __jump_table, \"aw\" \n"
" .align 2 \n"
@@ -29,7 +29,7 @@ label:
static __always_inline bool arch_static_branch_jump(struct static_key *key,
bool branch)
{
asm_volatile_goto(
asm goto(
"1: bsr32 %l[label] \n"
" .pushsection __jump_table, \"aw\" \n"
" .align 2 \n"

4
arch/mips/include/asm/jump_label.h
View File

@@ -36,7 +36,7 @@
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\t" B_INSN " 2f\n\t"
asm goto("1:\t" B_INSN " 2f\n\t"
"2:\t.insn\n\t"
".pushsection __jump_table, \"aw\"\n\t"
WORD_INSN " 1b, %l[l_yes], %0\n\t"
@@ -50,7 +50,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\t" J_INSN " %l[l_yes]\n\t"
asm goto("1:\t" J_INSN " %l[l_yes]\n\t"
".pushsection __jump_table, \"aw\"\n\t"
WORD_INSN " 1b, %l[l_yes], %0\n\t"
".popsection\n\t"

4
arch/parisc/include/asm/jump_label.h
View File

@@ -12,7 +12,7 @@
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\n\t"
asm goto("1:\n\t"
"nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".align %1\n\t"
@@ -29,7 +29,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\n\t"
asm goto("1:\n\t"
"b,n %l[l_yes]\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".align %1\n\t"

2
arch/powerpc/include/asm/bug.h
View File

@@ -74,7 +74,7 @@
##__VA_ARGS__)
#define WARN_ENTRY(insn, flags, label, ...) \
asm_volatile_goto( \
asm goto( \
"1: " insn "\n" \
EX_TABLE(1b, %l[label]) \
_EMIT_BUG_ENTRY \

4
arch/powerpc/include/asm/jump_label.h
View File

@@ -17,7 +17,7 @@
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\n\t"
asm goto("1:\n\t"
"nop # arch_static_branch\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".long 1b - ., %l[l_yes] - .\n\t"
@@ -32,7 +32,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\n\t"
asm goto("1:\n\t"
"b %l[l_yes] # arch_static_branch_jump\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".long 1b - ., %l[l_yes] - .\n\t"

8
arch/powerpc/include/asm/uaccess.h
View File

@@ -72,7 +72,7 @@ __pu_failed: \
* are no aliasing issues.
*/
#define __put_user_asm_goto(x, addr, label, op) \
asm_volatile_goto( \
asm goto( \
"1: " op "%U1%X1 %0,%1 # put_user\n" \
EX_TABLE(1b, %l2) \
: \
@@ -85,7 +85,7 @@ __pu_failed: \
__put_user_asm_goto(x, ptr, label, "std")
#else /* __powerpc64__ */
#define __put_user_asm2_goto(x, addr, label) \
asm_volatile_goto( \
asm goto( \
"1: stw%X1 %0, %1\n" \
"2: stw%X1 %L0, %L1\n" \
EX_TABLE(1b, %l2) \
@@ -132,7 +132,7 @@ do { \
#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
#define __get_user_asm_goto(x, addr, label, op) \
asm_volatile_goto( \
asm_goto_output( \
"1: "op"%U1%X1 %0, %1 # get_user\n" \
EX_TABLE(1b, %l2) \
: "=r" (x) \
@@ -145,7 +145,7 @@ do { \
__get_user_asm_goto(x, addr, label, "ld")
#else /* __powerpc64__ */
#define __get_user_asm2_goto(x, addr, label) \
asm_volatile_goto( \
asm_goto_output( \
"1: lwz%X1 %0, %1\n" \
"2: lwz%X1 %L0, %L1\n" \
EX_TABLE(1b, %l2) \

2
arch/powerpc/kernel/irq_64.c
View File

@@ -230,7 +230,7 @@ again:
* This allows interrupts to be unmasked without hard disabling, and
* also without new hard interrupts coming in ahead of pending ones.
*/
asm_volatile_goto(
asm goto(
"1: \n"
" lbz 9,%0(13) \n"
" cmpwi 9,0 \n"

4
arch/riscv/include/asm/jump_label.h
View File

@@ -17,7 +17,7 @@
static __always_inline bool arch_static_branch(struct static_key * const key,
const bool branch)
{
asm_volatile_goto(
asm goto(
" .align 2 \n\t"
" .option push \n\t"
" .option norelax \n\t"
@@ -39,7 +39,7 @@ label:
static __always_inline bool arch_static_branch_jump(struct static_key * const key,
const bool branch)
{
asm_volatile_goto(
asm goto(
" .align 2 \n\t"
" .option push \n\t"
" .option norelax \n\t"

4
arch/s390/include/asm/jump_label.h
View File

@@ -25,7 +25,7 @@
*/
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("0: brcl 0,%l[label]\n"
asm goto("0: brcl 0,%l[label]\n"
".pushsection __jump_table,\"aw\"\n"
".balign 8\n"
".long 0b-.,%l[label]-.\n"
@@ -39,7 +39,7 @@ label:
static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
asm_volatile_goto("0: brcl 15,%l[label]\n"
asm goto("0: brcl 15,%l[label]\n"
".pushsection __jump_table,\"aw\"\n"
".balign 8\n"
".long 0b-.,%l[label]-.\n"

4
arch/sparc/include/asm/jump_label.h
View File

@@ -10,7 +10,7 @@
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\n\t"
asm goto("1:\n\t"
"nop\n\t"
"nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"
@@ -26,7 +26,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\n\t"
asm goto("1:\n\t"
"b %l[l_yes]\n\t"
"nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"

2
arch/um/include/asm/cpufeature.h
View File

@@ -75,7 +75,7 @@ extern void setup_clear_cpu_cap(unsigned int bit);
*/
static __always_inline bool _static_cpu_has(u16 bit)
{
asm_volatile_goto("1: jmp 6f\n"
asm goto("1: jmp 6f\n"
"2:\n"
".skip -(((5f-4f) - (2b-1b)) > 0) * "
"((5f-4f) - (2b-1b)),0x90\n"

2
arch/x86/include/asm/cpufeature.h
View File

@@ -173,7 +173,7 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
*/
static __always_inline bool _static_cpu_has(u16 bit)
{
asm_volatile_goto(
asm goto(
ALTERNATIVE_TERNARY("jmp 6f", %P[feature], "", "jmp %l[t_no]")
".pushsection .altinstr_aux,\"ax\"\n"
"6:\n"

6
arch/x86/include/asm/jump_label.h
View File

@@ -24,7 +24,7 @@
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("1:"
asm goto("1:"
"jmp %l[l_yes] # objtool NOPs this \n\t"
JUMP_TABLE_ENTRY
: : "i" (key), "i" (2 | branch) : : l_yes);
@@ -38,7 +38,7 @@ l_yes:
static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
{
asm_volatile_goto("1:"
asm goto("1:"
".byte " __stringify(BYTES_NOP5) "\n\t"
JUMP_TABLE_ENTRY
: : "i" (key), "i" (branch) : : l_yes);
@@ -52,7 +52,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch)
{
asm_volatile_goto("1:"
asm goto("1:"
"jmp %l[l_yes]\n\t"
JUMP_TABLE_ENTRY
: : "i" (key), "i" (branch) : : l_yes);

2
arch/x86/include/asm/rmwcc.h
View File

@@ -18,7 +18,7 @@
#define __GEN_RMWcc(fullop, _var, cc, clobbers, ...) \
({ \
bool c = false; \
asm_volatile_goto (fullop "; j" #cc " %l[cc_label]" \
asm goto (fullop "; j" #cc " %l[cc_label]" \
: : [var] "m" (_var), ## __VA_ARGS__ \
: clobbers : cc_label); \
if (0) { \

10
arch/x86/include/asm/uaccess.h
View File

@@ -155,7 +155,7 @@ extern int __get_user_bad(void);
#ifdef CONFIG_X86_32
#define __put_user_goto_u64(x, addr, label) \
asm_volatile_goto("\n" \
asm goto("\n" \
"1: movl %%eax,0(%1)\n" \
"2: movl %%edx,4(%1)\n" \
_ASM_EXTABLE_UA(1b, %l2) \
@@ -317,7 +317,7 @@ do { \
} while (0)
#define __get_user_asm(x, addr, itype, ltype, label) \
asm_volatile_goto("\n" \
asm_goto_output("\n" \
"1: mov"itype" %[umem],%[output]\n" \
_ASM_EXTABLE_UA(1b, %l2) \
: [output] ltype(x) \
@@ -397,7 +397,7 @@ do { \
__typeof__(_ptr) _old = (__typeof__(_ptr))(_pold); \
__typeof__(*(_ptr)) __old = *_old; \
__typeof__(*(_ptr)) __new = (_new); \
asm_volatile_goto("\n" \
asm_goto_output("\n" \
"1: " LOCK_PREFIX "cmpxchg"itype" %[new], %[ptr]\n"\
_ASM_EXTABLE_UA(1b, %l[label]) \
: CC_OUT(z) (success), \
@@ -416,7 +416,7 @@ do { \
__typeof__(_ptr) _old = (__typeof__(_ptr))(_pold); \
__typeof__(*(_ptr)) __old = *_old; \
__typeof__(*(_ptr)) __new = (_new); \
asm_volatile_goto("\n" \
asm_goto_output("\n" \
"1: " LOCK_PREFIX "cmpxchg8b %[ptr]\n" \
_ASM_EXTABLE_UA(1b, %l[label]) \
: CC_OUT(z) (success), \
@@ -499,7 +499,7 @@ struct __large_struct { unsigned long buf[100]; };
* aliasing issues.
*/
#define __put_user_goto(x, addr, itype, ltype, label) \
asm_volatile_goto("\n" \
asm goto("\n" \
"1: mov"itype" %0,%1\n" \
_ASM_EXTABLE_UA(1b, %l2) \
: : ltype(x), "m" (__m(addr)) \

12
arch/x86/include/asm/virtext.h
View File

@@ -43,9 +43,9 @@ static inline int cpu_has_vmx(void)
*/
static inline int cpu_vmxoff(void)
{
asm_volatile_goto("1: vmxoff\n\t"
_ASM_EXTABLE(1b, %l[fault])
::: "cc", "memory" : fault);
asm goto("1: vmxoff\n\t"
_ASM_EXTABLE(1b, %l[fault])
::: "cc", "memory" : fault);
cr4_clear_bits(X86_CR4_VMXE);
return 0;
@@ -129,9 +129,9 @@ static inline void cpu_svm_disable(void)
* case, GIF must already be set, otherwise the NMI would have
* been blocked, so just eat the fault.
*/
asm_volatile_goto("1: stgi\n\t"
_ASM_EXTABLE(1b, %l[fault])
::: "memory" : fault);
asm goto("1: stgi\n\t"
_ASM_EXTABLE(1b, %l[fault])
::: "memory" : fault);
fault:
wrmsrl(MSR_EFER, efer & ~EFER_SVME);
}

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