RISC-V Fixes for 6.3-rc2

* RISC-V architecture-specific ELF attributes have been disabled in the
   kernel builds.
 * A fix for a locking failure while during errata patching that
   manifests on SiFive-based systems.
 * A fix for a KASAN failure during stack unwinding.
 * A fix for some lockdep failures during text patching.
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Merge tag 'riscv-for-linus-6.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Palmer Dabbelt:

 - RISC-V architecture-specific ELF attributes have been disabled in the
   kernel builds

 - A fix for a locking failure while during errata patching that
   manifests on SiFive-based systems

 - A fix for a KASAN failure during stack unwinding

 - A fix for some lockdep failures during text patching

* tag 'riscv-for-linus-6.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  RISC-V: Don't check text_mutex during stop_machine
  riscv: Use READ_ONCE_NOCHECK in imprecise unwinding stack mode
  RISC-V: fix taking the text_mutex twice during sifive errata patching
  RISC-V: Stop emitting attributes
This commit is contained in:
Linus Torvalds 2023-03-10 09:19:30 -08:00
commit 55a21105ec
8 changed files with 52 additions and 8 deletions

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@ -84,6 +84,13 @@ endif
# Avoid generating .eh_frame sections. # Avoid generating .eh_frame sections.
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
# The RISC-V attributes frequently cause compatibility issues and provide no
# information, so just turn them off.
KBUILD_CFLAGS += $(call cc-option,-mno-riscv-attribute)
KBUILD_AFLAGS += $(call cc-option,-mno-riscv-attribute)
KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax) KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax) KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)

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@ -111,7 +111,7 @@ void __init_or_module sifive_errata_patch_func(struct alt_entry *begin,
mutex_lock(&text_mutex); mutex_lock(&text_mutex);
patch_text_nosync(ALT_OLD_PTR(alt), ALT_ALT_PTR(alt), patch_text_nosync(ALT_OLD_PTR(alt), ALT_ALT_PTR(alt),
alt->alt_len); alt->alt_len);
mutex_lock(&text_mutex); mutex_unlock(&text_mutex);
cpu_apply_errata |= tmp; cpu_apply_errata |= tmp;
} }
} }

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@ -109,6 +109,6 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
#define ftrace_init_nop ftrace_init_nop #define ftrace_init_nop ftrace_init_nop
#endif #endif
#endif #endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* _ASM_RISCV_FTRACE_H */ #endif /* _ASM_RISCV_FTRACE_H */

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@ -9,4 +9,6 @@
int patch_text_nosync(void *addr, const void *insns, size_t len); int patch_text_nosync(void *addr, const void *insns, size_t len);
int patch_text(void *addr, u32 *insns, int ninsns); int patch_text(void *addr, u32 *insns, int ninsns);
extern int riscv_patch_in_stop_machine;
#endif /* _ASM_RISCV_PATCH_H */ #endif /* _ASM_RISCV_PATCH_H */

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@ -14,6 +14,10 @@ COMPAT_LD := $(LD)
COMPAT_CC_FLAGS := -march=rv32g -mabi=ilp32 COMPAT_CC_FLAGS := -march=rv32g -mabi=ilp32
COMPAT_LD_FLAGS := -melf32lriscv COMPAT_LD_FLAGS := -melf32lriscv
# Disable attributes, as they're useless and break the build.
COMPAT_CC_FLAGS += $(call cc-option,-mno-riscv-attribute)
COMPAT_CC_FLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
# Files to link into the compat_vdso # Files to link into the compat_vdso
obj-compat_vdso = $(patsubst %, %.o, $(compat_vdso-syms)) note.o obj-compat_vdso = $(patsubst %, %.o, $(compat_vdso-syms)) note.o

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@ -15,10 +15,19 @@
void ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex) void ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
{ {
mutex_lock(&text_mutex); mutex_lock(&text_mutex);
/*
* The code sequences we use for ftrace can't be patched while the
* kernel is running, so we need to use stop_machine() to modify them
* for now. This doesn't play nice with text_mutex, we use this flag
* to elide the check.
*/
riscv_patch_in_stop_machine = true;
} }
void ftrace_arch_code_modify_post_process(void) __releases(&text_mutex) void ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
{ {
riscv_patch_in_stop_machine = false;
mutex_unlock(&text_mutex); mutex_unlock(&text_mutex);
} }
@ -107,9 +116,9 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
{ {
int out; int out;
ftrace_arch_code_modify_prepare(); mutex_lock(&text_mutex);
out = ftrace_make_nop(mod, rec, MCOUNT_ADDR); out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
ftrace_arch_code_modify_post_process(); mutex_unlock(&text_mutex);
return out; return out;
} }

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@ -11,6 +11,7 @@
#include <asm/kprobes.h> #include <asm/kprobes.h>
#include <asm/cacheflush.h> #include <asm/cacheflush.h>
#include <asm/fixmap.h> #include <asm/fixmap.h>
#include <asm/ftrace.h>
#include <asm/patch.h> #include <asm/patch.h>
struct patch_insn { struct patch_insn {
@ -20,6 +21,8 @@ struct patch_insn {
atomic_t cpu_count; atomic_t cpu_count;
}; };
int riscv_patch_in_stop_machine = false;
#ifdef CONFIG_MMU #ifdef CONFIG_MMU
/* /*
* The fix_to_virt(, idx) needs a const value (not a dynamic variable of * The fix_to_virt(, idx) needs a const value (not a dynamic variable of
@ -60,8 +63,15 @@ static int patch_insn_write(void *addr, const void *insn, size_t len)
* Before reaching here, it was expected to lock the text_mutex * Before reaching here, it was expected to lock the text_mutex
* already, so we don't need to give another lock here and could * already, so we don't need to give another lock here and could
* ensure that it was safe between each cores. * ensure that it was safe between each cores.
*
* We're currently using stop_machine() for ftrace & kprobes, and while
* that ensures text_mutex is held before installing the mappings it
* does not ensure text_mutex is held by the calling thread. That's
* safe but triggers a lockdep failure, so just elide it for that
* specific case.
*/ */
lockdep_assert_held(&text_mutex); if (!riscv_patch_in_stop_machine)
lockdep_assert_held(&text_mutex);
if (across_pages) if (across_pages)
patch_map(addr + len, FIX_TEXT_POKE1); patch_map(addr + len, FIX_TEXT_POKE1);
@ -125,6 +135,7 @@ NOKPROBE_SYMBOL(patch_text_cb);
int patch_text(void *addr, u32 *insns, int ninsns) int patch_text(void *addr, u32 *insns, int ninsns)
{ {
int ret;
struct patch_insn patch = { struct patch_insn patch = {
.addr = addr, .addr = addr,
.insns = insns, .insns = insns,
@ -132,7 +143,18 @@ int patch_text(void *addr, u32 *insns, int ninsns)
.cpu_count = ATOMIC_INIT(0), .cpu_count = ATOMIC_INIT(0),
}; };
return stop_machine_cpuslocked(patch_text_cb, /*
&patch, cpu_online_mask); * kprobes takes text_mutex, before calling patch_text(), but as we call
* calls stop_machine(), the lockdep assertion in patch_insn_write()
* gets confused by the context in which the lock is taken.
* Instead, ensure the lock is held before calling stop_machine(), and
* set riscv_patch_in_stop_machine to skip the check in
* patch_insn_write().
*/
lockdep_assert_held(&text_mutex);
riscv_patch_in_stop_machine = true;
ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
riscv_patch_in_stop_machine = false;
return ret;
} }
NOKPROBE_SYMBOL(patch_text); NOKPROBE_SYMBOL(patch_text);

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@ -101,7 +101,7 @@ void notrace walk_stackframe(struct task_struct *task,
while (!kstack_end(ksp)) { while (!kstack_end(ksp)) {
if (__kernel_text_address(pc) && unlikely(!fn(arg, pc))) if (__kernel_text_address(pc) && unlikely(!fn(arg, pc)))
break; break;
pc = (*ksp++) - 0x4; pc = READ_ONCE_NOCHECK(*ksp++) - 0x4;
} }
} }