Unverified Commit 5014396a authored by Clément Léger's avatar Clément Léger Committed by Palmer Dabbelt
Browse files

riscv: blacklist assembly symbols for kprobe 



Adding kprobes on some assembly functions (mainly exception handling)
will result in crashes (either recursive trap or panic). To avoid such
errors, add ASM_NOKPROBE() macro which allow adding specific symbols
into the __kprobe_blacklist section and use to blacklist the following
symbols that showed to be problematic:
- handle_exception()
- ret_from_exception()
- handle_kernel_stack_overflow()

Signed-off-by: default avatarClément Léger <cleger@rivosinc.com>
Reviewed-by: default avatarCharlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20231004131009.409193-1-cleger@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 7f43d57b

arch/riscv/include/asm/asm.h

+10 −0
Original line number Diff line number Diff line
@@ -183,6 +183,16 @@ 
	REG_L x31, PT_T6(sp)

	.endm



/* Annotate a function as being unsuitable for kprobes. */

#ifdef CONFIG_KPROBES

#define ASM_NOKPROBE(name)				\

	.pushsection "_kprobe_blacklist", "aw";		\

	RISCV_PTR name;					\

	.popsection

#else

#define ASM_NOKPROBE(name)

#endif



#endif /* __ASSEMBLY__ */



#endif /* _ASM_RISCV_ASM_H */

arch/riscv/kernel/entry.S

+3 −0
Original line number Diff line number Diff line
@@ -111,6 +111,7 @@ SYM_CODE_START(handle_exception) 
1:

	tail do_trap_unknown

SYM_CODE_END(handle_exception)

ASM_NOKPROBE(handle_exception)



/*

 * The ret_from_exception must be called with interrupt disabled. Here is the
@@ -184,6 +185,7 @@ SYM_CODE_START_NOALIGN(ret_from_exception) 
	sret

#endif

SYM_CODE_END(ret_from_exception)

ASM_NOKPROBE(ret_from_exception)



#ifdef CONFIG_VMAP_STACK

SYM_CODE_START_LOCAL(handle_kernel_stack_overflow)
@@ -219,6 +221,7 @@ SYM_CODE_START_LOCAL(handle_kernel_stack_overflow) 
	move a0, sp

	tail handle_bad_stack

SYM_CODE_END(handle_kernel_stack_overflow)

ASM_NOKPROBE(handle_kernel_stack_overflow)

#endif



SYM_CODE_START(ret_from_fork)