On 3/5/24 00:28, Conor Dooley wrote:

From: Conor Dooley conor.dooley@microchip.com

The first multi-letter extension after the single-letter extensions does not have to be preceded by an underscore, which could cause the parser to mistakenly find a single-letter extension after the start of the multi-letter portion of the string. Three letters precede multi-letter extensions (s, x & z), none of which are valid single-letter extensions. The dt-binding also allows multi-letter extensions starting with h, but no such extension have been frozen or ratified, and the unprivileged spec no longer uses "h" as a prefix for multi-letter hypervisor extensions, having moved to "sh" instead. For that reason, modify the parser to stop at s, x & z to prevent this overrun, ignoring h.

Signed-off-by: Conor Dooley conor.dooley@microchip.com

The parser in U-Boot only supports single-letter extensions & the single-letter h has to be at the end of the single-letter section, so it would not be difficult to terminate parsing once a h is seen (you'd need to support the hypervisor extension to support additional hypervisor extensions after all) if in the future a multi-letter extension starting with h did come about. I've got no problem adding a special case for h, but I'm tempted to just remove the multi-letter h extensions from the binding, given there's actually not going to be any extensions ratified using that naming scheme.

CC: Rick Chen rick@andestech.com CC: Leo ycliang@andestech.com CC: Tom Rini trini@konsulko.com CC: Simon Glass sjg@chromium.org CC: Chanho Park chanho61.park@samsung.com CC: Heinrich Schuchardt xypron.glpk@gmx.de CC: Bin Meng bmeng.cn@gmail.com CC: Conor Dooley conor.dooley@microchip.com CC: palmer@dabbelt.com CC: u-boot@lists.denx.de

---

arch/riscv/cpu/cpu.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c index 8445c5823e..ecfefa1a02 100644 --- a/arch/riscv/cpu/cpu.c +++ b/arch/riscv/cpu/cpu.c @@ -49,14 +49,24 @@ static inline bool supports_extension(char ext) } if (!cpu_get_desc(dev, desc, sizeof(desc))) { /*

•  * skip the first 4 characters (rv32|rv64) and
  

•  * check until underscore
  

•  * skip the first 4 characters (rv32|rv64)
  

  */ for (i = 4; i < sizeof(desc); i++) {

• 	if (desc[i] == '_' || desc[i] == '\0')
  

• 		break;
  

• 	if (desc[i] == ext)
  

• 		return true;
  

• 	switch (desc[i]) {
  

• 	case 's':
  

• 	case 'x':
  

• 	case 'z':
  

• 	case '_':
  

• 	case '\0':
  

• 		/*
  

• 		 * Any of these characters mean the single
  

• 		 * letter extensions have all been consumed.
  

• 		 */
  

• 		return false;
  

• 	default:
  

• 		if (desc[i] == ext)
  

• 			return true;
  

• 	}
  

  } }

According to https://github.com/riscv/riscv-isa-manual/blob/main/src/naming.adoc the ISA string is case insensitive. Why can we assume here that it is lower case?

Best regards

Heinrich