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Michael Ellerman
b56d55a5aa
The flags argument to plpar_pte_protect() (aka. H_PROTECT), includes the key in bits 9-13, but currently we always set those bits to zero. In the past that hasn't been a problem because we always used key 0 for the kernel, and updateboltedpp() is only used for kernel mappings. However since commitd94b827e89("powerpc/book3s64/kuap: Use Key 3 for kernel mapping with hash translation") we are now inadvertently changing the key (to zero) when we call plpar_pte_protect(). That hasn't broken anything because updateboltedpp() is only used for STRICT_KERNEL_RWX, which is currently disabled on 64s due to other bugs. But we want to fix that, so first we need to pass the key correctly to plpar_pte_protect(). We can't pass our newpp value directly in, we have to convert it into the form expected by the hcall. The hcall we're using here is H_PROTECT, which is specified in section 14.5.4.1.6 of LoPAPR v1.1. It takes a `flags` parameter, and the description for flags says: * flags: AVPN, pp0, pp1, pp2, key0-key4, n, and for the CMO option: CMO Option flags as defined in Table 189‚ If you then go to the start of the parent section, 14.5.4.1, on page 405, it says: Register Linkage (For hcall() tokens 0x04 - 0x18) * On Call * R3 function call token * R4 flags (see Table 178‚ “Page Frame Table Access flags field definition‚” on page 401) Then you have to go to section 14.5.3, and on page 394 there is a list of hcalls and their tokens (table 176), and there you can see that H_PROTECT == 0x18. Finally you can look at table 178, on page 401, where it specifies the layout of the bits for the key: Bit Function ----------------- 50-54 | key0-key4 Those are big-endian bit numbers, converting to normal bit numbers you get bits 9-13, or 0x3e00. In the kernel we have: #define HPTE_R_KEY_HI ASM_CONST(0x3000000000000000) #define HPTE_R_KEY_LO ASM_CONST(0x0000000000000e00) So the LO bits of newpp are already in the right place, and the HI bits need to be shifted down by 48. Fixes:d94b827e89("powerpc/book3s64/kuap: Use Key 3 for kernel mapping with hash translation") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210331003845.216246-2-mpe@ellerman.id.au
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.